[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]
BILLING CODE 4910-13-P