[Federal Register Volume 63, Number 97 (Wednesday, May 20, 1998)]
[Proposed Rules]
[Pages 27696-27698]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-13406]



[[Page 27696]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-186-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 767 Series Airplanes

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 767 series 
airplanes. This proposal would require repetitive inspections to detect 
improper installation or fatigue damage of the end cap of the forward 
engine mount, and replacement of the end cap assembly with an improved 
assembly. Such replacement, when accomplished, would terminate the 
repetitive inspections. This proposal is prompted by a report of 
fatigue cracking of end cap bolts caused by improper installation. 
Subsequent investigation revealed that properly installed caps also are 
subject to early fatigue cracking. The actions specified by the 
proposed AD are intended to prevent failure of the end cap assembly, 
which could lead to separation of the engine from the airplane in the 
event of a primary thrust linkage failure.

DATES: Comments must be received by July 6, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 97-NM-186-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: Todd T. Martin, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-2770; 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 97-NM-186-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. 97-NM-186-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received a report of broken end cap bolts of the 
forward engine mount, which were found during overhaul of a Pratt & 
Whitney PW4000 engine that had been installed on a Boeing Model 747-400 
series airplane. Investigation revealed that the end cap had been 
installed backwards. A properly installed end cap assembly does not 
normally react any significant engine thrust loads; it is intended to 
provide a secondary load path if the primary thrust linkage fails. An 
end cap installed backwards will react the engine thrust loads along 
with the primary thrust linkage, a condition which will result in 
premature fatigue failure of the end cap or bolts. In addition, fatigue 
analysis and testing have confirmed that a properly installed end cap 
would fail within a low number of flight cycles after a primary thrust 
linkage failure. Failure of the end cap assembly, if not corrected, 
could lead to separation of the engine from the airplane in the event 
of a primary thrust linkage failure.
    There is a high degree of similarity between the configurations of 
the engine installations on the Model 747-400 and certain Model 767 
series airplanes. The FAA may consider rulemaking to address this 
condition on Model 747-400 series airplanes; therefore, this proposed 
rule is applicable only to Model 767 series airplanes.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Alert Service Bulletin 
767-71A0087, dated October 10, 1996, which describes procedures for 
repetitive visual inspections to detect improper installation or 
fatigue damage of the end cap of the forward engine mount, and 
replacement of the end cap assembly with an improved assembly. Such 
replacement would eliminate the need for the repetitive inspections. 
Accomplishment of this replacement, as described in the alert service 
bulletin, 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 accomplishment of the actions specified in 
the alert service bulletin described previously, except as discussed 
below.

Differences Between Proposed Rule and Alert Service Bulletin

    Boeing Alert Service Bulletin 767-71A0087 divides the affected 
airplanes into three groups depending upon the particular engine 
configuration of the affected airplane, and provides different 
procedures depending upon group classification and engine on-wing 
flight cycles. Operators should note that the alert service bulletin 
specifies that operators of certain Group 2 airplanes should contact 
the manufacturer for instructions. However, this proposed AD would not 
require that the manufacturer be contacted, but rather that Group 2 
airplanes (regardless of accumulated on-wing flight cycles) be treated 
the same as Group 1 airplanes. That is, this proposed AD would not 
distinguish between the two airplane groups; therefore, the proposed

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inspections, terminating actions, and compliance times would be 
identical for both Group 1 and Group 2 airplanes.
    In addition, some of the compliance times specified in this 
proposed rule are different from those stated in the alert service 
bulletin. Specifically, this proposed AD expresses certain compliance 
times in terms of both flight cycles and flight hours, whereas the 
alert service bulletin expresses certain compliance times in terms of 
flight hours only. The reason for this difference is to account for 
those airplanes on which average mission lengths vary significantly 
from the fleet norm.
    Additionally, the alert service bulletin specifies that the visual 
inspections required by this proposed AD may be accomplished in 
accordance with either the Boeing 767 Airplane Maintenance Manual or 
``an operator's equivalent procedure.'' However, this proposed AD 
requires that the actions be accomplished in accordance with the 
procedures specified in the Chapter 71-00-00 of the 767 Airplane 
Maintenance Manual. An ``operator's equivalent procedure'' may be used 
only if approved as an alternative method of compliance in accordance 
with the provisions specified in paragraph (e) of this proposed AD.

Cost Impact

    There are approximately 239 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 96 airplanes of U.S. registry 
would be affected by this proposed AD.
    It would take approximately 37 work hours per airplane (18.5 work 
hours per engine) to accomplish the proposed inspections, at an average 
labor rate of $60 per work hour. Based on these figures, the cost 
impact of this proposed inspection on U.S. operators is estimated to be 
$213,120, or $2,220 per airplane, per inspection cycle.
    It would take approximately 135 work hours per airplane (67.5 work 
hours per engine) to accomplish the proposed replacement of the forward 
engine mount end cap and bolts, at an average labor rate of $60 per 
work hour. Required parts would cost approximately $1,000 per airplane. 
Based on these figures, the cost impact of this proposed replacement on 
U.S. operators is estimated to be $873,600, or $9,100 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 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-186-AD.

    Applicability: Model 767 series airplanes; as listed in Boeing 
Alert Service Bulletin 767-71A0087, dated October 10, 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 
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 prevent possible separation of the engine from the airplane 
in the event of a primary thrust linkage failure, accomplish the 
following:
    (a) For Groups 1 and 2 airplanes: Except as provided by 
paragraph (c) of this AD, accomplish paragraphs (a)(1), (a)(2), and 
(a)(3) of this AD, as applicable, in accordance with Boeing Alert 
Service Bulletin 767-71A0087, dated October 10, 1996.
    (1) Within 500 flight hours or 300 flight cycles after the 
effective date of this AD, whichever occurs later: Accomplish Work 
Package 1 (visual inspection of the forward engine mount). 
Thereafter, repeat Work Package 1 at the intervals specified in the 
alert service bulletin until the requirements of either paragraph 
(a)(2) or (a)(3) of this AD are accomplished.
    (2) Prior to the accumulation of 16,000 total flight cycles on 
any engine or within 500 flight hours or 300 flight cycles after the 
effective date of this AD, whichever occurs latest: Accomplish Work 
Package 2 (non-destructive test inspection of the forward engine 
mount). Thereafter, repeat Work Package 2 on that engine at the 
intervals specified in the alert service bulletin until the 
requirements of paragraph (a)(3) of this AD are accomplished. 
Accomplishment of Work Package 2 constitutes terminating action for 
the repetitive inspections required by paragraph (a)(1) of this AD 
for that engine.
    (3) Within 3 years after the effective date of this AD: 
Accomplish Work Package 3 (end cap and bolt replacement of the 
forward engine mount). Accomplishment of Work Package 3 constitutes 
terminating action for the requirements of this AD.
    (b) For Group 3 airplanes: Within 3 years after the effective 
date of this AD, accomplish Work Package 4 (Bolt Replacement) in 
accordance with Boeing Alert Service Bulletin 767-71A0087, dated 
October 10, 1996.
    (c) Where Boeing Alert Service Bulletin 767-71A0087, dated 
October 10, 1996, specifies that the actions required by this AD may 
be accomplished in accordance with an ``operator's equivalent 
procedure,'' the actions must be accomplished in accordance with 
Chapter 71-00-00 of the Boeing 767 Airplane Maintenance Manual 
(AMM), as specified in the alert service bulletin.
    (d) If any discrepancy (including an improperly installed end 
cap or fatigue damage to the end cap assembly or thrust linkage) is 
found during any inspection required by this AD, prior to further 
flight, accomplish Work Package 3 in accordance with Boeing Alert 
Service Bulletin 767-71A0087, dated October 10, 1996.
    (e) As of the effective date of this AD, no person shall install 
a forward engine mount end cap having part number 310T3026-1 on any 
airplane.
    (f) An alternative method of compliance or adjustment of the 
compliance time that

[[Page 27698]]

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 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (g) 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 May 14, 1998.
John J. Hickey,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-13406 Filed 5-19-98; 8:45 am]
BILLING CODE 4910-13-U