[Federal Register Volume 67, Number 228 (Tuesday, November 26, 2002)]
[Rules and Regulations]
[Pages 70812-70828]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-29667]



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Part II





Department of Transportation





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Federal Aviation Administration



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14 CFR Parts 1, 25, and 97



1-g Stall Speed as the Basis for Compliance With Part 25 of the Federal 
Aviation Regulations; Final Rule

  Federal Register / Vol. 67, No. 228 / Tuesday, November 26, 2002 / 
Rules and Regulations  

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 1, 25, and 97

[Docket No. 28404; Amendment Nos. 1-49, 25-108, 97-1333]
RIN 2120-AD40


1-g Stall Speed as the Basis for Compliance With Part 25 of the 
Federal Aviation Regulations

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: This action amends the airworthiness standards for transport 
category airplanes to redefine the reference stall speed for transport 
category airplanes as a speed not less than the 1-g stall speed instead 
of the minimum speed obtained in a stalling maneuver. The FAA is taking 
this action to provide for a consistent, repeatable reference stall 
speed; ensure consistent and dependable maneuvering margins; provide 
for adjusted multiplying factors to maintain approximately the current 
requirements in areas where use of the minimum speed in the stalling 
maneuver has proven adequate; and harmonize the applicable regulations 
with those currently adopted in Change 15 to the European Joint 
Aviation Requirements-25 (JAR-25). These changes will provide a higher 
level of safety for those cases in which the current methods result in 
artificially low operating speeds.

EFFECTIVE DATE: December 26, 2002.

FOR FURTHER INFORMATION CONTACT: Don Stimson, Airplane and Flightcrew 
Interface Branch, ANM-111, Transport Airplane Directorate, Aircraft 
Certification Service, FAA, 1601 Lind Avenue SW., Renton, WA 98055-
4056; telephone (425) 227-1129; facsimile (425) 227-1320, e-mail 
[email protected].

SUPPLEMENTARY INFORMATION:

Availability of Rulemaking Documents

    You can get an electronic copy using the Internet by taking the 
following steps:
    (1) Go to the search function of the Department of Transportation's 
electronic Docket Management System (DMS) web page (http://dms.dot.gov/search).
    (2) On the search page type in the last four digits of the Docket 
number shown at the beginning of this notice. Click on ``search.''
    (3) On the next page, which contains the Docket summary information 
for the Docket you selected, click on the document number for the item 
you wish to view.
    You can also get an electronic copy using the Internet through the 
Office of Rulemaking's Web page at http://www.faa.gov/avr/armhome.htm 
or the Federal Register's Web page at http://www.access.gpo.gov/su_docs/aces/aces140.html.
    You can also get a copy by submitting a request to the Federal 
Aviation Administration, Office of Rulemaking, ARM-1, 800 Independence 
Avenue SW., Washington, DC, 20591, or by calling (202) 257-9680. Make 
sure to identify the amendment number or docket number of this 
rulemaking.

Small Business Regulatory Enforcement Fairness Act

    The Small Business Regulatory Enforcement Fairness Act (SBREFA) of 
1996 requires FAA to comply with small entity requests for information 
or advice about compliance with statutes and regulations within its 
jurisdiction. Therefore, any small entity that has a question regarding 
this document may contact their local FAA official, or the person 
listed under FOR FURTHER INFORMATION CONTACT. You can find out more 
about SBREFA on the Internet at our site, http://www.faa.gov/avr/arm/sbrefa.htm. For more information on SBREFA, e-mail us at [email protected].

Background

    These amendments are based on notice of proposed rulemaking (NPRM) 
Notice No. 95-17, which was published in the Federal Register on 
January 18, 1996 (61 FR 1260). In that notice, the FAA proposed 
amendments to 14 CFR parts 1, 25, 36, and 97 to redefine the reference 
stall speed (VSR) for transport category airplanes as the 1-
g stall speed instead of the minimum speed obtained in the stalling 
maneuver. The FAA received nearly 40 comments from 12 different 
commenters on the proposals contained in Notice No. 95-17. As a result 
of these comments, this final rule differs in some aspects from the 
original proposals.
    As explained in Notice No. 95-17, the stalling speed 
(VS) is defined as the minimum speed demonstrated in the 
performance stall maneuver described in Sec.  25.103 of 14 CFR part 25 
(part 25). VS has historically served as a reference speed 
for determining the minimum operating speeds required under part 25 for 
transport category airplanes. Examples of minimum operating speeds that 
are based on VS include the takeoff safety speed 
(V2), the final takeoff climb speed, and the landing 
approach speed. For example, under part 25, V2 must be at 
least 1.2 times VS, the final takeoff climb speed must be at 
least 1.25 times VS, and the landing approach speed must be 
at least 1.3 times VS.
    The speed margin, or difference in speed, between VS and 
each minimum operating speed provides a safety ``cushion'' to ensure 
that normal operating speeds are sufficiently higher than the speed at 
which the airplane stalls. Using multiplying factors applied to 
VS to provide this speed margin, however, assumes that 
VS provides a proper reference stall speed. Since 
VS is the minimum speed obtained in the stalling maneuver, 
it can be less than the lowest speed at which the airplane's weight is 
still supported entirely by aerodynamic lift. If VS is 
significantly less than this speed, applying multiplying factors to 
VS to determine the minimum operating speeds may not provide 
as large a speed margin as intended.
    A proper reference stall speed should provide a reasonably 
consistent approximation of the wing's maximum usable lift. Maximum 
usable lift occurs at the minimum speed for which the lift provided by 
the wing is capable of supporting the weight of the airplane. This 
speed is known as the 1-g stall speed because the load factor (the 
ratio of airplane lift to weight) at this speed is equal to 1.0 ``g'' 
(where ``g'' is the acceleration caused by the force of gravity) in the 
direction perpendicular to the flight path of the airplane. Speeds 
lower than the 1-g stall speed during the stalling maneuver represent a 
transient flight condition that, if used as a reference for the 
deriving minimum operating speeds, may not provide the desired speed 
margin to protect against inadvertently stalling the airplane.
    For transport category airplanes, the minimum speed obtained in the 
stall maneuver of Sec.  25.103 usually occurs near the point in the 
maneuver where the airplane spontaneously pitches nose-down or where 
the pilot initiates recovery after reaching a deterrent level of 
buffet, i.e., a vibration of a magnitude and severity that is a strong 
and effective deterrent to further speed reduction. Early generation 
transport category airplanes, which had fairly straight wings and non-
advanced airfoils, typically pitched nose-down near the 1-g stall 
speed. The minimum speed in the maneuver was easy to note and record, 
and served as an adequate approximation of the speed for maximum lift.
    For the recent generation of high speed transport category 
airplanes with swept wings and highly advanced airfoils, however, the 
minimum speed

[[Page 70813]]

obtained in the stalling maneuver can be substantially lower than the 
speed for maximum lift. Furthermore, the point at which the airplane 
pitches nose down or exhibits a deterrent level of buffet is more 
difficult to distinguish and can vary with piloting technique. As a 
result, the minimum speed in the stalling maneuver has become an 
inappropriate reference for most modern high speed transport category 
airplanes for establishing minimum operating speeds since it may: (1) 
Be inconsistently determined, and (2) represent a flight condition in 
which the load factor perpendicular to the flight path is substantially 
less than 1.0 g.
    In recent years, advanced technology transport category airplanes 
have been developed that employ novel flight control systems. These 
flight control systems incorporate unique protection features that are 
intended to prevent the airplane from stalling. They also prevent the 
airplane from maintaining speeds that are slower than a small 
percentage above the 1-g stall speed. Because of their unique design 
features, the traditional method of establishing VS as the 
minimum speed obtained in the stalling maneuver was inappropriate for 
these airplanes. The FAA issued special conditions for these airplanes 
to define the reference stall speed as not less than the 1-g stall 
speed for the flight requirements contained in subpart B of part 25.
    In these special conditions, the multiplying factors used to 
determine the minimum operating speeds were reduced in order to 
maintain equivalency with acceptable operating speeds used by previous 
transport category airplanes. Since the 1-g stall speed is generally 
higher than the minimum speed obtained in the stalling maneuver, 
retaining the current multiplying factors would have resulted in higher 
minimum operating speeds for airplanes using the 1-g stall speed as a 
basis for the reference stall speed. However, increasing the minimum 
operating speeds could impose costs on operators because payloads might 
have to be reduced to comply with the regulations at the higher 
operating speeds under some performance-limited conditions. Based on 
the service experience of the current fleet of transport category 
airplanes, the costs imposed would not be offset by a commensurate 
increase in safety.
    Several airplane types with conventional flight control systems 
have also been certificated using the 1-g stall speed as a lower limit 
to the reference stall speed. Because of the potential deficiencies in 
using the minimum speed demonstrated in the stalling maneuver, the FAA 
has been encouraging applicants to use the 1-g stall speed methodology 
in lieu of the minimum speed obtained in the stalling maneuver. 
Applicants generally desire to use 1-g stall speeds because the 1-g 
stall speeds are less dependent on pilot technique and other subjective 
evaluations. Hence, 1-g stall speeds are easier to predict and provide 
a higher level of confidence for developing predictions of overall 
airplane performance. Again, reduced multiplying factors are applied to 
the 1-g stall speeds to obtain minimum operating speeds equivalent to 
the speeds that have been found acceptable in operational service. 
Using 1-g stall speeds ensures that the airplane's minimum operating 
speeds will not be unreasonably low.

Discussion of the Proposals

    In Notice No. 95-17, the FAA proposed to define the reference stall 
speed in Sec.  25.103 as a speed not less than the 1-g stall speed, 
rather than the minimum speed obtained in the stalling maneuver. This 
proposal was made to provide a consistent basis for use in all type 
design certification requirements for transport category airplanes. The 
FAA proposed to introduce the symbol VSR to represent this 
speed and to indicate that it is different than the minimum speed 
obtained in the stalling maneuver, VS.
    In addition, the FAA proposed to reduce the multiplying factors 
that are used in combination with the reference stall speed to 
determine the minimum operating speeds by approximately 6 percent. This 
change would result in minimum operating speeds equivalent to those for 
most current transport category airplanes since the 1-g stall speed for 
these airplanes is approximately 6 percent higher than the minimum 
speed obtained in the stalling maneuver. Demonstrating a minimum 
stalling speed more than 6 percent slower than the 1-g stall speed, 
which is possible under the current standards, would provide an 
unacceptable basis for determining the minimum operating speeds. The 
proposed standards would prevent this situation from occurring. In this 
respect, the proposed standards would provide a higher level of safety 
than the existing standards.
    However, the proposed reduced factors would allow lower minimum 
operating speeds to be established for those airplanes that have a 
minimum speed in the stalling maneuver approximately equal to the 1-g 
stall speed. One particular class of airplanes for which this applies 
is airplanes equipped with devices that abruptly push the nose down 
(e.g., stick pushers) near the angle of attack for maximum lift. These 
devices are typically installed on airplanes with unacceptable natural 
stalling characteristics. The abrupt nose down push provides an 
artificial stall indication and acceptable stall characteristics, and 
prevents the airplane from reaching a potentially hazardous natural 
aerodynamic stall. Typically, the minimum speed obtained in this 
maneuver is approximately equal to the 1-g stall speed.
    Traditionally, the existing multiplying factors have been applied 
to these airplanes. The proposal to define the reference stall speed as 
the 1-g stall speed would generally have no impact for these airplanes, 
but reducing the multiplying factors would allow lower minimum 
operating speeds to be established. Therefore, this proposal would 
allow these airplanes to be operated at speeds and angles of attack 
closer to the pusher activation point than has been experienced in 
operational service.
    The FAA considered this reduction in operating speeds for pusher-
equipped airplanes to be acceptable, provided the pusher reliably 
performs its intended function and that unwanted operation is 
minimized. The FAA has addressed the majority of these concerns in a 
revision to Advisory Circular (AC) 25-7, the ``Flight Test Guide for 
Certification of Transport Category Airplanes.'' This revision, AC 25-
7A, dated March 31, 1998, provides criteria for the design and function 
of stall indication systems, including arming and disarming, indicating 
and warning devices, system reliability and safety, and system 
functional requirements. The FAA plans to address other concerns, such 
as system design and manufacturing tolerances, and system design 
features like filtering and phase advancing, in a future revision to AC 
25-7A.
    In addition to proposing to define the reference stall speed as a 
speed not less than the 1-g stall speed and to reduce the multiplying 
factors for establishing the minimum operating speeds, the FAA also 
proposed to require applicants to demonstrate adequate maneuvering 
capability during the takeoff climb, en route climb, and landing 
approach phases of flight. During a banked turn, a portion of the lift 
generated by the wing provides a force to help turn the airplane. To 
remain at the same altitude, the airplane must produce additional lift. 
Therefore, banking the airplane (at a constant speed and altitude) 
reduces the stall margin, which is the difference between the lift 
required for the maneuver and the maximum lift capability of the wing. 
As the bank

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angle increases, the stall margin is reduced proportionately. This bank 
angle effect on the stall margin can be determined analytically, and 
the multiplying factors applied to VSR to determine the 
minimum operating speeds are intended to ensure that an adequate stall 
margin is maintained.
    In addition to the basic effect of bank angle, however, modern wing 
designs also typically exhibit a significant reduction in maximum lift 
capability with increasing Mach number. The magnitude of this Mach 
number effect depends on the design characteristics of the particular 
wing. For wing designs with a large Mach number effect, the maximum 
bank angle that can be achieved while retaining an acceptable stall 
margin can be significantly reduced. Because the effect of Mach number 
can be significant, and because it can also vary greatly for different 
wing designs, the multiplying factors applied toVSR are 
insufficient to ensure that adequate maneuvering capability exists at 
the minimum operating speeds.
    To address this issue, the FAA proposed to require a minimum bank 
angle capability in a coordinated turn without encountering stall 
warning or any other characteristic that might interfere with normal 
maneuvering. This requirement would be added to Sec.  25.143 as a new 
paragraph (g). The proposed minimum bank angles were derived by adding 
a 15 degree allowance for wind gusts and inadvertent overshoot to a 
maneuvering capability the FAA considers necessary for the specific 
cases identified in the proposed new paragraph. These proposed maneuver 
margin requirements would increase the level of safety in maneuvering 
flight.
    Consistent with the proposed maneuver margin requirements, the FAA 
proposed adding Sec. Sec.  25.107(c)(3), 25.107(g)(2), and 
25.125(a)(2)(iii) to reference Sec.  25.143(g) in the list of 
constraints applicants must consider when selecting the minimum takeoff 
safety speed, final takeoff speed, and reference landing speeds, 
respectively. The normal all-engines-operating takeoff climb speed 
selected by the applicant would also have to provide the minimum bank 
angle capability specified in the proposed Sec.  25.143(g).
    Section 25.145(a) requires that there be adequate longitudinal 
control available to promptly pitch the airplane's nose down from at or 
near the stall in order to return to the original trim speed. The 
intent of this requirement is to ensure sufficient pitch control for a 
prompt recovery if the airplane is inadvertently slowed to the point of 
stall. The FAA proposed to change the wording of this requirement to 
replace ``VS'' with ``the stall,'' ``Sec.  25.103(b)(1)'' 
with ``Sec.  25.103(a)(6),'' and ``at any speed'' with ``at any 
point.'' These changes would be consistent with the proposed change to 
the definition of the reference stall speed and the proposed 
reformatting of Sec.  25.103.
    Although compliance with Sec.  25.145(a) must be demonstrated both 
with power off and with maximum continuous power, there is no intention 
to require flight test demonstrations of full stalls at engine powers 
above that specified in Sec.  25.201(a)(2). Instead of performing a 
full stall at maximum continuous power, compliance will be assessed by 
demonstrating sufficient static longitudinal stability and nose down 
control margin when the deceleration is ended at least one second past 
stall warning during a one knot per second deceleration. The static 
longitudinal stability during the maneuver and the nose down control 
power remaining at the end of the maneuver must be sufficient to assure 
compliance with the requirement.
    Section 25.207 requires that a warning of an impending stall must 
be provided in order to prevent the pilot from inadvertently stalling 
the airplane. The warning must occur at a speed sufficiently higher 
than the stall speed to allow the pilot time to take action to avoid a 
stall. The speed difference between the stall speed and the speed at 
which the stall warning occurs is known as the stall warning margin. 
The FAA proposed amending the size of the stall warning margin required 
by Sec.  25.207(c) because of the change in definition of the reference 
stall speed.
    Currently, the stall warning must begin at a speed exceeding 
VS by seven knots, or a lesser margin if the stall warning 
has enough clarity, duration, distinctiveness, or other similar 
properties. Requiring the same seven knot warning margin to be provided 
relative to VSR would result in an increase to the minimum 
operating speeds. This increase in the minimum operating speeds would 
be necessary to meet the maneuvering margin requirements proposed in 
Sec.  25.143(g), which are defined relative to the stall warning speed. 
However, as discussed previously, requiring an increase to the minimum 
operating speeds would impose costs to airplane operators that cannot 
be justified by service experience.
    On the other hand, if the stall warning margin were reduced to 
retain approximately the same stall warning speed, the warning would 
occur only one or two knots prior to reaching the 1-g stall speed. 
Although reaching the 1-g stall speed is not likely to be a 
catastrophic occurrence, the FAA considers such a small stall warning 
margin to be unacceptable. The FAA proposed requiring a stall warning 
margin of at least 3 knots or 3 percent, whichever is greater, relative 
to VSR. The FAA's proposal was made on the basis that this 
margin represents a reasonable balance between providing the pilot with 
enough warning to avert an impending stall, and providing adequate 
maneuvering capability at the minimum operating speeds. This proposal 
would retain the existing level of safety.
    The FAA proposed to require a larger stall warning margin for 
airplanes equipped with devices that abruptly push the nose down at a 
selected angle of attack (e.g., stick pushers). Inadvertent operation 
of such a device, especially close to the ground, can have more serious 
consequences than a comparable situation in which the pilot of an 
airplane without the device inadvertently slows to VSR. 
Therefore, the FAA proposed adding Sec.  25.207(d) to require the stall 
warning, for airplanes equipped with one of these devices, to occur at 
least 5 knots or 5 percent, whichever is greater, above the speed at 
which the device activates. This proposal was made on the basis of 
retaining the existing level of safety for airplanes equipped with such 
devices.
    The FAA proposed to add a new paragraph, Sec.  25.207(e), to 
require that, in a slow-down turn with load factors up to 1.5 g and 
deceleration rates up to 3 knots per second, sufficient stall warning 
must exist to prevent stalling when recovery is initiated not less than 
one second after stall warning occurs. The FAA considered this proposed 
requirement necessary to provide adequate stall warning during a 
dynamic maneuver, such as a collision avoidance maneuver. In addition, 
this new paragraph would provide a quantitative requirement with which 
to assess whether ``sufficient margin to prevent inadvertent stalling * 
* * in turning flight'' has been provided as required by Sec.  
25.207(a). This proposal would increase the level of safety during 
maneuvering flight.
    The FAA proposed to add a new paragraph, Sec.  25.207(f), to 
require that stall warning be provided for abnormal airplane 
configurations likely to be used following system failures. This 
proposal would add a requirement currently contained in JAR-25 and is 
consistent with current transport category airplane designs. There 
would be no impact on the existing level of safety.
    On modern transport category airplanes, the natural buffet or 
vibration

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caused by the airflow separating and reattaching itself to the wing as 
the airplane approaches the stall speed is usually not strong enough by 
itself to provide an effective stall warning. Therefore, stall warning 
on modern transport category airplanes is usually provided through an 
artificial means, such as a stick shaker that shakes the pilot's 
control column. Production tolerances associated with these systems can 
result in variations in the size of the stall warning margin for 
different airplanes manufactured under the same approved type design.
    The FAA considers the stall warning margins proposed in Sec. Sec.  
25.207(c) and (d) to be the minimum acceptable warning margins, and 
that these margins should not be reduced by production tolerances 
associated with a system added to the airplane to provide an artificial 
stall warning. The FAA intends for the proposed stall warning margins 
to be available at the most critical tolerance expected in production. 
Applicants would be expected to demonstrate compliance with the 
proposed stall warning margin either by flight testing with the stall 
warning system set to its critical tolerance setting, or by adjusting 
flight test data obtained at some other setting.
    The tolerances associated with the stall warning system must also 
be considered in relation to the proposed minimum maneuvering 
requirements of Sec.  25.143(g). As proposed, Sec.  25.143(g) would 
require that the airplane be capable of reaching a minimum bank angle 
during a coordinated turn without encountering stall warning. Because 
the proposed requirements already provide the capability to overshoot 
the intended bank angle by 15 degrees, the small differences in the 
speed at which the stall warning system operates due to system 
tolerances are not as critical. Therefore, the FAA intends for the 
minimum bank angles in the proposed Sec.  25.143(g) to apply at the 
designed nominal setting of the stall warning system. To ensure that 
large production tolerances do not adversely impact the airplane's 
maneuvering capability free of stall warning, the bank angle capability 
specified in the proposed Sec.  25.143(g) should not be reduced by more 
than two degrees with the stall warning system operating at its most 
critical tolerance. Applicants would be expected to demonstrate this 
capability either by flight test with the system set to its critical 
tolerance, or by analytically adjusting flight test data obtained at 
some other setting.
    To be consistent with the proposed revision of the definition of 
the reference stall speed, the FAA proposed to incorporate reduced 
multiplying factors throughout part 25, where appropriate, in 
requirements that use speeds based on a multiple of the reference stall 
speed. The FAA also proposed numerous minor wording and structural 
changes to various sections to improve editorial clarity and to 
harmonize with the wording and structure proposed for JAR-25. Note that 
the proposed change to the term ``1.3 VS0'' in Sec.  
25.175(d) reflects not only the change in multiplying factor, but also 
corrects a typographical error. (``1.3 VS0'' should have 
been ``1.8 VS0.'')
    The FAA proposed to add the nomenclature ``final takeoff speed'' 
and ``reference landing speed'' and the abbreviations 
``VFTO'' and ``VREF'' to denote these speeds, 
respectively, to part 1 of the FAR. These terms and abbreviations, 
which are commonly used in the aviation industry, would be referenced 
throughout the proposed amendments to part 25. The reference landing 
speed would be defined as the speed of the airplane, in a specified 
landing configuration, at the point where it descends through the 
landing screen height in the determination of the landing distance for 
manual landings. The term ``landing screen height'' refers to the 
height of the airplane at the beginning of the defined landing 
distance. This height is normally 50 feet above the landing surface 
(see Sec.  25.125(a)), but approvals have been granted for steep 
approaches that use a landing screen height of 35 feet. The final 
takeoff speed would be defined as the speed of the airplane that exists 
at the end of the takeoff path in the en route configuration with one 
engine inoperative.
    The FAA also proposed to add the abbreviations VSR, 
VSR0, and VSRI to part 1, and use them in part 25 
to denote the reference stall speed corresponding to different airplane 
configurations. In addition, the FAA proposed adding the abbreviation 
VSW to part 1 to refer to the speed at which the onset of 
stall warning occurs.
    The FAA proposed to amend Sec.  C36.9(e)(1) of Appendix C to part 
36 by replacing ``1.3 VS + 10 knots'' with ``VREF 
+ 10 knots'' and by removing the words ``or the speed used in 
establishing the approved landing distance under the airworthiness 
regulations constituting the type certification basis of the airplane, 
whichever speed is greatest.'' The words proposed for deletion would no 
longer be necessary because VREF would denote the speed used 
in establishing the approved landing distance under the airworthiness 
regulations constituting the type certification basis of the airplane. 
Also, VREF would refer to the speed at the landing screen 
height, regardless of whether that speed for a particular airplane is 
1.3 VS, 1.23 VSR, or some higher speed.
    In the same manner, the FAA proposed to amend Sec.  97.3(b) by 
replacing ``1.3 VS0'' with ``VREF.'' As noted 
above, VREF would refer to the speed at the landing screen 
height used in establishing the approved landing distance under the 
airworthiness regulations constituting the type certification basis of 
the airplane, regardless of whether that speed for a particular 
airplane is 1.3 VS, 1.23 VSR, or some higher 
speed.
    These proposals were discussed extensively with the European Joint 
Aviation Authorities (JAA) with the intent of harmonizing the 
certification requirements related to stall speed for transport 
category airplanes. The Joint Aviation Requirements (JAR) 25 prescribes 
the airworthiness standards for transport category airplanes that are 
accepted by the aviation regulatory authorities of a number of European 
states. The JAA introduced an equivalent proposal to the FAA's NPRM 95-
17, called Notice of Proposed Amendment (NPA) 25B-215, to amend JAR-25 
accordingly. The JAA's final 1-g stall requirements, which are 
equivalent to those adopted by the FAA in this rulemaking, were adopted 
by the JAA as part of Change 15 to JAR-25, dated October 1, 2000.

Discussion of the Comments

    The FAA received nearly 40 comments from 12 different commenters on 
the proposals contained in Notice No. 95-17. The commenters include 
airplane pilots, manufacturers, operators, and the associations 
representing them, foreign airworthiness authorities, an organization 
specializing in flight testing, and private citizens. In general, the 
proposal to redefine the reference stall speed for transport category 
airplanes as the 1-g stall speed instead of the minimum speed obtained 
in a stalling maneuver was supported, although there were comments 
critical of specific details, and some commenters were supportive only 
if the current minimum speed method would be retained as an option that 
would be available for the certification of small transport category 
airplanes.
    Those commenters who recommend retaining the minimum stall speed 
methodology for small transport category airplanes--small airplane 
manufacturers and the association representing them--believe that the 
proposed changes introduce additional cost and complexity into 
applicants'

[[Page 70816]]

type certification programs with no increase in safety for this class 
of airplanes.
    One manufacturer of small transport category airplanes notes that 
when 1-g stall speeds were determined for one of their airplanes, the 
resulting operating speeds were virtually the same as those determined 
using the current requirements. This commenter also states that 
variation in piloting technique remains an issue even if the stall 
speeds are defined as a 1-g condition, and a more expensive flight test 
data system is needed to determine where the 1-g stall break occurs. 
The commenter points out that straight (i.e., non-swept) winged 
airplanes, for which the discussion in Notice No. 95-17 implied the 
current minimum speed method is adequate, will continue to be designed 
and produced in the future. On airplanes with swept wings, due to 
different stiffness characteristics between large and small airplanes, 
which result in different responses to aerodynamic influences, the 
minimum speed in the stalling maneuver is not difficult to obtain on 
small transport category airplanes. The commenter concludes that the 
current methods should be retained for airplanes weighing less than 
75,000 pounds because of the costs involved in changing to the 1-g 
stall speed methodology for no apparent increase in safety. (100,000 
pounds is suggested as an appropriate cutoff by another commenter.)
    The FAA disagrees that the proposed rule changes significantly 
increases cost and does not increase safety. Cost data supplied by one 
commenter substantially overstates the incremental cost of the test 
instrumentation and other items needed to support a 1-g stall speed 
evaluation. This commenter allocates the entire cost of a new data 
collection system, including purchase, installation, and calibration, 
to the proposed rule change, stating that this new system would be 
needed to determine the ``g-break'' denoting the 1-g stall speed.
    The only additional instrumentation the FAA considers necessary to 
determine the 1-g stall speed instead of the minimum speed in the 
stalling maneuver would be accelerometers capable of resolving the load 
factor normal to the flight path. At the minimum, one accelerometer 
aligned along the expected 1-g stall pitch angle may provide acceptable 
data. Determining the point at which the 1-g stall condition is reached 
is most readily accomplished by a continuous calculation of the load 
factor-corrected lift coefficient and noting the point at which this 
parameter is first a maximum. Experience to date with applicants 
voluntarily complying with the proposed requirements has not 
highlighted any significant difficulties in determining the 1-g stall 
speed using typically existing data recording equipment. These 
applicants have included manufacturers of both large and small 
transport category airplanes.
    The FAA is not surprised that for one of the commenter's airplane 
types, the current requirements and the 1-g stall proposal yielded 
virtually the same minimum operating speeds. As noted in Notice No. 95-
17 and repeated in the background discussion above, the proposed change 
to the multiplying factors that are applied to the reference stall 
speed to obtain the minimum operating speeds was intentionally chosen 
to yield equivalent operating speeds, on average, for current transport 
category airplanes. However, the proposed standards would prevent the 
reference stall speed from being more than six percent slower than the 
1-g stall speed, which the current standards do not prohibit. In this 
respect, the proposed standards would provide a higher level of safety 
than the existing standards by ensuring that unreasonably low minimum 
operating speeds will not be obtained.
    The FAA agrees that the use of a 1-g stall speed may not entirely 
remove the effect of pilot technique from being a factor during the 
flight tests to determine the reference stall speed. However, the use 
of a 1-g stall speed would significantly mitigate this effect. 
Subjective assessments of airplane behavior for identifying the stalled 
condition (using the criteria specified in Sec.  25.201(d)) would no 
longer be used to determine the reference stall speed. (These criteria 
will continue to be used, however, for evaluating the airplane handling 
characteristics during the stalling maneuver.) Test pilot techniques 
that take advantage of these subjective assessments and allow 
unreasonably low load factors, and hence unreasonably low stall speeds, 
to be achieved would no longer be permitted.
    In addition, it is usually much easier to measure airspeed 
accurately at the 1-g stall condition than at the minimum speed reached 
in the stalling maneuver. Based on the experience gained from the many 
type certification programs that have already used the 1-g stall speed 
methodology, the FAA has determined that this methodology provides a 
more consistent, repeatable reference stall speed than the existing 
method.
    One commenter notes that the International Civil Aviation 
Organization's (ICAO) Airworthiness Technical Manual (Document 9051, 
1987) uses the abbreviation VS1g to denote the 1-g stall 
speed, which is the reference speed for determining the minimum 
operating speeds for transport category airplanes with a certified 
takeoff mass of over 5,700 kg. The commenter suggests that the FAA 
could further international standardization by adopting ICAO's 
VS1g abbreviation to denote the reference stall speed as a 
part of the rulemaking to redefine the reference stall speed as a 1-g 
stall speed.
    The FAA actively promotes international standardization and has 
been working closely with the regulatory authorities of Europe and 
Canada during this rulemaking. The FAA considered using the 
abbreviation VS1g to denote the reference stall speed; 
however, the reference stall speed may not always be equal to the 1-g 
stall speed. It is only required to be no less than the 1-g stall 
speed. Other design constraints may dictate using a reference stall 
speed that is higher than the 1-g stall speed. Since the reference 
stall speed may be different than the 1-g stall speed, the abbreviation 
VSR was proposed and has been adopted in Sec.  1.2 to denote 
the reference stall speed. This abbreviation has also been adopted by 
the JAA of Europe and is expected to be adopted by the Canadian 
regulatory authority. There were no comments on the other proposed 
abbreviations nor on the proposed definitions for final takeoff speed 
and reference landing speed. Therefore, these abbreviations and 
definitions are adopted as proposed.
    One commenter questions the reason for the new wording in Sec.  
25.103(a)(1) to describe the option of idle or zero thrust. The 
commenter does not see the new wording as an improvement in clarity. 
The current rule states that zero thrust must be used in determining 
the stalling speed, except that idle thrust may be used when it does 
not appreciably affect the stalling speed. Stated in this manner, the 
rule permits the use of zero thrust when idle thrust causes an increase 
in the stalling speed. On some turboprop airplanes, where flight idle 
thrust may be negative, a lower stall speed may be demonstrated using 
zero thrust than would occur with idle thrust.
    The FAA considers such a loss of stall speed margin in a normal 
flight condition to be unacceptable. In Notice No. 95-17, the FAA 
proposed a change such that the reference stall speed must be 
determined with idle thrust, except in cases where that thrust level 
causes an appreciable decrease in the stall speed. For such cases, not 
more than zero thrust must be used. There were no

[[Page 70817]]

comments regarding the substance of the proposed change; therefore, 
this section is adopted as proposed.
    One commenter notes that while the proposal to the reference stall 
speed in terms of a 1-g stall speed would reduce the amount of scatter 
in the flight test data used to determine the stall speed, a 
significant amount of scatter would remain. To further limit the amount 
of experimental error inherent in the data analysis process, the 
commenter suggests defining the reference stall speed in terms of the 
maximum normal force coefficient instead of the maximum lift 
coefficient. Using the normal force coefficient would yield slightly 
higher reference stall speeds, which could penalize an airplane's load 
carrying capability due to the resulting increase in minimum takeoff 
and landing speeds, but certification costs might be reduced because 
the data reduction process would be simplified.
    The FAA agrees that defining the reference stall speed in terms of 
the maximum normal force coefficient instead of the maximum lift 
coefficient may further reduce flight test data scatter and simplify 
data acquisition and analysis. However, these slight benefits are 
outweighed by the potentially significant economic penalties associated 
with the resulting higher reference stall speed. Many recent airplane 
types have been certified using 1-g stall criteria similar to those 
contained in Notice No. 95-17 and this experience does not indicate any 
significant problems in data quality or in the acquisition and analysis 
process. Data scatter using the proposed 1-g stall criteria is 
inconsequential compared to the data uncertainty inherent in the 
current stall speed definition. Therefore, the commenter's suggested 
change is not being adopted. However, the FAA would find it acceptable 
if an applicant proposed using the higher reference stall speeds 
derived from the maximum normal coefficient in order to simplify the 
data acquisition and analysis process. The proposed amendment need not 
be changed to allow this option.
    A commenter suggests that it is technically more accurate in Sec.  
25.103(c) to refer to the lift coefficient in the definition of 
VCLMAX as the load factor-corrected lift coefficient. The 
commenter also considers the proposed definition of VCLMAX 
to be ambiguous and lacking in guidance material that would provide 
clarification. Other commenters made various editorial and formatting 
suggestions to further improve the clarity of Sec.  25.103. The FAA 
agrees with these suggestions and has modified the proposal 
accordingly. In addition, the FAA proposes to revise Advisory Circular 
(AC) 25-7A, ``Flight Test Guide for Certification of Transport Category 
Airplanes,'' to add clarifying guidance material. A notice of proposed 
advisory circular revisions was published in the Federal Register on 
November 21, 2002.
    Detailed comments were received from one commenter regarding the 
effect of the proposed rules on airplanes equipped with devices that 
abruptly push the nose down (e.g., stick pushers) to define the point 
of stall. As noted in Notice No. 95-17, this proposal would allow 
airplanes equipped with such devices that have a trigger point set 
close to or before CLMAX to achieve lower minimum operating 
speeds than under the existing requirements, and hence, operate at 
speeds and angles-of-attack closer to the device activation point than 
has been experienced in operational service. The FAA considered this 
aspect of the proposal to be acceptable provided the device performs 
its intended function and unwanted operation is minimized.
    The commenter points out that ensuring operation when desired and 
preventing unwanted operation are contradictory goals that result in 
design tradeoffs. Regardless of the design choice, however, allowing 
operation closer to the device activation point increases both the 
probability of reaching the activation point, where the device may fail 
to operate, and the probability of unwanted operation. Considering 
these aspects, the commenter contends that the proposed standards would 
reduce the level of safety relative to the current standards.
    The commenter suggests adding the stipulation, for airplanes 
equipped with a device that abruptly pushes the nose down at a selected 
angle-of-attack, that VSR must not be less than the greater 
of 2 knots or 2 percent above the speed at which the device activates. 
The commenter further suggests that this additional requirement need 
not apply to turbopropeller powered airplanes that demonstrate a 
significant reduction in stall speed in the one-engine-inoperative 
power-on condition. The commenter points out that this additional 
requirement is very similar in scope and intent to the Notice No. 95-17 
proposed requirements for stall warning, where, in addition to the 
requirement applying to all transport category airplanes that stall 
warning be 3 knots or 3 percent above VSR, the stall warning 
for airplanes equipped with devices that abruptly push the nose down at 
a selected angle-of-attack would be 5 knots or 5 percent above the 
speed at which the device operates. The commenter believes that the 
proposed stall warning requirements represent an acknowledgment that 
the class of airplanes cannot be treated the same as conventionally 
stalling airplanes with respect to minimum operating speeds and 
associated margins.
    The FAA agrees with the commenter's analysis and fundamental 
principle that in terms of the protection from stall provided by such a 
device, the characteristics resulting from its operation, and its 
reliability and safety, there are significant differences from a 
conventionally stalling airplane. Also, the difference between the 1-g 
stall speed and the minimum speed obtained in the stalling maneuver for 
this class of airplanes is closer to 0 to 3 percent, rather than the 6 
percent average for conventionally stalling airplanes upon which the 
reduction in operating speed factors was based. Permitting a reduction 
in the operating speeds for this class of airplanes could potentially 
result in a reduction in safety that is not justified by existing 
operational experience.
    The commenter's suggested additional constraint on VSR 
represents a reasonable means to retain approximately equivalent safety 
without penalizing airplanes for which the device trigger point is at 
an angle-of-attack well beyond CLMAX. Therefore, Sec.  
25.103(d) is revised accordingly to require, for airplanes equipped 
with a device that abruptly pushes the nose down at a selected angle-
of-attack, that VSR not be less than 2 percent or 2 knots, 
whichever is greater, above the speed at which the device operates. The 
suggested exception for turbopropeller powered airplanes that 
demonstrate a significant reduction in stall speed in the one-engine-
inoperative power-on condition is not included, however, because the 
applicable minimum operating speeds already allow for a significant 
effect of power on stall speeds.
    The effect of this provision is to increase the minimum operating 
speeds, relative to the Notice No. 95-17 proposals, for airplanes 
equipped with devices that abruptly push the nose down at a selected 
angle-of-attack, but only if the device activates at a speed higher 
than VCLMAX (at a load factor of one) minus 2 knots or 2 
percent. This requirement for a supplementary speed margin, in 
combination with criteria added to AC 25-7A, dated March 31, 1998, for 
system arming and disarming, indicating and warning devices, system 
reliability and safety, and system functional requirements are intended 
to provide an equivalent level of safety to the requirements existing 
prior to the adoption of this amendment. Other

[[Page 70818]]

considerations, such as the effect of system design and manufacturing 
tolerances, and system design features like filtering and phase 
advancing are also relevant, and should be considered when showing 
compliance with the applicable requirements. The FAA is currently 
trying to harmonize its policy in these areas with those of Transport 
Canada and the JAA, and intends to add guidance in these areas in a 
future revision to AC 25-7A.
    The FAA received several comments regarding the proposed addition 
of specific maneuvering requirements as a new Sec.  25.143(g). One 
commenter suggests that the FAA should perform a rigorous study before 
including a specific gust margin in airplane maneuvering requirements. 
The commenter points out that the same atmospheric gust would have 
different effects at different airspeeds, and that using the same gust 
margin throughout causes the proposed after takeoff maneuvering 
requirement at V2 speed to be unduly restrictive. Similarly, 
another commenter states that the need for a 15-degree overshoot 
capability should first be justified by the FAA. This commenter 
suggests that a 5-degree overshoot, as specified as an objective for 
accomplishing steep turns in the ``Airplane Transport Pilot and Type 
Rating Practical Test Standards,'' would be more reasonable.
    Several commenters claim that the proposed maneuvering 
requirements, particularly the one associated with the final takeoff 
speed (VFTO), are excessive and would be difficult to meet 
without increasing the operating speeds. One commenter notes that for 
an airplane equipped with a stick pusher that activates near 
CLMAX, due to design tolerances for the stick pusher and 
stall warning systems, V2 and VFTO would most 
likely be set by the proposed maneuvering requirements rather than the 
1.13 and 1.18 factors applied to VSR, respectively. Another 
commenter notes that the maneuvering requirement associated with 
VFTO relates to a one-engine-inoperative condition of short 
duration, after which the airplane is accelerated to the en route climb 
speed. This commenter suggests that a maneuvering bank angle of 30 
degrees, the same as specified for the takeoff safety speed 
(V2) one-engine-inoperative condition, would be more 
appropriate for this condition.
    This commenter further states that for many existing large 
transport category airplanes, an early onset of natural stall warning 
results in a larger stall warning margin than the minimum margin 
required by the regulations. At VFTO, these airplanes would 
have a maneuvering capability to stall warning of less than the 
proposed 40 degrees of bank, possibly as low as 27 degrees. Requiring 
40 degrees of bank capability would necessitate an increase in 
VFTO, which could affect the net takeoff flight path used 
for clearance of distant obstacles. Either a different departure path 
may be necessary in the event of an engine failure, or takeoff weight 
may have to be reduced. The commenter considers the existing rule to be 
adequate, and the potential penalties associated with the FAA's 
proposal to be unjustifiable.
    This commenter also questions whether the proposed 40 degree bank 
angle requirement at VFTO was based on a 25 degree bank 
angle limit used by many current flight guidance systems. If so, this 
commenter considers such reasoning to be flawed in that not all flight 
guidance systems use 25 degrees as their bank angle limit. In some 
cases, flight guidance systems are limited to a 15 degree bank angle at 
the final takeoff speed.
    As a final comment on this section, this commenter suggests that if 
the FAA believes that increased bank angles are appropriate for the en 
route flight paths, which are of longer time duration, this need should 
be addressed separately from the takeoff flight path requirements. 
However, the commenter does not consider it necessary to do so as this 
commenter is unaware of any associated safety issues.
    The FAA disagrees that the maneuvering requirements specified in 
the proposed Sec.  25.143(g) are excessive, including the proposed 40 
degree bank angle requirement at VFTO. These maneuvering 
requirements are comparable to the maneuvering capability implied by 
the current regulations assuming the stall warning margin is near the 
regulatory minimum. Safety records and operating practices indicate 
that low speed maneuvering capability is a genuine concern. Some 
airports necessitate close-in maneuvering on a regular or contingency 
basis. Accidents and incidents have occurred due to windshear, icing, 
and high-lift device anomalies. The ability to tolerate such 
operational conditions can depend on the maneuvering capability at the 
designated minimum operating speeds.
    The proposed maneuvering requirements consist of the minimum bank 
angle capability the FAA deems adequate for the specified regimes of 
flight combined with a further 15 degrees of bank angle to provide a 
safety margin for various operational factors. These operational 
factors include both potential environmental conditions (e.g., 
turbulence, wind gusts) and an allowance for piloting imprecision 
(e.g., inadvertent overshoots). Because this safety margin does not 
represent either a specific gust margin or expected piloting precision 
alone, the FAA does not consider it necessary to either perform a 
rigorous study of the effect of atmospheric gusts nor to restrict the 
size of the margin to a piloting test standards objective as suggested 
by the commenters. The allowance and magnitude of the proposed bank 
angle margin is also consistent with typical industry practice.
    The maneuvering requirement at V2 speed with one engine 
inoperative is derived from the 15 degree bank angle allowed under 
Sec.  121.189(f) after takeoff plus the specified 15 degree safety 
margin. At the higher speed of VFTO, after the airplane has 
transitioned to the en route configuration and is farther along in the 
flight path, it is reasonable to require additional maneuvering 
capability appropriate to that phase of flight. The FAA considers an 
additional 10 degrees of maneuvering capability to be a reasonable 
expectation for a minimum capability after transitioning to the en 
route configuration and accelerating to the final takeoff climb speed. 
This same level of maneuvering capability exists on most transport 
category airplanes currently in service, and the FAA has determined 
that there is not a compelling reason to set a lower minimum standard. 
The FAA considers this same maneuvering capability (25 degrees of bank 
plus a 15 degree safety margin) to also be appropriate for the normal 
all-engines-operating takeoff case as well as for the landing approach.
    For those airplane types for which the proposed maneuvering 
requirements would lead to an increase in VFTO, any 
resulting penalty is expected to be small. An increase in 
VFTO would only cause a penalty (in terms of a reduced 
payload capability) when the takeoff weight is restricted due to an 
obstacle that must be cleared in the final takeoff climb segment and 
cannot be avoided by turning or using an alternative flight path 
procedure (e.g., retracting the flaps at the maximum level-off height 
or extending the second segment to the takeoff thrust time limit). 
Recent FAA acceptance of proposals to increase the time limit for using 
takeoff thrust from five minutes to ten minutes should further reduce 
the potential for economic penalties resulting from an increase in 
VFTO.
    In addition to receiving comments on the minimum bank angles 
proposed for the new Sec.  25.143(g), the FAA received comments on the 
footnotes accompanying the table of conditions to

[[Page 70819]]

be demonstrated. A commenter notes that because the trigger point of an 
artificial stall warning device may vary with thrust or power setting, 
the proposed wording of footnote 1 may not cover the most critical 
condition for determining the airplane's maneuver margin. This 
commenter suggests adding the phrase ``or any greater thrust or power 
if more critical'' to the thrust/ power setting references in footnotes 
1 and 3 to the table in Sec.  25.143(g).
    Although the FAA agrees with the intent of this comment, the FAA 
believes that the comment may stem from a misinterpretation of the 
proposed requirement. The condition specified in the proposed footnote 
1 to Sec.  25.143(g) represents the highest thrust or power setting for 
the applicable conditions of weight, altitude, and temperature. If 
system design features or other relevant characteristics result in any 
condition of weight, altitude, or temperature being more critical than 
another, compliance with this requirement must be demonstrated for the 
most critical condition of weight, altitude, and temperature. This 
point is addressed further in guidance material being proposed for 
inclusion into AC 25-7A (a notice of proposed advisory circular 
revisions will be published in the Federal Register shortly after 
publication of this final rule).
    The commenter further suggests simplifying the text of footnote 3 
by replacing the FAA proposed text with, ``The critical thrust or power 
for all engines operating should be that which in the event of an 
engine failure would result in the minimum climb gradient specified in 
Sec.  25.121, or any greater thrust or power if more critical.'' 
Although the FAA agrees with the intent of simplifying this footnote, 
the wording proposed in Notice No. 95-17 is needed to address all-
engines-operating climb procedures, such as those used for noise 
abatement, that may use a thrust or power setting less than that used 
during the takeoff. Therefore, the FAA does not concur with the 
commenter's suggestion.
    Section 25.143(g) is adopted as proposed.
    One commenter suggests that the Notice No. 95-17 proposal to 
replace ``VS'' with ``the stall'' in Sec.  25.145(a) is 
misleading and inaccurate relative to the Notice No. 95-17 supporting 
discussion. The commenter believes that changing ``VS'' to 
``the stall'' is unsatisfactory for two reasons: (1) ``The stall'' is a 
vague terminology that might generally be defined by Sec.  25.201(d), 
but without defining the configuration (i.e., flaps, center-of-gravity 
position, power, etc.); and (2) The Notice No. 95-17 preamble 
discussion states that the demonstration should only have to be 
conducted down to stall warning speed plus one second, which is less 
demanding than the proposed new Sec.  25.145(a). Therefore, the 
commenter suggests adding the words ``In a deceleration'' at the 
beginning of Sec.  25.145(a) and replacing the proposed reference to 
``the stall'' with ``one second after stall warning.'' Guidance could 
then be provided in AC 25-7 to clarify that there must be sufficient 
longitudinal control in this maneuver to provide confidence that 
pushout from an actual stall could still be accomplished.
    The FAA does not intend for the change in the reference stall speed 
to alter the basic requirement of Sec.  25.145(a), namely that the 
capability exists on transport category airplanes, at the specified 
configurations and power settings, to pitch the nose down from any 
point in the stalling maneuver and regain the trim speed. The 
commenter's suggested change would reduce the stringency of the 
regulatory requirement, while depending on non-regulatory guidance 
material to provided assurances that equivalent capability is retained.
    Because the FAA cannot rely on non-regulatory material to establish 
a capability required of the airplane, the FAA has not adopted the 
commenter's suggested change. However, to improve clarity, the words 
``the stall,'' proposed in Notice No. 95-17, have been replaced by 
``stall identification (as defined in Sec.  25.201(d))'' in the adopted 
Sec.  25.145(a). In addition, techniques to show compliance with this 
requirement without performing a stall at maximum continuous power/
thrust were included in the recent issuance of AC 25-7A. Consistent 
with the preamble discussion of Notice No. 95-17, compliance at maximum 
continuous power may be assessed by demonstrating sufficient static 
longitudinal stability and nose down control margin when the 
deceleration is ended at least one second past stall warning during a 
one knot per second deceleration. The static longitudinal stability 
during the maneuver and the nose down control power remaining at the 
end of the maneuver must be sufficient to assure compliance with the 
requirement.
    Two comments were received regarding the flight test demonstrations 
to show compliance with Sec.  25.177. Both comments were relative to 
the safety aspects of conducting full rudder sideslips at low 
airspeeds, as required by the current rule, although both commenters 
also noted that this situation may be exacerbated by the lower speeds 
that can result from the proposed change. The proposed changes were not 
intended to result in overall lower speeds. Because these comments 
raise issues with not only speed, but also rudder deflection, they are 
considered beyond the scope of the Notice No. 95-17 proposals, and 
Sec.  25.177 has been adopted as proposed. These comments will be 
retained for consideration of potential future rulemaking to address 
the concerns expressed by the commenters.
    There were many comments on the proposed changes to the stall 
warning requirements of Sec.  25.207. One commenter requests explicit 
criteria to address whether or not a stick shaker is required to 
provide stall warning, or if a visual or aural warning is sufficient. 
This same commenter also asked whether production tolerances affecting 
the stall warning margin will be addressed in AC 25-7.
    The issue of what constitutes an acceptable artificial stall 
warning is beyond the scope of this rulemaking. However, as stated in 
the current Sec.  25.207(b) (and unchanged by this rulemaking), ``a 
visual stall warning device that requires the attention of the crew 
within the cockpit is not acceptable by itself.'' The FAA is 
considering future rulemaking to further address the issue of what 
constitutes an acceptable stall warning. Regarding stall warning 
tolerances, the FAA has proposed the inclusion of material addressing 
stall warning system tolerances into a proposed revision to AC 25-7A (a 
notice of proposed advisory circular revisions will be published in the 
Federal Register shortly after publication of this final rule). This 
material is consistent with the FAA positions expressed in the preamble 
of Notice No. 95-17.
    Several commenters took issue with the proposed three percent or 
three knots stall warning margin of Sec.  25.207(c). One commenter 
believes that the proposal represents an unjustified increase in the 
severity of this requirement relative to the current rules. This 
commenter notes that a requirement for stall warning to begin one 
percent above the 1-g stall speed would be equivalent to the current 
requirement of a seven percent margin from the minimum speed obtained 
in the stalling maneuver. As a compromise, this commenter suggests a 
two percent or two knot stall warning margin relative to the redefined 
reference stall speed. Another commenter has a concern over possible 
difficulties in showing compliance with the proposed arbitrary 
numerical margin for airplanes with a gradual loss of lift

[[Page 70820]]

as the angle-of-attack for maximum lift is exceeded. Both of these 
commenters request that any increase in the severity of this 
requirement: (1) Be tempered such that inappropriate design changes are 
not imposed for small shortfalls in meeting the strict numerical 
criteria; and (2) be taken into account in the Aviation Rulemaking 
Advisory Committee (ARAC) discussions of stall warning margin when 
operating in icing conditions.
    Another commenter has concerns that the change in stall warning 
margin requirements will reduce the margin that is currently required 
and therefore would not retain the existing level of safety. This 
commenter believes that the proposed margin would not represent a 
reasonable balance between providing the pilot with enough warning to 
avert an impending stall and providing adequate maneuvering capability 
at the minimum operating speeds. This commenter suggests retaining the 
current seven knot stall warning margin from the reference stall speed, 
even though the reference stall speed would be redefined as the 1-g 
stall speed, in order to retain the existing level of safety.
    Another commenter considers the proposed Sec.  25.207(c) to 
represent an unjustified increase in the currently required minimum 
stall warning margin that would inhibit use of part of the airplane 
flight envelope within which the airplane is controllable without risk 
of structural damage. The commenter remarks that in windshear avoidance 
maneuvers, the likelihood of escape is maximized by flying at the 
minimum controllable airspeed. The commenter also disagrees with the 
statement made in Notice No. 95-17 that a speed lower than the 1-g 
stall speed represents a transient flight condition. The commenter 
notes that in steady climbing flight, the lift force needed to sustain 
steady flight is less than the airplane weight, and for larger climb 
angles, steady flight is sustainable at speeds lower than the 1-g stall 
speed. This commenter suggests revising the proposed Sec.  25.207(c) to 
require the stall warning to begin at the greater of: (1) A speed 
higher than either one knot or one percent higher than the reference 
stall speed; or (2) seven knots or seven percent higher than the speed 
at the occurrence of a stall (as defined in Sec.  25.201(d)).
    Other comments were received on the proposed Sec.  25.207(c) 
relative to the engine thrust or power setting associated with the 
proposed three percent or three knot stall warning margin. Two 
commenters support removing the reference to ``engines idling and 
throttles closed'' so that the same stall warning margin would apply to 
all power and thrust settings. One commenter suggests that to be 
consistent with the proposed Sec.  25.103(a)(1) it is unnecessary to 
refer to throttles. This commenter also questions why the proposal 
states that ``Sec.  25.103(a)(5) does not apply'' when defining the 
reference stall speed to be used in connection with this requirement.
    In combination with adopting the 1-g stall speed as the appropriate 
benchmark for the low speed end of an airplane's limit flight envelope, 
the FAA considers a warning three knots or three percent prior to 
reaching this speed to be the minimum margin needed to prevent the crew 
from inadvertently slowing beyond this speed. A categorical statement 
regarding the severity of this requirement relative to the current 
requirement cannot be made since the effect of the change in the 
reference stall speed will vary with airplane type (and with the high 
lift device configuration on a given type). It would, however, be 
inappropriate to couple the existing seven percent margin requirement 
relative to the minimum speed reached in the stalling maneuver with the 
redefined reference stall speed as one commenter suggests.
    The FAA does not consider the proposed stall warning margin to 
unduly restrict access to useable parts of the airplane flight 
envelope. Relative to windshear escape, the dynamic nature of windshear 
warrants, if anything, a larger speed margin to the stalled condition. 
Using current windshear escape procedures, frequent and irregular 
penetrations of the stall warning margin are more likely to occur. This 
type of trained maneuver was not envisioned when the current stall 
warning requirements were promulgated. Regarding the comment that for 
climbing flight the lift force will be less than the airplane's weight, 
this condition is irrelevant for establishing the reference stall speed 
or defining a reasonable stall warning margin. The FAA has determined 
that the intent of the proposal is sufficiently clear in this respect.
    The FAA agrees that the stall warning margin for other than idle 
thrust or power settings should be addressed. The FAA did not intend to 
restrict consideration of the adequacy of the stall warning margin to 
only the idle thrust or power condition. The general requirement for a 
stall warning with sufficient margin to prevent inadvertently stalling 
prescribed by Sec.  25.207(a) applies to all normal configurations and 
flight conditions. The three knot or three percent warning margin 
reference in the proposed Sec.  25.207(c) would specifically quantify 
this requirement for the conditions under which VSR is 
determined. At other conditions, the FAA would have expected an 
equivalent margin to that prescribed by Sec.  25.207(c). However, there 
is an inherent difficulty in either specifying an appropriate warning 
margin or determining an equivalent warning margin to that specified in 
the proposed Sec.  25.207(c) for conditions other than idle thrust or 
power, straight flight, and the center-of-gravity position defined in 
the proposed Sec.  25.103(a)(5), because VSR is undefined for those 
other conditions.
    In response to the comments, and to clarify the situation regarding 
the acceptable stall warning margin for conditions other than those 
under which VSR is defined, the FAA has revised the proposed Sec.  
25.207(c) by specifying that stall warning must begin at least five 
knots or five percent, whichever is greater, prior to the speed at 
which the airplane is considered stalled (as defined in Sec.  
25.201(d)). This is also the stall warning margin required by JAR-25 
prior to the adoption of Change 15, and is considered to neither 
increase nor decrease the current level of safety. By referencing the 
speed at which the stall is identified for determining the adequacy of 
the stall warning margin, and not limiting this requirement to specific 
conditions of thrust or power, bank angle, or center-of-gravity 
position, the adopted rule requires that the five knot or five percent 
margin must be available at all thrust/power settings, bank angles, and 
center-of-gravity positions.
    The FAA expects this stall warning margin to be demonstrated for 
the conditions of bank angle, power, and center-of-gravity position 
prescribed for the stall demonstration tests by Sec.  25.201(a). If, 
however, the stall warning margin may be affected by the system design 
(e.g., a stall warning or stall identification system that modifies the 
stall warning or stall identification system as a function of thrust, 
bank angle, angle-of-attack rate, etc.), compliance with the adopted 
Sec.  25.207(c) should be demonstrated at the most critical conditions 
in terms of stall warning margin.
    The proposed three knot or three percent (whichever is greater) 
stall warning margin requirement relative to VSR is retained 
in Sec.  25.207(d) as an additional criterion applicable to that 
specific flight condition. The reference to throttles has been removed, 
as has the statement that the proposed Sec.  25.103(a)(5) should not 
apply when

[[Page 70821]]

defining the reference stall speed to be used in connection with this 
requirement. In response to the commenter's question, the reference to 
Sec.  25.103(a)(5) had been proposed because the proposed definition of 
the reference stall speed would have required that the center-of-
gravity position for determining the reference stall speed would be 
that which results in the highest value of the reference stall speed. 
Since the center-of-gravity position at which the proposed three knot 
or three percent stall warning requirement would apply was not 
specified, it presumably would apply to all center-of-gravity 
positions. Therefore, without the proposed statement, a literal 
interpretation of the proposed requirement would have required the 
stall warning speed at any center-of-gravity position to be three knots 
or three percent above the stall speed evaluated at the most adverse 
center-of-gravity position. This was not the intention. Any evaluation 
of the effect of center-of-gravity position on the stall warning margin 
should be based on the same center-of-gravity position for both the 
stall speed and the stall warning speed.
    The proposed wording, along with additional explanatory material 
that would have been proposed for addition to AC 25-7A, was intended to 
clarify that for center-of-gravity positions other than that specified 
in the proposed Sec.  25.103(a)(5), the same center-of-gravity position 
should be used for both the stall speed and the stall warning speed. 
However, due to the potential for confusion over the proposed wording, 
and because the explicit stall warning speed margin prescribed by the 
proposed Sec.  25.207(c) only applies to the conditions under which VSR 
is determined, the proposed wording regarding center-of-gravity 
position has been removed. Instead, the center-of-gravity position 
specified in Sec.  25.103(b)(5) (re-numbered from the proposed Sec.  
25.103(a)(5)) has been included in the list of conditions for which the 
specific three knot or three percent stall warning margin of the 
adopted Sec.  25.207(d) applies. For other center-of-gravity positions, 
the acceptable stall warning margin is now addressed in the adopted 
Sec.  25.207(c).
    Because of the differences between naturally stalling airplanes and 
those that employ a device to abruptly push the nose down at a selected 
angle of attack to identify the stall, the FAA proposed that the stall 
warning margin for airplanes that employ these devices would be 
required to be five knots or five percent prior to the speed at which 
the device activates. The application of Sec.  25.207(d), as adopted, 
in combination with the adopted new requirement of Sec.  25.103(d) will 
ensure that there must be a 5 knot or 5 percent stall warning margin 
relative to VSR for these airplanes. Therefore, the proposed Sec.  
25.207(d) is removed.
    The stall speed margins required by the adopted Sec. Sec.  
25.207(c) and (d) must be available in terms of calibrated airspeed. 
Normally, test demonstrations at the conditions specified in Sec.  
25.201 (Stall demonstration) will be sufficient to show compliance with 
these requirements. However, if the stall warning margin for a 
particular airplane type varies significantly with power or thrust, 
center-of-gravity position, bank angle, of some other characteristic, 
additional test conditions may be necessary.
    As with other part 25 requirements, shortfalls in demonstrating 
compliance with the literal terms of the stall warning margin 
requirements would necessitate either a design change, an exemption 
(per Sec.  11.25), or features that would provide equivalent safety 
using an alternate means of compliance (per Sec.  21.21(b)(1)). Other 
rulemaking projects in which the stall warning margin is an issue 
(e.g., discussions of flight in icing conditions by the ARAC) will be 
considered on their own merits.
    Several commenters object to the accelerated stall warning margin 
requirement proposed as a new Sec.  25.207(e). Some of the commenters 
claim that, in some cases, attempts to demonstrate compliance with this 
proposed requirement during flight testing resulted in maneuvers that 
the commenters consider inappropriate for a transport category 
airplane. These commenters provide several examples of the maneuvers 
they described as inappropriate. Other commenters note that the phrase 
``to prevent stalling'' needs further clarification. One commenter 
questions the lack of a bank angle stipulation in the proposed 
requirement and provided an analysis indicating that bank angles of 
about 45 degrees have the greatest effect on aerodynamics. This 
commenter also claims that a prescribed load factor and deceleration 
rate are not simultaneously achievable at CLMAX. The 
commenter suggests revising the proposed Sec.  25.207(e) to specify 30 
degree banked turns (for consistency with the turning flight stall 
characteristics demonstration required by Sec.  25.201(a)) with 
accelerated rates of entry into the stall, up to the greater of 1.5g 
load factor and 3 knots per second speed reduction. This suggestion was 
made by other commenters as well.
    The FAA concurs that detailed guidance material may be helpful to 
ensure an appropriate and consistent demonstration of compliance with 
the proposed accelerated stall warning requirement. This material will 
be presented in the proposed revisions to AC 25-7A, which will be 
published in the Federal Register shortly after publication of this 
final rule.
    The purpose of the proposed requirement is to ensure that adequate 
stall warning exists to prevent an inadvertent stall under the most 
demanding conditions likely to occur in normal flight. The proposed 
conditions of 1.5g and a three knots per second entry rate (i.e., 
airspeed deceleration rate) correspond to the steep turn maneuver 
prescribed in part 121, Appendices E and F for pilot initial and 
proficiency training, respectively, plus some margin for error (three 
degrees more bank and a decreasing airspeed). The elevated load factor 
will emphasize any adverse stall characteristics, such as wing drop or 
asymmetric wing flow breakdown, while also investigating Mach and 
potential aeroelastic effects on available lift. The proposed three 
knots per second deceleration rate is intended to result in a 
reasonable penetration beyond the onset of stall warning. A 30-degree 
banked turn maneuver, as proposed by several of the commenters, 
produces a load factor of only 1.15g, which the FAA does not consider 
high enough to evaluate the effect of elevated load factor on the 
capability to prevent an inadvertent stall.
    As noted by one of the commenters, the bank angle used during the 
maneuver to demonstrate compliance with this proposed requirement may 
affect the airplane's stall characteristics. However, this aspect is 
considered secondary to the primary effect of an elevated load factor 
on the stall warning margin. For this reason, Sec.  25.207(e) is 
revised from the version published in the NPRM to prescribe a load 
factor rather than a bank angle. An acceptable means of producing this 
load factor would be a 48-degree banked turn in level flight.
    As adopted, Sec.  25.207(e) requires an airspeed deceleration rate 
of greater than two knots per second instead of rates up to three knots 
per second. This change clarifies the intent of achieving a reasonable 
deceleration rate rather than one specific value, and will result in 
the intended penetration beyond the onset of stall warning. The FAA 
anticipates that with typical test techniques, requiring a deceleration 
rate of greater than two knots per second will result in deceleration 
rates close to

[[Page 70822]]

three knots per second. The power and trim conditions are now specified 
in the rule in order to ensure consistent application of this 
requirement.
    To clarify the meaning of the phrase ``to prevent stalling,'' the 
parenthetical expression, ``(as defined in Sec.  25.201(d)),'' has been 
added in the adopted Sec.  25.207(e). Therefore, any of the acceptable 
indications of a stall applicable to stall demonstration testing is 
also considered an indication that the airplane has stalled during the 
accelerated stall warning demonstration. If any of these indications of 
a stall occur during the accelerated stall warning demonstration, 
compliance with Sec.  25.207(e) will not have been demonstrated.
    Two commenters offered comments relative to subpart C (Structure) 
of part 25. One of these commenters suggests that the interpretation of 
the stall speed used in subpart C be undertaken urgently as part of the 
Harmonization Work Program. The other commenter suggests that either 
subpart C should be reworked to reflect the introduction of 
VSR or Sec.  25.103 should introduce definitions of 
VS0 and VS1 in terms of VSR.
    These comments regarding subpart C of part 25 are beyond the scope 
of this rulemaking, which is confined to the definition of the stall 
speed used for airplane performance determination and handling 
characteristics. This amendment does not affect the stall speeds used 
in subpart C for structural analysis.
    Further consideration by the FAA regarding the proposed revisions 
to Sec. Sec.  1.1 (Definition of reference landing speed) and 97.3(b) 
(Definition of aircraft approach category) has resulted in minor 
changes in the adopted rule relative to the original proposals. The 
proposed definition of reference landing speed had used the term 
``landing screen height'' to identify the point in the approach at 
which the reference landing speed is determined. Although this term is 
defined in the preamble discussion of the rule proposal, it is not 
defined or used elsewhere within the regulations. The landing distance 
requirements of Sec.  25.125 specify this height as the 50 foot height, 
and the adopted definition of reference landing speed in Sec.  1.1 has 
been changed to be consistent with this requirement.
    The preamble discussion references approvals of steep approach 
operations that use a ``landing screen height'' of less than the 50 
foot height prescribed by the Sec.  25.125 landing distance 
requirements. These types of approvals are not the norm, however, and 
should be processed as equivalent safety findings, special conditions, 
or exemptions, whichever is appropriate for the specific case.
    In addition to replacing ``landing screen height'' with ``50 foot 
height,'' the words ``for manual landings'' have been removed from the 
definition of ``reference landing speed'' since the applicable Sec.  
25.125 landing distance requirements make no such distinction. Approval 
of automatic landing systems, including consideration of associated 
landing speeds and distances, is addressed in FAA ACs 20-57A, 120-28D, 
and 120-29.
    Further review of the proposed change to Sec.  97.3(b) indicated a 
potential for confusion with respect to its application to aircraft 
certificated using VS, the minimum speed in the stalling 
maneuver, rather than VSR. There is some concern that the 
proposed replacement of 1.3 VS0 with VREF may 
introduce terminology which is not well understood by all potential 
users of the airspace system, and that information provided in some 
Airplane Flight Manuals may not be consistent with the new terminology. 
Therefore, as adopted, Sec.  97.3(b) will continue to reference 1.3 
VS0 for use in those cases where VREF is not 
specified.
    One adverse comment was received on the proposed change to Sec.  
C36.9(e)(1) of Appendix C to part 36. The commenter notes that the 
proposed change could result in increasing the speed used to show 
compliance with the approach noise requirements for those cases where 
VREF is greater than 1.23 VSR0 (or 1.3 
VS for airplanes certificated under the existing stall speed 
requirements). The commenter states that this increased speed can 
result in higher certificated noise levels. The commenter objects to 
the increased stringency and believes it to be an inappropriate 
consequence of changing to the 1-g stall speed reference. The commenter 
also notes the importance of arriving at harmonized criteria with the 
JAA for the approach speed used for noise certifications.
    The FAA disagrees with the commenter. The proposed amendment would 
have replaced the words ``1.3 VS + 10 knots'' with 
``VREF + 10 knots'' and removed the words ``or the speed 
used in establishing the approved landing distance under the 
airworthiness regulations constituting the type certification basis of 
the airplane, whichever speed is greatest.'' The effect of the proposal 
would have been to require a steady approach speed of VREF + 
10 knots over the approach noise measuring point during the flight test 
measurement of approach noise levels.
    The reference to 1.3 VS in the current Sec.  C36.9(e)(1) 
had been derived from the Sec.  25.125 landing requirements, i.e., 1.3 
VS was interpreted to be the speed at the 50 foot height. 
Further away from the runway, at the point at which the approach noise 
is measured (6,562 feet from the runway threshold), the airplane is 
likely to be at a somewhat higher speed. Higher speeds are used during 
the approach to provide greater stall and controllability margins, 
especially in the presence of winds and gusts, with the additional 
speed being bled off by the time the airplane is at the 50 foot height. 
As stated in the preamble to the amendment that added part 36 to the 
FAR, ``The intent of this proposal was to require an airspeed that is 
highly typical of normal approach airspeeds, so that a realistic 
approach speed is generated. The speed 1.3 VS + 10 knots is 
such an airspeed and is therefore specified * * *'' The ten knot 
increment applied to 1.3 VS represents the typical approach 
speed at the approach noise measuring point.
    In a later amendment to part 36 (Amendment 36-5), the FAA 
recognized that, for various reasons, a speed higher than 1.3 
VS may be used in establishing the landing distance under 
Sec.  25.125. Amendment 36-5 added the words ``or the speed used in 
establishing the approved landing distance under the airworthiness 
regulations constituting the type certification basis of the airplane, 
whichever speed is greatest'' to the ``1.3 VS + 10 knots'' 
speed requirement over the approach noise measuring point.
    The additional 10 knot speed increment added to 1.3 VS 
was not added to ``the speed used in establishing the approved landing 
distance under the airworthiness regulations constituting the type 
certification basis of the airplane.'' The FAA has since determined, 
however, that the ten knot speed increment should be applied to the 
speed used to determine the landing distance under Sec.  25.125, 
regardless of whether that speed is 1.3 VS or some higher 
speed. The flightcrew does not know whether the approach speed provided 
in their manuals is based on 1.3 VS or some higher speed and 
will use the same procedures and speed increments in either case.
    The FAA's proposal would have set the speed over the approach noise 
measuring point at VREF +10 knots. Since VREF is 
the speed used to determine the landing distance, a consistent speed 
increment would be applied to the speed applicable to the 50 foot 
height, regardless of whether VREF is determined by stall 
speed,

[[Page 70823]]

controllability requirements, or some other parameter.
    Subsequent to the publication of Notice 95-17, Working Group 1 
(WG1) of the International Civil Aviation Organization (ICAO) Committee 
on Aviation Environmental Protection (CAEP) recommended to the ICAO 
CAEP that the noise certification approach reference speed contained in 
Volume I of Annex 16 to the Convention on International Civil Aviation 
(the ICAO International Standard and Recommended Practice for Aircraft 
Noise Certification) be changed to VREF + 10 knots. The WG1 
was established by the CAEP to provide technical guidance regarding 
revisions to Annex 16, Volume 1. The United States is a member of both 
the ICAO CAEP and WG1. The WG1 did not view the adoption of 
VREF + 10 knots as having a significant effect on 
stringency. At its 5th meeting, which was held in January 2001, the 
ICAO CAEP accepted the WG1 recommendation regarding adoption of 
VREF + 10 knots. This recommendation was subsequently 
included in Amendment 7 of Annex 16, Volume 1, which was adopted by the 
ICAO Council on June 29, 2001.
    As a member of the ICAO Council, CAEP and WG1, the FAA supported 
the conclusion to use VREF + 10 knots. The commenter has 
provided no support for the expressed effect on stringency. The concern 
expressed by the commenter regarding the use of harmonized criteria 
between the FAA and JAA would be eliminated by FAA adoption of the 
Annex 16, Amendment 7 requirement, considering that Annex 16 is the 
basis for the JAA noise certification requirements. Accordingly, the 
FAA adopted the Annex 16, Amendment 7 requirement as part of Amendment 
24 to part 36, which was published in the Federal Register on July 8, 
2002 (67 FR 45193).
    Other than the changes noted above, the proposed changes to part 25 
are adopted as proposed in Notice No. 95-17.

Paperwork Reduction Act

    In accordance with the Paperwork Reduction Act of 1995 (44 U.S.C. 
3507(d)), there are no requirements for information collection 
associated with this amendment.

International Compatibility

    In keeping with U.S. obligations under the Convention on 
International Civil Aviation, it is FAA policy to comply with 
International Civil Aviation Organization (ICAO) Standards and 
Recommended Practices to the maximum extent practical. The FAA has 
reviewed the corresponding ICAO Standards and Recommended Practices and 
the Joint Aviation Authorities regulations, where they exist, and has 
identified no differences in these amendments and the foreign 
regulations.

Regulatory Evaluation Summary

Economic Evaluation, Regulatory Flexibility Determination, 
International Trade Impact Assessment, and Unfunded Mandates Assessment

    Changes to Federal regulations must undergo several economic 
analyses. First, Executive Order 12866 directs each Federal agency to 
propose or adopt a regulation only if the agency makes a reasoned 
determination that the benefits of the intended regulation justify its 
costs. Second, the Regulatory Flexibility Act of 1980 requires agencies 
to analyze the economic impact of regulatory changes on small entities. 
Third, the Trade Agreements Act (19 U.S.C. section 2531-2533) prohibits 
agencies from setting standards that create unnecessary obstacles to 
the foreign commerce of the United States. In developing U.S. 
standards, this Trade Act requires agencies to consider international 
standards. Where appropriate, agencies are directed to use those 
international standards as the basis of U.S. standards. And fourth, the 
Unfunded Mandates Reform Act of 1995 requires agencies to prepare a 
written assessment of the costs, benefits and other effects of proposed 
or final rules. This requirement applies only to rules that include a 
Federal mandate on State, local or tribal governments or the private 
sector, likely to result in a total expenditure of $100 million or more 
in any one year (adjusted for inflation.)
    In conducting these analyses, the FAA has determined that this 
final rule: (1) Has benefits that do justify its costs; (2) is not a 
``significant rulemaking'' either as defined in the Executive Order or 
in DOT's Regulatory Policies and Procedures; (3) will not have a 
significant impact on a substantial number of small entities; (4) will 
lessen restraints on international trade; and (5) will not contain a 
significant intergovernmental or private sector mandate.
    These analyses, available in the docket, are summarized as follows.

Economic Evaluation

The Benefits Estimate

    This rule supports the existing level of safety because type 
certification for part 25 airplanes based on 1-g criteria is common 
practice, the FAA having accepted 1-g stall criteria since the mid-80s 
for most part 25 type certifications, in many cases through the Issue 
Paper process. This rule establishes the codification of this practice, 
and thus adds the safety benefit of preventing deviation from this 
practice. The FAA has not attempted to quantify this benefit.
    The FAA also expects this rule will result in added benefits in the 
form of cost savings to those affected manufacturers that carry out 
type certification to both FAR and JAR requirements. Historically, U.S. 
manufacturers that certificate part 25 airplanes to both FAA and JAA 
requirements using 1-g stall speed criteria have done so by working out 
separate arrangements with both authorities. The FAA expects compliance 
with a single harmonized FAA/JAA regulatory standard will be simpler 
and more direct than compliance through separate arrangements, and that 
cost savings will result. The FAA has not attempted to quantify this 
benefit.

The Estimate of Costs and Its Evolution

    As noted, the FAA has accepted 1-g stall speed criteria for most 
part 25 type certification projects since the mid-1980s. The FAA 
expects this rule will not change the substance of accepted 
certification practices. Thus, no more than minimal additional 
certification costs will be associated with this new rule.
    However, as certification practices and aviation technology have 
evolved since the mid-1980s, the costs of certification at 1-g have 
changed. As these costs have changed, manufacturers' estimates of 
comparative certification costs have changed; and FAA's estimates of 
the costs associated with this rule have changed.
    This final rule evaluation was begun in 1999. It completes the 
regulatory evaluation process that began with research pursuant to a 
1996 NPRM. Comments to the docket in response to that NPRM were 
received in 1996. Pursuant to this final rule evaluation, providers of 
previously received information were asked to review, clarify and 
update their information as necessary. Their clarifications and 
updates, together with the previous research and analysis are the basis 
for the conclusions developed in this final rule evaluation.
    While the costs provided in the 1996 comments were much higher than 
those of the 1996 NPRM, the 1999 clarifications and updates brought the 
costs developed in this final rule evaluation more into line with those 
of the NPRM. Cost estimates for typical

[[Page 70824]]

type certification projects that use 1-g stall speed as the reference 
datum have evolved as follow:
    [sbull] In 1996, the NPRM concluded that the costs of 1-g 
compliance differed depending upon the size of the airplane certified. 
In then-current dollars, the NPRM estimated compliance costs of 
$195,000 for a type certification for large part 25 airplanes. For 
small part 25 airplanes, the NPRM estimate included a one-time cost of 
$70,000 for each manufacturer and subsequent type certification costs 
of $250,000. This final rule evaluation concludes that neither 
regulatory nor practical distinctions between small and large airplanes 
allow the unambiguous grouping by size category needed to support the 
level of economic analysis characteristic of final rules.
    [sbull] In 1996, comments received in response to the NPRM gave 
additional compliance costs per type certification in then-current 
dollars that ranged from $331,412 for instrumentation costs plus 
$35,029 for testing and analysis, to an undifferentiated $1,000,000 per 
type certification project.
    [sbull] For this final rule evaluation, the baseline for cost 
comparisons is the estimate of the current cost of type certification 
using minimum stall speed as the reference datum for a typical part 25 
airplane. Building on the NPRM, the comments to the Docket, and the 
clarifications and updates, this final rule evaluation estimates 
typical additional compliance costs of about $130,000 for a type 
certification program conducted at 1-g for a part 25 airplane, 
expressed in 1999 dollars.
    [sbull] During the time the FAA has been accepting certification at 
1-g, additional costs of instrumentation have become small to 
negligible. Falling instrumentation costs and rising instrumentation 
capability have resulted in acceptable test data being achieved by 
adding as little additional instrumentation as one accelerometer to the 
test equipment required for certification at minimum stall speed. (The 
estimated uninstalled cost of an accelerometer appropriate to this use 
is the minimal cost of $500 to $2,000, in 1999 dollars. Further, 
accelerometer and gyroscopic components already present in the inertial 
navigation systems incorporated on modern transport category airplanes 
are the fundamental starting point for instrumentation sufficient to 
measure a 1-g stall speed.)
    In summary, for a typical part 25 airplane, the current industry 
practice of type certification using 1-g stall as the reference datum 
adds a minor cost ($130,000) for flight-testing and analysis to the 
costs of the baseline alternative of type certification using minimum 
speed stall. This practice also is expected to add very minor or no 
cost for additional instrumentation beyond that required for the type 
certification baseline.
    This final evaluation notes the possibility, also raised in the 
NPRM and in the 1999 clarifications and updates, that codification of 
this ongoing practice, and its consequent extension to all U.S. 
manufacturers and to all part 25 airplanes they will certificate in the 
future, could have an adverse impact on marketing efforts by 
manufacturers. (In general, this rule reduces the multiplying factors 
used to convert reference speed to minimum operational speeds by about 
6 percent. When the reduced multiplying factors are applied to the 1-g 
stall speed, which is generally about 6 percent higher than minimum 
speed stall, the resulting minimum operating speeds generally will 
result in the same values produced by using minimum stall speed as the 
reference datum. However, variation is possible. This possible 
variation is at the heart of assertions of marketing impact. No such 
impact is considered in this evaluation, for the reasons that follow:

--The possible differences in operational speeds between type 
certification using 1-g stall speed and type certification using 
minimum stall speed are in the low single digits when expressed as 
speeds
--The very large number of possible combinations of airplane types, 
operational conditions, operators' services and airport characteristics 
forestalls practical quantitative consideration of the possible small 
consequences noted above
--Any operational consequence of certification at 1-g already results 
from ongoing industry practice and cannot also be considered to result 
from this rule
--The possible differences in operational speeds between type 
certification using 1-g stall speed and type certification using 
minimum stall speed are in the low single digits when expressed as 
speeds

Benefits/Costs Comparison

    The FAA finds that this rule improves the codification of current 
industry practices that have evolved over a period of about 15 years. 
These practices already result in the benefits of the current level of 
safety. With one exception, this rule will add little or nothing to 
these benefits. The exception is the elimination of the possibility 
that a future part 25 airplane might not be certificated based on 1-g 
stall speed criteria. Removing this possibility ensures that the 
benefits being received cannot be reduced, thus diminishing the current 
level of safety. The agency has not attempted to quantify either this 
added benefit or the benefits already being received.
    Another additional benefit of improved codification is that type 
certification to both FAR and JAR requirements will be simpler, more 
direct and consequently less costly. The agency has not attempted to 
quantify this harmonization benefit.
    Because it is an improvement of the codification of voluntary 
industry practices, the FAA concludes that this rule will add little or 
no cost to the industry. The agency estimates that affected 
manufacturers already voluntarily incur costs of about $130,000 (in 
1999 dollars) for each type certification project they base on 1-g 
stall speed criteria, beyond the costs they would incur in type 
certification based on minimum stall speed criteria.
    The FAA concludes that while this final rule will add little or 
nothing to the safety benefits and the certification costs that already 
result from voluntary industry practices, it does add safety and 
harmonization benefits. Thus, the FAA believes this rule is cost 
effective.

Regulatory Flexibility Determination

    The Regulatory Flexibility Act of 1980 (RFA) establishes ``as a 
principle of regulatory issuance that agencies shall endeavor, 
consistent with the objective of the rule and of applicable statutes, 
to fit regulatory and informational requirements to the scale of the 
business, organizations, and governmental jurisdictions subject to 
regulation.'' To achieve that principle, the Act requires agencies to 
solicit and consider flexible regulatory proposals and to explain the 
rationale for their actions. The Act covers a wide-range of small 
entities, including small businesses, not-for-profit organizations and 
small governmental jurisdictions.
    Agencies must perform a review to determine whether a proposed or 
final rule will have a significant economic impact on a substantial 
number of small entities. If the determination is that it will, the 
agency must prepare a regulatory flexibility analysis as described in 
the Act.
    However, if an agency determines that a proposed or final rule is 
not expected to have a significant economic impact on a substantial 
number of small entities, section 605(b) of the 1980 act provides that 
the head of the agency may so certify and a regulatory flexibility 
analysis is not required. The certification must include a statement 
providing the factual basis for this determination, and the reasoning 
should

[[Page 70825]]

be clear. For aircraft manufacturers, a small entity is one with 1,500 
or fewer employees.
    Evaluation of this final rule in terms of this standard shows that 
no current manufacturer of transport category airplanes is a small 
manufacturer. Although the future entry of a small manufacturer into 
the business of manufacturing transport category airplanes is possible, 
such an unusual single entrant could not be construed to equate to a 
``substantial number.''
    Finally, no regulatory flexibility analysis is required for this 
rule because it adds little or nothing to the costs that otherwise 
would be required for type certification of a transport category 
airplane by a manufacturer of any size. Therefore the impact of this 
rule would not be significant whether it fell on a large or on a small 
manufacturer.
    In light of these arguments, the FAA certifies that the rule change 
will not have a significant economic impact on a substantial number of 
small entities, and a regulatory flexibility analysis is not required.

International Trade Impact Analysis

    The Trade Agreement Act of 1979 prohibits Federal agencies from 
engaging in any standards or related activities that create unnecessary 
obstacles to the foreign commerce of the United States. Legitimate 
domestic objectives, such as safety, are not considered unnecessary 
obstacles. The statute also requires consideration of international 
standards and where appropriate, that they be the basis for U.S. 
standards.
    Because this rule is a part of a harmonization process that will 
result in a single FAA/JAA regulatory standard, it reduces a barrier to 
international trade. Thus, in accordance with the above statute, the 
FAA has assessed the potential effect of this final rule and has 
determined that it will support the Act.

Unfunded Mandates Reform Act

    The Unfunded Mandates Reform Act of 1995 (the Act), enacted as 
Public Law 104-4 on March 22, 1995 is intended, among other things, to 
curb the practice of imposing unfunded Federal mandates on State, 
local, and tribal governments.
    Title II of the Act requires each Federal agency to prepare a 
written statement assessing the effects of any Federal mandate in a 
proposed or final agency rule that may result in a $100 million or more 
expenditure (adjusted annually for inflation) in any one year by State, 
local, and tribal governments, in the aggregate, or by the private 
sector; such a mandate is deemed to be a ``significant regulatory 
action.'' This final rule does not contain such a mandate. Therefore, 
the assessment requirements of Title II of the Unfunded Mandates Reform 
Act of 1995 do not apply.

Executive Order 3132, Federalism

    The FAA has analyzed this final rule under the principles and 
criteria of Executive Order 13132, Federalism. We determined that this 
action will not have a substantial direct effect on the State, or the 
relationship between the national Government and the States, or on the 
distribution of power and responsibilities among the various levels of 
government. Therefore, we determined that this final rule does not have 
federalism implications.

Regulations Affecting Interstate Aviation in Alaska

    Section 1205 of the FAA Reauthorization Act of 1996 (110 Stat. 
3213) requires the Administrator, when modifying regulations in Title 
14 of the CFR in a manner affecting interstate aviation in Alaska, to 
consider the extent to which Alaska is not served by transportation 
modes other than aviation, and to establish such regulatory 
distinctions as he or she considers appropriate. Because this rule 
would apply to the certification of future designs of transport 
category airplanes and their subsequent operation, it could, if 
adopted, affect interstate aviation in Alaska.

Environmental Analysis

    FAA Order 1050.1D defines FAA actions that may be categorically 
excluded from presentation of a National Environmental Policy Act 
(NEPA) environmental impact statement. In accordance with FAA Order 
1050.1D, appendix 4, paragraph 4(j), this rulemaking action qualifies 
for a categorical exclusion.

Energy Impact

    The energy impact of this amendment has been assessed in accordance 
with the Energy Policy and Conservation Act (EPCA) Public Law 94-163, 
as amended (42 U.S.C. 6362) and FAA Order 1053.1. It has been 
determined that the final rule is not a major regulatory action under 
the provisions of the EPCA.

List of Subjects

14 CFR Part 1

    Air transportation.

14 CFR Part 25

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

14 CFR Part 97

    Air traffic control, Airports, Navigation (air), Weather.

The Amendments

    In consideration of the foregoing, the Federal Aviation 
Administration (FAA) amends Chapter I of Title 14 Code of Federal 
Regulations (CFR) parts 1, 25, and 97 as follows:

PART 1--DEFINITIONS AND ABBREVIATIONS

    1. The authority citation for part 1 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701.

    2. Section 1.1 is amended by adding new definitions in alphabetical 
order to read as follows:


Sec.  1.1  General definitions.

* * * * *
    Final takeoff speed means the speed of the airplane that exists at 
the end of the takeoff path in the en route configuration with one 
engine inoperative.
* * * * *
    Reference landing speed means the speed of the airplane, in a 
specified landing configuration, at the point where it descends through 
the 50 foot height in the determination of the landing distance.
* * * * *

    3. Section 1.2 is amended by adding new abbreviations in 
alphabetical order to read as follows:


Sec.  1.2  Abbreviations and symbols.

* * * * *
    VFTO means final takeoff speed.
* * * * *
    VREF means reference landing speed.
* * * * *
    VSR means reference stall speed.
    VSR0 means reference stall speed in the landing 
configuration.
    VSR1 means reference stall speed in a specific 
configuration.
    VSW means speed at which onset of natural or artificial 
stall warning occurs.
* * * * *

PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES

    4. The authority citation for part 25 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

    5. Section 25.103 is revised to read as follows:


Sec.  25.103  Stall speed.

    (a) The reference stall speed, VSR, is a calibrated 
airspeed defined by the

[[Page 70826]]

applicant. VSR may not be less than a 1-g stall speed. 
VSR is expressed as:
[GRAPHIC] [TIFF OMITTED] TR26NO02.001

where:
VCLMAX = Calibrated airspeed obtained when the load factor-
corrected lift coefficient
[GRAPHIC] [TIFF OMITTED] TR26NO02.002

is first a maximum during the maneuver prescribed in paragraph (c) of 
this section. In addition, when the maneuver is limited by a device 
that abruptly pushes the nose down at a selected angle of attack (e.g., 
a stick pusher), VCLMAX may not be less than the speed 
existing at the instant the device operates;
nZW = Load factor normal to the flight path at 
VCLMAX
W = Airplane gross weight;
S = Aerodynamic reference wing area; and
q = Dynamic pressure.

    (b) VCLMAX is determined with:
    (1) Engines idling, or, if that resultant thrust causes an 
appreciable decrease in stall speed, not more than zero thrust at the 
stall speed;
    (2) Propeller pitch controls (if applicable) in the takeoff 
position;
    (3) The airplane in other respects (such as flaps and landing gear) 
in the condition existing in the test or performance standard in which 
VSR is being used;
    (4) The weight used when VSR is being used as a factor 
to determine compliance with a required performance standard;
    (5) The center of gravity position that results in the highest 
value of reference stall speed; and
    (6) The airplane trimmed for straight flight at a speed selected by 
the applicant, but not less than 1.13VSR and not greater 
than 1.3VSR.
    (c) Starting from the stabilized trim condition, apply the 
longitudinal control to decelerate the airplane so that the speed 
reduction does not exceed one knot per second.
    (d) In addition to the requirements of paragraph (a) of this 
section, when a device that abruptly pushes the nose down at a selected 
angle of attack (e.g., a stick pusher) is installed, the reference 
stall speed, VSR, may not be less than 2 knots or 2 percent, 
whichever is greater, above the speed at which the device operates.

    6. Section 25.107 is amended by revising paragraphs (b)(1) 
introductory text, b(1)(ii), (b)(2) introductory text, b(2)(ii), (c)(1) 
and (c)(2), and by adding new paragraphs (c)(3) and (g) to read as 
follows:


Sec.  25.107  Takeoff speeds.

* * * * *
    (b) * * *
    (1) 1.13VSR for--
* * * * *
    (ii) Turbojet powered airplanes without provisions for obtaining a 
significant reduction in the one-engine-inoperative power-on stall 
speed;
    (2) 1.08VSR for--
* * * * *
    (ii) Turbojet powered airplanes with provisions for obtaining a 
significant reduction in the one-engine-inoperative power-on stall 
speed; and
* * * * *
    (c)* * *
    (1) V2MIN;
    (2) VR plus the speed increment attained (in accordance 
with Sec.  25.111(c)(2)) before reaching a height of 35 feet above the 
takeoff surface; and
    (3) A speed that provides the maneuvering capability specified in 
Sec.  25.143(g).
* * * * *
    (g) VFTO, in terms of calibrated airspeed, must be 
selected by the applicant to provide at least the gradient of climb 
required by Sec.  25.121(c), but may not be less than--
    (1) 1.18 VSR; and
    (2) A speed that provides the maneuvering capability specified in 
Sec.  25.143(g).

    7. Section 25.111 is amended by revising paragraph (a) introductory 
text to read as follows:


Sec.  25.111  Takeoff path.

    (a) The takeoff path extends from a standing start to a point in 
the takeoff at which the airplane is 1,500 feet above the takeoff 
surface, or at which the transition from the takeoff to the en route 
configuration is completed and VFTO is reached, whichever 
point is higher. In addition--
* * * * *

    8. Section 25.119 is amended by revising paragraph (b) to read as 
follows:


Sec.  25.119  Landing climb: All-engines-operating.

* * * * *
    (b) A climb speed of not more than VREF.

    9. Section 25.121 is amended by revising paragraphs (c) 
introductory text, (d) introductory text, (d)(2) and (d)(3), and by 
adding paragraph (d)(4) to read as follows:


Sec.  25.121  Climb: One-engine-inoperative.

* * * * *
    (c) Final takeoff. In the en route configuration at the end of the 
takeoff path determined in accordance with Sec.  25.111, the steady 
gradient of climb may not be less than 1.2 percent for two-engine 
airplanes, 1.5 percent for three-engine airplanes and 1.7 percent for 
four-engine airplanes, at VFTO and with
* * * * *
    (d) Approach. In a configuration corresponding to the normal all-
engines-operating procedure in which VSR for this 
configuration does not exceed 110 percent of the VSR for the 
related all-engines-operating landing configuration, the steady 
gradient of climb may not be less than 2.1 percent for two-engine 
airplanes, 2.4 percent for three-engine airplanes, and 2.7 percent for 
four engine airplanes, with
* * * * *
    (2) The maximum landing weight;
    (3) A climb speed established in connection with normal landing 
procedures, but not more than 1.4 VSR; and
    (4) Landing gear retracted.

    10. Section 25.125 is amended by revising paragraph (a)(2) to read 
as follows:


Sec.  25.125  Landing.

    (a) * * *
    (2) A stabilized approach, with a calibrated airspeed of 
VREF, must be maintained down to the 50 foot height. 
VREF may not be less than
    (i) 1.23 VSR0;
    (ii) VMCL established under Sec.  25.149(f); and
    (iii) A speed that provides the maneuvering capability specified in 
Sec.  25.143(g).
* * * * *

    11. Section 25.143 is amended by adding a new paragraph (g) to read 
as follows:


Sec.  25.143  General.

* * * * *
    (g) The maneuvering capabilities in a constant speed coordinated 
turn at forward center of gravity, as specified in the following table, 
must be free of stall warning or other characteristics that might 
interfere with normal maneuvering:

[[Page 70827]]



--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                   Maneuvering bank
           Configuration                         Speed                angle in a                             Thrust power setting
                                                                   coordinated turn
--------------------------------------------------------------------------------------------------------------------------------------------------------
Takeoff............................  V2                                    30[deg]   Asymmetric WAT-Limited.\1\
Takeoff............................  \2\V2 + XX                            40[deg]   All-engines-operating climb.\3\
En route...........................  VFTO                                  40[deg]   Asymmetric WAT-Limited.\1\
Landing............................  VREF                                  40[deg]   Symmetric for -3[deg] flight path angle.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ A combination of weight, altitude, and temperature (WAT) such that the thrust or power setting produces the minimum climb gradient specified in Sec.
    25.121 for the flight condition.
\2\ Airspeed approved for all-engines-operating initial climb.
\3\ That thrust or power setting which, in the event of failure of the critical engine and without any crew action to adjust the thrust or power of the
  remaining engines, would result in the thrust or power specified for the takeoff condition at V2, or any lesser thrust or power setting that is used
  for all-engines-operating initial climb procedures.



    12. Section 25.145 is amended by revising paragraphs (a) 
introductory text, (a)(1), (b)(1), (b)(4), (b)(6), and (c) introductory 
text to read as follows:


Sec.  25.145  Longitudinal control.

    (a) It must be possible, at any point between the trim speed 
prescribed in Sec.  25.103(b)(6) and stall identification (as defined 
in Sec.  25.201(d)), to pitch the nose downward so that the 
acceleration to this selected trim speed is prompt with
    (1) The airplane trimmed at the trim speed prescribed in Sec.  
25.103(b)(6);
* * * * *
    (b) * * *
    (1) With power off, flaps retracted, and the airplane trimmed at 
1.3 VSR1, extend the flaps as rapidly as possible while 
maintaining the airspeed at approximately 30 percent above the 
reference stall speed existing at each instant throughout the maneuver.
* * * * *
    (4) With power off, flaps retracted, and the airplane trimmed at 
1.3 VSR1, rapidly set go-around power or thrust while 
maintaining the same airspeed.
* * * * *
    (6) With power off, flaps extended, and the airplane trimmed at 1.3 
VSR1, obtain and maintain airspeeds between VSW 
and either 1.6 VSR1 or VFE, whichever is lower.
    (c) It must be possible, without exceptional piloting skill, to 
prevent loss of altitude when complete retraction of the high lift 
devices from any position is begun during steady, straight, level 
flight at 1.08 VSR1 for propeller powered airplanes, or 1.13 
VSR1 for turbojet powered airplanes, with--
* * * * *


Sec.  25.147  [Amended]

    13. Section 25.147 is amended in paragraphs (a) introductory text, 
(a)(2), (c) introductory text, and (d) by revising the expression ``1.4 
VS1'' to read ``1.3 VSR1.''


Sec.  25.149  [Amended]

    14. Section 25.149 is amended in paragraph (c) introductory text by 
revising the expression ``1.2 VS'' to read ``1.13 
VSR.''


Sec.  25.161  [Amended]

    15. Section 25.161 is amended in paragraphs (b), (c)(1), (c)(2), 
(c)(3) and (d) introductory text by revising the expression ``1.4 
VS1'' to read ``1.3 VSR1''; and in paragraph 
(e)(3) by revising the expression ``0.013 VS02'' 
to read ``0.013 VSR02.''


Sec.  25.175  [Amended]

    16. Section 25.175 is amended: a. In paragraphs (a)(2), (b)(1) 
introductory text, (b)(2) introductory text, (b)(3) introductory text 
and (c)(4) by revising the expression ``1.4 VS1'' to read 
``1.3 VSR1'';
    b. In paragraph (b)(2)(ii) by revising the expression 
``VMO + 1.4 VS1/2'' to read ``(VMO + 
1.3 VSR1)/2'';
    c. In paragraph (c) introductory text by revising the expressions 
``1.1 VS1'' to read ``VSW'' and ``1.8 
VS1'' to read ``1.7 VSR1'';
    d. In paragraph (d) introductory text by revising the expressions 
``1.1 VSO'' to read ``VSW'' and ``1.3 
VS0'' to read ``1.7 VSR0''; and
    e. In paragraph (d)(5) by revising the expression ``1.4 
VS0'' to read ``1.3 VSR0.''


Sec.  25.177  [Amended]

    17. Section 25.177 is amended in paragraph (c) by revising the 
expression ``1.2 VS1'' to read ``1.13 VSR1.''


Sec.  25.181  [Amended]

    18. Section 25.181 is amended in paragraphs (a) introductory text 
and (b) by revising the reference to ``1.2 VS'' to read 
``1.13 VSR.''

    19. Section 25.201 is amended by revising paragraphs (a)(2) and 
(b)(4) to read as follows:


Sec.  25.201  Stall demonstration.

    (a) * * *
    (2) The power necessary to maintain level flight at 1.5 
VSR1 (where VSR1 corresponds to the reference 
stall speed at maximum landing weight with flaps in the approach 
position and the landing gear retracted).
    (b) * * *
    (4) The airplane trimmed for straight flight at the speed 
prescribed in Sec.  25.103(b)(6).
* * * * *

    20. Section 25.207 is amended by revising paragraphs (b) and (c), 
and by adding new paragraphs (d), (e), and (f) to read as follows:


Sec.  25.207  Stall warning.

* * * * *
    (b) The warning must be furnished either through the inherent 
aerodynamic qualities of the airplane or by a device that will give 
clearly distinguishable indications under expected conditions of 
flight. However, a visual stall warning device that requires the 
attention of the crew within the cockpit is not acceptable by itself. 
If a warning device is used, it must provide a warning in each of the 
airplane configurations prescribed in paragraph (a) of this section at 
the speed prescribed in paragraphs (c) and (d) of this section.
    (c) When the speed is reduced at rates not exceeding one knot per 
second, stall warning must begin, in each normal configuration, at a 
speed, VSW, exceeding the speed at which the stall is 
identified in accordance with Sec.  25.201(d) by not less than five 
knots or five percent CAS, whichever is greater. Once initiated, stall 
warning must continue until the angle of attack is reduced to 
approximately that at which stall warning began.
    (d) In addition to the requirement of paragraph (c) of this 
section, when the speed is reduced at rates not exceeding one knot per 
second, in straight flight with engines idling and at the center-of-
gravity position specified in Sec.  25.103(b)(5), VSW, in 
each normal configuration, must exceed VSR by not less than 
three knots or three percent CAS, whichever is greater.
    (e) The stall warning margin must be sufficient to allow the pilot 
to prevent

[[Page 70828]]

stalling (as defined in Sec.  25.201(d)) when recovery is initiated not 
less than one second after the onset of stall warning in slow-down 
turns with at least 1.5g load factor normal to the flight path and 
airspeed deceleration rates of at least 2 knots per second, with the 
flaps and landing gear in any normal position, with the airplane 
trimmed for straight flight at a speed of 1.3 VSR, and with 
the power or thrust necessary to maintain level flight at 1.3 
VSR.
    (f) Stall warning must also be provided in each abnormal 
configuration of the high lift devices that is likely to be used in 
flight following system failures (including all configurations covered 
by Airplane Flight Manual procedures).


Sec.  25.231  [Amended]

    21. Section 25.231 is amended in paragraph (a)(2) by revising the 
word ``altitude'' to read ``attitude'' and by revising the expression 
``80 percent of VS1'' to read ``75 percent of 
VSR1.''


Sec.  25.233  [Amended]

    22. Section 25.233 is amended in paragraph (a) by revising the 
reference ``0.2 VS0'' to read ``0.2 VSR0.''


Sec.  25.237  [Amended]

    23. Section 25.237 is amended in paragraphs (a), (b)(1), and (b)(2) 
by revising the reference ``0.2 VS0'' to read ``0.2 
VSR0.''

    24. Section 25.735 is amended by revising paragraphs (f)(2) and (g) 
to read as follows:


Sec.  25.735  Brakes and braking systems.

* * * * *
    (f) * * *
    (2) Instead of a rational analysis, the kinetic energy absorption 
requirements for each main wheel-brake assembly may be derived from the 
following formula, which must be modified in cases of designed unequal 
braking distributions.
[GRAPHIC] [TIFF OMITTED] TR26NO02.000


where--
KE = Kinetic energy per wheel (ft.-lb.);
W = Design landing weight (lb.);
V = VREF/1.3
VREF = Airplane steady landing approach speed, in knots, at the maximum 
design landing weight and in the landing configuration at sea level; 
and
N = Number of main wheels with brakes.
* * * * *
    (g) In the landing case, the minimum speed rating of each main 
wheel-brake assembly (that is, the initial speed used in the 
dynamometer tests) may not be more than the V used in the determination 
of kinetic energy in accordance with paragraph (f) of this section, 
assuming that the test procedures for wheel-brake assemblies involve a 
specified rate of deceleration, and, therefore, for the same amount of 
kinetic energy, the rate of energy absorption (the power absorbing 
ability of the brake) varies inversely with the initial speed.
* * * * *


Sec.  25.773  [Amended]

    25. Section 25.773 is amended in paragraph (b)(1)(i) by revising 
the expression ``1.6 VS1'' to read ``1.5 VSR1.''


Sec.  25.1001  [Amended]

    26. Section 25.1001 is amended in paragraphs (c)(1) and (c)(3) by 
revising the expression ``1.4 VS1'' to read ``1.3 
VSR1.''


Sec.  25.1323  [Amended]

    27. Section 25.1323 is amended in paragraph (c)(1) by revising the 
expression ``1.3 VS1'' to read ``1.23 VSR1'' and 
in paragraph (c)(2) by revising the expression ``1.3 VS0'' 
to read ``1.23 VSR0.''


Sec.  25.1325  [Amended]

    28. Section 25.1325 is amended in paragraph (e) by revising the 
expressions ``1.3 VS0'' and ``1.8 VS1'' to read 
``1.23 VSR0'' and ``1.7 VSR1,'' respectively.


Sec.  25.1587  [Amended]

    29. Section 25.1587 is amended by in paragraph (b)(2) by revising 
the expression ``VS'' to read ``VSR.''

PART 97--STANDARD INSTRUMENT APPROACH PROCEDURES

    30. The authority citation for part 97 is revised to read as 
follows:

    Authority: 49 U.S.C. 106(g), 40103, 40106, 40113, 40114, 40120, 
44502, 44514, 44701, 44719, 44721-44722.

    31. Section 97.3 is amended by revising the first two sentences of 
paragraph (b) introductory text to read as follows:


Sec.  97.3  Symbols and terms used in procedures.

* * * * *
    (b) Aircraft approach category means a grouping of aircraft based 
on a speed of VREF, if specified, or if VREF is 
not specified, 1.3 VS0 at the maximum certificated landing 
weight. VREF, VS0, and the maximum certificated 
landing weight are those values as established for the aircraft by the 
certification authority of the country of registry. * * *
* * * * *

    Issued in Washington, DC on November 14, 2002.
Marion C. Blakey,
Administrator.
[FR Doc. 02-29667 Filed 11-25-02; 8:45 am]
BILLING CODE 4910-13-U