[Federal Register Volume 59, Number 93 (Monday, May 16, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-11522]
[[Page Unknown]]
[Federal Register: May 16, 1994]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 94-NM-59-AD; Amendment 39-8912; AD 94-10-05]
Airworthiness Directives; Boeing Model 747 Series Airplanes
Equipped With Pratt & Whitney JT9D-3 and -7 Series Engines
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 certain Boeing Model 747 series airplanes. This action
requires inspections of the forward lower engine mount bolts for
migration and damage, inspections of the bolt bushings for damage,
torque checks of the nuts installed on these bolts, and correction of
any discrepancies. This amendment is prompted by reports of migration
of the bolts that attach the forward engine mount universal block to
the engine lugs. The actions specified in this AD are intended to
prevent migration of the bolts out of the engine lug joint, which could
result in loss of the engine from the strut.
DATES: Effective May 31, 1994.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of May 31, 1994.
Comments for inclusion in the Rules Docket must be received on or
before July 15, 1994.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 94-NM-59-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: Tim Backman, Aerospace Engineer,
Airframe Branch, ANM-120S, Seattle Aircraft Certification Office, FAA,
Transport Airplane Directorate, 1601 Lind Avenue SW., Renton,
Washington 98055-4056; telephone (206) 227-2776; fax (206) 227-1181.
SUPPLEMENTARY INFORMATION: Five operators of Boeing Model 747 series
airplanes, equipped with Pratt & Whitney JT9D-3 and -7 series engines,
have reported cases of migration of the bolts that attach the forward
engine mount universal block to the engine lugs. Investigation of the
most recent case, which occurred in February 1994, revealed that an
engine mount bolt's self-locking nut was missing and the bolt had
partially migrated out of the forward engine mount universal block to
engine lug joint. The bolt migrated approximately one inch inboard, so
that the bolt retainer device sheared and the bolt head came in contact
with the thrust reverser air supply duct; this caused the duct to be
chafed, dented, and cracked. The reason for the missing self-locking
nut has not been determined.
A similar incident was reported in 1982. During troubleshooting of
the fan thrust reverser, one operator found an engine mount bolt that
had migrated due to the loss of the self-locking nut. Like the most
recent case, the reason for the missing self-locking nut was not
determined. Prior to this incident, two other operators had reported
migration of this same bolt after the loss of the nut and washer.
If the bolt were to completely migrate out of the joint, the engine
could separate from the strut. Separation of an engine from the strut
could result in reduced controllability of the airplane.
The FAA has reviewed and approved Boeing Alert Service Bulletin
747-71A2269, dated April 14, 1994, that describes procedures for
repetitive inspections of the forward lower engine mount bolt for
migration and replacement of the nuts if bolt migration exists. It also
describes procedures for inspecting the bolts and bolt bushings for
damage, replacing damaged bolts and bushings, installing new nuts and
modified washers for these bolts, and torque-checking the nut.
The FAA also has reviewed and approved Boeing Service Bulletin 747-
71-2192, dated March 2, 1984, that contains procedures for installing
steel retention brackets. Installation of these brackets will improve
secondary retention of the two bolts that engage the universal block at
the lower forward engine mount.
Since an unsafe condition has been identified that is likely to
exist or develop on other Boeing Model 747 series airplanes of the same
type design, this AD is being issued to prevent complete migration of
the forward lower engine mount bolt out of the joint, which could
result in the separation of the engine from the strut. This AD requires
repetitive visual inspections of the bolt for migration and replacement
of the nuts if bolt migration exists; inspection of the bolts and bolt
bushings for damage, and replacement of damaged bolts and bushings; and
a torque check of the nut. These actions are required to be
accomplished in accordance with Boeing Alert Service Bulletin 747-
71A2269, described previously.
Operators who have previously installed steel retention brackets,
in accordance with Boeing Service Bulletin 747-71-2192, as well as nuts
having part number NAS1805 and certain modified washers, are permitted
to conduct the repetitive inspections for bolt migration at longer
intervals than operators without these items installed on the airplane.
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.
The FAA is considering further rulemaking action to revise this
rule to require the installation of steel retention brackets, nuts
having part number NAS1805, and modified washers on all engine mount
bolts. However, the proposed compliance time for these actions is
sufficiently long so that notice and time for prior public comment
would not be impracticable.
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 notice must submit a self-addressed,
stamped postcard on which the following statement is made: ``Comments
to Docket Number 94-NM-59-AD.'' The postcard will be date stamped and
returned to the commenter.
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 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 14 CFR part
39 of the Federal Aviation Regulations as follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C.
106(g); and 14 CFR 11.89.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new
airworthiness directive:
94-10-05 Boeing: Amendment 39-8912. Docket 94-NM-59-AD.
Applicability: Model 747 series airplanes; equipped with Pratt &
Whitney JT9D-3 and -7 series engines (does not apply to -70 series
engines); certificated in any category.
Compliance: Required as indicated, unless accomplished
previously.
To prevent complete migration of the forward lower engine mount
bolt out of the joint, which could result in the separation of the
engine from the strut, accomplish the following:
(a) For all applicable airplanes: Within 60 days after the
effective date of this AD, visually inspect the forward lower engine
mount for migration of the forward lower engine mount bolts, both
transverse and forward-aft, in accordance with Boeing Alert Service
Bulletin 747-71A2269, dated April 14, 1994 (hereafter referred to as
``the service bulletin''). The maximum gap for the transverse bolt
and the forward-aft bolt in the joint is 0.06 inch; a bolt is
considered to have migrated if the gap exceeds this value. Prior to
further flight, accomplish the requirements of either paragraph (b)
or (c) of this AD, as applicable.
(b) For airplanes not equipped with a steel retention bracket
installed in accordance with Boeing Service Bulletin 747-71-2192 or
its production equivalent, accomplish the following:
(1) If the inspection required by paragraph (a) of this AD
indicates that the bolt has not migrated, accomplish paragraphs
(b)(1)(i) and (b)(1)(ii) of this AD:
(i) Prior to further flight, perform a torque check of the nut
in accordance with the service bulletin. If the torque is outside of
the range specified in the service bulletin, prior to further
flight, replace the nut with a new nut having part number NAS1805
and associated washer.
(ii) Repeat the inspection for migration of bolts with nuts
having part number BACN10JC at intervals not to exceed 2,100 flight
hours. Repeat the inspection for migration of bolts with nuts having
part number NAS1805 at intervals not to exceed 3,200 flight hours.
(2) If the inspection required by paragraph (a) of this AD
indicates that the bolt has migrated, accomplish paragraph (b)(2)(i)
of this AD, and either paragraph (b)(2)(ii) or paragraph
(b)(2)(iii), as applicable:
(i) Prior to further flight, remove the nut and replace it with
a new nut having part number NAS1805 and associated washer, in
accordance with the service bulletin. Thereafter, repeat the
inspection for migration of these bolts at intervals not to exceed
3,200 flight hours.
(ii) Except as provided by paragraph (b)(2)(iii) of this AD:
Prior to further flight, remove the bolt and visually inspect it for
damage, in accordance with Part V of the service bulletin; and
visually inspect the bolt bushings for damage, in accordance with
Part III of the service bulletin. If the bolt is damaged, prior to
further flight, replace the bolt with a new bolt having the same
part number. If the bushings are damaged, prior to further flight,
replace the bushings.
(iii) The inspections of the bolt and bolt bushings required by
paragraph (b)(2)(ii) of this AD may be deferred for a maximum of
3,200 flight hours, provided that all of the following apply:
(A) The bolt is visually inspected for thread damage as
described in Part IV of the service bulletin and no damage is found;
and
(B) The nut threads are still fully engaged with the bolt; and
(C) The migrated bolt has not contacted adjacent structure or
systems; and
(D) The bolt is repositioned back to clamp-up position, as
described in Part IV of the service bulletin.
(c) For airplanes equipped with a steel retention bracket
installed in accordance with Boeing Service Bulletin 747-71-2192 or
its production equivalent, accomplish the following:
(1) If the inspection required by paragraph (a) of this AD
indicates that the bolt has not migrated, accomplish paragraphs
(c)(1)(i) and (c)(1)(ii) of this AD:
(i) Prior to further flight, ensure that the washer on the nut
side does not rotate freely. If the washer rotates freely, prior to
further flight, replace the nut with a new nut having part number
NAS1805 and associated washer.
(ii) Repeat the inspection for migration of bolts with nuts
having part number BACN10JC at intervals not to exceed 3,200 flight
hours. Repeat the inspection for migration of bolts with nuts having
part number NAS1805 at intervals not to exceed 6,000 flight hours.
(2) If the inspection required by paragraph (a) of this AD
indicates that the bolt has migrated, accomplish paragraph (c)(2)(i)
of this AD, and either paragraph (c)(2)(ii) or paragraph
(c)(2)(iii), as applicable:
(i) Prior to further flight, remove the nut and replace it with
a new nut having part number NAS1805 and associated washer, in
accordance with the service bulletin. Thereafter, repeat the
inspection for migration of these bolts at intervals not to exceed
6,000 flight hours.
(ii) Except as provided by paragraph (c)(2)(iii) of this AD:
Prior to further flight, remove the bolt and visually inspect it for
damage, in accordance with Part V of the service bulletin; and
visually inspect the bolt bushings for damage, in accordance with
Part III of the service bulletin. If the bolt is damaged, prior to
further flight, replace the bolt with a new bolt having the same
part number. If the bushings are damaged, prior to further flight,
replace the bushings.
(iii) The inspections of the bolt and bolt bushings required by
paragraph (c)(2)(ii) of this AD may be deferred for a maximum of
3,200 flight hours, provided that all of the following apply:
(A) The bolt is visually inspected for thread damage, as
described in Part IV of the service bulletin, and no damage is
found; and
(B) The nut threads are still fully engaged with the bolt; and
(C) The migrated bolt has not contacted adjacent struture or
systems; and
(D) The bolt is repositioned back to clamp-up position, as
described in Part IV of the service bulletin.
(d) 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: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
(e) 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.
(f) The actions shall be done in accordance with Boeing Alert
Service Bulletin 747-71A2269, dated April 14, 1994. 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.
(g) This amendment becomes effective on May 31, 1994.
Issued in Renton, Washington, on May 6, 1994.
S.R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 94-11522 Filed 5-13-94; 8:45 am]
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