[Federal Register Volume 70, Number 186 (Tuesday, September 27, 2005)]
[Rules and Regulations]
[Pages 56343-56344]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 05-19206]



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  Federal Register / Vol. 70, No. 186 / Tuesday, September 27, 2005 / 
Rules and Regulations  

[[Page 56343]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM304; Special Conditions No. 25-299-SC]


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

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued for the Airbus Model 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 affect 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.

EFFECTIVE DATE: October 27, 2005.

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: 

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 (Model A318-121 and 
A318-122) or with optional CFMI CFM56 engines (Model 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 Code of Federal Regulations (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 Sec.  21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, the Airbus Model A318 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.
    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 Sec.  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 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 novel under the provisions of Sec.  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 torque load that affect sudden engine stoppage 
conditions. Because of rapid improvements in airplane technology, the 
applicable airworthiness regulations do not contain adequate or 
appropriate safety standards for these design features. The special 
conditions for the Airbus Model A318 airplane, equipped with Pratt and 
Whitney PW6000 engines, 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.
    Since 1957, Civil Aviation Regulation 4b.216 and its successors, 
currently Sec.  25.361(b), have required that engine mounts and 
supporting structures be designed to withstand the limit engine torque 
load which is posed by sudden engine stoppage due to malfunction or 
structural failure, such as compressor jamming. Design torque loads 
associated with typical failure scenarios were estimated by the engine 
manufacturer and provided to the airframe manufacturer as limit loads. 
These limit loads were considered simple, pure

[[Page 56344]]

static torque loads. However, 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, if they 
become jammed.
    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 
those produced by the generation of engines in existence when the 
current regulation was developed.
    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 condition would 
distinguish between the more common failure events involving transient 
deceleration conditions with temporary loss of thrust capability and 
those rare events resulting from structural failures. Associated with 
these events, the proposed criteria establish design limit and ultimate 
load conditions.

Discussion of Comments

    Notice of proposed special conditions No. 25-05-03-SC for the 
Airbus Model A318 airplanes equipped with Pratt and Whitney PW6000 
engines, was published in the Federal Register on April 11, 2005 (70 
CFR 18321). No comments were received. However, the FAA has 
reconsidered the inclusion of auxiliary power units in these special 
conditions. While Sec.  25.361(b) is interpreted to apply to auxiliary 
power units, the novel or unusual design features identified above do 
not apply to them. Therefore, auxiliary power units are excluded from 
those special conditions and would continue to be treated under the 
current Sec.  25.361(b). Except for the removal of auxiliary power 
units, these special conditions are adopted as proposed.

Applicability

    As discussed above, these special conditions are applicable to 
Airbus Model 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 other type designs 
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.

Condition

    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.

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 Airbus Model A318 airplane equipped 
with Pratt and Whitney PW6000 engines.
    For turbine engine installations other than auxiliary power units, 
in lieu of compliance with Sec.  25.361(b), the following special 
condition applies:
    (a) 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 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 (b)(1), any other engine 
structural failure that results in higher loads.
    (c) The ultimate loads developed from the conditions specified in 
paragraphs (b)(1) and (b)(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 September 14, 2005.
Kalene C. Yanamura,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 05-19206 Filed 9-26-05; 8:45 am]
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