[Federal Register Volume 65, Number 86 (Wednesday, May 3, 2000)]
[Proposed Rules]
[Pages 25696-25697]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-11064]



[[Page 25696]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-98-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747 Series Airplanes 
Equipped With Pratt & Whitney (PW) JT9D-7Q and JT9D-7Q3 Turbofan 
Engines

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 747 series 
airplanes. This proposal would require a detailed visual inspection to 
detect evidence of wear or contact between the precooler support 
fitting and link assembly; and rework and reidentification of the 
fitting. This proposal is prompted by a report of rupturing of a 
diffuser case on a PW JT9D-7Q engine due to cracking in the outer 
pressure wall in the rear skirt area. The actions specified by the 
proposed AD are intended to prevent contact between the precooler 
support link and the precooler support fitting, which could contribute 
to an uncontained failure of the diffuser case and damage to the 
airplane.


DATES: Comments must be received by June 19, 2000.


ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2000-NM-98-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: Dionne Krebs, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, 1601 
Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 227-
2250; 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 Number 2000-NM-98-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    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. 2000-NM-98-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    In January 1997, the diffuser case on a Pratt & Whitney (PW) JT9D-
7Q engine ruptured when the engine was at takeoff power at the 
beginning of a takeoff roll. The engine was installed on a Boeing Model 
747-251 airplane. Both engine side cowl doors, a precooler, and other 
hardware were ejected from the engine as a result of the rupture of the 
diffuser case. The escaping gas and engine debris blew out the engine 
pylon access panels and created holes, cracks, and other damage to the 
leading edge, aileron, and flaps of the wing.
    The diffuser case fracture was due to a crack that most likely 
developed in a toolmark that was left by a blending operation adjacent 
to the dog-bone-shaped embossment at the 11 o'clock circumferential 
location of the outer pressure wall of the case in the area of the rear 
skirt. Although extensive investigation of the incident could not 
determine the source of the vibration that caused the crack to progress 
in a high-cycle fatigue mode, the investigation did reveal evidence of 
contact between the precooler support link and the precooler support 
fitting.
    Contact between the precooler support link and the precooler 
support fitting may result in additional vibration through the mount 
boss to the case. The additional vibration caused by contact of the 
support link and the support fitting may have contributed to 
propagation of the crack. Such contact between the precooler support 
link and precooler support fitting, if not corrected, could contribute 
to an uncontained failure of the diffuser case and damage to the 
airplane.

Explanation of Relevant Service Information

    Boeing has issued Service Letter 747-SL-36-089, dated August 10, 
1998, which describes procedures for reworking certain precooler 
support fittings. Accomplishment of the action specified in the service 
letter 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 a detailed visual inspection to detect 
evidence of wear or contact between the precooler support fitting and 
link assembly; and rework and reidentification of the fitting. The 
rework would be required to be accomplished in accordance with the 
service letter described previously.

Cost Impact

    There are approximately 79 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 27 airplanes of U.S. registry 
would be affected by this proposed AD.
    It would take approximately 2 work hours per airplane to accomplish 
the proposed inspection, and that the average labor rate is $60 per 
work hour. Based on these figures, the cost impact of the proposed 
inspection on U.S. operators is estimated to be $3,240, or $120 per 
airplane.
    It would take approximately 16 work hours per airplane to 
accomplish the proposed rework, and that the average labor rate is $60 
per work hour. No parts are required to accomplish the rework. Based on 
these figures, the cost impact of the proposed rework on U.S.

[[Page 25697]]

operators is estimated to be $25,920, or $960 per airplane.
    The cost impact figures discussed above are 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 a substantial direct 
effect 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, it 
is determined that this proposal would not have federalism implications 
under Executive Order 13132.
    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 2000-NM-98-AD.

    Applicability: Model 747 airplanes, certificated in any 
category; equipped with Pratt & Whitney JT9D-7Q and JT9D-7Q3 
turbofan engines.

    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 (c) 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 contact between the precooler support link and the 
precooler support fitting, which could contribute to an uncontained 
failure of the diffuser case and damage to the airplane, accomplish 
the following:
    (a) For any precooler support fitting having P/N 65B90924-1 or 
P/N 65B90924-600 that has not been reworked to the dimensions 
specified in Boeing Service Letter 747-SL-36-089, dated August 10, 
1998: Within 6,000 hours time-in-service after the effective date of 
this AD, or within 18 months after the effective date of this AD, 
whichever occurs first, perform a detailed visual inspection to 
detect evidence of contact wear or contact between the precooler 
support fitting and link assembly, P/N 69B93162-1 or 69B93162-3, in 
accordance with the service letter.
    (1) If no evidence of contact wear or contact between the 
precooler support fitting and link assembly is found: At the next 
engine removal, rework the precooler support fitting to the 
dimensions specified in the service letter, in accordance with the 
service letter; and permanently and legibly reidentify the support 
fitting as P/N 65B09024-601.
    (2) If any evidence of contact wear or contact between the 
precooler support fitting and link assembly is found: Prior to 
further flight, rework the precooler support fitting to the 
dimensions specified in the service letter, in accordance with the 
service letter; and permanently and legibly reidentify the support 
fitting as P/N 65B09024-601.

    Note 2: For the purposes of this AD, a detailed visual 
inspection is defined as: ``An intensive visual examination of a 
specific structural area, system, installation, or assembly to 
detect damage, failure, or irregularity. Available lighting is 
normally supplemented with a direct source of good lighting at 
intensity deemed appropriate by the inspector. Inspection aids such 
as mirror, magnifying lenses, etc., may be used. Surface cleaning 
and elaborate access procedures may be required.''

    (b) For any precooler support fitting having P/N 65B90924-1 or 
P/N 65B90924-600 that has been reworked to the dimensions specified 
in Boeing Service Letter 747-SL-36-089, dated August 10, 1998, but 
has not been permanently and legibly reidentified: Within 6,000 
hours time-in-service or 18 months after the effective date of this 
AD, whichever occurs first, permanently and legibly reidentify the 
reworked fitting as P/N 65B09024-601.

Alternative Methods of Compliance

    (c) 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 Permit

    (d) 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.

    Issued in Renton, Washington, on April 27, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-11064 Filed 5-2-00; 8:45 am]
BILLING CODE 4910-13-P