AD Amdt-39-11456

[Federal Register Volume 64, Number 235 (Wednesday, December 8, 1999)]
[Rules and Regulations]
[Pages 68618-68620]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 99-31472]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-323-AD; Amendment 39-11456; AD 99-25-13]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 777-200 and -300 Series 
Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to all Boeing Model 777-200 and -300 series airplanes. 
This action requires revising the Limitations Section of the Airplane 
Flight Manual to prohibit the dispatch of certain airplanes under 
certain conditions. This amendment also requires repetitive inspections 
to ensure correct operation of the backup generators; and, for certain 
airplanes, a one-time inspection to detect damage of the engine 
external gearbox; and corrective actions, if necessary. This amendment 
is prompted by reports of inflight shutdowns due to sheared backup 
generator shafts. The actions specified in this AD are intended to 
prohibit the dispatch of an airplane with an engine-mounted backup 
generator having a sheared shaft; and to detect and correct damage to 
the engine, which could result in inflight shutdowns.

DATES: Effective December 23, 1999.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of December 23, 1999.
    Comments for inclusion in the Rules Docket must be received on or 
before February 7, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 99-NM-323-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056.
    The service information referenced in this AD 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; or at 
the Office of the Federal Register, 800 North Capitol Street, NW., 
suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Ed Hormel, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, 
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-2681; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION: The FAA has received reports of two recent 
inflight engine shutdowns that were initiated by a failure of the 
engine-driven backup generator (including a sheared shaft), and 
consequent failure of the engine gearbox oil pump due to contamination 
from the damaged backup generator drive bearing in the engine gearbox. 
Most backup generator shaft shear events are the result of leaking 
driveshaft seals, or improper servicing of the backup generator during 
maintenance. The current Model 777 Master Minimum Equipment List allows 
airplane operation for up to 10 days with a failed backup generator 
shaft. Both inflight shutdowns occurred on Boeing Model 777 series 
airplanes equipped with Rolls-Royce Trent 800 series turbofan engines. 
However, the FAA has determined that the same unsafe condition may also 
occur on General Electric GE90 and Pratt & Whitney PW4000 series 
turbofan engines, since the same backup generators are installed on 
airplanes having these engines.
    Investigation continues in determining the exact reason for the 
backup generator shaft shear events and consequent engine failures. 
However, the FAA considers that improper servicing of the backup 
generator oil system could be a contributing factor. Consequently, 
improper servicing or improper replacement of the backup generator by 
the same individual, on both engines on the same flight, could lead to 
the failure of both generators, and result in a common-cause failure 
and inflight shutdown of both engines.

Explanation of Relevant Service Information

    The FAA has reviewed and approved the following Boeing 777 Service 
Letters that recommend temporary revisions to the backup generator 
servicing and dispatch (operational) procedures for Model 777 series 
airplanes equipped with Trent 800, GE90, and PW4000 series turbofan 
engines.
    <bullet> 777-SL-24-023-B, dated August 16, 1999, ``Back Up 
Generator Servicing and Dispatch Requirements--Temporary Revision--RR 
Installations.''
    <bullet> 777-SL-24-024, dated August 16, 1999, ``Back Up Generator 
Servicing and Dispatch Requirements--Temporary Revision--GE 
Installations.''
    <bullet> 777-SL-24-025, dated August 18, 1999, ``Back Up Generator 
Servicing and Dispatch Requirements--Temporary Revision--PW 
Installations.''
    The FAA also has reviewed and approved Rolls-Royce Service Bulletin 
RB.211-72-C813, Revision 1, dated July 16, 1999, which describes 
certain maintenance actions (i.e., an inspection of the engine external 
gearbox to detect damage, and corrective actions, if necessary) for 
Trent 800 series turbofan engines, which are recommended by Rolls-Royce 
in the event of a backup generator low oil pressure/shaft shear event.

Explanation of the Requirements of the Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other Boeing Model 777 series airplanes of the same 
type design, this AD is being issued to require revising the 
Limitations Section of the Airplane Flight Manual (AFM) to prohibit the 
dispatch of Model 777 series airplanes having backup generators with 
sheared shafts; and to prohibit any extended twin-engine operations 
(ETOPS) flight until a non-ETOPS flight of at least one hour in 
duration is accomplished, following replacement of the backup generator 
on both the left and right engines with a new or serviceable backup 
generator. This amendment also requires repetitive inspections to 
ensure correct operation of the backup generators; and, for certain 
airplanes, a one-time inspection to detect damage of the engine 
external gearbox; and corrective actions, if necessary. The actions are 
required to be

[[Page 68619]]

accomplished in accordance with the service information described 
previously except as discussed below.

Differences Between the AD and the Service Information

    Boeing Service Letters 777-SL-24-023-B and 777-SL-24-024 recommend 
against the dispatch of Boeing Model 777 series airplanes equipped with 
Trent 800 or GE90 series turbofan engines having a sheared shaft on the 
backup generator. Service Letter 777-SL-24-025, applicable to Boeing 
Model 777 series airplanes equipped with PW4000 series turbofan 
engines, does not recommend against the operation of Model 777 series 
airplanes having a sheared shaft on the backup generator. However, this 
AD prohibits dispatch of any Model 777 series airplane having a sheared 
shaft on the backup generator. This AD also prohibits any extended 
twin-engine operations (ETOPS) flight until a non-ETOPS flight of at 
least one hour in duration is accomplished, following replacement of 
the backup generator on both the left and right engines with a new or 
serviceable backup generator.
    In addition, this AD requires certain Rolls-Royce Trent 800 engine 
maintenance actions that are recommended in Rolls-Royce Service 
Bulletin RB.211-72-C813, Revision 1, but that are not included in the 
Boeing Service Letter 777-SL-24-023-B for Rolls-Royce engines. Such 
maintenance actions are required by this AD if a backup generator shaft 
has sheared within the last 250 flight hours, or if the gearbox 
inspections specified in Revision 1 of the Rolls-Royce service bulletin 
were not accomplished.

Interim Action

    This is considered to be interim action until final action is 
identified, at which time the FAA may consider further rulemaking.

Determination of Rule's Effective Date

    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the 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 that 
summarizes each FAA-public contact concerned with the substance of this 
AD will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 99-NM-323-AD.'' The postcard will be date stamped and 
returned to the commenter.

Regulatory Impact

    The regulations adopted herein will 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 final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a ``significant regulatory 
action'' under Executive Order 12866. It has been determined further 
that this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket. 
A copy of it, if filed, may be obtained from the Rules Docket at the 
location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends 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:

99-25-13  Boeing: Amendment 39-11456. Docket 99-NM-323-AD.

    Applicability: Model 777-200 and -300 series airplanes equipped 
with Rolls-Royce Trent 800, General Electric GE90, or Pratt & 
Whitney PW4000 series turbofan engines; certificated in any 
category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
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 (f) 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 prohibit dispatch of an airplane with an engine-mounted 
backup generator having a sheared shaft; and to detect and correct 
damage to the engine, which could result in inflight shutdowns; 
accomplish the following:

Revisions to the Airplane Flight Manual

    (a) For all airplanes: Within 14 days after the effective date 
of this AD, revise the Limitations Section of the FAA-approved 
Airplane Flight Manual (AFM) to include the following information. 
This may be accomplished by inserting a copy of this AD in the AFM.
    ``Dispatch of the airplane with an engine-mounted backup 
generator having a sheared shaft is prohibited.
    Following replacement of the backup generator on both the left 
and right engines,

[[Page 68620]]

extended twin-engine operations (ETOPS) flight is prohibited until a 
non-ETOPS flight of at least one hour in duration is accomplished.''

Prohibited Servicing or Replacement

    (b) For all airplanes: As of 14 days after the effective date of 
this AD, servicing of both the left and right backup generators or 
replacement of both backup generators with new or serviceable 
components by the same individual prior to the same flight is 
prohibited.

One-Time Actions for Rolls-Royce Engines

    (c) For airplanes equipped with Rolls-Royce Trent 800 series 
turbofan engines: Within 14 days after the effective date of this 
AD, determine whether the status message ``ELEC BACKUP GEN L(R)'' 
and the maintenance message ``Backup generator L(R) has a sheared 
shaft'' have occurred within the last 250 flight hours prior to the 
effective date of this AD. If these messages have occurred during 
that time, accomplish follow-on corrective actions, as applicable, 
at the times specified in paragraphs C.1.(c) and D. of Rolls-Royce 
Service Bulletin RB.211-72-C813, Revision 1, dated July 16, 1999, in 
accordance with the procedures specified in the service bulletin.

    Note 2: Boeing Service Letter 777-SL-24-023-B, dated August 16, 
1999, references Rolls-Royce Service Bulletin RB.211-72-C813, 
Revision 1, dated July 16, 1999, as an additional source of service 
information to accomplish certain actions required by this AD.

Inspections and Corrective Actions

    (d) Within 14 days after the effective date of this AD, and 
thereafter prior to each flight: Accomplish paragraph (d)(1), 
(d)(2), or (d)(3) of this AD, as applicable.

Rolls-Royce Engines

    (1) For airplanes equipped with Rolls-Royce Trent 800 series 
turbofan engines, accomplish paragraphs (d)(1)(i) and (d)(1)(ii) of 
this AD.
    (i) Inspect the Electrical Maintenance Page of the engine 
indicating and crew alerting system (EICAS), and perform follow-on 
corrective actions, as applicable, at the times specified in and in 
accordance with the procedures specified in Boeing Service Letter 
777-SL-24-023-B, dated August 16, 1999.
    (ii) If the status message ``ELEC BACKUP GEN L(R)'' is active: 
Prior to further flight, inspect the Maintenance Access Terminal 
(MAT) for certain maintenance messages indicating a sheared shaft or 
low oil pressure, as specified in Step 2.a. of Boeing Service Letter 
777-SL-24-023-B, dated August 16, 1999; and accomplish the 
corrective actions specified in Steps 2.a.(1) or 2.a.(2), as 
applicable, in accordance with that service letter.

General Electric Engines

    (2) For airplanes equipped with General Electric GE90 series 
turbofan engines: If the status message ``ELEC BACKUP GEN L(R)'' is 
active, prior to further flight, inspect the MAT for certain 
maintenance messages indicating a sheared shaft or low oil pressure, 
as specified in Step 1.a. of Boeing Service Letter 777-SL-24-024, 
dated August 16, 1999; and accomplish the corrective actions 
specified in Steps 1.a.(1) or 1.a.(2), as applicable, in accordance 
with the service letter.

Pratt & Whitney Engines

    (3) For Model 777 series airplanes equipped with Pratt & Whitney 
PW4000 series turbofan engines: If the status message ``ELEC BACKUP 
GEN L(R)'' is active, prior to further flight, inspect the MAT for 
certain maintenance messages indicating a sheared shaft or low oil 
pressure, as specified in Step 1.a. of Boeing Service Letter 777-SL-
24-025, dated August 18, 1999, in accordance with that service 
letter.
    (i) If any of the specified maintenance messages is active, 
prior to further flight, remove and replace the backup generator in 
accordance with Airplane Maintenance Manual (AMM) 24-25-01-000-801 
or 24-25-01-400-801, as applicable.
    (ii) If the backup generator shaft is found to be sheared, or 
either of the low oil pressure messages are active, prior to further 
flight, accomplish the corrective actions specified in Step 1.a.(1) 
of Boeing Service Letter 777-SL-24-025, dated August 18, 1999, in 
accordance with that service letter.

Flight Test After Replacement of Backup Generators

    (e) For all airplanes: As of 14 days after the effective date of 
this AD, following any replacement of the backup generator on both 
the left and right engines, accomplish paragraphs (c)(1) and (c)(2) 
of this AD at the times specified in those paragraphs.
    (1) Prior to any ETOPS flight, conduct a non-revenue test flight 
of at least one hour in duration, or a non-ETOPS flight that is 
either a non-revenue or revenue flight of at least one hour in 
duration.
    (2) Prior to further flight after accomplishment of the action 
required by paragraph (e)(1) of this AD: Verify accomplishment of 
the maintenance actions required by paragraph (d)(1), (d)(2), or 
(d)(3) of this AD, as applicable.

Alternative Methods of Compliance

    (f) 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), FAA, Transport Airplane Directorate. 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 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

Special Flight Permits

    (g) Special flight permits may be issued in accordance with 
Secs. 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.

Incorporation by Reference

    (h) Except as provided by paragraphs (a) and (d)(3)(i) of this 
AD, the actions shall be done in accordance with Rolls-Royce Service 
Bulletin RB.211-72-C813, Revision 1, dated July 16, 1999; Boeing 
Service Letter 777-SL-24-023-B, dated August 16, 1999; Boeing 
Service Letter 777-SL-24-024, dated August 16, 1999; or Boeing 
Service Letter 777-SL-24-025, dated August 18, 1999; as applicable. 
This incorporation by reference was approved by the Director of the 
Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 
51. Copies may be obtained from Boeing Commercial Airplane Group, 
P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be 
inspected at the FAA, Transport Airplane Directorate, 1601 Lind 
Avenue, SW., Renton, Washington; or at the Office of the Federal 
Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
    (i) This amendment becomes effective on December 23, 1999.

    Issued in Renton, Washington, on November 30, 1999.
D.L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-31472 Filed 12-7-99; 8:45 am]
BILLING CODE 4910-13-U