[Federal Register Volume 60, Number 111 (Friday, June 9, 1995)]
[Notices]
[Pages 30751-30754]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-14172]




  Federal Register / Vol. 60, No. 111 / Friday, June 9, 1995 / 
Notices   
[[Page 30751]] 

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration


Advisory Circular 25-7, Flight Test Guide for Certification of 
Transport Category Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of changes to advisory circular.

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SUMMARY: This notice describes the changes to Advisory Circular (AC) 
25-7, ``Flight Test Guide for Certification of Transport Category 
Airplanes,'' that accompany Amendment 25-84, published elsewhere in 
this issue of the Federal Register.

FOR FURTHER INFORMATION CONTACT:
Donald K. Stimson, Flight Test and Systems Branch, ANM-111, Transport 
Airplane Directorate, Aircraft Certification Service, FAA, 1601 Lind 
Avenue SW., Renton, WA 98055-4056; telephone (206) 227-1129; facsimile 
(206) 227-1320.

SUPPLEMENTARY INFORMATION:

Discussion

    On May 22, 1990, the Aerospace Industries Association of America, 
Inc. (AIA) and the Association Europeenne des Constructeurs de Materiel 
Aerospatial (AECMA) jointly petitioned the FAA and the European Joint 
Aviation Authorities (JAA) to harmonize certain airworthiness 
requirements that apply to transport category airplanes. In their 
petition, a summary of which was published in the July 17, 1990, 
edition of the Federal Register (55 FR 137), AIA and AECMA also 
recommended changes to Advisory Circular (AC) 25-7, ``Flight Test Guide 
for Certification of Transport Category Airplanes,'' to ensure that the 
harmonized standards would be interpreted and applied consistently.
    Part 25 of the Federal Aviation Regulations (FAR) prescribes the 
United States airworthiness standards for transport category airplanes. 
Advisory Circular (AC) 25-7 provides guidelines that the FAA has found 
acceptable for flight testing transport category airplanes to 
demonstrate compliance with those airworthiness standards. Revisions to 
part 25, in response to the AIA/AECMA petition, were proposed by the 
FAA in Notice of Proposed Rulemaking (NPRM) 94-15, which was published 
in the Federal Register on April 22, 1994 (59 FR 19296). The proposed 
revisions to AC 25-7 were published in the same issue of the Federal 
Register as NPRM 94-15 (59 FR 19303).
    Amendment 25-84, which resulted from publication of Notice 94-15, 
is published elsewhere in this issue of the Federal Register. The 
changes to AC 25-7 that accompany Amendment 25-84 are detailed below. 
Copies of the affected pages will be available for distribution shortly 
after publication of this notice.

Revisions to AC 25-7 to Accompany Amendment 25-84

1. Replace Paragraph 16.a With the Following

    a. Section 25.119(a) states that the engines are to be set at the 
power or thrust that is available eight seconds after initiating 
movement of the power or thrust controls from the minimum flight idle 
position to the go-around power or thrust setting. The procedures given 
are for the determination of this maximum thrust for showing compliance 
with the climb requirements of Sec. 25.119.

2. Replace Paragraph 16.b.(3) With the Following

    (3) For the critical air bleed configuration, stabilize the 
airplane in level flight with symmetric power on all engines, landing 
gear down, flaps in the landing position, at a speed of 1.3 VS0, 
simulating the estimated minimum climb limiting landing weights at an 
altitude sufficiently above the selected test altitude so that the time 
to descend to the test altitude with the throttles closed equals the 
appropriate engine r.p.m. stabilization time determined in paragraph 
(2). Retard the throttles to the flight idle position and descend at 
1.3 VS to approximately the test altitude; when the appropriate 
time has elapsed, rapidly advance the power or thrust controls to the 
go-around power or thrust setting. The power or thrust controls may 
first be advanced to the forward stop and then retarded to the go-
around power or thrust setting. At the applicant's option, additional 
less critical bleed configurations may be tested.

3. Add the Following Sections to Paragraph 20.a

    (1) The maximum forces given in the table in Sec. 25.143(c) for 
pitch and roll control for short-term application are applicable to 
maneuvers in which the control force is only needed for a short period. 
Where the maneuver is such that the pilot will need to use one hand to 
operate other controls (such as during the landing flare or a go-
around, or during changes of configuration or power resulting in a 
change of control force that must be trimmed out) the single-handed 
maximum control forces will be applicable. In other cases (such as 
takeoff rotation, or maneuvering during en route flight), the two-
handed maximum forces will apply.
    (2) Short-term and long-term forces should be interpreted as 
follows:
    (i) Short-term forces are the initial stabilized control forces 
that result from maintaining the intended flight path following 
configuration changes and normal transactions from one flight condition 
to another, or from regaining control following a failure. It is 
assumed that the pilot will take immediate action to reduce or 
eliminate such forces by re-trimming or changing configuration or 
flight conditions, and consequently short-term forces are not 
considered to exist for any significant duration. They do not include 
transient force peaks that may occur during the configuration change, 
change of flight conditions, or recovery of control following a 
failure.
    (ii) Long-term forces are those control forces that result from 
normal or failure conditions that cannot readily be trimmed out or 
eliminated.

4. Add the Following Sections to Paragraph 20

    d. Acceptable Means of Compliance. An acceptable means of 
compliance with the requirement that stick forces may not be excessive 
when maneuvering the airplane is to demonstrate that, in a turn for 
0.5g incremental normal acceleration (0.3g above 20,000 feet) at speeds 
up to VFC/MFC, the average stick force gradient does not 
exceed 120 lbs/g.
    e. Interpretive Material. (1) The objective of Sec. 25.143(f) is to 
ensure that the limit strength of any critical component on the 
airplane would not be exceeded in maneuvering flight. In much of the 
structure, the load sustained in maneuvering flight can be assumed to 
be directly proportional of the load factor applied. However, this may 
not be the case for some parts of the structure, e.g., the tail and 
rear fuselage. Nevertheless, it is accepted that the airplane load 
factor will be a sufficient guide to the possibility of exceeding limit 
strength on any critical component if a structural investigation is 
undertaken whenever the design positive limit maneuvering load factor 
is closely approached. If flight testing indicates that the design 
positive limit maneuvering load factor could be exceeded in steady 
maneuvering flight with a 50-pound stick force, the airplane structure 
should be evaluated for the anticipated load at a 50-pound stick force. 
The airplane will be considered to have been overstressed if limit 
strength has been exceeded in any critical [[Page 30752]] component. 
For the purposes of this evaluation, limit strength is defined as the 
larger of either the limit design loads envelope increased by the 
available margins of safety, or the ultimate static test strength 
divided by 1.5.
    (2) Minimum Stick Force to Reach Limit Strength. (i) A stick force 
of at least 50 pounds to reach limit strength in steady maneuvers or 
wind-up turns in considered acceptable to demonstrate adequate minimum 
force at limit strength in the absence of deterrent buffeting. If heavy 
buffeting occurs before the limit strength condition is reached, a 
somewhat lower stick force at limit strength may be acceptable. The 
acceptability of a stick force of less than 50 pounds at the limit 
strength condition will depend upon the intensity of he buffet, the 
adequacy of the warning margin (i.e., the load factor increment between 
the heavy buffet and the limit strength condition), and the stick force 
characteristics. In determining the limit strength condition for each 
critical component, the contribution of buffet loads to the overall 
maneuvering loads should be taken into account.
    (ii) This minimum stick force applies in the en route configuration 
with the airplane trimmed for straight flight, at all speeds above the 
minimum speed at which the limit strength condition can be achieved 
without stalling. No minimum stick force is specified for other 
configurations, but the requirements of Sec. 25.143(f) are applicable 
in these conditions.
    (3) Stick Force Characteristics. (i) At all points within the 
buffet onset boundary determined in accordance with Sec. 25.251(e), but 
not including speeds above VFC/MFC, the stick force should 
increase progressively with increasing load factor. Any reduction in 
stick force gradient with change of load factor should not be so large 
or abrupt as to impair significantly the ability of the pilot to 
maintain control over the load factor and pitch attitude of the 
airplane.
    (ii) Beyond the buffet onset boundary, hazardous stick force 
characteristics should not be encountered within the permitted 
maneuvering envelope as limited by paragraph 20.e.(3)(iii). It should 
be possible, by use of the primary longitudinal control alone, to pitch 
the airplane rapidly nose down so as to regain the initial trimmed 
conditions. The stick force characteristics demonstrated should comply 
with the following:
    (A) For normal acceleration increments of up to 0.3g beyond buffet 
onset, where these can be achieved, local reversal of the stick force 
gradient may be acceptable, provided that any tendency to pitch up is 
mild and easily controllable.
    (B) For normal acceleration increments of more than 0.3g beyond 
buffet onset, where these can be achieved, more marked reversals of the 
stick force gradient may be acceptable. It should be possible for any 
tendency to pitch up to be contained within the allowable maneuvering 
limits without applying push forces to the control column and without 
making a large and rapid forward movement of the control column.
    (iii) In flight tests to satisfy paragraphs 20.e.(3) (i) and (ii), 
the load factor should be increased until either:
    (A) The level of buffet becomes sufficient to provide a strong and 
effective deterrent to further increase of load factor; or
    (B) Further increase the load factor requires a stick force in 
excess of 150 pounds (or in excess of 100 pounds when beyond the buffet 
onset boundary) or is impossible because of the limitations of the 
control system; or
    (C) The positive limit maneuvering load factor established in 
compliance with Sec. 25.337(b) is achieved.
    (4) Negative Load Factors. It is not intended that a detailed 
flight test assessment of the maneuvering characteristics under 
negative load factors should necessarily be made throughout the 
specified range of conditions. An assessment of the characteristics in 
the normal flight envelope involving normal accelerations from 1g to 
zero g will normally be sufficient. Stick forces should also be 
assessed during other required flight testing involving negative load 
factors. Where these assessments reveal stick force gradients that are 
unusually low, or that are subject to significant variation, a more 
detailed assessment, in the most critical of the specified conditions, 
will be required. This may be based on calculations provided these are 
supported by adequate flight test or wind tunnel data.

5. Replace Paragraph 21.a.(e) With the Following

    (3) Section 25.145(c) contains requirements associated primarily 
with attempting a go-around maneuver from the landing configuration. 
Retraction of the high-lift devices from the landing configuration 
should not result in a loss of altitude if the power or thrust controls 
are moved to the go-around setting at the same time that flap/slat 
retraction is begun. The design features involved with this requirement 
are the rate of flap/slat retraction, the presence of any flap gates, 
and the go-around power or thrust setting.
    (i) Flap gates, which prevent the pilot from moving the flap 
selector through the gated position without a separate and distinct 
movement of the selector, allow compliance with these requirements to 
be demonstrated in segments. High lift device retraction must be 
demonstrated beginning from the maximum landing position to the first 
gated position, between gated positions, and from the last gated 
position to the fully retracted position.
    (ii) The go-around power or thrust setting should be the same as is 
used to comply with the approach and landing climb performance 
requirements of Secs. 25.121(d) and 25.119, and the controllability 
requirements of Secs. 25.145(b)(3), 25.145(b)(4), 25.145(b)(5), 
25.149(f), and 25.149(g). The controllability requirements may limit 
the go-around power or thrust setting.

6. Replace Paragraph 21.c.(3)(i)(E) With the Following

    (E) Engine power at flight idle and the go-around power or thrust 
setting.

7. Replace Paragraph 21.c.(4)(ii) With the Following

    (ii) The airplane should be trimmed at a speed of 1.4 VS. 
Quickly set go-around power or thrust while maintaining the speed of 
1.4 VS. The longitudinal control force should not exceed 50 lbs. 
throughout the maneuver without changing the trim control.

8. Replace Paragraph 21.c.(6)(ii) With the Following

    (ii) Test procedure: With the airplane stable in level flight at a 
speed of 1.1 VS for propeller driven airplanes, or 1.2 VS for 
turbojet powered airplanes, retract the flaps to the full up position, 
or the next gated position, while simultaneously setting go-around 
power. Use the same power or thrust as is used to comply with the 
performance requirement of Sec. 25.121(d), as limited by the applicable 
controllability requirements. It must be possible, without requiring 
exceptional piloting skill, to prevent losing altitude during the 
maneuver. Trimming is permissible at any time during the maneuver. If 
gates are provided, conduct this test beginning from the maximum 
landing flap position to the first gate, from gate to gate, and from 
the last gate to the fully retracted position. (The gate design 
requirements are specified within the rule.) Keep the landing gear 
extended throughout the test. [[Page 30753]] 

9. Revise the First Sentence of Paragraph 23.a by Replacing ``Landing 
Approach (VMCL)'' by ``Approach and Landing VMCL and 
VMCL-2).'' Revise the Second Sentence in the Same Paragraph by 
Replacing ``VMCL'' with ``VMCL and VMCL-2''

10. Replace Paragraph 23.b.(2)(iii) With the Following

    (iii) During determination of VMCG, engine failure recognition 
should be provided by:
    (A) The pilot feeling a distinct change in the directional tracking 
characteristics of the airplane, or
    (B) The pilot seeing a directional divergence of the airplane with 
respect to the view outside the airplane.

11. Replace Paragraph 23.b.(3) With the Following

    (3) Minimum Control Speed During Approach and Landing (VMCL)--
Sec. 25.149(f).
    (i) This section is intended to ensure that the airplane is safely 
controllable following an engine failure during an all-engines-
operating approach and landing. From a controllability standpoint, the 
most critical case usually consists of an engine failing after the 
power or thrust has been increased to perform a go-around from an all-
engines-operating approach. Section 25.149(f) requires the minimum 
control speed to be determined that allows a pilot of average skill and 
strength to retain control of the airplane after the critical engine 
becomes inoperative and to maintain straight flight with less than five 
degrees of bank angle. Section 25.149(h) requires that sufficient 
lateral control be available at VMCL to roll the airplane through 
an angle of 20 degrees, in the direction necessary to initiate a turn 
away from the inoperative engine, in not more than five seconds when 
starting from a steady flight condition.
    (ii) Conduct this test using the most critical of the all-engines-
operating approach and landing configurations, or at the option of the 
applicant, each of the all-engines-operating approach and landing 
configurations. The procedures given in paragraph 23.b.(1)(ii) for 
VMCA may be used to determine VMCL, except that flap and trim 
settings should be appropriate to the approach and landing 
configurations, the power or thrust on the operating engine(s) should 
be set to the go-around power or thrust setting, and compliance with 
all VMCL requirements of Secs. 25.149 (f) and (h) must be 
demonstrated.

12. Add the Following New Sections to Paragraph 23.b.(3)

    (iii) For propeller driven airplanes, the propeller must be in the 
position it achieves without pilot action following engine failure, 
assuming the engine fails while at the power or thrust necessary to 
maintain a three degree approach path angle.
    (iv) At the option of the applicant, a one-engine-inoperative 
landing minimum control speed, VMCL(1 out), may be determined in 
the conditions appropriate to an approach and landing with one engine 
having failed before the start of the approach. In this case, only 
those configurations recommended for use during an approach and landing 
with one engine inoperative need be considered. The propeller of the 
inoperative engine, if applicable, may be feathered throughout. The 
resulting value of VMCL(1 out) may be used in determining the 
recommended procedures and speeds for a one-engine-inoperative approach 
and landing.

13. Replace and Re-Designate Paragraphs 23.b.(4), 23.b.4(ii), and 
23.b.4(ii)(A) With the Following

    (4) Minimum Control Speed With One Engine Inoperative During 
Approach and Landing (VMCL-2)--Sec. 25.149(g).
    (iii) Conduct this test using the most critical approved one-
engine-inoperative approach or landing configuration (usually the 
minimum flap deflection), or at the option of the applicant, each of 
the approved one-engine-inoperative approach and landing 
configurations. The following demonstrations are required to determine 
VMCL-2:
    (A) With the power or thrust on the operating engines set to 
maintain a minus 3 degree glideslope with one critical engine 
inoperative, the second critical engine is made inoperative and the 
remaining operating engine(s) are advanced to the go-around power or 
thrust setting. The VMCL-2 speed is established by the procedures 
presented in paragraph 23.b.(1)(ii) for VMCA, except that flap and 
trim setting should be appropriate to the approach and landing 
configurations, the power or thrust on the operating engine(s) should 
be set to the go-around power or thrust setting, and compliance with 
all VMCL-2 requirements of Secs. 25.149(g) and (h) must be 
demonstrated.

14. Add the Following New Section to Paragraph 23.b.(4)

    (ii) For propeller driven airplanes, the propeller of the engine 
inoperative at the beginning of the approach may be in the feathered 
position. The propeller of the more critical engine must be in the 
position it automatically assumes following engine failure.
    (iii)(C) Starting from a steady straight flight condition, 
demonstrate that sufficient lateral control is available at VMCL-2 
to roll the airplane through an angle of 20 degrees in the direction 
necessary to initiate a turn away from the inoperative engines in not 
more than five seconds. This maneuver may be flown in a bank-to-bank 
roll through a wings level attitude.
    (iv) At the option of the applicant, a two-engines-inoperative 
landing minimum control speed, VMCL-2(2 out), may be determined in 
the conditions appropriate to an approach and landing with two engines 
having failed before the start of the approach. In this case, only 
those configurations recommended for use during an approach and landing 
with two engines inoperative need be considered. The propellers of the 
inoperative engines, if applicable, may be feathered throughout. The 
values of VMCL-2 or VMCL-2(2 out) should be used as guidance 
in determining the recommended procedures and speeds for a two-engines-
inoperative approach and landing.

15. Add the Following New Section to Paragraph 23.b

    (5) Autofeather Effects. Where an autofeather or other drag 
limiting system is installed and will be operative at approach power 
settings, its operation may be assumed in determining the propeller 
position achieved when the engine fails. Where automatic feathering is 
not available, the effects of subsequent movements of the engine and 
propeller controls should be considered, including fully closing the 
power lever of the failed engine in conjunction with maintaining the 
go-around power setting on the operating engine(s).

16. Replace Paragraph 29.b.(3)(i) With the Following

    (i) The pitch control reaches the aft stop is held full aft for two 
seconds, or until the pitch attitude stops increasing, whichever occurs 
later. In the case of turning flight stalls, recovery may be initiated 
once the pitch control reaches the aft stop when accompanied by a 
rolling motion that is not immediately controllable (provided the 
rolling motion complies with Sec. 25.203 (c)).

17. Replace Paragraph 29.b.(3)(ii) With the Following

    (ii) An uncommanded, distinctive and easily recognizable nose down 
pitch that cannot be readily arrested. This nose down pitch may be 
accompanied [[Page 30754]] by a rolling motion that is not immediately 
controllable, provided that the rolling motion complies with 
Sec. 25.203(b) or (c) as appropriate.

18. Remove Paragraph 29.b.(3)(iii) (and Redesignate Paragraph 29.b.(3) 
(iv) and (v) as 29.b.(3) (iii) and (iv), Respectively

    (iii) A roll that cannot be readily arrested with normal use of 
lateral/directional control.

19. Replace Paragraph 29.d.(3)(i) With the Following

    (i) The airplane should be trimmed for hands-off flight at a speed 
20 percent to 40 percent above the stall speed, with the appropriate 
power setting and configuration. Then, using only the primary 
longitudinal control, establish and maintain a deceleration (entry 
rate) consistent with that specified in Secs. 25.201(c)(1) or 
25.201(c)(2), as appropriate, until the airplane is stalled. Both power 
and pilot selectable trim should remain constant throughout the stall 
and recovery (angle of attack has decreased to the point of no stall 
warning).

20. Replace Paragraph 29.d.(3)(iii) With the Following

    (iii) In addition, for turning flight stalls, apply the 
longitudinal control to achieve airspeed deceleration rates up to 3 
knots per second. The intent of evaluating higher deceleration rates is 
to demonstrate safe characteristics at higher rates of increase of 
angle of attack than are obtained from the 1 knot per second stalls. 
The specified airspeed deceleration rate, and associated angle of 
attack rate, should be maintained up to the point at which the airplane 
stalls.

21. Replace Paragraph 29.d.(3)(iv) With the Following

    (iv) For those airplanes where stall is defined by full nose-up 
longitudinal control for both forward and aft c.g., the time at full 
aft stick during characteristics testing should be not less than that 
used for all speed determination. For turning flight stalls, however, 
recovery may be initiated once the pitch control reaches the aft stop 
when accompanied by a rolling motion that is not immediately 
controllable (provided the rolling motion complies with 
Sec. 25.203(c)).

22. Add the Following New Section to Paragraph 29.d.(3)

    (vi) In level wing stalls the bank angle may exceed 20 degrees 
occasionally, provided that lateral control is effective during 
recovery.

    Issued in Renton, Washington, on March 9, 1995.
Ronald T. Wojnar,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service, ANM-100.
[FR Doc. 95-14172 Filed 6-8-95; 8:45 am]
BILLING CODE 4910-13-M