[Federal Register: March 17, 2003 (Volume 68, Number 51)]
[Rules and Regulations]
[Page 12581-12582]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr17mr03-3]
[[Page 12581]]
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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.
[[Page 12582]]
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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