[Federal Register Volume 61, Number 223 (Monday, November 18, 1996)]
[Proposed Rules]
[Pages 58665-58667]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-29481]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM-134; Notice No. SC-96-7-NM]
Special Conditions: Empresa Brasileira de Aeronautica S.A.,
(EMBRAER) Model EMB-145 Airplane; Thrust Reverser Systems
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed special conditions.
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SUMMARY: This notice proposes special conditions 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. This notice contains 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).
DATES: Comments must be received on or before January 2, 1997.
ADDRESSES: Comments on this proposal may be mailed in duplicate to:
Federal Aviation Administration, Office of the Assistant Chief Counsel,
Attention: Rules Docket (ANM-7), Docket No. NM-134, 1601 Lind Avenue
SW, Renton, Washington 98055-4056; or delivered in duplicate to the
Office of the Assistant Chief Counsel at the above address. Comments
must be marked: Docket No. NM-134. Comments may be inspected in the
Rules Docket weekdays, except Federal holidays, between 7:30 a.m. and
4:00 p.m.
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 206-227-2191.
SUPPLEMENTARY INFORMATION:
Comments Invited
Interested persons are invited to participate in the making of
these proposed special conditions by submitting such written data,
views, or arguments as they may desire. Communications should identify
the regulatory docket or notice number and be submitted in duplicate to
the address specified above. All communications received on or before
the closing date for comments will be considered by the Administrator
before further rulemaking action on this proposal is taken. The
proposals contained in this notice may be changed in light of the
comments received. All comments received will be available, both before
and after the closing date for comments, in the Rules Docket for
examination by interested parties. A report summarizing each
substantive public contact with FAA personnel concerning this
rulemaking will be filed in the docket. Commenters wishing the FAA to
acknowledge receipt of their comments submitted in response to this
notice must include a self-addressed, stamped postcard on which the
following statement is made: ``Comments to Docket No. NM-134.'' The
postcard will be date/time stamped and returned to the commenter.
Background
EMBRAER first made application for a US 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 power plants, 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 transport 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 increase 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.
[[Page 58666]]
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 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's 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 of the FAR, 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 of the FAR 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. This airworthiness
regulation only addresses dry runway performance and does not require
thrust reversers or give performance credit for their availability. 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 of the FAR and therefore proposes
to apply a special condition to the EMB-145 in accordance with
Sec. 21.16 of the FAR. 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 Sec. 21.101, Empresa Brasileira de
Aeronautica S.A., must show that the Model EMB-145 meets the applicable
regulations in effect on the date of application for the Model EMB-145.
In addition, the certification basis includes certain other special
conditions not relevant to this proposed special condition.
In addition, if the regulations incorporated by reference do not
provide adequate standards will respect to the change, the applicant
must comply with certain regulations in effect on the date of
application for the change. The FAA has determined that the Model EMB-
145 airplane must also be shown to comply with Part 25 as amended by
Amendments 25-1 through 25-75.
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 of the FAR 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. 21.101(b)(2).
[[Page 58667]]
In addition to the applicable airworthiness regulation and special
condition, the Model EMB-145 must comply with the fuel vent and exhaust
emission requirements of Part 25 and the noise certification
requirements of Part 36.
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 the same novel or unusual design feature, the
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.
As described 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 of 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 the FAA for
approval of these features on the airplane.
List of Subjects in 14 CFR Part 25
Air Transportation, Aircraft, Aviation safety, Safety.
The authority citation for these special conditions continues to
read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701-44702, 44704.
The Proposed Special Conditions
Accordingly, the Federal Aviation Administration (FAA) proposes the
following special conditions as part of the type certification basis
for the Empresa Brasileira de Aeronautica S.A., Model EMB-145
airplanes.
1. Require Embraer to account for the effect of wet runway surfaces
on accelerate-stop distances for the Model EMB-145 in accordance with
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 predicted on the wet runway accelerate-stop criteria
contained in NPRM93-8.
Issued in Renton, Washington, on November 7, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service, ANM-100.
[FR Doc. 96-29481 Filed 11-15-96; 8:45 am]
BILLING CODE 4910-13-M
