[Federal Register Volume 63, Number 2 (Monday, January 5, 1998)]
[Proposed Rules]
[Pages 169-171]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-118]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-78-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 777 Series Airplanes 
Equipped With Pratt & Whitney Engines and Used in Extended Range Twin-
Engine Operations (ETOPS)

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Boeing Model 777 series 
airplanes equipped with Pratt & Whitney engines. This proposal would 
require replacement of the integrated drive generator (IDG) and the 
backup generator with a new IDG and a new backup generator. This 
proposal is prompted by reports of IDG shaft failure resulting from 
design problems in the hydraulic and mechanical systems of the 
generator, and by reports of backup generator failure resulting from 
the failure of the oil pressure switch. The actions specified by the 
proposed AD are intended to prevent continued degradation of the power 
system, which could result in loss of electrical power.

DATES: Comments must be received by February 19, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 97-NM-78-AD, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056. Comments may be inspected at this location 
between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal 
holidays.
    The service information referenced in the proposed rule may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington.

FOR FURTHER INFORMATION CONTACT: Chris Hartonas, Aerospace Engineer, 
Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane 
Directorate, Seattle Aircraft Certification Office; 1601 Lind Avenue, 
SW., Renton, Washington 98055-4056; telephone (425) 227-2864; fax (425) 
227-1181.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket No. 97-NM-78-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRM's

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules 
Docket No. 97-NM-78-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has been monitoring the reliability of the electrical power 
system

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of the Boeing Model 777 series airplane since its introduction into 
service. Design modifications that have improved the reliability of the 
electrical power system have been incorporated on Model 777 series 
airplanes equipped with Rolls-Royce and General Electric engines; these 
modifications are proposed to be incorporated on Model 777 series 
airplanes equipped with Pratt & Whitney engines and used in extended 
range twin-engine operations (ETOPS) to bring systems reliability 
within acceptable levels.
    The FAA has received reports indicating that the backup generator 
and the shaft of the integrated drive generator (IDG) failed on certain 
Boeing Model 777 series airplanes. Specifically, the FAA received five 
reports of IDG shaft failures. Investigation revealed problems with the 
generator's hydraulic and mechanical systems.
    Further, numerous failures of the backup generator have been 
reported by operators. Investigation revealed that the pressure relief 
valve in the backup generator may cause excessive fluctuation of the 
oil-in pressure. This fluctuation may result in failure of the low oil 
pressure switch, and consequent failure of the backup generator.
    These conditions, if not corrected, could result in continued 
degradation of the power system and consequent loss of electrical 
power.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 777-24-
0012, dated August 1, 1996, which describes procedures for replacing 
the IDG with a unit having a different part number. Replacement of the 
existing IDG with an IDG of improved design will reduce torque on the 
IDG shaft and wear on the IDG fixed blocks.
    The FAA also has reviewed and approved Boeing Service Bulletin 777-
24-0017, Revision 1, dated April 10, 1997, which describes procedures 
for replacing the backup generator with a new backup generator.
    Accomplishment of the actions specified in the service bulletins is 
intended to adequately address the identified unsafe condition.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require replacement of the IDG and the backup 
generator with a new IDG and a new backup generator. The actions would 
be required to be accomplished in accordance with the service bulletins 
described previously.

Cost Impact

    There are approximately 38 Boeing Model 777 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 22 
airplanes of U.S. registry would be affected by this proposed AD, that 
it would take approximately 18 work hours per airplane to accomplish 
the proposed actions, and that the average labor rate is $60 per work 
hour. Required parts would cost approximately $50,000 per airplane. 
Based on these figures, the cost impact of the proposed AD on U.S. 
operators is estimated to be $1,123,760, or $51,080 per airplane.
    The cost impact figure discussed above is based on assumptions that 
no operator has yet accomplished any of the proposed requirements of 
this AD action, and that no operator would accomplish those actions in 
the future if this AD were not adopted.

Regulatory Impact

    The regulations proposed herein would not have substantial direct 
effects on the States, on the relationship between the national 
government and the States, or on the distribution of power and 
responsibilities among the various levels of government. Therefore, in 
accordance with Executive Order 12612, it is determined that this 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, will not have a significant economic impact, 
positive or negative, on a substantial number of small entities under 
the criteria of the Regulatory Flexibility Act. A copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
part 39 of the Federal Aviation Regulations (14 CFR part 39) as 
follows:

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

Boeing: Docket 97-NM-78-AD.

    Applicability: Model 777 series airplanes equipped with Pratt & 
Whitney engines and used in Extended Range Twin-Engine Operations 
(ETOPS); as listed in Boeing Service Bulletins 777-24-0017, Revision 
1, dated April 10, 1997, and 777-24-0012, dated August 1, 1996; 
certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
otherwise modified, altered, or repaired in the area subject to the 
requirements of this AD. For airplanes that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (b) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent failure of the integrated drive generator (IDG) shaft 
and the backup generator, which could result in continued 
degradation of the power system and consequent loss of electrical 
power, accomplish the following:
    (a) Within 8 months after the effective date of this AD, 
accomplish the requirements of paragraphs (a)(1) and (a)(2) of this 
AD, as applicable.
    (1) For airplanes identified in Boeing Service Bulletin 777-24-
0012, dated August 1, 1996: Replace the IDG with a new IDG in 
accordance with Figure 1 or Figure 2 of the service bulletin, as 
applicable.
    (2) For airplanes identified in Boeing Service Bulletin 777-24-
0017, Revision 1, dated April 10, 1997: Replace the backup generator 
and its engine wiring harness with new components in accordance with 
the service bulletin.
    (b) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Seattle Aircraft Certification 
Office (ACO). Operators shall submit their requests through an 
appropriate FAA Principal Maintenance Inspector, who may add 
comments and then send it to the Manager, Seattle ACO.

    Note 2: Information concerning the existence of approved 
alternative methods of

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compliance with this AD, if any, may be obtained from the Seattle 
ACO.

    (c) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the airplane to a location where 
the requirements of this AD can be accomplished.

    Issued in Renton, Washington, on December 29, 1997.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-118 Filed 1-2-98; 8:45 am]
BILLING CODE 4910-13-P