[Federal Register Volume 70, Number 68 (Monday, April 11, 2005)]
[Proposed Rules]
[Pages 18321-18322]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 05-7192]


 ========================================================================
 Proposed Rules
                                                 Federal Register
 ________________________________________________________________________
 
 This section of the FEDERAL REGISTER contains notices to the public of 
 the proposed issuance of rules and regulations. The purpose of these 
 notices is to give interested persons an opportunity to participate in 
 the rule making prior to the adoption of the final rules.
 
 ========================================================================
 

  Federal Register / Vol. 70, No. 68 / Monday, April 11, 2005 / 
Proposed Rules  

[[Page 18321]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM304; Notice No. 25-05-03-SC]


Special Conditions: Airbus Model A318 Airplanes Equipped With 
Pratt and Whitney PW6000 Engines; Sudden Engine Stoppage

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed special conditions.

-----------------------------------------------------------------------

SUMMARY: This document proposes special conditions for Airbus Models 
A318-121 and A318-122 airplanes equipped with Pratt and Whitney PW6000 
engines. These airplanes will have novel or unusual design features 
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 proposed 
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: Comments must be received on or before May 26, 2005.

ADDRESSES: Comments on this proposal may be mailed in duplicate to: 
Federal Aviation Administration, Transport Airplane Directorate, Attn: 
Rules Docket (ANM-113), Docket No. NN304, 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. NM304. 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: Tim Dulin, FAA, International Branch, 
ANM-116, Transport Airplane Directorate, Aircraft Certification 
Service, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; 
telephone (425) 227-2141; facsimile (425) 227-1232.

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 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 
this proposal for 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 December 22, 1998, Airbus submitted an application to the FAA to 
amend Type Certificate No. A28NM to include the new Model A318 airplane 
equipped with Pratt and Whitney PW6000 engines (Models A318-121 and 
A318-122) or with optional CFMI CFM56 engines (Models A318-111 and 
A318-112). On May 14, 2002, Airbus applied for extension of the 
application for the Model A318 airplanes equipped with PW6000 engines 
and selected a new reference date of application of November 15, 2001.
    The Airbus Model A318 airplane is a shortened reduced capacity 
version of the Model A320-200. The Model A318 will have a maximum 
passenger capacity of 136 versus a maximum passenger capacity of 179 
for the Model A320 series airplanes and 145 for the Model A319 series 
airplanes. The fuselage length is reduced by four and one half frames 
(94 inches) compared to the Model A319 series airplanes. The maximum 
takeoff weight will be 59,000 kg (130,000 pounds) with growth options 
to 68,000 kg (150,000 pounds) versus maximum takeoff weight range of 
68,000 kg to 77,000 kg for the Model A320 series airplanes and 64,000 
kg to 75,500 kg for the Model A319 series airplanes. The Model A318 
will be powered by all new Pratt and Whitney PW6000 engines or by CFMI 
CFM56-5B engines all in the 22,000 to 24,000 pound thrust range. Other 
changes include a new engine/nacelle and pylon adaptation for the 
PW6000 engine installation.

Type Certification Basis

    Under the provisions of 14 CFR 21.101, Airbus must show that the 
Model A318 airplane, equipped with Pratt and Whitney PW6000 engines, 
meets the applicable provisions of the regulations incorporated by 
reference in Type Certificate No. A28NM or the applicable regulations 
in effect on the date of application for the change to the type 
certificate.
    The regulations incorporated by reference in the type certificate 
are commonly referred to as the ``original type certification basis.''
    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 Airbus Model A318 airplane, 
equipped with Pratt and Whitney PW6000 engines, because of a novel or 
unusual design feature, special conditions are prescribed under the 
provisions of 14 CFR 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 21.101.
    Special conditions are initially applicable to the model for which 
they are issued. Should the type certificate for that model be amended 
later to

[[Page 18322]]

include any other model that incorporates the same novel or unusual 
design feature, or should any other model already included on the same 
type certificate be modified to incorporate 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.

Novel or Unusual Design Features

    The Airbus Model A318 airplane, equipped with Pratt and Whitney 
PW6000 engines, will incorporate novel or unusual design features 
involving engine size and torque load that affect sudden engine 
stoppage conditions.

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 is rare.
    Relative to the engine configurations that existed when the rule 
was developed in 1957, the present generation of engines is 
sufficiently different and novel to justify issuance of special 
conditions to establish appropriate design standards. The latest 
generation of jet engines is 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 Airbus Models A318-121 and A318-122 (equipped with Pratt 
and Whitney PW6000 engines).
    Airbus Models A318-111 and A318-112 (equipped with CFMI CFM56-5B 
engines) will not be subject to the same special conditions because 
these engines and their supporting structure are unchanged from the 
basic Model A320, for which no special conditions were applied.
    In order to maintain the level of safety envisioned in Sec.  
25.361(b), more comprehensive criteria are needed for the new 
generation of high bypass engines. The proposed special conditions 
would distinguish between the more common seizure events and those rare 
seizure events resulting from structural failures. For these rare 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 
Airbus Models A318-121 and A318-122 airplanes equipped with Pratt and 
Whitney PW6000 engines. Should Airbus 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.

Conclusion

    This action affects certain novel or unusual design features on the 
Airbus Model A318 airplane equipped with Pratt and Whitney PW6000 
engines. 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 Airbus Model A318 airplane equipped with Pratt and Whitney PW6000 
engines.
    In lieu of compliance with 14 CFR 25.361(b), the following special 
condition applies:
    1. Sudden Engine Stoppage.
    (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 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 March 24, 2005.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 05-7192 Filed 4-8-05; 8:45 am]
BILLING CODE 4910-13-P