[Federal Register Volume 61, Number 22 (Thursday, February 1, 1996)]
[Rules and Regulations]
[Pages 3550-3552]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-1572]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 95-NM-276-AD; Amendment 39-9496; AD 96-03-01]


Airworthiness Directives; Boeing Model 747 Series Airplanes

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 lower engine mount to determine if the 
tangential link upper bolt and nut are oriented properly, and if the 
tangential link upper bolt nut is torqued within certain limits. This 
action also requires replacement of the bolt and nut with serviceable 
parts, if necessary, and requires certain follow-on actions for 
airplanes on which the upper bolt is missing. Terminating action is 
also provided by this AD. This amendment is prompted by reports of 
migration of bolts completely from the tangential link of the aft 
engine mount, a condition which would reduce the capability of the 
retention system for the engine. The actions specified in this AD are 
intended to prevent separation of the engine from the airplane due to 
migration of the tangential link upper bolt.

DATES: Effective February 16, 1996.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of February 16, 1996.
    Comments for inclusion in the Rules Docket must be received on or 
before April 1, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 95-NM-276-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: Tammy L. Dow, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue SW., Renton, Washington; telephone (206) 227-2771; fax 
(206) 227-1181.

SUPPLEMENTARY INFORMATION: Recently, the FAA received reports 
indicating that the upper bolt and nut of the tangential link of the 
aft engine on Model 747 airplanes were found to have migrated out of 
proper position. In three cases, the bolt had completely backed out of 
the hole. Analysis conducted by the manufacturer demonstrated that the 
nuts used to secure the bolts may not provide adequate run-on torque. 
Additionally, there was evidence that lubricants were used on the 
threads of some of the bolts. These conditions can allow the nut to 
rotate and disengage from the bolt. With no nut or other retention for 
the bolt, normal vibration causes the bolt to loosen and migrate out of 
the tangential link. Loss of the bolt would reduce the capability of 
the engine retention system, and could result in cracking of the engine 
turbine exhaust case due to the increased load. This condition, if not 
corrected, could 

[[Page 3551]]
result in separation of the engine from the airplane.
    The FAA has reviewed and approved Boeing Alert Service Bulletin 
747-71A2277, dated November 29, 1995, which describes procedures for 
repetitive inspections of the lower engine mount to verify if the 
tangential link upper bolt nut is properly oriented and to verify that 
the tangential link upper bolt nut is torqued within certain limits. 
Additionally, the service bulletin describes procedures for the 
replacement of the bolt and nut with serviceable parts, if necessary. 
The alert service bulletin also describes certain other follow-on 
procedures for airplanes on which the tangential link upper bolt is 
missing. Those procedures involve a visual inspection to detect damage 
and deformation of the lower engine mount lugs that attach the affected 
safety link; magnetic particle inspections to detect cracking of the 
lower engine mount lugs; detail visual inspections to detect cracking, 
bulging, discoloration, and corrosion of the engine mounts and adjacent 
structures; and replacement of the lower engine mount fittings with 
serviceable parts, if necessary; installation of new safety links, 
bolts, and nuts; and installation of the tangential link upper bolt.
    The FAA also has reviewed and approved Boeing Service Bulletin 747-
71-2206, Revision 1, dated November 12, 1987 (as revised by Boeing 747 
Notice of Status Change No. 747-71-2206 NSC 1, dated December 4, 1987, 
and Boeing 747 Notice of Status Change No. 747-71-2206 NSC 2, dated 
March 17, 1988). This service information describes procedures for 
replacement of the safety links with modified safety links. 
Accomplishment of this replacement eliminates the need for repetitive 
inspections of lower engine mount bolt and nut.
    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 possible separation of 
the engine from the airplane due to consequences associated with the 
complete migration of the tangential link upper bolt. This action 
requires repetitive visual inspections to verify if the tangential link 
upper bolt is correctly oriented; inspections to determine if the 
tangential link upper bolt nut is torqued within certain limits; and 
replacement of the bolt and nut with serviceable parts, if necessary. 
This action also requires certain other follow-on procedures for 
airplanes on which the tangential link upper bolt is missing. 
Additionally, this AD provides for replacement of the safety links as 
optional terminating action for the repetitive inspection requirements. 
The actions are required to be accomplished in accordance with the 
service bulletins described previously.
    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.
    This is considered to be interim action. Once final action is 
identified, the FAA may consider further rulemaking.

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 rule must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 95-NM-276-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 that it 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 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 USC 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

96-03-01 Boeing: Amendment 39-9496. Docket 95-NM-276-AD.

    Applicability: Model 747 series airplanes, as listed in Boeing 
Alert Service Bulletin 747-71A2277, dated November 29, 1995; 
certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
otherwise 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 use the authority 
provided in paragraph (c) of this AD to request approval from the 
FAA. This approval may address either no action, if the 

[[Page 3552]]
current configuration eliminates the unsafe condition; or different 
actions necessary to address the unsafe condition described in this 
AD. Such a request should include an assessment of the effect of the 
changed configuration on the unsafe condition addressed by this AD. 
In no case does the presence of any modification, alteration, or 
repair remove any airplane from the applicability of this AD.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent separation of the engine from the airplane, 
accomplish the following:
    (a) Within 90 days after the effective date of this AD, 
accomplish the requirements of paragraphs (a)(1) and (a)(2) of this 
AD in accordance with Boeing Alert Service Bulletin 747-71A2277, 
dated November 29, 1995.
    (1) Perform a visual inspection to ensure that installation of 
the tangential link upper bolt nut is on the forward side of the 
engine mount fitting.
    (i) If the tangential link upper bolt nut is installed on the 
forward side of the engine mount fitting, repeat the visual 
inspection at intervals not to exceed 18 months.
    (ii) If the tangential link upper bolt is not installed on the 
forward side of the engine mount fitting, prior to further flight, 
remove the nut, bolt, and washers and reinstall the nut, bolt, and 
washers in accordance with the alert service bulletin. Thereafter, 
repeat the visual inspection at intervals not to exceed 18 months.
    (iii) If the tangential link upper bolt is missing from the 
engine mount fitting, prior to further flight, perform the various 
follow-on actions in accordance with the alert service bulletin. 
(The follow-on actions include visual inspections, magnetic particle 
inspections, replacement of the lower engine mount fitting with a 
serviceable part, if necessary; installation of new safety links, 
bolts, and nuts; and installation of a new tangential link upper 
bolt.) Thereafter, repeat the visual inspection at intervals not to 
exceed 18 months.
    (2) Perform an inspection to verify that the torque value of the 
tangential link upper bolt (on both sides of the mount) is within 
the limits specified in the alert service bulletin.
    (i) If the torque value of the tangential link upper bolt nut is 
within the limits specified in the alert service bulletin, repeat 
the inspection (verification) at intervals not to exceed 18 months.
    (ii) If the torque value of the tangential link upper bolt nut 
is outside the limits specified in the alert service bulletin, prior 
to further flight, perform a visual inspection of the tangential 
link upper bolt and washer for any damage or discrepancy, in 
accordance with the alert service bulletin.
    (A) If no damage or discrepancy of the tangential link upper 
bolt and washers is found, prior to further flight, replace the bolt 
nut with a new or serviceable part in accordance with the alert 
service bulletin. Thereafter, repeat the inspection (verification) 
specified in paragraph (a)(2) of this AD at intervals not to exceed 
18 months.
    (B) If any damage or discrepancy of the tangential link upper 
bolt and washers is found, prior to further flight, replace the 
damaged or discrepant part with a new or serviceable part, and 
replace the bolt nut with a new or serviceable part, in accordance 
with the alert service bulletin. Thereafter, repeat the inspection 
(verification) specified in paragraph (a)(2) of this AD at intervals 
not to exceed 18 months.
    (b) Replacement of the safety links with modified safety links 
in accordance with Boeing Service Bulletin 747-71-2206, dated April 
16, 1987; or Boeing Service Bulletin 747-71-2206, Revision 1, dated 
November 12, 1987, as revised by Boeing Notice of Status Change No. 
747-71-2206 NSC 1, dated December 4, 1987, and Boeing Notice of 
Status Change No. 747-71-2206 NSC 2, dated March 17, 1988; 
constitutes terminating action for the repetitive inspection 
requirements of this AD.
    (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 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (d) 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.
    (e) The inspections, replacement, and follow-on actions shall be 
done in accordance with Boeing Alert Service Bulletin 747-71A2277, 
dated November 29, 1995. 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.
    (f) This amendment becomes effective on February 16, 1996.

    Issued in Renton, Washington, on January 22, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-1572 Filed 1-31-96; 8:45 am]
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