[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
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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
