[Federal Register Volume 68, Number 51 (Monday, March 17, 2003)]
[Rules and Regulations]
[Pages 12581-12582]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-6332]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM245; Special Conditions No. 25-229-SC]


Special Conditions: Bombardier Aerospace Model BD-100-1A10; 
Sudden Engine Stoppage

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions; request for comments.

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SUMMARY: These special conditions are issued to Bombardier Aerospace 
for the Model BD-100-1A10 airplane. This airplane will have a novel or 
unusual design feature when compared to the state of technology 
envisioned in the airworthiness standards for transport category 
airplanes, associated with engine size and torque load which affects 
sudden engine stoppage. The applicable airworthiness regulations do not 
contain adequate or appropriate safety standards for this design 
feature. These special conditions contain the additional safety 
standards that the Administrator considers necessary to establish a 
level of safety equivalent to that established by the existing 
airworthiness standards.

DATES: The effective date of these special conditions is March 6, 2003. 
Comments must be received on or before May 1, 2003.

ADDRESSES: Comments on these special conditions may be mailed in 
duplicate to: Federal Aviation Administration, Transport Airplane 
Directorate, Attn: Rules Docket (ANM-113), Docket No. NM245, 1601 Lind 
Avenue SW., Renton, Washington 98055-4056; or delivered in duplicate to 
the Transport Airplane Directorate at the above address. All comments 
must be marked: Docket No. NM245. Comments may be inspected in the 
Rules Docket weekdays, except Federal holidays, between 7:30 a.m. and 4 
p.m.

FOR FURTHER INFORMATION CONTACT: Todd Martin, FAA Airframe/Cabin Safety 
Branch, ANM-115, Transport Airplane Directorate, Aircraft Certification 
Service, 1601 Lind Avenue SW., Renton, Washington 98055-4056; telephone 
(425) 227-1178; facsimile (425) 227-1320.

SUPPLEMENTARY INFORMATION:

FAA Determination as to Need for Public Process

    The FAA has determined that notice and opportunity for prior public 
comment are unnecessary in accordance with 14 CFR 11.38, because the 
FAA has provided previous opportunities to comment on substantially 
identical special conditions and has fully considered and addressed all 
the substantive comments received. Based on a review of the comment 
history and the comment resolution, the FAA is satisfied that new 
comments are unlikely. The FAA therefore finds that good cause exists 
for making these special conditions effective upon issuance.

Comments Invited

    Although this action is in the form of final special conditions 
and, for the reasons stated above, is not preceded by notice and an 
opportunity for public comment, comments are invited on these special 
conditions. We invite interested persons to participate in this 
rulemaking by submitting written comments, data, or views. The most 
helpful comments reference a specific portion of the special 
conditions, explain the reason for any recommended change, and include 
supporting data. We ask that you send us two copies of written 
comments.
    We will file in the docket all comments we receive, as well as a 
report summarizing each substantive public contact with FAA personnel 
concerning these special conditions. The docket is available for public 
inspection before and after the comment closing date. If you wish to 
review the docket in person, go to the address in the ADDRESSES section 
of this preamble between 7:30 a.m. and 4 p.m., Monday through Friday, 
except Federal holidays.
    We will consider all comments we receive on or before the closing 
date for comments. We will consider comments filed late if it is 
possible to do so without incurring expense or delay. We may change 
these special conditions in light of the comments we receive.
    If you want the FAA to acknowledge receipt of your comments on 
these special conditions, include with your comments a pre-addressed, 
stamped postcard on which the docket number appears. We will stamp the 
date on the postcard and mail it back to you.

Background

    On June 28, 1999, Bombardier Aerospace applied for a new type 
certificate for their Model BD-100-1A10 airplane. The BD-100-1A10 is a 
medium range transport category airplane, powered by two rear fuselage-
mounted Allied Signal AS907 engines. This engine model is a high bypass 
turbofan engine, with 6826 lb. takeoff thrust at sea level flat rated 
to ISA+20[deg].

Type Certification Basis

    Under the provisions of 14 CFR 21.17, Bombardier Aerospace must 
show that the Model BD-100-1A10 meets the applicable provisions of part 
25, as amended by Amendments 25-1 through 25-98. The type certification 
basis for the Model BD-100-1A10 will therefore include 14 CFR part 25, 
effective February 1, 1965, including Amendments 25-1 through 25-98; 14 
CFR, part 34, effective September 10, 1990, including Amendment 34-1, 
and any subsequent amendments that will be applicable on the date the 
type certificate is issued; and 14 CFR part 36, effective December 1, 
1969, including Amendments 36-1 through 36-22, and any subsequent 
amendments that will be applicable on the date the type certificate is 
issued. The certification basis may also include certain exceptions, 
exemptions, and other special conditions that are not relevant to these 
special conditions:
    If the Administrator finds that the applicable airworthiness 
regulations (that is, part 25) do not contain adequate or appropriate 
safety standards for the Model BD-100-1A10 airplane because of a novel 
or unusual design feature, special conditions are prescribed under the 
provisions of Sec.  21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, the Model BD-100-1A10 must comply with the fuel vent and 
exhaust emission requirements of part 34 and the noise certification 
requirements of part 36; and the FAA must issue a finding of regulatory 
adequacy pursuant to Section 611 of Public Law 92-574, the ``Noise 
Control Act of 1972.''
    Special conditions, as defined in Sec.  11.19, are issued in 
accordance with Sec.  11.38 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, the special conditions would also apply to the 
other model under the provisions of Sec.  21.101(a)(1) [Amendment 21-
69, effective September 16, 1991].

Novel or Unusual Design Features

    The Bombardier Aerospace Model BD-100-1A10 will incorporate novel 
or unusual design features involving engine size and torque load that 
affect sudden engine stoppage conditions.

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Discussion

    The limit engine torque load imposed by sudden engine stoppage due 
to malfunction or structural failure (such as compressor jamming) has 
been a specific requirement for transport category airplanes since 
1957. In the past, the design torque loads associated with typical 
failure scenarios have been estimated by the engine manufacturer and 
provided to the airframe manufacturer as limit loads. These limit loads 
were considered simple, pure torque static loads. The size, 
configuration, and failure modes of jet engines have changed 
considerably from those envisioned when the engine seizure requirement 
of Sec.  25.361(b) was first adopted. Current engines are much larger 
and are now designed with large bypass fans capable of producing much 
larger torque loads if they become jammed. It is evident from service 
history that the frequency of occurrence of the most severe sudden 
engine stoppage events is rare.
    Relative to the engine configurations that existed when the rule 
was developed in 1957, the present generation of engines are 
sufficiently different and novel to justify issuance of special 
conditions to establish appropriate design standards. The latest 
generation of jet engines are capable of producing, during failure, 
transient loads that are significantly higher and more complex than the 
generation of engines that were present when the existing standard was 
developed. Therefore, the FAA has determined that special conditions 
are needed for the Bombardier Aerospace Model BD-100-1A10 airplane.
    In order to maintain the level of safety envisioned in Sec.  
25.361(b), more comprehensive criteria is needed for the new generation 
of high-bypass engines. The special conditions would distinguish 
between the more common engine failure events and those rare events 
resulting from structural failures. For these rarer but more severe 
seizure events, the criteria could allow some deformation in the engine 
supporting structure (ultimate load design) in order to absorb the 
higher energy associated with the high-bypass engines, while at the 
same time protecting the adjacent primary structure in the wing and 
fuselage by providing a higher safety factor. The criteria for the more 
severe events would no longer be a pure static torque load condition, 
but would account for the full spectrum of transient dynamic loads 
developed from the engine failure condition.

Applicability

    As discussed above, these special conditions are applicable to the 
Bombardier Aerospace Model BD-100-1A10 airplane. Should Bombardier 
Aerospace apply at a later date for a change to the type certificate to 
include another model incorporating the same novel or unusual design 
feature, these special conditions would apply to that model as well 
under the provisions of Sec.  21.101(a)(1) [Amendment 21-69, effective 
September 16, 1991].

List of Subjects in 14 CFR Part 25

    Aircraft, Aviation safety, 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 Bombardier Aerospace Model BD-100-1A10 
airplanes.
    1. Sudden Engine Stoppage. In lieu of compliance with Sec.  
25.361(b), the following special conditions apply:
    a. For turbine engine installations, the engine mounts, pylons, and 
adjacent supporting airframe structure must be designed to withstand 1g 
level flight loads acting simultaneously with the maximum limit torque 
loads imposed by each of the following:
    (1) Sudden engine deceleration due to a malfunction which could 
result in a temporary loss of power or thrust.
    (2) The maximum acceleration of the engine.
    b. For auxiliary power unit installations, the power unit mounts 
and adjacent supporting airframe structure must be designed to 
withstand 1g level flight loads acting simultaneously with the maximum 
limit torque loads imposed by each of the following:
    (1) Sudden auxiliary power unit deceleration due to malfunction or 
structural failure.
    (2) The maximum acceleration of the auxiliary power unit.
    c. For engine supporting structure, an ultimate loading condition 
must be considered that combines 1g flight loads with the transient 
dynamic loads resulting from each of the following:
    (1) The loss of any fan, compressor, or turbine blade.
    (2) Where applicable to a specific engine design, and separately 
from the conditions specified in paragraph c(1) above, any other engine 
structural failure that results in higher loads.
    d. The ultimate loads developed from the conditions specified in 
paragraphs c(1) and c(2) above are to be multiplied by a factor of 1.0 
when applied to engine mounts and pylons and multiplied by a factor of 
1.25 when applied to adjacent supporting airframe structure.

    Issued in Renton, Washington, on March 6, 2003.
Ali Bahrami,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 03-6332 Filed 3-14-03; 8:45 am]
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