[Federal Register Volume 59, Number 112 (Monday, June 13, 1994)]
[Unknown Section]
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From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-13626]


  Federal Register / Vol. 59, No. 112 / Monday, June 13, 1994 /
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[[Page Unknown]]

[Federal Register: June 13, 1994]


                                                   VOL. 59, NO. 112

                                              Monday, June 13, 1994

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 93-NM-182-AD; Amendment 39-8932; AD 94-12-04]

 

Airworthiness Directives; Boeing Model 747 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain Boeing Model 747 series airplanes, that requires 
repetitive inspections to detect cracking in certain fuselage skin lap 
joints, and repair, if necessary. This amendment is prompted by the 
results of extensive pressure fatigue tests conducted by the 
manufacturer. The actions specified by this AD are intended to detect 
and repair fatigue cracking in certain lap joints, which will ensure 
safe operation of airplanes that have exceeded their economic design 
goal.

DATES: Effective July 13, 1994.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of July 13, 1994.

ADDRESSES: 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 Federal 
Aviation Administration (FAA), Transport Airplane Directorate, Rules 
Docket, 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: Steven C. Fox, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (206) 227-2777; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations to include an airworthiness directive (AD) that is 
applicable to certain Boeing Model 747 series airplanes was published 
in the Federal Register on December 17, 1993 (58 FR 65943). That action 
proposed to require repetitive high frequency eddy current (HFEC) 
inspections to detect cracking in certain fuselage skin lap joints, and 
repair, if necessary.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.
    One commenter supports the proposed rule.
    One commenter requests that Revision 1 of Boeing Service Bulletin 
747-53-2367, dated January 27, 1994, be included as an additional 
source of service information. The FAA concurs. Since the issuance of 
the proposal, the FAA has reviewed and approved Revision 1 of Boeing 
Service Bulletin 747-53-2367, dated January 27, 1994, which clarifies 
the procedures for accomplishment of the inspections described in the 
Initial Release of the service bulletin, dated December 18, 1991 (which 
was referenced in the proposal as the sole source of appropriate 
service information). Therefore, paragraphs (a) and (c) of the final 
rule have been revised to reference Revision 1 of the service bulletin 
as an additional source of service information.
    This same commenter requests that the proposed rule be revised to 
include a reporting requirement to keep Boeing and the FAA advised of 
findings of cracks. The FAA does not concur. The FAA has determined 
that the unsafe condition addressed by this AD (which is to detect and 
repair fatigue cracking in certain lap joints) will be adequately 
addressed by paragraph (a) of the final rule, which requires the 
inspection of certain lap joints, and paragraph (c) of the final rule, 
which requires the repair of all cracks found during the inspection. 
Therefore, since the final rule requires repetitive inspections to 
detect cracks and repair of all findings of cracks, the FAA finds that 
a reporting requirement would unduly burden operators.
    This commenter further requests that the proposed rule be revised 
to compensate for operators that fly with cabin pressure differentials 
of 2.0 psi or less when calculating the number of flight cycles to 
determine the compliance time. The FAA does not concur. The FAA finds 
that operating at cabin pressure differentials of 2.0 psi or less is 
applicable to only one operator. Since there are numerous factors that 
affect the calculation of flight cycles, such as total number of low 
pressure cycles, amount of thrust, number of gross weight flight 
cycles, etc., the FAA has determined that these mitigating factors 
could be best evaluated through requests for alternative methods of 
compliance, as provided for in paragraph (d) of the final rule.
    One commenter requests that the proposed compliance time of 22,000 
flight cycles be extended to 25,000 flight cycles to inspect the lap 
joints in areas outside of Stringer 14 since data indicate that 
cracking in these areas did not occur until after 25,000 flight cycles. 
The FAA does not concur. In developing an appropriate compliance time 
for this AD, the FAA not only evaluated the fatigue test data that was 
provided by the manufacturer, but took into consideration the size of 
the test sample: the test results were based upon just one airplane 
that had no loads and was not pressurized. Based on this data, the FAA 
determined that 22,000 flight cycles represented a conservative 
threshold for initiating inspections so as to ensure that any cracking 
initiation would be found in a timely manner.
    Another commenter requests that the proposed compliance time of 
3,000 flight cycles to perform the repetitive inspections be extended 
to 4,300 flight cycles to coincide with operators' regularly scheduled 
maintenance periods. The FAA does not concur. The FAA has determined 
that the compliance time, as proposed, represents the maximum interval 
of time allowable for the affected airplanes to continue to operate 
without compromising safety. In developing this inspection interval, 
the FAA evaluated the reliability of the inspection method and the 
results of fatigue test data. The FAA found that extending this 
interval by more than one-third would allow cracks to propagate 
undetected, which would adversely affect the structural integrity of 
the airplane.
    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with the change previously 
described. The FAA has determined that this change will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.
    There are approximately 723 Model 747 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 183 
airplanes of U.S. registry will be affected by this AD, that it will 
take approximately 14 work hours per airplane to accomplish the 
required actions, and that the average labor rate is $55 per work hour. 
Based on these figures, the total cost impact of the AD on U.S. 
operators is estimated to be $140,910, or $770 per airplane.
    The total cost impact figure discussed above is based on 
assumptions that no operator has yet accomplished any of the 
requirements of this AD action, and that no operator would accomplish 
those actions in the future if this AD were not adopted.
    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.
    For the reasons discussed above, I certify that this action: (1) Is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it 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:

94-12-04  Boeing: Amendment 39-8932. Docket 93-NM-182-AD.

    Applicability: Model 747-100, -200, -300, 747SP, and 747SR 
series airplanes, as listed in Boeing Service Bulletin 747-53-2367, 
dated December 18, 1991, certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent structural failure in the fuselage due to fatigue 
cracking in certain lap joints, accomplish the following:
    (a) Prior to the accumulation of 22,000 full pressure flight 
cycles (or, if the external skin panel of an affected lap joint has 
been replaced: Prior to the accumulation of 22,000 full pressure 
flight cycles since skin replacement), or within 1,000 landings 
after the effective date of this AD, whichever occurs later, perform 
an external surface high frequency eddy current (HFEC) inspection of 
the skin around the upper row of fasteners in accordance with the 
Accomplishment Instructions of Boeing Service Bulletin 747-53-2367, 
dated December 18, 1991; or Revision 1, dated January 27, 1994.
    (b) If no crack is found, repeat the inspection at intervals not 
to exceed 3,000 full pressure flight cycles.
    (c) If any crack is found, accomplish paragraphs (c)(1) and 
(c)(2) of this AD.
    (1) Prior to further flight, perform an open hole HFEC 
inspection to detect cracking in the upper row fastener holes 
between the adjacent frames in accordance with the Accomplishment 
Instructions of Boeing Service Bulletin 747-53-2367, dated December 
18, 1991; or Revision 1, dated January 27, 1994. Prior to further 
flight, repair any crack found in accordance with the 747 Structural 
Repair Manual, Chapter 53-30-03.
    (2) Repeat the inspection required by paragraph (a) of this AD 
at intervals not to exceed 3,000 full pressure flight cycles.
    (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), 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: 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 
Secs. 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 inspections shall be done in accordance with Boeing 
Service Bulletin 747-53-2367, dated December 18, 1991; or Boeing 
Service Bulletin 747-53-2367, Revision 1, dated January 27, 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 July 13, 1994.

    Issued in Renton, Washington, on May 31, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-13626 Filed 6-10-94; 8:45 am]
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