[Federal Register Volume 67, Number 37 (Monday, February 25, 2002)]
[Proposed Rules]
[Pages 8485-8487]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-4411]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM205; Special Conditions No. 25-01-05-SC]


Special Conditions: Fairchild Dornier GmbH, Model 728-100; Sudden 
Engine Stoppage

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

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SUMMARY: This notice proposes special conditions for the Fairchild 
Dornier GmbH Model 728-100 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.

[[Page 8486]]


DATES: Comments must be received on or before April 11, 2002.

ADDRESSES: Comments on this proposal may be mailed in duplicate to: 
Federal Aviation Administration, Transport Airplane Directorate, 
Attention: Rules Docket (ANM-113), Docket No. NM205, 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. NM205. 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: Tom Groves, FAA, International Branch, 
ANM-116, Transport Airplane Directorate, Aircraft Certification 
Service, 1601 Lind Avenue SW., Renton, Washington 98055-4056; telephone 
(425) 227-1503; facsimile (425) 227-1149.

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA invites interested persons to participate in this 
rulemaking by submitting written comments, data, or views. The most 
helpful comments reference a specific portion of the proposal, 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 proposed 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 notice 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 the 
proposed special conditions in light of the comments we receive.
    If you want the FAA to acknowledge receipt of your comments on this 
proposal, 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 May 5, 1998, Fairchild Dornier GmbH applied for a type 
certificate for their new Model 728-100 airplane. The Model 728-100 
airplane is a 70-85 passenger twin-engine regional jet with a maximum 
takeoff weight of 77,600 pounds.

Type Certification Basis

    Under the provisions of 14 CFR 21.17, Fairchild Dornier must show 
that the Model 728-100 airplane meets the applicable provisions of part 
25, as amended by Amendments 25-1 through 25-96. Fairchild Dornier GmbH 
has also applied to extend the certification basis to include 
Amendments 25-97, 25-98, and 25-104.
    If the Administrator finds that the applicable airworthiness 
regulations (i.e., 14 CFR part 25) do not contain adequate or 
appropriate safety standards for the Model 728-100 airplane because of 
a novel or unusual design feature, special conditions are prescribed 
under the provisions of Sec. 21.16.
    Special conditions, as defined in 14 CFR 11.19, are issued in 
accordance with Sec. 11.38 and become part of the type certification 
basis in accordance with 14 CFR 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 14 CFR 21.101(a)(1).
    In addition to the applicable airworthiness regulations and special 
conditions, the Model 728-100 airplane 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 issue a 
finding of regulatory adequacy pursuant to section 611 of Public Law 
92-574, the ``Noise Control Act of 1972.''

Novel or Unusual Design Features

    The Fairchild Dornier GmbH Model 728-100 airplane will incorporate 
novel or unusual design features involving engine size and torque load 
that affect sudden engine stoppage conditions. Fairchild Dornier GmbH 
proposes to treat the sudden engine stoppage condition resulting from 
structural failure as an ultimate load condition. Section 25.361(b)(1) 
of part 25 specifically defines the seizure torque load, resulting from 
structural failure, as a limit load condition.

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. 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 are 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 Fairchild Dornier GmbH Model 728-100 airplane.
    In order to maintain the level of safety envisioned in 
Sec. 25.361(b), a more comprehensive criteria is needed for the new 
generation of high bypass engines. The proposed special conditions 
would distinguish between the more common seizure events and those 
rarer seizure events resulting from structural failures. For these 
rarer but severe seizure events, the proposed 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 
Fairchild Dornier GmbH Model 728-100 airplane. Should Fairchild Dornier 
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 section 21.101(a)(1). Fairchild Dornier has submitted 
applications for certification

[[Page 8487]]

of both increased and reduced passenger capacity derivatives of the 
Model 728-100 airplane. These derivative models are designated the 
Model 928-100 airplane and the Model 528-100 airplane, respectively. As 
currently proposed, these derivative models share the same design 
feature of a high-bypass ratio fan jet engine as the Model 728-100 
airplane, and it is anticipated that they will be included in the 
applicability of these proposed special conditions.

Conclusion

    This action affects only certain novel or unusual design features 
on the Fairchild Dornier GmbH Model 728-100 airplane. It is not a rule 
of general applicability, and it affects only the applicant who applied 
to the FAA for approval of these features on the airplane.

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 Proposed Special Conditions

    Accordingly, the Federal Aviation Administration (FAA) proposes the 
following special conditions as part of the type certification basis 
for Fairchild Dornier GmbH Model 728-100 airplanes.
    1. Sudden Engine Stoppage. In lieu of compliance with 14 CFR 
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 the 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 1.(c)(1), 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 February 13, 2002.
Ali Bahrami,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 02-4411 Filed 2-22-02; 8:45 am]
BILLING CODE 4910-13-P