[Federal Register Volume 63, Number 165 (Wednesday, August 26, 1998)]
[Proposed Rules]
[Pages 45628-45639]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-22751]



[[Page 45627]]

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Part V





Department of Transportation





_______________________________________________________________________



Federal Aviation Administration



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14 CFR Parts 91, 121, 135



Terrain Awareness and Warning System; Proposed Rule

  Federal Register / Vol. 63, No. 165 / Wednesday, August 26, 1998 / 
Proposed Rules  

[[Page 45628]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 91, 121, 135

[Docket No. 29312; Notice No. 98-11]
RIN 2120-AG46


Terrain Awareness and Warning System

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking.

-----------------------------------------------------------------------

SUMMARY: The Federal Aviation Administration (FAA) proposes to issue 
operating rules that would prohibit operation of turbine-powered U.S.-
registered airplanes type certificated to have six or more passenger 
seats, exclusive of pilot and copilot seating, unless that airplane is 
equipped with an FAA-approved terrain awareness and warning system 
(also referred to as an enhanced ground proximity warning system). This 
proposal would affect aircraft operated under parts 91, 121 and 135. 
Because operators under part 125 and operators of U.S.-registered 
airplanes under part 129 must comply with part 91, they would also have 
to meet this requirement. This change is needed because there have been 
several accident investigations and studies that have shown a need to 
expand the safety benefits of ground proximity warning systems to 
certain additional operations. In addition, these investigations and 
studies have shown that there is a need to increase the warning times 
and situational awareness of flight crews to decrease the risk of 
controlled flight into terrain accidents.

DATES: Comments must be received by November 24, 1998.

ADDRESSES: Comments on this notice should be mailed, in triplicate to: 
Federal Aviation Administration, Office of the Chief Counsel, 
Attention: Rules Docket (AGC-200), Docket No. 29312, 800 Independence 
Avenue, SW., Washington, DC 20591. Comments may also be sent 
electronically to the Rules Docket by using the following Internet 
address: [email protected]. Comments must be marked Docket No. 
29312. Comments may be examined in the Rules Docket in Room 915G on 
weekdays between 8:30 a.m. and 5:00 p.m., except on Federal holidays.

FOR FURTHER INFORMATION CONTACT: Manuel Macedo, Aircraft Engineering 
Division, AIR-100, Aircraft Certification Service, Federal Aviation 
Administration, 800 Independence Avenue, SW., Washington, DC 20591; 
Telephone: (202) 267-9566.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in this proposed 
rulemaking by submitting such written data, views, or arguments as they 
may desire. Comments relating to the environmental, energy, federalism, 
or economic impact that may result from adopting the proposals in this 
notice are also invited. Comments that provide the factual basis 
supporting the views and suggestions presented are particularly helpful 
in developing reasoned regulatory decisions. Communications should 
identify the regulatory docket number and be submitted in triplicate to 
the above specified address. All communications and a report 
summarizing any substantive public contact with FAA personnel 
concerning this rulemaking will be filed in the docket. The docket is 
available for public inspection both before and after the closing date 
for receiving comments.
    Before taking any final action on this proposal, the Administrator 
will consider all comments made on or before the closing date for 
comments, and the proposal may be changed in light of the comments 
received.
    The FAA will acknowledge receipt of a comment if the commenter 
includes a self-addressed, stamped postcard with the comment. The 
postcard should be marked ``Comments to Docket No. 29312.'' When the 
comment is received by the FAA, the postcard will be dated and returned 
to the commenter.

Availability of the Notice

    Any person may obtain a copy of this notice of proposed rulemaking 
(NPRM) by submitting a request to the Federal Aviation Administration, 
Office of Rulemaking, 800 Independence Avenue SW., Washington, DC 
20591, or by calling (202) 267-9677. Communications must identify the 
notice number of this NPRM. Persons interested in being placed on a 
mailing list for future FAA NPRM's should request a copy of Advisory 
Circular No. 11-2A, Notice of Proposed Rulemaking Distribution System, 
which describes application procedures.
    An electronic copy of this document may be downloaded using a modem 
and suitable communications software from the FAA regulations section 
of the Fedworld electronic bulletin board service (telephone: 703-321-
3339). Internet users may reach the FAA's web page at http://
www.faa.gov or the Federal Register's webpage at http://
www.access.gpo.gov/NARA/index.html for access to recently published 
rulemaking documents.

Background

    Beginning in the early 1970's, a number of studies looked at the 
occurrence of ``controlled flight into terrain'' (CFIT)-type accidents, 
where a properly functioning airplane under the control of a fully 
qualified and certificated crew is flown into terrain (or water or 
obstacles) with no apparent awareness on the part of the crew.
    Findings from these studies indicated that many such accidents 
could have been avoided if a warning device called a ground proximity 
warning system (GPWS) was used. As a result of these studies and 
recommendations from the National Transportation Safety Board (NTSB), 
in 1974 the FAA required all part 121 certificate holders (i.e., those 
operating large turbine-powered airplanes) and some part 135 
certificate holders (i.e., those operating large turbojet airplanes) to 
install Technical Standard Order (TSO) approved GPWS equipment 
(Secs. 121.360 and 135.153). (39 FR 44439, December 18, 1974).
    In 1978 the FAA extended the GPWS requirement to part 135 
certificate holders operating smaller airplanes: turbojet-powered 
airplanes with 10 or more passenger seats. These operators were 
required to install TSO-approved GPWS equipment or alternative ground 
proximity advisory systems that provide routine altitude callouts 
whether or not there is any imminent danger (Sec. 135.153). (43 FR 
28176, June 29, 1978). This requirement was considered necessary 
because of the complexity, size, speed, and flight performance 
characteristics of these airplanes. The GPWS equipment was considered 
essential in helping the pilots of these airplanes to regain altitude 
quickly and avoid what could have been a CFIT-type accident.
    Installation of GPWS's or alternative FAA-approved advisory systems 
was not required on turbo-propeller powered (turboprop) airplanes 
operated under part 135 because, at that time, the general consensus 
was that the performance characteristics of turboprop airplanes made 
them less susceptible to CFIT accidents. For example, it was thought 
that turboprop airplanes had a greater ability to respond quickly in 
situations where altitude control was inadvertently neglected, as 
compared to turbojet airplanes. However later studies, including 
investigations by the NTSB, analyzed CFIT accidents involving turboprop 
airplanes and found that many of these accidents could have been 
avoided if GPWS equipment had been used.

[[Page 45629]]

    Some of these studies also compared the effectiveness of the 
alternative ground proximity advisory system to the GPWS. GPWS was 
found to be superior in that it would warn only when necessary, provide 
maximum warning time with minimal unwanted alarms, and use command-type 
warnings.
    Based on these reports and NTSB recommendations, in 1992 the FAA 
amended Sec. 135.153 to require GPWS equipment on all turbine-powered 
airplanes with 10 or more passenger seats. (57 FR 9944, March 20, 
1992).

NTSB Recommendations

    Following the investigation of a CFIT accident south of Dulles 
International Airport on June 18, 1994, involving a Learjet 25D in 
which there were 12 fatalities, the NTSB recommended (Recommendation A-
95-35) that the FAA mandate that all turbojet-powered airplanes 
equipped with six or more passenger seats have an operating ground 
proximity warning system installed. That recommendation also made 
reference to an earlier, similar NTSB recommendation (Recommendation A-
92-055) resulting from a 1991 CFIT accident involving a Beechjet 400. 
Both planes were corporate jets flying under part 91 and were not 
required to have GPWS equipment installed.
    More recently, the NTSB issued Recommendation A-96-101, based on 
its investigation of a CFIT accident northeast of Cali, Colombia, on 
December 20, 1995, involving an American Airlines Boeing 757 airplane 
operating under part 121, which resulted in 159 fatalities. The NTSB 
recommended that the FAA examine the effectiveness of enhanced ground 
proximity warning equipment (described in the following section), and 
if found effective, require all transport-category aircraft to be 
equipped with this equipment. Although the accident airplane was 
equipped with the mandatory GPWS, the GPWS did not provide the warning 
in time for the crew to successfully avoid the mountainous terrain.

Terrain Awareness and Warning System (Enhanced Ground Proximity 
Warning System)

    Advances in terrain mapping technology have permitted the 
development of a new type of ground proximity warning system that 
provides greater situational awareness for flight crews. The FAA has 
approved certain installations of this type of equipment, known as the 
enhanced ground proximity warning system (EGPWS). However, in this 
NPRM, the FAA is using the broader term ``terrain awareness and warning 
system'' (TAWS) because the FAA expects that a variety of systems may 
be developed in the near future that would meet the improved standards 
being proposed in this NPRM.
    TAWS improves on existing systems by providing the flight crew 
automatic advanced aural and visual warning of impending terrain, much 
earlier warning, forward looking capability, and operability in landing 
configuration. These improvements provide more time for the flight crew 
to make smoother and gradual corrective action. These functions are 
more fully described under ``Functions and Approval of TAWS.''

Volpe National Transportation Systems Center Studies

    In recent years, the FAA commissioned several studies by DOT's 
Volpe National Transportation Systems Center (VNTSC) to examine the 
effectiveness of GPWS and EGPWS in preventing CFIT accidents in various 
aircraft categories and operations. These are described below.

Part 91 Study

    In 1996, the FAA commissioned VNTSC to consider the installation of 
current GPWS or EGPWS on all part 91 turbine-powered airplanes of 6 or 
more passenger seats. Although NTSB Recommendation A-95-35 addressed 
only turbojets, the FAA expanded the study focus to include all 
turbine-powered airplanes because of the results of the previous 
studies and rulemaking discussed earlier.
    Forty-four CFIT accidents that occurred between 1985 and 1994 were 
studied. The airplanes involved had from six to ten passenger seats and 
were operating under part 91. Eleven were turbojets and 33 were 
turboprops. Because these flights were not conducted under parts 121 or 
135, GPWS was not required and none of the airplanes had GPWS 
installed. By using computer modeling techniques, VNTSC came to the 
following conclusions: (1) GPWS meeting TSO-C92 could have avoided 33 
of the 44 (75%) accidents and 96 fatalities; and (2) EGPWS could have 
avoided 42 of the 44 (95%) accidents and 126 fatalities. The EGPWS 
evaluated in the Volpe studies would meet the TAWS requirements 
proposed in this NPRM. A more detailed analysis is included in FAA 
study DOT-TSC-FA6D1-96-01, Investigation of Controlled Flight Into 
Terrain, which is included in the public docket for this rulemaking, or 
can be obtained by contacting the Aircraft Engineering Division, AIR-
100, Aircraft Certification Service, Federal Aviation Administration, 
800 Independence Avenue, SW., Washington, DC 20591; Telephone: (202) 
267-9566.

Part 121/135 Study

    Later in 1996, the FAA commissioned VNTSC for a second study 
focusing on a retrofit of GPWS with EGPWS on airplanes operated under 
part 121 and part 135. This study documents an investigation of CFIT 
aircraft accidents involving aircraft flying under part 121 and 135 
flight rules, or their foreign equivalents, and evaluating the 
potential for accident prevention by EGPWS.
    There were over 100 fatal CFIT accidents worldwide during the study 
period of 1985 to 1995. A list of 47 domestic and 104 foreign accidents 
of aircraft with characteristics similar to those that would be covered 
by the proposed rule was compiled. Of these totals, 38 domestic 
accidents and 96 foreign accidents involved fatalities. Due to resource 
constraints, detailed analysis of all these accidents was not possible. 
The staff of the VNTSC developed a methodology and scheme for selecting 
a representative sample for detailed study and analysis. While not an 
exhaustive compilation of all CFIT accidents, it represents an effort 
to review the characteristics of most major CFIT accidents. From this 
process nine accidents were selected for detailed analysis worldwide.
    Analysis showed that four of the nine accidents (44%) should have 
been prevented by the basic GPWS equipment that had been installed. 
However, in two cases the GPWS equipment was either disconnected or it 
malfunctioned. In the other two cases, poor flight crew coordination 
led to inaction following the GPWS warning, rather than decisive 
recovery maneuvers, until impact could not be avoided.
    In contrast, EGPWS warning times would have been more than the 
warning time of GPWS (which was assumed by VNTSC to be 12-15 seconds) 
in all nine cases. In seven, warning times expected with EGPWS exceeded 
those of GPWS by over 20 seconds; two of these cases involved 
differences of over one minute. In general, EGPWS should have provided 
an additional margin in which flight crews could assess their 
situation, discover errors, regain situational awareness, and take 
appropriate action before impact. In only one case was an assumed EGPWS 
warning duration only slightly above the 12-15 second minimum. In this 
case it can be argued that if the visual forward looking terrain

[[Page 45630]]

display in EGPWS had been installed, it may have prevented the pilot's 
fatal wrong turn towards the mountains in the first place. Thus, it is 
reasonable to assume that EGPWS could probably have prevented all nine 
(100%) of these accidents.

VNTSC Conclusion: GPWS vs. EGPWS

    The VNTSC part 121/135 study credits GPWS as a significant factor 
in reducing the frequency of CFIT accidents since 1975. However, these 
accidents have not been totally eliminated for two major reasons:
    First, many of the GPWS systems currently in use are earlier 
generation systems, installed after the first GPWS rulemaking in the 
1970's. Since that time, GPWS equipment has been improved. These 
advances typically involve improvements in terrain detection logic that 
enables increased terrain warning durations in the order of 10-15 
seconds on average resulting in additional time for the pilot that can 
be crucial in preventing accidents. The NTSB addressed this issue by 
recommending to the FAA that early generation GPWS equipment be 
upgraded. (NTSB recommendations A-92-39 through A-92-42.)
    As a result, in 1996, the FAA revised TSO-C92b and issued TSO-C92c. 
Specifically, this new TSO added new requirements and features to GPWS: 
aural warnings that would identify the reason for GPWS warnings; the 
inclusion of airspeed in the logic that determines GPWS warning times; 
altitude callouts during nonprecision approaches; and warnings based on 
airport location and aircraft position data.
    Second, even with these added features, GPWS equipment has two 
important limitations: (1) GPWS does not have the capability to ``look 
forward,'' but instead only ``looks down,'' relying on radio altimeter 
data. For this reason, there is little or no warning if the terrain 
ahead of an airplane rises in a steep gradient. This limitation is 
known as the ``vertical cliff'' limitation. (2) To prevent nuisance 
ground proximity warnings during final approach, for an aircraft in 
stabilized descent on a non-precision approach (i.e., one in which 
lateral, but not vertical or glide slope, guidance is provided), with 
gear and flaps extended, all GPWS warning modes are desensitized. Thus 
a flight crew will receive no warning if their aircraft is not in fact 
lined up with a runway. This limitation is known as the ``non-precision 
approach (NPA) trap'' limitation.
    In its conclusion, the VNTSC states that there is compelling 
evidence of the potential effectiveness of EGPWS in preventing CFIT 
accidents. EGPWS would have provided the same or increased warning 
durations over GPWS had each aircraft continued along the accident 
track, and should have provided sufficient warning to effectively 
prevent all nine cases studied. The study emphasized that the CFIT 
accident prevention in all cases would have resulted not so much from 
increased warning durations following system detection of terrain 
threats, as from the fact that flight crews, given a continuous terrain 
display, would have perceived these terrain threats and responded to 
them well before EGPWS was required to generate warnings.
    Elaborating further, the study states that the continuous terrain 
display feature of EGPWS may be even more important than the terrain 
threat detection/alert/warning features in breaking the chain of 
decisions leading to CFIT. Flight crews lacking visual perspective are 
given a continuous display of nearby terrain, greatly heightening 
situational awareness. Rather than a ``last ditch'' warning of imminent 
danger, the continuous terrain display would allow crews to maneuver to 
avoid terrain long before it ever becomes an obstruction to their 
flight path. It thus represents a pivotal advance in providing flight 
crew terrain awareness.
    The FAA agrees that the terrain situation awareness display is a 
valuable function and therefore proposes to mandate its use. However, 
the alerting functions also are critical. Because of the various 
piloting duties, functions and activities, a pilot does not monitor one 
instrument 100% of the time, and this will be the case with a terrain 
situation awareness display. The alerting functions provide the final 
safety margin that directs the pilot to take life-saving action.
    While recognizing the terrain awareness benefits of the terrain 
display, the VNTSC study also recognizes that such a display may 
present a new set of challenges to pilots. The TAWS's topographical map 
display will offer a temptation for pilots to use it for navigational 
purposes. Pilot training should emphasize that other aircraft systems 
are intended for this purpose, and any TAWS terrain display features 
are intended only to provide terrain awareness, not for aerial 
navigation. See also Notice N8110.64, Enhanced Ground Proximity Warning 
System, which provides guidance on EGPWS and specifies that Airplane 
Flight Manuals should state that EGPWS shouldn't be used for 
navigational purposes.
    In light of the potential savings of human life and the economic 
costs of destroyed or damaged aircraft, the report recommends that the 
FAA amend 14 CFR parts 121 and 135 to require mandatory installation in 
affected aircraft fleets of TAWS. A more detailed discussion and 
analysis is included in FAA study DOT-TSC-FA6D1-96-03, Investigation of 
Controlled Flight Into Terrain (For Selected Aircraft Accidents 
Involving Aircraft Flying Under FAR Parts 121 and 135 Flight Rules and 
the Potential for Their Prevention by Enhanced Ground Proximity Warning 
System (EGPWS)).

Functions and Approval of TAWS

Functions of TAWS

    Recent technological advancements--such as more precise navigation 
systems, increased computer memory storage and better display 
technology--have allowed the development of terrain alerting and 
warning systems. Current systems under development have three common 
features: (1) Use of airplane position information from the airplane's 
navigation system(s), (2) an onboard terrain data base, and (3) a means 
of displaying the surrounding terrain. All systems currently under 
development function in the following same manner. Airplane position 
information from the airplane navigation system is fed to the TAWS 
computer. The TAWS computer compares the airplane's current position 
and flight path with the terrain data base also in the TAWS computer. 
If there is a potential threat of collision with terrain, the TAWS 
computer sends warning alerts to the airplane's audio system. The TAWS 
computer also inputs display data to either the weather radar, the 
Electronic Flight Information System (EFIS) or some other display 
screen on which then is shown the surrounding terrain with the threat 
terrain highlighted. Specific certification requirements for the TAWS 
is contained in TSO-C151.
    An example of a specific TAWS currently certificated by the FAA 
handles the above functions as follows:
(1) Alerting Times
    The function of the new proposed TAWS standard is to prevent CFIT 
by providing alerting times earlier than those provided by existing 
ground proximity warning systems manufactured in accordance with 
Technical Standard Order (TSO)-C92c. Typically GPWS aural and visual 
warnings occur about 20 seconds or less before potential impact with 
terrain.

[[Page 45631]]

The visual warning is usually a blinking light and the aural warning is 
usually a message through the airplane's audio system.
    Studies indicate that average combined pilot and aircraft reaction 
time to avoid a CFIT after warning is within the 12 to 15 second range. 
The FAA has approved for installation a TAWS (the EGPWS) that provides 
an initial alert approximately 60 seconds before potential impact and 
another alert about 30 seconds before potential impact. These alerts 
are both aural and visual. These alerting times were based on data from 
actual CFIT accidents and were chosen by the manufacturer as the best 
compromise to provide timely alerts while still minimizing nuisance 
alarms. Human factors research and FAA experience show that, if an 
aural cockpit alarm sounds too often as a false alarm, the flight crew 
will either begin to ignore it or will be tempted to disable the 
system. Therefore, while the forward looking capability of TAWS could 
provide an alert far in advance of potential impact, the alerting time 
must be as short as possible, while still allowing an adequate time to 
avoid impact. The FAA will carefully evaluate the alerting times for 
each proposed TAWS, but expects that manufacturers will provide at 
least 20 seconds in advance of a potential impact.
(2) Forward Looking Capability
    The increased alerting function is made possible by a ``forward 
looking'' feature. This function in turn is made possible by inputting 
aircraft position from the global positioning system (GPS) or a flight 
management system (FMS) into the TAWS computer in which a terrain 
database is already stored. Using aircraft position, performance and 
configuration data, the TAWS computer calculates an envelope along the 
projected flight path of the aircraft and compares that to the terrain 
database. If there is a potential impact with terrain, the system 
provides appropriate aural and visual alerts. This feature also makes 
possible a terrain (situational) awareness display that could be used 
on a dedicated TAWS display screen, a weather radar, or an EFIS display 
screen. Terrain within certain vertical distances of the aircraft is 
displayed in various color densities. The FAA would accept green, 
yellow and red because these are the colors currently available on the 
weather radar display.
(3) Terrain Clearance Floor
    TAWS also provides a terrain clearance floor that adds an 
additional element of protection to the GPWS warning modes. The terrain 
clearance floor creates an increasing terrain clearance envelope around 
the intended airport runway directly related to the distance from the 
runway. The terrain clearance floor alerts are based on aircraft 
location, nearest runway center point position, and radio altitude. The 
terrain clearance floor provides an alert based on insufficient terrain 
clearance even when in landing configuration. This is an improvement 
over the current GPWS, which becomes deactivated when an airplane's 
wing flaps and landing gear are in landing configuration.
    If an airport has glide-slope equipment that is operating, the 
flight crew can rely on that equipment to guide the airplane; the TAWS 
terrain clearance floor function may not be needed. However, if the 
airport does not have glide-slope equipment or it is not operating, the 
flight crew must perform a non-precision approach. In this case, if the 
flight crew is unaware of its location and comes in too low or too 
soon, the terrain clearance floor function would generate an aural 
alarm.

Approval of TAWS

    Currently, the FAA approves the manufacture and installation of 
Ground Proximity Warning Systems through Technical Standard Orders. 
Sections 121.360 and 135.153 require the use of GPWS meeting TSO-C92, 
which has been reissued as TSO-C92a, TSO-C92b, and TSO-C92c. The FAA 
does not intend to revise TSO-C92c to include TAWS requirements.
    Instead, the FAA is developing and will issue a new and separate 
TSO for TAWS. The new TSO-C151, Terrain Awareness and Warning System, 
is being developed through the FAA TSO process which allows for public 
comments. Any person desiring to review and comment on the draft TSO-
C151 may obtain a copy of the draft TSO-C151 from the person mentioned 
in the section entitled FOR FURTHER INFORMATION CONTACT. This TSO would 
be the means to obtain FAA approval of the TAWS product. The FAA also 
will develop and issue a TAWS advisory circular (AC). This AC would 
describe an acceptable means of obtaining FAA installation approval. 
Notice 8110.64, Enhanced Ground Proximity Warning System (EGPWS) is the 
current interim guidance to be used for the installation and approval 
of TAWS. The FAA has issued a policy statement that states that the 
contents of Notice 8110.64 shall remain valid until the TSO and AC are 
published.
    An applicant that meets the proposed requirements of TSO-C151 also 
will be entitled to a TSO-C92c authorization, if requested, with a TSO-
C151 authorization. The performance and environmental standards of TSO-
C92c are included within TSO-C151. Any equipment bearing a TSO-C151 
label will meet the requirements of FAR part 121.360 and 135.153.

The Proposal

    The FAA is proposing to add Secs. 91.223, 121.354, and 135.154 to 
require the installation of FAA-approved terrain awareness and warning 
systems (TAWS). The FAA is also proposing to amend Secs. 121.360 and 
135.153 to add an expiration date of four years after the effective 
date of the final rule for the use of current GPWS systems, thereafter, 
compliance with those sections would not be allowed in lieu of the 
provisions proposed herein.
    For operations under part 121 the proposed rule would apply to all 
turbine-powered airplanes. For all other operations (parts 91, 125, 
129, and 135) the proposed rule would apply to all turbine-powered 
airplanes type certificated to have six or more passenger seats, 
excluding any pilot seat. The FAA proposes that, beginning one year 
after the effective date of the final rule, U.S.-registered airplanes 
manufactured after that date be equipped with TAWS. The FAA also 
proposes that existing turbine-powered airplanes be equipped with TAWS 
within four years after the effective date of the final rule. This 
requirement for existing airplanes would apply to all airplanes 
manufactured on or before one year after the effective date of the 
final rule. (For more discussion of the compliance dates and how they 
were chosen, see the Regulatory Evaluation Summary later in this 
preamble.)
    The proposal would therefore ensure that all applicable airplanes 
operated under parts 91, 121, and 135 have the most up-to-date and 
effective equipment needed to help prevent CFIT accidents. The proposal 
would also ensure that operators under part 125 and operators of U.S.-
registered airplanes under part 129, who must also comply with part 91, 
are similarly equipped in order to prevent CFIT accidents.
    The FAA is also proposing that operators include in their Airplane 
Flight Manuals the appropriate procedures for operating and responding 
to the audio and visual warnings of TAWS.
    The FAA is not proposing changes to current training requirements 
in this NPRM. However recent new training requirements on crew resource 
management (CRM) for flight crewmembers should provide additional

[[Page 45632]]

safeguards in conjunction with the use of TAWS. This requirement will 
apply to flight crewmembers operating under parts 121 and 135 and will 
take effect on March 19, 1998. (60 FR 65940, December 20, 1995).
    The proposed rule would apply only to turbine-powered airplanes. 
The FAA specifically requests comments on whether it should require the 
installation of TAWS on reciprocating engine-powered airplanes. What 
would be the impact on safety of such a requirement? Are there 
technical reasons why TAWS is or is not appropriate for reciprocating 
engine-powered airplanes? Should TAWS be required for reciprocating 
engine-powered airplanes of a certain size? The FAA will study data and 
information submitted by commenters in response to these questions 
before making a determination as to whether TAWS should be required for 
reciprocating engine-powered airplanes. If the decision is made to 
require TAWS on reciprocating engine-powered airplanes it will be 
addressed in a separate rulemaking.

Impact of the Proposed Rule

    The impact of the proposed rule on operations under parts 91, 121, 
and 135 would be similar to the impact of the installation of TAWS on 
newly manufactured airplanes, i.e., installation would be required 
beginning one year after the effective date of the final rule. Because 
operators under part 125 and operators of U.S.-registered airplanes 
under part 129 must comply with part 91, they would also have to meet 
this requirement.
    The requirement for TAWS on existing airplanes would impact 
operators under the affected parts differently. Those operators under 
part 91 (including operators under part 125 and operators of U.S.-
registered airplanes under part 129) who are currently not required to 
have GPWS would, in most cases, be required to install TAWS within the 
four year compliance period. In those cases where GPWS was previously 
installed on a voluntary basis, operators would also be required to 
retrofit their airplanes with TAWS within four years. Retrofits would 
also apply in cases where part 125 operators lease part 121 airplanes 
that are already equipped with GPWS.
    For existing airplanes under parts 121 and 135, which currently 
must have GPWS, operators would be required to retrofit their airplanes 
to install TAWS within four years. It should also be noted that the 
proposed rule adds to the existing part 135 requirement by requiring 
TAWS on an additional group of airplanes: those type certificated to 
have six to nine passenger seats, excluding any pilot seat. The current 
rule requires GPWS for airplanes with 10 or more seats under part 135. 
If the operators of this group of airplanes have not already installed 
EGPWS voluntarily, the proposed rule would require a new installation 
of TAWS. The FAA acknowledges that this proposal may require the 
retrofit of aircraft that are equipped with current generation GPWS. 
For example, the 1992 rule discussed earlier, required GPWS on all 
turbine-powered airplanes with 10 or more passenger seats. The FAA 
specifically requests comment on the requirement for TAWS for such 
airplanes. (e.g. Should the retrofit be required only in airplanes 
carrying more than a certain number of passengers?)

Regulatory Evaluation Summary

    Proposed changes to Federal regulations must undergo several 
analyses. First Executive Order 12866 directs that each Federal agency 
shall propose or adopt a regulation only upon 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 effect of regulatory changes on small entities. Third, the 
Office of Management and Budget directs agencies to assess the effects 
of regulatory changes on international trade. Finally, the Unfunded 
Mandates Reform Act of 1995 requires that agencies assess the impact of 
regulatory changes on State, local tribal governments and private 
sector. In conducting these analyses, the FAA has determined that this 
rule: (1) Would generate benefits that justify its costs and is a 
``significant regulatory action'' as defined in the Executive Order; 
(2) is significant as defined in DOT's Regulatory Policies and 
Procedures; (3) would have a significant impact on a substantial number 
of small entities, (4) would not constitute a barrier to international 
trade, and (5) would not impose a significant intergovernmental mandate 
on State, local or tribal governments.

Costs and Benefits for Airplanes Operated Under 14 CFR Part 121

    Under the assumption that in-service airplanes must be equipped 
with a terrain awareness and warning system by January 1, 2003 (four 
years after an assumed effective date of December 31, 1998), the FAA 
estimates that approximately 6,000 in-service airplanes operating under 
14 CFR part 121 would be affected by the proposed rule. In addition, 
the proposal would impact approximately 400 newly manufactured turbojet 
and turboprop transports delivered to part 121 air carriers per year. 
These estimates--which are based on Aircraft Registry records, 
insurance data, and proprietary forecasts--do not account for voluntary 
installations of TAWS equipment. Overall, the FAA projects that 
approximately 1,100 airplanes operating under 14 CFR part 121 would be 
equipped with TAWS by the year 2002 in the absence of any requirement. 
Adjusting these estimates to account for voluntary installations, 
however, would not significantly affect the conclusions since the 
effect would be roughly proportional on both total benefits and costs.
    The FAA approves TAWS installations either through Supplemental 
Type Certificates issued to an applicant other than the airframe 
manufacturer; or, in the case of the manufacturer, either a STC or a 
FAA-approved type-design change. Discussions with industry indicate 
that a typical first-of-type certification program would cost 
approximately $79,000 for a part 121 turbojet airplane model and 
$37,000 for a part 121 turboprop airplane model. These costs include 
FAA engineering and administrative costs. First-of-type STC's would 
then be amended to cover additional model-variants. The FAA estimates 
that such amendments, also called ``follow-ons,'' could be developed at 
a cost of approximately $67,000 for turbojets and $26,000 for 
turboprops (again, inclusive of FAA costs).
    Accurately estimating the number of STC's required by the proposed 
rule is problematic since flight deck equipment may differ between 
operators of the same model-variant. For example, several different 
approvals may be required for different, say, B737-400's depending on 
the equipment options selected by the various operators. This analysis 
assumes 68 first-of-type certification programs and 84 follow-on 
programs. It should be noted that, even when multiple firms perform 
retrofits on a particular model-variant, the FAA would not necessarily 
require multiple certification or follow-on programs: in practice, only 
the first entity would incur full STC development costs. Subsequent 
firms could then purchase the STC incurring incremental expenses 
associated with ground and flight testing.
    The FAA estimates that total STC costs (including follow-ons) for 
14 CFR part 121 operators would be approximately $8.4 million, or $7.1 
million at present value (assuming that STC expenses are uniformly 
distributed

[[Page 45633]]

during the period 1999-2000, and that the discount rate is 7%).
    Since ground proximity warning systems are already required for 
part 121 operators, equipment and installation costs associated with 
this proposal would include: (1) For newly manufactured airplanes, the 
difference in cost between current generation GPWS and TAWS, and, (2) 
for in-service airplanes, the cost of removing the existing ground 
proximity warning system and replacing it with TAWS (net the rebate 
value of the GPWS equipment). Since GPWS and TAWS units are 
approximately the same weight, and since TAWS requires no more 
maintenance than GPWS, incremental part 121 operating and maintenance 
costs associated with the proposed rule are negligible.
    Retrofit costs depend on the type of equipment already in use in an 
affected airplane. Differences in costs can be ascribed to the relative 
trade-in values of various vintages of GPWS units and the fact that, in 
some cases, GPWS includes an integral windshear detection system. (In 
some cases, operators may be forced to replace both the GPWS and 
windshear detection systems. The analysis accounts for this additional 
cost where applicable.) Unit (i.e. per airplane) retrofit costs can be 
summarized as follows: (1) In-service turbojet airplanes equipped with 
early-generation GPWS--$59,480, (2) in-service turbojet airplanes 
equipped with current-generation GPWS--$64,980, (3) newly manufactured 
turbojet airplanes--$12,000, (4) in-service 30+ passenger turboprop 
airplanes equipped with early-generation GPWS--$59,480, (5) in-service 
30+ passenger turboprop airplanes equipped with current-generation 
GPWS--$57,280, (6) newly manufactured 30+ passenger turboprop 
airplanes--$12,000, (7) in-service less-than-30-seat turboprop 
airplanes--$20,600, (8) newly manufactured less-than-30-seat turboprop 
airplanes--$2,000.
    These unit costs include: TAWS system costs, installation kit 
costs, installation labor costs, an adjustment for spares and simulator 
installations (assumed to be 10% of TAWS systems costs), and 
adjustments for additional navigation equipment and displays required 
in some aircraft. Aside from the provision for simulator units, 
incremental training costs are assumed to be negligible. The FAA 
invites comment on these cost assumptions.
    The FAA estimates that TAWS equipment and installation costs for 
the affected in-service 14 CFR part 121 fleet would be approximately 
$361.5 million, or $297.0 million at present value. Total equipment and 
installation costs for newly manufactured airplanes delivered to part 
121 air carriers during the ten year forecast period 1999-2008 would be 
approximately $47.5 million, or $31.3 million at present value. 
Therefore, total part 121 costs--including certification costs, 
retrofit costs, and incremental TAWS costs for newly manufactured 
airplanes delivered between 1999 and 2008--would be approximately 
$408.9 million, or $328.3 million at present value.
    The benefits of TAWS again depend on the type of GPWS unit it would 
replace. The risk reduction potential of TAWS when measured against an 
early-generation GPWS system, for example, is higher than the risk 
reduction potential measured against a current-generation system. Risk 
reduction estimates for various combinations of airplane types and GPWS 
vintages are based on analyses of eight CFIT accidents involving 14 CFR 
part 121 air carriers (this includes two part 135 air carriers now 
required to operate under 14 CFR part 121) which occurred during the 
ten-year period 1986-1995. The analyses--conducted by the Volpe 
National Transportation Systems Center and referred to earlier in the 
preamble--took into consideration, among other things, the type of GPWS 
equipment (if any), on-board at the time of the accident, and the 
relative effects of current-generation GPWS versus TAWS. On the basis 
of the Volpe results, the FAA estimates the following rates of CFIT 
risk reduction: (1) Turbojet airplanes equipped with early-generation 
GPWS--0.079 averted accidents per million flight hours, (2) turbojet 
airplanes equipped with current-generation GPWS--0.048 averted 
accidents per million flight hours, (3) 30+ passenger turboprop 
airplanes equipped with early-generation GPWS--0.079 averted accidents 
per million flight hours, (4) 30+ passenger turboprop airplanes 
equipped with current-generation GPWS--0.048 averted accidents per 
million flight hours, (5) less-than-30-seat turboprop airplanes--0.118 
averted accidents per million flight hours.
    Estimates of lifecycle benefits were calculated on a per-airplane 
basis and summed over all affected part 121 airplanes to obtain an 
estimate of the expected fleet benefits. The calculations took into 
consideration: (1) The passenger capacity of each airplane, (2) average 
load factors for various types of operations, (3) the number of flight 
crew, (4) the probability of fatalities given a CFIT accident, (5) the 
expected value of the airplane at the time of accident, and (6) the 
expected remaining service life of the airplane.
    The FAA estimates that total lifecycle benefits for the affected 14 
CFR part 121 fleet (including the lifecycle benefits accruing to newly 
manufactured airplanes delivered during the period 1999-2008) are 
approximately $5.9 billion, or $2.1 billion at present value. 
Therefore, the ratio of discounted benefits to discounted costs is 
approximately 6.5 to 1.0.
    Three of the eight preventable part 121 CFIT accidents occurred 
during international operations of U. S. carriers. The FAA evaluated 
the benefits and costs of lesser requirements on operators conducting 
only domestic flights. This analysis, however, showed substantial 
benefits associated with the TAWS requirement for in-service airplanes 
flying only domestic routes. (See the Preliminary Regulatory 
Evaluation, Section VII ``Analysis of Alternatives.'')

Costs and Benefits for Airplanes Operated Under 14 CFR Part 135

    The FAA estimates that approximately 1,100 in-service airplanes 
operating under 14 CFR part 135 would be affected by the proposed rule. 
Approximately 800 of these are 10-30 seat airplanes that are currently 
required to have GWPS, and 300 are 6-9 seat turbojets and turboprops 
currently not required to have GPWS. In addition, the rule would affect 
approximately 500 new turbojet and turboprop airplanes delivered to 
part 135 air carriers during the period 1999-2008. The FAA is not aware 
of any large scale efforts to voluntarily equip part 135 airplanes with 
terrain awareness and warning systems.
    The FAA estimates that total certification costs for typical 14 CFR 
part 135 turbojet and turboprop airplane models would be approximately 
$28,000 and $20,000, respectively. An estimate of total part 135 
certification costs, then, is obtained by multiplying the per-
certification costs by an estimate of the total number of 
certifications required. As in the analysis of part 121, predicting the 
number of required STC's for part 135 is problematic owing to potential 
differences between and within airplane model-variants. In some cases, 
more than one TAWS STC may be required per model, in other cases, one 
STC may cover more than one model. The FAA estimates that approximately 
50 turbojet STC's and 32 turboprop STC's would be required to retrofit 
the affected part 135 fleet. Therefore, total fleet certification costs 
are approximately $2.1 million, or $1.8 million at present value 
(again,

[[Page 45634]]

assuming that certification costs are uniformly distributed during the 
period 1999-2000 and that the discount rate is 7%).
    As noted earlier, the incremental costs (and benefits) of the rule 
depend in part on the type of GPWS equipment already in service. 
Operators who already have GPWS equipment, for example, would incur no 
additional operating or maintenance costs. In the absence of detailed 
information on which particular airplanes have or do not have GPWS, the 
FAA assumes that all airplanes are in compliance with current Federal 
Aviation Regulations--but do not exceed those requirements (that is, 
there is no adjustment made for voluntary GPWS installations). Thus, it 
is assumed that all 6-9 passenger seat turbine engine airplanes are not 
equipped with any type of ground proximity warning system.
    Unit equipment and installation costs for affected part 135 
airplanes are as follows: (1) In-service turbojet airplanes seating 6-9 
passengers--$27,950, (2) newly-manufactured turbojet airplane seating 
6-9 passengers--$26,475, (3) in-service turbojet airplanes seating 10 
or more passengers--$24,300, (4) newly manufactured turbojet airplanes 
seating 10 or more passengers--$7,000, (5) in-service turboprop 
airplanes seating 6-9 passengers--$30,150, (6) newly-manufactured 
turboprop airplanes seating 6-9 passengers--$28,575, (7) in-service 
turboprop airplanes seating 10 or more passengers--$24,300, (8) newly 
manufactured turboprop airplanes seating 10 or more passengers--$7,000. 
(Recall that GPWS is already required for 10-30 seat airplanes. 
Therefore, incremental TAWS cost for newly manufactured airplanes in 
this group equal the difference in cost between TAWS and basic GPWS.) 
As before, these costs include: TAWS equipment costs, installation kit 
costs, GPS and display costs, and an adjustment for a radar altimeter 
(not present on some aircraft).
    As noted above, incremental operating and maintenance costs are 
only associated with airplanes lacking GPWS equipment--by assumption 
airplanes seating 6-9 passengers. The FAA estimates that the weight of 
an average TAWS installation would be approximately 9 pounds for a 
turbojet airplane and 8 pounds for a turboprop airplane. Annual 
maintenance costs are approximately 5% of TAWS equipment costs, 
therefore annual incremental operating (fuel consumption) and 
maintenance costs equal $870 and $936 for 6-9 passenger turbojet and 
turboprop airplanes, respectively.
    Total lifecycle costs for the affected 14 CFR part 135 fleet--
including certification, equipment, installation, operating and 
maintenance costs--would be approximately $45.2 million, or $30.8 
million at present value. Again, this total includes projected 
lifecycle costs for newly manufactured 6+ seat turbojet and turboprop 
airplanes delivered to part 135 operators between 1999 and 2008.
    Following the procedure discussed under part 121, the estimated 
benefits for 14 CFR part 135 operations are a function of airplane 
seating capacity, load factors, annual flight hours, GPWS equipage, 
etc. Again, expected TAWS benefits for any particular airplane depend 
on whether or not the airplane already has GPWS and, if it does, the 
vintage of system installed. Risk reduction estimates are as follows: 
(1) Turbojet airplanes seating 6-9 passengers--0.861 accidents averted 
per million flight hours, (2) turbojet airplanes seating 10 or more 
passengers--0.036 accidents averted per million flight hours, (3) 
turboprop airplanes seating 6-9 passengers--2.310 accidents averted per 
million flight hours, (4) turboprop airplanes seating 10 or more 
passengers--0.091 accidents averted per million flight hours. For 
airplanes with 6-9 seats, risk estimates are based on analyses of 
approximately 40 accidents involving turbojet and turboprop airplanes 
operating under 14 CFR part 91. For airplanes with 10-30 seats, risk 
estimates are based on the service experience of similar airplanes 
operated under 14 CFR part 121. (At the time of this writing, the FAA 
has asked the Volpe center to review the part 135 CFIT accident data 
from the original study
    Based on these results, the FAA projects that TAWS benefits--that 
is the value of reduced CFIT risks--for 14 CFR part 135 operators would 
be approximately $84.4 million, or $38.2 million at present value 
(including benefits accruing to affected part 135 airplanes delivered 
between 1999 and 2008). Therefore, the ratio of discounted benefits to 
discounted costs would be approximately 1.24 to 1.0.
    The FAA notes that in the case of airplanes carrying fewer numbers 
of passengers, there is a clear overall net benefit in requiring TAWS 
to replace early generation GPWS. While relative benefits are lower for 
smaller aircraft that have only recently been retrofitted with current 
generation GPWS, excepting such airplanes could create a situation 
where the FAA would require more sophisticated equipment for 
noncommercial aircraft as compared with some commercial aircraft.

Costs and Benefits for Airplanes Operated Under 14 CFR Part 91

    Affected 14 CFR part 91 airplanes, for the purpose of this 
analysis, are defined as a residual--i.e. the total affected fleet of 
U.S. registered turbine powered airplanes minus the affected 14 CFR 
parts 121 and 135 fleets. The part 91 residual includes general 
aviation aircraft (corporate, business, personal, instruction, aerial 
application, and other), large airplanes (having a seating capacity of 
20 or more or a maximum payload capacity of 6,000 pounds or more) 
operating under 14 CFR part 125, and U.S. registered airplanes 
operating under 14 CFR part 129. Under this simple residual approach, 
the FAA estimates that approximately 5,500 turbojet airplanes and 5,700 
turboprop airplanes (not operating under 14 CFR parts 121 and 135) 
would be affected by the proposed rule. The FAA estimates that an 
additional 220 newly manufactured turboprops and 120 newly manufactured 
turbojets would be affected annually.
    The FAA estimates that the proposed rule would require 
approximately 57 STC's at a total cost of $1.3 million, or $1.1 million 
at present value (assuming that certification costs are uniformly 
distributed over the period 1999-2000, and that the discount rate is 
7%).
    Per airplane equipment and installation costs would be 
approximately $27,950 and $30,150 for typical in-service turbojet and 
turboprop airplanes, respectively. TAWS equipment and installation 
costs for newly manufactured airplanes--approximately $26,475 per 
turbojet airplane and $28,575 per turboprop airplane--are slightly 
lower reflecting lower installation costs.
    Annual incremental operating and maintenance costs would be 
approximately $870 for turboprop airplanes and $936 for turbojet 
airplanes. Total lifecycle costs for the affected (residual) 14 CFR 
part 91 fleet, then, are approximately $642.9 million, or $415.3 
million at present value. As in the analyses of 14 CFR parts 121 and 
135, cost estimates include lifecycle costs for in-service airplanes 
and newly manufactured airplanes delivered between 1999 and 2008.
    Estimates of the benefits accruing to part 91 operators are based 
on the Volpe accident analyses (discussed above). Of the 44 accidents, 
11 involved turbojets and 33 involved turboprops. Probable cause, as 
determined by NTSB, was pilot error in all cases--principally through 
failure to maintain proper altitude, use of improper instrument flight 
rules or visual flight rules

[[Page 45635]]

procedures, or poor planning/decision-making. Volpe analyses determined 
that current technology ground proximity warning systems could have 
prevented 33 of the 44 accidents. On the other hand, TAWS could have 
prevented 42 of the 44 accidents; 11 turbojet airplane accidents and 31 
turboprop airplane accidents. On the basis of the accident history, the 
FAA estimates that TAWS would prevent 2.46 turboprop airplane accidents 
per million flight hours and 0.86 turbojet airplane accidents per 
million flight hours. This translates to fleet benefits of 
approximately $1.5 billion, or $663 million at present value. 
Therefore, the ratio of discounted benefits to discounted costs is 
approximately 1.6 to 1.0.
    The FAA invites comment on these estimates. Comments should include 
details such as: (1) Alternative cost assumptions, (2) alternative 
aircraft population forecasts, (3) the extent of voluntary industry 
action, etc.

Analysis of Alternatives

    The FAA concludes that this NPRM is a significant regulatory action 
based on the proposal's expected cost, its potential impact on safety, 
and the extent of public interest in this issue. For matters determined 
to be significant, Executive Order 12866 requires ``an assessment, 
including the underlying analysis, of costs and benefits of potentially 
effective and reasonably feasible alternatives to the planned 
regulation.'' Accordingly, the FAA has considered regulatory options to 
identify the least intrusive and most cost-effective means of achieving 
the goal of reducing the probability of CFIT accidents.
    The alternatives considered fall under two general groupings: (1) 
require different levels of TAWS or GPWS technologies for different 
subsegments of the regulated population, and (2) impose different 
compliance deadlines on different subsegments of the regulated 
population.

Different Levels of TAWS or GPWS for Different Subsegments of the 
Regulated Population

    One group of alternatives consists of options that would require 
different levels of TAWS or GPWS technologies for different subsegments 
of the regulated population (including the option of not requiring GPWS 
or TAWS equipment at all). There are three broad classifications of 
TAWS/GPWS technologies: (1) Early-generation GPWS, (2) current-
generation or upgraded GPWS (with improved capabilities and a lower 
probability for nuisance warnings), and (3) TAWS. It is possible to 
identify several regulatory alternatives, then, based on these 
technology levels.
    One alternative would be to exclude certain types of airplanes or 
operators from a TAWS or GPWS requirement altogether. Based on its 
evaluation of benefits and costs, the FAA does not consider this to be 
the best option. Excluding operators of 6-9 seat airplanes, for 
example, would run contrary to a significant body of analyses--by the 
DOT, FAA and NTSB--that indicates that a TAWS requirement would result 
in substantial reductions in CFIT casualties and property losses.
    Another alternative would be to require GPWS without regard to 
technology. Under this option, any vintage of GPWS--even the oldest 
systems--would be compliant. Approximately 95% of the world's 
commercial airline fleet are equipped with some form of ground 
proximity warning system. Also, anecdotal evidence suggests that there 
are some other, non-air carrier operators who have voluntarily 
installed GPWS. This alternative, therefore, would primarily affect 
general aviation operators and commercial operators of 6-9 seat turbine 
powered airplanes. There are two drawbacks to this option. First, a 
detailed analysis shows that the greatest potential for CFIT fatality 
reductions is produced by requiring TAWS in commercial airplanes that 
are already equipped with GPWS. For 14 CFR part 121, for example, TAWS 
is expected to reduce the accident rate by up to 0.079 per million 
flight hours. The FAA's analysis of part 135 carriers--most of whom 
already have current generation GPWS technology--also shows that 
significant benefits, which more than justify the costs, can be 
realized by requiring TAWS retrofit. Second, this option would 
effectively force on-demand air taxi and other general aviation 
operators to a higher standard than that required for the largest 
commercial carriers. This follows since early generation GPWS systems 
are no longer being produced for installation in the United States. 
This option would therefore require small operators to install upgraded 
GPWS or TAWS while many part 121 operators could legally continue to 
use technology developed over 20 years ago.
    A third alternative would be to require current technology GPWS 
only. This alternative would also reduce the number of affected 
airplanes. The FAA estimates that approximately 3,200 airplanes 
operating under 14 CFR part 121, and 1,100 airplanes operating under 14 
CFR part 135 already have upgraded GPWS equipment (or will have such 
equipment by the projected effective date of the proposed rule). Under 
this alternative, these airplanes would not require retrofit. In 
addition, incremental costs associated with the purchase of newly 
manufactured airplanes would be zero for part 121 operators and many 
part 135 operators. (Again, this follows since early generation GPWS 
units are no longer being produced for installation in the United 
States.) Limiting the requirement to upgraded GPWS would also 
marginally reduce compliance costs for some affected operators since 
upgraded GPWS would be less expensive than TAWS in some cases. A 
variant of this alternative would be to except smaller aircraft that 
may have been required to, or have voluntarily been equipped with 
current generation GPWS. The FAA concludes, however, that this 
exception may result in requiring more sophisticated equipment on 
certain noncommercial aircraft relative to some commercial aircraft.
    There are safety and cost-effectiveness concerns with this 
alternative. It clearly provides a lower level of safety than the 
proposed rule; moreover, although this option is substantially cheaper 
than the proposed rule, ironically its costs do not justify its 
benefits for some types of operations. For example, in some cases the 
limited risk reduction potential would not justify replacing early-
generation GPWS with upgraded current-generation systems. For airplanes 
that currently lack any GPWS, the FAA concludes that requiring only 
upgraded GPWS is a suboptimal strategy based on the relatively small 
difference in cost between upgraded GPWS versus TAWS combined with the 
relatively large differential in risk reduction potential between the 
two systems. Finally, significant safety benefits would be foregone for 
those airplanes already equipped with current-generation GPWS.
    Clearly, there are dozens of combinations of the two previous 
alternatives involving different subsegments of the U.S. registered 
fleet. In general, they include: (1) Exempting, or imposing reduced 
requirements on, in-service aircraft, (2) exempting, or imposing 
reduced requirements on, domestic operations; (3) exempting, or 
imposing reduced requirements on, non-part 121 operations; (4) 
exempting, or imposing reduced requirements on, operations not 
involving the carrying of passengers for compensation or hire.
    The FAA does not favor options requiring TAWS installation only for 
newly manufactured airplanes. While it is true that this alternative 
would

[[Page 45636]]

significantly reduce compliance costs (indeed, some manufacturers are, 
or will soon be, offering TAWS as standard equipment), 30 or more years 
would elapse before the entire non-TAWS fleet is retired and replaced 
with TAWS-equipped airplanes. The foregone benefits--reduced 
fatalities, injuries, and property loss--associated with such a 
strategy are serious disadvantages of this alternative.
    The FAA also considered options that would combine TAWS 
installations for certain newly manufactured airplanes, with a GPWS 
requirement for in-service airplanes equipped with no, or early-
generation, GPWS. While less costly than the proposed rule, such 
alternatives would actually be less cost-effective: significant safety 
benefits associated with replacing upgraded GPWS with TAWS would be 
foregone, and, as noted earlier, in many cases it does not make 
economic sense to replace early-generation GPWS systems with upgraded 
systems.
    The accident history shows that substantial benefits can be 
achieved by requiring TAWS on international flights. An obvious 
alternative, then, would be to require TAWS retrofit only for airplanes 
conducting international operations, and impose lesser requirements for 
the remainder of the U.S. registered fleet (for example, require TAWS 
on newly manufactured airplanes only). Under this strategy, operators 
conducting only domestic flights would incur little or no costs. While 
the FAA acknowledges that a greater-than-proportional share of CFIT 
fatalities involving U.S. registered airplanes involve international 
operations, analyses (see the discussion of DOT Volpe National 
Transportation Systems Center analysis in the preamble, for example) 
show that substantial reductions in CFIT risks can be achieved by also 
requiring TAWS for domestic operations.
    As part of its analysis, the FAA estimated the domestic CFIT rate 
for 14 CFR part 121 carriers. This study showed that the discounted 
TAWS benefits--considering the domestic CFIT accident rate alone--would 
exceed discounted costs--associated with retrofitting the entire 
turbine-powered part 121 fleet--by approximately 50%.
    Finally, the FAA considered the option of requiring TAWS only on 
aircraft carrying passengers for compensation or hire. Accident 
analyses by the NTSB and DOT, however, show that a TAWS requirement 
would provide substantial safety benefits--that justify TAWS costs--for 
non-commercial, general aviation airplanes.

Different Compliance Deadlines for Different Subsegments of the 
Regulated Population

    Economic and safety considerations complicate the selection of a 
meaningful compliance period. With too long a period, important safety 
benefits may be foregone; with too short a period, the cost burden on 
industry becomes excessive. For in-service airplanes, the compliance 
alternatives can be summarized as follows: (1) Select a compliance 
period shorter than 4 years, (2) select a compliance period longer than 
4 years, (3) different combinations of compliance years and equipment 
requirements.
    Shortening the compliance period for TAWS installation, while 
beneficial from the standpoint of reduced CFIT risk, would raise 
important economic and technical problems. First, in the absence of 
technical standards and a substantial body of TAWS installation/
retrofit experience--particularly for general aviation airplane types--
approximately 200 STC's (or STC follow-ons) or type design change 
programs would have to be undertaken by industry and processed and 
approved by the FAA. Substantially shortening the compliance period for 
TAWS retrofit could impinge on other modification or repair work (which 
may also have safety implications) and could necessitate a reallocation 
of FAA resources and disrupt other FAA projects.
    Second, production information provided by the manufacturer of the 
only existing TAWS-compliant system indicates that building a 
sufficient number of units to accommodate a shorter deadline would be 
problematic. Theoretically, the FAA could grant extensions, but 
widespread use of this authority would result in inefficiencies--to 
modification centers, operators, and the FAA--and, in the end, result 
in no sooner achieving full fleet compliance than simply selecting a 
more appropriate compliance deadline in the first place.
    Other costs associated with a shorter deadline include: (1) 
Increased probability of service disruption, (2) decreased likelihood 
of the availability of competing TAWS products, and (3) difficulties in 
drafting and approving FAA technical standards for TAWS technology.
    The principle objection to lengthening the compliance period is 
that the flying public would forego significant safety benefits without 
a substantial decrease in costs. The FAA's analysis indicates that 
delaying the compliance deadline beyond the current proposal would not 
result in lower downtime or certification costs. Rather, cost savings 
would equal the modest return to capital (that would be spent on TAWS 
equipment) that would be realized during the short time that the 
operator could postpone retrofit. It is true that a longer compliance 
period would permit some airplanes to be retired without retrofit. 
However, these airplanes would have to be replaced with TAWS compliant 
aircraft (either through purchase or lease), therefore the net cost 
savings is negligible.
    The FAA also considered a hybrid two-stage approach designed to: 
(1) Give operators of older airplanes a cheaper compliance option, and 
(2) require quicker fleet installation of at least a current generation 
GPWS unit. In this approach, all U.S. registered turbine-powered 
airplanes with 6 or more passenger seats would be required to have a 
minimum of upgraded GPWS within an initial compliance period (e.g. 1 
year); and an FAA-approved terrain awareness and warning system by a 
second compliance period (e.g. 5 years). Theoretically, costs for many 
operators would be lower due to lower GPWS costs and the availability 
of GPWS STC's for most affected airplane models. There are two problems 
with this approach
    First, this proposal increases the likelihood of service 
disruptions. The two-stage approach only makes sense if the initial and 
secondary compliance deadlines are sufficiently far apart. If the 
initial and secondary deadlines were only separated by one or two 
years, for example, it is unlikely that any operator would choose to 
install an upgraded GPWS system. Delaying the secondary (TAWS) deadline 
is unacceptable to FAA for the safety reasons cited above. Thus, the 
initial deadline--affecting all airplanes with no or early-generation 
GPWS equipment--would have to be relatively early. Depending on the 
specific date chosen, the initial deadline could require retrofit of 
over 12,000 airplanes (with current generation GPWS) within a one or 
two year period.
    Second, FAA's analysis of the affected airplane population 
indicates that a large number of operators of airplanes that would need 
to be retrofitted by the initial deadline would choose to have TAWS 
equipment (primarily because they would expect these airplanes to be 
in-service after the secondary deadline). As noted above, it is 
unlikely that TAWS production will be able to accommodate this demand. 
Thus, operators who could not obtain TAWS would have to install 
upgraded GPWS and then retrofit TAWS approximately five years later. 
That is, the FAA would

[[Page 45637]]

compel some operators--most likely smaller operators with little market 
influence--to retrofit twice within five years.
    Third, as noted above, it is difficult to justify retrofitting 
upgraded GPWS in place of an existing early-generation system. The cost 
difference between GPWS and TAWS is relatively small--especially in 
consideration of the trade-in value of the existing unit (in some 
installations upgraded GPWS may be more expensive than TAWS)--but the 
difference in risk reduction is substantial. A preliminary analysis (of 
a compliance alternative that would require upgraded GPWS within one 
year and TAWS within five years) showed that the projected reduction in 
the part 121 CFIT accident rate associated with replacing early GPWS 
with TAWS was three times the rate reduction associated with replacing 
early GPWS with upgraded GPWS.
    The FAA invites comment on the alternatives discussed in this 
section and suggestions or other regulatory alternatives that have not 
been considered. Submitted alternatives should include an analysis of 
the issues discussed here, including: (1) Technical feasibility, (2) 
economic considerations (e.g. TAWS production constraints, probability 
of service disruption, supplier competition), and (3) public safety 
impacts.

Initial Regulatory Flexibility Determination and Analysis

    The Regulatory Flexibility Act of 1980 (RFA) was enacted by 
Congress to ensure that small entities are not unnecessarily and 
disproportionately burdened by government regulations. Specifically, 
the RFA requires federal agencies to prepare an initial regulatory 
flexibility analysis for any proposed rule that would have a 
``significant economic impact on a substantial number of small 
entities.'' The purpose of this analysis is to ensure that the agency 
has considered all reasonable regulatory alternatives that would 
minimize the rule's economic burdens for affected small entities, while 
achieving its safety objectives.
    Entities potentially affected by the proposed rule include 
manufacturers of transport category airplanes, manufacturers of TAWS/
GPWS systems, and air carriers. In addition, the rule would affect many 
other types of small entities which operate turbine-powered airplanes 
seating six or more passengers under 14 CFR part 91 (e.g. small 
business, governments, and other private or public organizations). 
There are thousands of operators of such airplanes and, therefore, 
potentially thousands of entities representing hundreds of industries, 
organizations, and institutions. The FAA acknowledges, therefore, that 
a substantial number of small entities could be significantly affected 
by the proposed rule.
    As noted above, the proposed rule is the culmination of an analysis 
of a number of alternatives (in fact, the FAA has ruled out several 
alternatives that would have imposed more costly requirements on small 
entities). Three cost-reducing compliance options were considered for 
small entities specifically: (1) Exclude small entities, (2) extend 
compliance deadline for small entities, and (3) establish lesser 
technical requirements for small entities.
    The FAA's analysis indicates that the option to exempt small 
entities from the requirements of the proposed rule is not justified. 
In fact, as noted in the preamble, the accident history of part 91 
operators (many of whom are small entities) forms the basis of the 
NTSB's recommendation to require ground proximity warning systems on 
smaller turbojet and turboprop airplanes.
    The FAA also considered options that would lengthen the compliance 
period for small operators. The requirement as proposed, however, would 
place a modest burden on small entities with respect to time 
constraints. Small entities--by definition operating small numbers of 
airplanes--would have four years from the effective date of the rule to 
complete retrofit work. As noted earlier, delaying the compliance 
deadline beyond the current proposal would not result in lower downtime 
or certification costs. Rather, cost savings would equal the modest 
return to capital (that would be spent on TAWS equipment) that would be 
realized during the short time that the operator could postpone 
retrofit. On the other hand, lengthening the compliance period would 
expose airplane occupants to significant safety risks for a longer 
period of time.
    Finally, the FAA's analysis indicates that compliance options that 
would permit non-TAWS technologies are not cost-effective. For 
airplanes not equipped with any ground proximity warning system, TAWS 
units would provide up to 23% greater CFIT risk reduction over current-
generation GPWS at very little additional cost. (In fact, in some 
installations, upgraded GPWS may be more expensive than TAWS.) In cases 
where aircraft already have GPWS, VNTSC and FAA analyses indicate that 
the safety benefits of TAWS outweigh the costs of retrofit.
    The FAA invites comments on its analysis of small entity impacts 
and alternatives. Comments should include: (1) Compliance issues that 
are specific to small entities (e.g. cost and technical feasibility), 
(2) public safety impacts, and (3) other small entity compliance 
alternatives not considered here.

International Trade Impact Assessment

    Recognizing that nominally domestic regulations often affect 
international trade, the Office of Management and Budget directs 
Federal Agencies to assess whether or not a rule or regulation will 
affect any trade-sensitive activity. The proposed rule could 
potentially affect international trade by burdening domestic businesses 
or air carriers with requirements that are not applicable to their 
foreign competitors. In general, the FAA concludes that the potential 
international trade impacts associated with the proposed rule would be 
negligible. Many domestic and foreign air carriers are already 
voluntarily installing TAWS equipment in recognition of the substantial 
safety benefits. A summary of potential impacts follows.
    There is only one line of FAA-approved systems that meets the 
requirements of the proposed rule. The proposed requirement could give 
the manufacturer of this product line a competitive advantage relative 
to foreign and domestic competitors by creating a substantial and 
immediate demand for enhanced GPWS units. Monopolistic control of this 
large market, in turn, may permit the manufacturer to take advantage of 
scale economies and learning curve effects--advantages that would be 
unavailable to other potential manufacturers who have not yet developed 
TAWS equipment. This production cost advantage may permit the dominant 
manufacturer to set prices so as to exclude market entry, but maintain 
economic profits. (``Economic profits'' in the sense that they are 
above the standard return for that particular industry.)
    The FAA's analysis indicates that the proposed rule would have a 
negligible effect on the competitive position of domestic airframe 
manufacturers. Under the proposed rule, domestic manufacturers, could 
continue to offer basic GPWS units on airplanes sold to foreign 
customers (if the airplane is not U.S. registered). Foreign airframe 
manufacturers, on the other hand, would be required to equip airplanes 
sold to U.S. customers (operating under 14 CFR parts 91, 121, or 135) 
with TAWS.
    Domestic firms leasing aircraft to foreign operators may be 
adversely

[[Page 45638]]

affected by the part 91 provisions of the proposed rule. Domestic 
leasing companies, for liability reasons or to position themselves to 
lease to both 14 CFR part 121 and foreign carriers, often choose to 
maintain U.S. registered fleets. Thus, their lease prices would have to 
reflect TAWS retrofit costs while the prices of foreign competitors 
would not (in some cases, the lessee is directly responsible for 
modifications required by airworthiness directive or regulations--but 
in either case the disincentive effect is the same). Given the small 
cost of TAWS relative to average airplane values, the FAA concludes 
that the potential international trade impact would be small. Also, 
TAWS equipped airplanes would be safer and thus more attractive to 
potential lessees--and their passengers. Increased patronage 
attributable to the operation of safer airplanes would also partially 
offset the costs of compliance.
    The potential impact to air carriers is, again, a function of the 
aircraft registration. Foreign air carriers operating U.S. registered 
airplanes would be required to install TAWS as would U.S. air carriers. 
To this extent, operators of U.S. registered airplanes would have costs 
not applicable to non-U.S. registered competitors.
    Conversely, CFIT accidents are a leading cause of commercial 
aviation fatalities worldwide. It is likely that knowledgeable 
passengers would be more than willing to pay the small difference in 
price to travel on an airplane equipped with TAWS. Voluntary industry 
initiatives to install enhanced ground proximity warning systems are 
consistent with the view that TAWS benefits far exceed its costs, and 
could have beneficial effects for domestic airlines competing for 
international passenger traffic.

Unfunded Mandates Reform Act Analysis

    Title II of the Unfunded Mandates Reform Act of 1995 (the Act), 
enacted as Pub. L. 104-4 on March 22, 1995, requires each Federal 
agency, to the extent permitted by law, to prepare a written assessment 
of the effects of any Federal mandate in a proposed or final agency 
rule that may result in the expenditure by State, local, and tribal 
governments, in the aggregate, or by the private sector, of $100 
million or more (adjusted annually for inflation) in any one year. 
Section 204(a) of the Act, 2 U.S.C. 1534(a), requires the Federal 
agency to develop an effective process to permit timely input by 
elected officers (or their designees) of State, local, and tribal 
governments on a proposed ``significant intergovernmental mandate.'' A 
``significant intergovernmental mandate'' under the Act is any 
provision in a Federal agency regulation that will impose an 
enforceable duty upon State, local, and tribal governments, in the 
aggregate, or by the private sector, of $100 million (adjusted annually 
for inflation) in any one year. Section 203 of the Act, 2 U.S.C. 1533, 
which supplements section 204(a), provides that before establishing any 
regulatory requirements that might significantly or uniquely affect 
small governments, the agency shall have developed a plan that, among 
other things, provides for notice to potentially affected small 
governments, if any, and for a meaningful and timely opportunity to 
provide input in the development of regulatory proposals.
    The FAA has determined that the proposed rule would likely have an 
economic impact on the private sector exceeding $100 million in certain 
years; and that the economic impact to State, local, and tribal 
governments would be far less than this threshold. Since the proposed 
rule does not impose an enforceable duty upon State, local, and tribal 
governments in the aggregate, of $100 million (adjusted annually for 
inflation) in any one year, the FAA concludes that it does not 
constitute a significant intergovernmental mandate as defined in the 
Act.

Federalism Implications

    The regulations proposed herein would not have substantial direct 
effects on the States, on the relationship between the national 
government and the States, or on the distribution of power and 
responsibilities among the various levels of government. Therefore, in 
accordance with Executive Order 12612, it is determined that this rule 
does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.

Paperwork Reduction Act

    As required by the Paperwork Reduction Act of 1995 (44 U.S.C. 
3507(d)), the FAA has submitted a copy of these proposed sections to 
the Office of Management and Budget for its review. The agency is not 
collecting information. This NPRM proposes to mandate a Terrain 
Awareness and Warning System for all turbine powered airplanes of 6 or 
more passenger seating. TAWS is a passive, electronic, safety device 
located in the avionics bay of the airplane. TAWS alerts pilots when 
there is terrain in the airplanes' flight path. Since there is not an 
actual collection of information, we cannot estimate a burden hour 
total. However, for the purpose of controlling this submission, we will 
assign a one hour burden to the package. There is a total cost estimate 
of 140 million dollars per year, for installation of the passive, 
electronic, safety device.
    Organizations and individuals desiring to submit comments on the 
information, billing, and collection requirements should direct them to 
the Office of Information and Regulatory Affairs, OMB, Room 10202, New 
Executive Office Building, Washington, DC 20503; Attention: Desk 
Officer for Federal Aviation Administration. These comments should 
reflect whether the proposed collection is necessary; whether the 
agency's estimate of the burden is accurate; how the quality, utility 
and clarity of the information to be collected can be enhanced; and how 
the burden of the collection can be minimized. A copy of the comments 
also should be submitted to the FAA Rules Docket.
    OMB is required to make a decision concerning the collection of 
information contained in this NPRM between 30 and 60 days after 
publication in the Federal Register. Therefore, a comment to OMB is 
best assured of having its full effect if OMB receives it within 30 
days of publication. This does not affect the deadline for the public 
to comment on the NPRM.

International Compatibility

    The FAA has reviewed corresponding International Civil Aviation 
Organization international standards and recommended practices and 
Joint Aviation Authorities requirements. TAWS is a new system recently 
developed by American industry. The FAA intends to work through the 
ICAO process to harmonize this rule with the international community.

List of Subjects

14 CFR Part 91

    Aircraft, Aviation safety.

14 CFR Part 121

    Aircraft, Aviation safety, Safety.

14 CFR Part 135

    Aircraft, Aviation safety.

The Proposed Amendment

    For the reasons discussed above, the Federal Aviation 
Administration proposes to amend 14 CFR parts 91, 121, and 135 as 
follows:

PART 91--GENERAL OPERATING AND FLIGHT RULES

    1. The authority citation for part 91 continues to read as follows:


[[Page 45639]]


    Authority: 49 U.S.C. 106(g), 40103, 40113, 40120, 44101, 44111, 
44701, 44709, 44711, 44712, 44715, 44716, 44717, 44722, 46306, 
46315, 46316, 46502, 46504, 46506-46507, 47122, 47508, 47528-47531.

    2. Section 91.223 is added to read as follows:


Sec. 91.223  Terrain awareness and warning system.

    (a) Airplanes manufactured after [one year after the effective date 
of the final rule]. No person may operate a turbine-powered U.S.-
registered airplane type certificated to have six or more passenger 
seats, excluding any pilot seat, unless that airplane is equipped with 
an approved terrain awareness and warning system, including a terrain 
situational awareness display, that meets the requirements of TSO-C151.
    (b) Airplanes manufactured on or before [one year after the 
effective date of the final rule]. No person may operate a turbine-
powered U.S.-registered airplane type certificated to have six or more 
passenger seats, excluding any pilot seat, after [4 years after the 
effective date of the final rule] unless that airplane is equipped with 
an approved terrain awareness and warning system, including a terrain 
situational awareness display, that meets the requirements of TSO-C151.
    (c) Airplane Flight Manual. The Airplane Flight Manual shall 
contain appropriate procedures for--
    (1) The use of the terrain awareness and warning system; and
    (2) Proper flight crew reaction with respect to the terrain 
awareness and warning system audio and visual warnings.

PART 121--OPERATING REQUIREMENTS; DOMESTIC, FLAG, AND SUPPLEMENTAL 
OPERATIONS

    3. The authority citation for part 121 continues to read as 
follows:

    Authority: 49 U.S.C. 106(g), 40113, 40119, 44101, 44701-44702, 
44705, 44709-44711, 44713, 44716-44717, 44722, 44901, 44903-44904, 
44912, 46105.

    4. Section 121.354 is added to read as follows:


Sec. 121.354  Terrain awareness and warning system.

    (a) Airplanes manufactured after [one year after the effective date 
of the final rule]. No person may operate a turbine-powered airplane 
unless that airplane is equipped with an approved terrain awareness and 
warning system, including a terrain situational awareness display, that 
meets the requirements of TSO-C151.
    (b) Airplanes manufactured on or before [one year after the 
effective date of the final rule]. No person may operate a turbine-
powered airplane after [four years after the effective date of the 
final rule], unless that airplane is equipped with an approved terrain 
awareness and warning system, including a terrain situational awareness 
display, that meets the requirements of TSO-C151.
    (c) Airplane Flight Manual. The Airplane Flight Manual shall 
contain appropriate procedures for--
    (1) The use of the terrain awareness and warning system; and
    (2) Proper flight crew reaction with respect to the terrain 
awareness and warning system audio and visual warnings.
    5. Section 121.360 is amended by adding paragraph (g) to read as 
follows:


Sec. 121.360  Ground proximity warning--glide slope deviation alerting 
system.

* * * * *
    (g) This section expires on [four years after the effective date of 
the final rule].

PART 135--OPERATING REQUIREMENTS: COMMUTER AND ON-DEMAND OPERATIONS

    6. The authority citation for part 135 continues to read as 
follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701-44702, 44705, 44709, 
44711-44713, 44715-44717, 44722.

    7. Section 135.153 is amended by adding paragraph (f) to read as 
follows:


Sec. 135.153  Ground proximity warning system.

* * * * *
    (f) This section expires on [four years after the effective date of 
the final rule].
    8. Section 135.154 is added to read as follows:


Sec. 135.154  Terrain awareness and warning system.

    (a) Airplanes manufactured after [one year after the effective date 
of the final rule]. No person may operate a turbine-powered airplane 
type certificated to have six or more passenger seats, excluding any 
pilot seat, unless that airplane is equipped with an approved terrain 
awareness and warning system, including a terrain situational awareness 
display, that meets the requirements of TSO-C151.
    (b) Airplanes manufactured on or before [one year after the 
effective date of the final rule]. No person may operate a turbine-
powered airplane type certificated to have six or more passenger seats, 
excluding any pilot seat, after [insert date 4 years after the 
effective date of the final rule], unless that airplane is equipped 
with an approved terrain awareness and warning system, including a 
terrain awareness and warning system, that meets the requirements of 
TSO-C151.
    (c) Airplane Flight Manual. The Airplane Flight Manual shall 
contain appropriate procedures for--
    (1) The use of the terrain awareness and warning system; and
    (2) Proper flight crew reaction with respect to the terrain 
awareness and warning system audio and visual warnings.

    Issued in Washington, DC, on August 19, 1998.
Thomas E. McSweeny,
Director, Aircraft Certification Service.
[FR Doc. 98-22751 Filed 8-25-98; 8:45 am]
BILLING CODE 4910-13-P