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[Federal Register Volume 62, Number 167 (Thursday, August 28, 1997)]
[Rules and Regulations]
[Pages 45523-45526]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-22919]

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Rules and Regulations
                                                Federal Register
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The Code of Federal Regulations is sold by the Superintendent of Documents. 
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Federal Register / Vol. 62, No. 167 / Thursday, August 28, 1997 / 
Rules and Regulations

[[Page 45523]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM-134; Special Conditions No. 25-ANM-131]

Special Conditions: Empresa Brasileira de Aeronautica S.A., 
(EMBRAER) Model EMB-145 Airplane; Thrust Reverser Systems

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are for the Empresa Brasileira de 
Aeronautica S.A., (EMBRAER) Model EMB-145 airplane. This airplane will 
have a novel or unusual design feature associated with thrust reversers 
as optional equipment. These special conditions contain the additional 
safety standards which the Administrator considers necessary to 
establish a level of safety equivalent to that established by the 
airworthiness standards of part 25 of the Federal Aviation Regulations 
(FAR).

EFFECTIVE DATE: September 29, 1997.

FOR FURTHER INFORMATION CONTACT: Colin Fender, FAA, Flight Test and 
Systems Branch of the Transport Standards Staff, ANM-111, Transport 
Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue 
SW, Renton, Washington 98055-4056; telephone 425-227-2191.

SUPPLEMENTARY INFORMATION:

Background

    Embraer first made application for a U.S. Type Certificate for the 
Model EMB-145 on August 30, 1989, to the FAA Atlanta Aircraft 
Certification Office through the Brazilian Centro Tecnico Aeroespacial 
(CTA). On June 2, 1992, Embraer filed for an extension of that 
application. The EMB-145 is a 50 passenger, pressurized, low-winged, 
``T'' tailed, transport category airplane with retractable tricycle 
type landing gear. The airplane is powered by two Allison Model AE3007A 
high bypass ratio turbofan engines mounted on the aft fuselage, which 
are controlled by a Full Authority Digital Engine Control (FADEC). The 
cockpit will include a complete set of Electronic Flight 
Instrumentation and Engine Indication and Crew Alerting Systems (EFIS 
and EICAS).
    Embraer has proposed to certificate and market the EMB-145 with 
thrust reversers as optional equipment. Thrust reversers have been 
shown to play a significant role in reducing accelerate-stop distances 
on wet and contaminated runways and have contributed to the transport 
category airplane fleet's accelerate-stop safety record.
    The establishment of the transport category airplane safety record, 
with regard to accelerate-stop and landing overruns, is tied to the 
availability of auxiliary braking means that are independent of wheel-
brake, tire, and runway surface interaction. On early transport 
category airplanes with propellers driven by reciprocating engines or 
turbine powerplants, auxiliary braking was provided by commanding the 
propellers to a reverse pitch position, causing a deceleration, rather 
than acceleration, of air through the propeller disk. Due to the large 
diameter of the propellers, this was quite an effective braking means. 
Though these early transports did not have the high operating speeds of 
today's jet fleet, they also did not benefit from the sophisticated 
wheel-brake antiskid systems available today. As runway friction 
conditions degrade to those associated with a surface covered by ice, 
even today's antiskid systems will provide little in the way of 
stopping force. As runway friction conditions degrade, the braking 
contribution of reverse pitch systems increases considerably.
    As the first generation turbojet-powered transport category 
airplanes went into service in the latter half of the 1950s, thrust 
reverser systems were developed to provide this same type of auxiliary 
braking as reverse pitch propellers by reversing the engine exhaust 
flow. As powerplant technology evolved and low bypass ratio turbofan 
engines entered commercial service in the early 1960's, thrust 
reversers were developed to reverse both the fan and core exhaust 
flows, thus maintaining the availability of auxiliary braking. With the 
advent of large high bypass ratio turbofan engines in the late 1960s, 
many thrust reverser systems reversed the fan exhaust flow only, which 
provided a substantial auxiliary braking effect due to the majority of 
the total inlet flow going through the fan section. Numerous test 
programs, by both research organizations and aerospace manufacturers, 
have substantiated the increased stopping benefit provided by thrust 
reversers as runway surface friction conditions deteriorate.
    The vast majority of jet-powered transport category airplanes in 
service have been of the large, passenger carrying variety. Research 
shows that with the exception of a very limited number of airplane 
types, some of which had considerably slower takeoff and landing speeds 
than their counterparts, all these large, passenger carrying, turbojet/
turbofan-powered transports included thrust reverser systems as part of 
their basic design (i.e., as standard equipment). The last such 
aircraft certified without thrust reversers as part of the basic design 
was the British Aerospace 146 (BAe 146) in 1983. When the sheer 
numerical majority of these large transports is combined with their 
high-use operating environment, often requiring takeoffs and landings 
to be made on slippery runway surfaces, it is clear that thrust 
reversers must have played a role in establishing their excellent 
safety record.
    It should also be noted that as the number of small transport 
category airplanes in service has increased, notably corporate jets and 
regional airliners, there has been an increasing tendency for these 
airplanes to be equipped with some type of thrust reversing system. 
Nearly all the regional airliners are turbopropeller-powered with 
reverse pitch capability, and an increasing number of corporate jets 
include thrust reversers as standard equipment.
    The accelerate-stop and landing distances presented in the FAA 
approved Airplane Flight Manual (AFM) are determined from measurements 
of the various influential parameters taken during certification flight 
tests. These flight tests are

[[Page 45524]]

accomplished by FAA test pilots (or manufacturers' Designated 
Engineering Representative (DER) test pilots) under controlled 
conditions on dry runways. In the operational environment, even on dry 
runways, the ability of an airplane to match the AFM accelerate-stop 
performance is based on many factors, including the correct and timely 
execution of procedures by the pilot and maximum stopping performance 
being available from the wheel braking system. As runway surface 
conditions degrade to wet, contaminated, or icy, the accompanying 
reduction in available friction will result in an increase in stopping 
distances, causing the wet runway accelerate-stop distances to exceed 
the dry runway accelerate-stop distances published in the AFM. 
Obviously, if the takeoff is runway length-limited as determined from 
the dry runway AFM accelerate-stop distances, and the runway surface is 
anything but dry, the probability for an overrun accident is increased 
significantly. (This increased risk factor is acknowledged for the 
landing scenario in part 121, the operating rules for air carriers and 
commercial operators of large aircraft, which requires an increase in 
the landing field length required for landings on wet runways.)
    In the operating conditions described above, any additional braking 
means, such as thrust reversers, will be beneficial. This is 
particularly true since the braking contribution of reverse thrust 
increases as runway surface friction decreases. This inverse 
relationship between reverse thrust braking contribution and runway 
surface friction is further enhanced as ground speed increases.
    Since 1990 the Transport Airplane Directorate (TAD) has been 
developing new part 25 accelerate-stop criteria that includes 
accountability for the degradation in stopping force due to wet runway 
surfaces. Test results obtained from several research organizations 
showed a fixed stopping distance factor of two, relative to dry runway 
stopping distances, to be representative of what could be expected in 
normal operations. The proposed accelerate-stop standards, published as 
Notice of Proposed Rulemaking (NPRM) 93-8, assumed a similar 
degradation in braking by prescribing a wet/dry braking coefficient of 
friction ratio of one-half (i.e.,  WET = 0.5  DRY) as 
the primary basis for calculating wet runway accelerate-stop distances. 
An integral part of the proposed wet runway accelerate-stop rule is 
credit for the amount of reverse thrust available (provided certain 
reliability and controllability criteria are met).
    The accelerate-stop certification basis for the EMB-145 is 
Sec. 25.109, as amended by Amendment 25-42, effective March 1, 1978. 
Thrust reversing systems are not required by the FAR and, when 
installed, no performance credit is granted for their availability in 
the dry runway accelerate-stop distances required by Sec. 25.109, as 
amended by Amendment 25-42, effective March 1, 1978. However, the vast 
majority of transport category airplanes in service at the time the 
regulatory changes of Amendment 25-42 were promulgated were equipped 
with thrust reversers. Consequently, the certification of transport 
category airplanes intended to be operated in Part 121-type commercial 
service without thrust reversers was not envisaged at the time 
Amendment 25-42 was promulgated.
    In consideration of the intended operation of the EMB-145, the FAA 
considers the non-inclusion of thrust reversers into the basic airplane 
to be an unusual design feature that is not adequately addressed by the 
airworthiness regulations of part 25, and therefore proposes to apply 
special conditions to the EMB-145 in accordance with Sec. 21.16. In 
accordance with the preamble material to Amendment 25-54 (page 274), 
addressing the definition of a novel or unusual design feature (as used 
in Sec. 21.16), the non-inclusion of thrust reversers in the basic EMB-
145 design can be considered a ``novel or unusual design feature'' 
since such designs were not envisaged at the time the current 
airworthiness standard (i.e., Sec. 25.109, Amendment 25-42) was 
developed. This application requires the development of requirements 
not fully addressed by part 25 nor by any published FAA guidance.
    These special conditions provide all the necessary requirements to 
determine acceptability of the EMB-145 without the incorporation of 
thrust reversers.

Type Certification Basis

    Under the provisions of 14 CFR 21.17, Empresa Brasileira de 
Aeronautica S.A. must show that the Model EMB-145 meets the applicable 
provisions of part 25, as amended by Amendments 25-1 through 25-84.
    In addition to the applicable airworthiness regulations and special 
conditions, the Model EMB-145 must comply with the fuel vent and 
exhaust emission requirements of 14 CFR part 34 and the noise 
certification requirements of 14 CFR part 36, and the FAA must make a 
finding of regulatory adequacy pursuant to section 611 of Public Law 
92-574, the ``Noise Control Act of 1972.''
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., part 25 as amended) do not contain adequate or 
appropriate safety standards for the Model EMB-145 because of a novel 
or unusual design feature, special conditions are prescribed under the 
provisions of Sec. 21.16.
    Special conditions, as appropriate, are issued in accordance with 
Sec. 11.49 after public notice, as required by Secs. 11.28 and 
11.29(b), and become part of the type certification basis in accordance 
with Sec. 21.17(a)(2).
    Special conditions are initially applicable to the model for which 
they are issued. Should the type certificate for that model be amended 
later to include any other model that incorporates the same novel or 
unusual design feature, these special conditions would also apply to 
the other model under the provisions of Sec. 21.101(a)(1).

Novel or Unusual Design Features

    The Model EMB-145 will have an unusual design feature which is the 
lack of incorporation of thrust reversers as standard equipment.

Discussion of Comments

    Notice of Proposed Special Conditions No. SC-96-7-NM for the 
Empresa Brasileira de Aeronautica S.A., (EMBRAER) Model EMB-145, was 
published in the Federal Register on November 18, 1996. Three 
commenters submitted comments.
    All commenters state the special conditions are inappropriate since 
thrust reversers are not required for part 25 certification and part 25 
airplanes not equipped with thrust reversers have exhibited the same 
level of safety as those with thrust reversers. The FAA does not 
contest the fact that part 25 does not require thrust reversers. With 
regard to the level of safety issue, it is obvious that the additional 
braking provided by reverse thrust will always improve safety, and the 
amount of that improvement will increase with decreasing runway surface 
friction. The only accelerate-stop performance information required to 
be in the Airplane Flight Manual (AFM) by the current part 25 
airworthiness regulations is based on a dry runway surface; these dry 
runway accelerate-stop distances may (and will) be used with no 
adjustments for takeoffs made on wet and contaminated runways. This 
could be of critical importance for an airplane the size of the EMB-
145, which in all likelihood will see a sizable number of operations on 
relatively short

[[Page 45525]]

runways, thus increasing the probability of its being dry runway 
takeoff or landing field length-limited.
    One commenter states that the main consideration of the special 
conditions is that the non-inclusion of thrust reversers is classified 
as an unusual design feature because the EMB-145 is intended for 
operation in part 121-type commercial service. Consequently, the 
commenter states the special conditions are not appropriate under part 
25 since the certification basis is independent of the rules an 
airplane might be operated under. The FAA does not agree with the 
commenter's statement. The overall operational safety of an airplane is 
as much the concern of the Aircraft Certification Service of the FAA as 
it is the Flight Standards Service, particularly where aircraft 
performance is a consideration since it is the Aircraft Certification 
Service personnel who witness the flight testing and approve the 
resulting Airplane Flight Manual performance that scheduled operations 
will be based on.
    Similarly, another commenter states that if performance credit is 
of established benefit in part 121-type commercial operations, the 
appropriate rule to require thrust reversers would be under part 121 
and not the certification rules (i.e., part 25). The FAA questions the 
use of the term ``performance credit'' since no performance credit has 
been given in the past, as discussed in the preceding paragraph. The 
FAA understands this comment to mean if thrust reversers have provided 
benefits in part 121-type operations, then any rule to require their 
installation should be proposed under part 121. The FAA disagrees with 
this comment. The FAA's job is to ensure the safety of the traveling 
public; whether that is done through the Aircraft Certification Service 
or the Flight Standards Service is irrelevant in this case. As 
discussed in the notice of proposed special conditions, the thrust 
reverser issue is addressed in this context because the FAA has found 
that Embraer's type certificate application presents a novel or unusual 
design feature for which the applicable airworthiness standards do not 
provide adequate safety standards. In accordance with 14 CFR 
Sec. 21.16, special conditions are the appropriate mechanism for 
dealing with such issues.
    One commenter states that if the FAA considers the increased 
stopping benefit provided by thrust reversers as substantiation (sic) 
for requiring their installation, then performance credit should be 
granted for their use. The FAA has for many years gone on record as 
being opposed to granting general performance credit for the use of 
thrust reversers. One of the primary reasons for this position is that 
thrust reversers provided some compensation for the minimal amount of 
conservatism assumed in determining the accelerate-stop distances that 
takeoffs will be predicated on rejected takeoff accident data indicate 
that pilots do not always recognize and respond to a failure condition 
at or near V1 in the time period assumed in calculating the 
AFM accelerate-stop distances. The FAA has proposed to grant 
performance credit for thrust reversers in the determination of 
accelerate-stop distances on wet runways, provided the stopping 
distances are based on the associated reduced wheel-brake stopping 
force available and certain reliability and controllability criteria 
are met.
    One commenter notes that the proposed special conditions do not 
address the Master Minimum Equipment List (MMEL) allowance for 
airplanes to have thrust reversers rendered inoperative, and that the 
FAA did not consider the economic implications of this issue. The FAA 
does not consider this to be a relevant argument against requiring the 
installation of thrust reversers on the EMB-145. The MMEL allowance 
referred to by the commenter is classified as Level C which, among 
other things, places a 10-day limitation on the thrust reversers being 
inoperative. The 10-day limitation is, in part, based on the 
probability of occurrence of a situation in which the additional 
braking force provided by reverse thrust would be beneficial.
    One commenter states that the inclusion of a proposed rule (i.e., 
NPRM 93-8) as a certification requirement was not appropriate. A 
related comment from another commenter noted that FAA's Aircraft 
Certification Service management has stated the FAA would not invoke 
unadopted regulations or policy on active certification programs. The 
FAA is not mandating compliance with the criteria of NPRM 93-8 as a 
certification requirement. Embraer has the option of installing thrust 
reversers on the airplane and determining accelerate-stop distances in 
accordance with part 25 at the amendment level described in the type 
certification basis for the EMB-145. It should also be noted that in 
ongoing certification programs, the FAA Transport Airplane Directorate 
routinely considers proposed rules as showing an equivalent level of 
safety to existing part 25 regulations.
    One commenter also states that NPRM 93-8 is not harmonized with the 
European Joint Aviation Authorities (JAA) requirements. This statement 
is incorrect. The criteria of NPRM 93-8 was developed in conjunction 
with the JAA; requirements identical to those of NPRM 93-8 can be found 
in the equivalent AAA Notice of Proposed Amendment.
    One commenter requests the FAA submit this major change in 
certification philosophy to the appropriate regulatory/industry forum. 
The FAA discussed the philosophy embodied in Notice No. SC-96-7-NM with 
flight test specialists from several foreign civil airworthiness 
authorities during its development. The FAA is within its legal bounds 
by treating airplanes on a case-by-case basis with special conditions 
in accordance with Sec. 21.16. The FAA does not believe it is necessary 
to submit the certification philosophy embodied in Notice No. SC-96-7-
NM to a regulatory/industry forum since the wet runway accelerate-stop 
criteria in NPRM 93-8, which gives performance credit for available 
reverse thrust on wet runways, will encourage manufacturers to 
incorporate thrust reversers as part of the basic design of their 
airplanes.
    One commenter states that the FAA's contention that thrust 
reversers have played a significant role in the safety record of 
transport category airplanes is not supported by any form of factual 
information or data. The FAA disputes this commenter's position. A 
significant amount of testing has been conducted over the last 40 years 
that has repeatedly proven the increased benefit of reverse thrust as 
the runway surface condition deteriorates in terms of available wheel-
braking force. It is obviously difficult to point at a particular 
rejected takeoff as an example since any successful field length-
limited RTO that may have occurred on a wet or contaminated runway, 
whose takeoff weight was limited by a dry runway accelerate-stop 
distance, would not have been recorded. However, it stands to reason 
that the probability of such a case occurring would be very low without 
the additional braking force contribution provided by thrust reversers.
    As discussed above, these special conditions are applicable to the 
EMB-145. Should Empresa Brasileira de Aeronautica S.A. apply at a later 
date for a change to the type certificate to include another model 
incorporating the same novel or unusual design feature, the special 
conditions would apply to that model as well under the provisions of 
Sec. 21.101(a)(1).
    Conclusion: This action affects only certain novel or unusual 
design features on one model of airplane. It is not a rule of general 
applicability, and it affects only the manufacturer who applied to

[[Page 45526]]

the FAA for approval of these features on the airplane.

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, Federal Aviation Administration, 
Reporting and recordkeeping requirements.

    The authority citation for these special conditions is as follows:

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

The Special Conditions

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the type certification basis for the Empresa Brasileira de Aeronautica 
S.A., Model EMB-145 airplanes not equipped with thrust reversers.
    1. The effect of wet runway surfaces on accelerate-stop distances 
for the Model EMB-145 must be accounted for in accordance with the 
criteria contained in NPRM 93-8 and its associated guidance.
    2. Takeoff limitations for operation of the EMB-145 on wet runway 
surfaces must be predicated on the wet runway accelerate-stop criteria 
contained in NPRM 93-8.

    Issued in Renton, Washington, on August 18, 1997.
Stewart R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service, ANM-100.
[FR Doc. 97-22919 Filed 8-27-97; 8:45 am]
BILLING CODE 4910-13-P
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