[Federal Register Volume 62, Number 29 (Wednesday, February 12, 1997)]
[Proposed Rules]
[Pages 6499-6502]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-3433]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-12-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes to revise an existing airworthiness 
directive (AD), applicable to certain Boeing Model 747 series 
airplanes, that currently requires repetitive inspections of the access 
doors to the midspar/spring beam fuse pins on all engine pylons to 
detect cracks on the external surface; repetitive inspections of each 
midspar/spring beam fuse pin to detect if it protrudes beyond its 
mating nut by a specified distance; and repair of any discrepancy 
found. The actions specified by that AD are intended to prevent 
migration of this fuse pin, which, if not detected and corrected in a 
timely manner, could result in failure of the engine pylon and 
consequent separation of the engine from the wing. This new action 
would increase the intervals between inspections of the access doors 
and each midspar/spring beam fuse pin, and consequently decrease the 
frequency of inspections. This proposal is prompted by new data 
provided the manufacturer indicating

[[Page 6500]]

that the reported migration of the fuse pin was apparently the result 
of an incorrectly installed nut.

DATES: Comments must be received by March 10, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 97-NM-12-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: Tamara L. Dow, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (206) 227-2771; fax (206) 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-12-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-103, Attention: Rules 
Docket No. 97-NM-12-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On December 23, 1996, the FAA issued AD 96-26-52, amendment 39-9868 
(62 FR 302, January 3, 1997), which is applicable to certain Boeing 
Model 747 series airplanes. It requires repetitive detailed visual 
inspections of the access doors to the midspar/spring beam fuse pins on 
all engine pylons to detect cracks on the external surface, and repair, 
if necessary. In addition, the AD requires repetitive detailed visual 
inspections of each midspar/spring beam fuse pin to detect if it 
protrudes beyond its mating nut by a specified distance, and repair, if 
necessary.
    That action was prompted by a report indicating that a fuse pin had 
migrated on an inboard spring beam fitting on the Number 1 engine pylon 
of a Boeing Model 747-400 airplane.
    The requirements of that AD are intended to prevent migration of 
this fuse pin, which, if not detected and corrected in a timely manner, 
could result in failure of the engine pylon and consequent separation 
of the engine from the wing.

Actions Since Issuance of Previous Rule

    Subsequent to the issuance of that AD, the manufacturer conducted 
an additional inspection and analysis of the fuse pin (and its mated 
self-locking nut) whose migration had been reported to the FAA, and 
which was pertinent to the incident that prompted the issuance of AD 
96-26-52.
    The manufacturer reports that, normally, when a self-locking nut is 
correctly installed, the last 2 to 3 threads of the nut will show signs 
of this installation. However, according to the data gathered from the 
recent inspection, no such signs were found associated with the nut 
that was used on the migrant fuse pin. Based on that observation and 
further testing, the manufacturer has concluded that the self-locking 
nut was incorrectly installed on the fuse pin that was the subject of 
the reported incident. The migration of that fuse pin was apparently 
attributed to the incorrect installation of its mating nut, and not to 
some other phenomenon.

FAA's Conclusions

    The new information presented the by manufacturer have led the FAA 
to reconsider the current inspection requirements of AD 96-26-52. Based 
on these new data, as well as the fact that there have been no reported 
findings of discrepancies associated with the fuse pins as a result of 
the inspections required by AD 96-26-52, the FAA finds that the 
repetitive inspection intervals that are currently required by that AD 
may be unnecessarily conservative.
    AD 96-26-52 currently requires that the inspections be conducted at 
intervals not to exceed 150 landings or 1,000 hours time-in-service, 
whichever occurs first. However, the FAA has determined that the 
repetitive interval can be extended to 1,000 landings or 18 months, 
whichever occurs first, without compromising safety. This interval 
would closely parallel regularly scheduled maintenance inspections 
(``C'' checks) for the majority of affected operators. Operators then 
will be able to conduct the inspections when the airplanes are located 
at a main base, where special equipment and trained personnel would be 
readily available, if necessary.
    The FAA finds that inspections conducted at the revised interval 
will provide an acceptable level of safety and will ensure that any 
discrepancies are found and detected in a timely manner.
    Further, this revised schedule will provide an effective program of 
regular inspections during the period prior to accomplishing the 
modifications of the nacelle strut and wing structure required by AD 
95-13-05 [amendment 39-9285 (60 FR 33333, June 28, 1995), as corrected 
at 60 FR 35452, July 7, 1995] and AD 95-13-06 [amendment 39-9286 (60 FR 
33338, June 28, 1995), as corrected at 60 FR 37500, July 20, 1995]. 
Once those modifications are accomplished, the inspections required by 
this AD are no longer necessary.

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 action would revise AD 96-26-52. It would continue to require:
    1. repetitive inspections of the access doors to the midspar/spring 
beam fuse pins on all engine pylons to detect cracks on the external 
surface;
    2. repetitive inspections of each midspar/spring beam fuse pin to 
detect if it protrudes beyond its mating nut by a specified distance; 
and
    3. repair of any discrepancy found.
    However, this proposed action would revise the AD by increasing the 
intervals between the repetitive inspections to

[[Page 6501]]

1,000 landings or 18 months, whichever occurs first.

Cost Impact

    There are approximately 459 Boeing Model 747 series airplanes of 
the affected design in the worldwide fleet, and the FAA estimates that 
44 airplanes of U.S. registry would be affected by this proposed AD.
    It would take approximately 4 work hours per airplane to accomplish 
each cycle of proposed inspections, at an average rate of $60 per work 
hour. Based on these figures, the cost impact of the proposed AD on 
U.S. operators is estimated to be $10,560 per inspection cycle, or $240 
per airplane, per inspection cycle. (By increasing the intervals 
between inspections, this proposed AD would result in inspections being 
conducted less frequently than is now required.)
    The cost impact figure discussed above is 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 removing amendment 39-9868 (62 FR 
302, January 3, 1997), and by adding a new airworthiness directive 
(AD), to read as follows:

    BOEING: Docket 97-NM-12-AD. Revises AD 96-26-52, amendment 39-
9868.

    Applicability: Model 747 series airplanes having line numbers 1 
through 1046, inclusive; certificated in any category; that meet all 
of the following criteria:
    <bullet> Equipped with Pratt & Whitney Model PW4000 series 
engines, or General Electric Model CF6-80C2 series engines, or Rolls 
Royce Model RB211 series engines;
    <bullet> On which fuse pins having part numbers 310U2301-101, -
116, -117, or -120 (``third generation'' fuse pins) are installed at 
the midspar/spring beam fittings of the engine pylon; and
    <bullet> On which the modification of the nacelle strut and wing 
structure in accordance with Boeing Alert Service Bulletin 747-
54A2156 or Boeing Alert Service Bulletin 747-54A2157, as applicable, 
has not been accomplished.

    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 request approval for an 
alternative method of compliance in accordance with paragraph (c) 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 failure of the engine pylon and consequent separation 
of the engine from the wing, due to migration of the fuse pins 
installed at the midspar/spring beam fittings of the pylon, 
accomplish the following:
    (a) Within 15 days after January 8, 1997 [the effective date of 
AD 96-26-52, amendment 39-9868), accomplish the requirements of 
paragraphs (a)(1) and (a)(2) of this AD.
    (1) Perform a detailed visual inspection of the access doors to 
each midspar/spring beam fuse pin on each engine pylon to detect 
cracks on the external surface of the doors.
    (i) If no cracking is detected during the inspection, repeat 
that inspection at intervals not to exceed 1,000 landings or 18 
months, whichever occurs first.
    (ii) If any cracking is detected during the inspection, prior to 
further flight, repair in accordance with a method approved by the 
Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport 
Airplane Directorate. Thereafter, repeat the inspection at intervals 
not to exceed 1,000 landings or 18 months, whichever occurs first.
    (2) Gain access through the aft fairing doors of each engine 
pylon to each midspar/spring beam fuse pin and its mating, self-
locking nut, and perform a detailed visual inspection of each fuse 
pin to verify that at least one thread of the fuse pin protrudes 
beyond its mating, self-locking nut.
    (i) If no discrepancy is detected during the inspection, repeat 
that inspection at intervals not to exceed 1,000 landings or 18 
months, whichever occurs first.
    (ii) If the inspection reveals that at least one thread does not 
protrude beyond its mating, self-locking nut, prior to further 
flight, repair in accordance with a method approved by the Manager, 
Seattle ACO, FAA, Transport Airplane Directorate. Thereafter, repeat 
the inspection at intervals not to exceed 1,000 landings or 18 
months, whichever occurs first.
    (b) Accomplishment of the modification of the nacelle strut and 
wing structure in accordance with Boeing Alert Service Bulletin 747-
54A2156, Revision 2, dated December 21, 1995, or earlier revisions 
(for airplanes equipped with General Electric Model CF6-80C2 series 
engines, or Pratt & Whitney PW4000 series engines); or Boeing Alert 
Service Bulletin 747-54A2157, Revision 2, dated November 14, 1996, 
or earlier revisions (for airplanes with Rolls Royce Model RB211 
series engines); as applicable; constitutes terminating action for 
the repetitive detailed visual inspections required by paragraphs 
(a)(1) and (a)(2) 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 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.


[[Page 6502]]


    Issued in Renton, Washington, on February 5, 1997.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-3433 Filed 2-11-97; 8:45 am]
BILLING CODE 4910-13-U