[Federal Register Volume 59, Number 15 (Monday, January 24, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-1542]


[[Page Unknown]]

[Federal Register: January 24, 1994]


                                                    VOL. 59, NO. 15

                                           Monday, January 24, 1994
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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 93-NM-189-AD]

 

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 the adoption of a new airworthiness 
directive (AD) that is applicable to certain Boeing Model 747 series 
airplanes. This proposal would require inspections to detect cracking 
in certain fuselage upper deck tension ties, and repair or modification 
of any cracked tension ties. This proposal is prompted by reports of 
fatigue cracking in tension ties. The actions specified by the proposed 
AD are intended to prevent failure of two or more tension ties and the 
resultant rapid decompression of the airplane.

DATES: Comments must be received by March 21, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 93-NM-189-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9 a.m. and 3 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: 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:

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 93-NM-189-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. 93-NM-189-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    Recently, the FAA has received reports of fatigue cracking in the 
tension ties on several Boeing Model 747 series airplanes. Most of the 
cracks were found in the aft channel of the tension tie. These cracks 
usually occurred in the upper flange of the aft channel of the tension 
tie. Only one crack was found in the forward channel of the tension 
tie. The cause of this fatigue cracking has been attributed to the 
tension ties bending under cabin pressurization loads. This condition, 
if not corrected, could result in rapid decompression of the airplane 
in the event of failure of two or more tension ties.
    These reports of fatigue cracks were received in response to the 
Supplemental Structural Inspection Program, which was required to be 
implemented by AD 93-06-01, Amendment 39-8526 (58 FR 19571, April 15, 
1993). The purpose of that AD is to implement an inspection program 
that detects the potential for cracking in specific areas of the 
airplane that are critical for flight safety. Whenever cracks are found 
in a Structural Significant Item, the FAA takes rulemaking action to 
correct these findings of an unsafe condition. This proposal is in 
response to such a finding.
    On September 4, 1984, the FAA issued AD 84-19-01, amendment 39-4913 
(49 FR 36365, September 17, 1984), to require inspections of the 
tension tie at body station (BS) 760 on a certain group of Model 747 
series airplanes, and at BS 780 on certain other Model 747 series 
airplanes. The inspections proposed by this rulemaking action do not 
retract the inspection requirements of that AD.
    The FAA has reviewed and approved Boeing Service Bulletin 747-53-
2371, dated July 29, 1993, that describes procedures for repetitive 
detailed visual inspections of the outboard ends of certain tension 
ties, and repair or modification of cracked tension ties. This 
modification entails trimming the cracked portion of the channel of the 
tension tie.
    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require repetitive detailed visual inspections of the 
outboard ends of certain tension ties, and repair or modification of 
cracked tension ties. The actions would be required to be accomplished 
in accordance with the service bulletin described previously.
    There are approximately 203 Boeing Model 747 series airplanes of 
the affected design in the worldwide fleet. The FAA estimates that 113 
airplanes of U.S. registry would be affected by this proposed AD, that 
it would take approximately 5 work hours per airplane to accomplish the 
proposed actions, and that the average labor rate is $55 per work hour. 
Based on these figures, the total cost impact of the proposed AD on 
U.S. operators is estimated to be $31,075, or $275 per airplane. This 
total cost figure assumes that no operator has yet accomplished the 
proposed requirements of this AD action.
    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 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:

Boeing: Docket 93-NM-189-AD.

    Applicability: Model 747 series airplanes, as listed in Boeing 
Service Bulletin 747-53-2371, dated July 29, 1993, certificated in 
any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent rapid decompression of the airplane due to failure of 
two or more tension ties, accomplish the following:
    (a) Prior to the accumulation of 1,000 flight cycles after the 
effective date of this AD, unless accomplished previously within the 
last 2,000 flight cycles, perform a detailed visual inspection to 
detect cracking of the outboard end tension ties, in accordance with 
Boeing Service Bulletin 747-53-2371, dated July 29, 1993.
    (1) If no cracking is detected, repeat the inspection thereafter 
at intervals not to exceed 3,000 flight cycles until the repair or 
modification required by paragraph (a)(2) of this AD is 
accomplished.
    (2) If any cracking is detected, prior to further flight, repair 
or modify the cracked tension tie in accordance with the service 
bulletin. Accomplishment of this repair or modification terminates 
the repetitive inspection requirement of paragraph (a) of this AD.
    Note 1: Although AD 84-19-01, amendment 39-4913, requires 
inspections of the tension ties at body station (BS) 760 on a 
certain group of Model 747 series airplanes, and at BS 780 on 
certain other Model 747 series airplanes, the inspections required 
by this AD do not retract the inspection requirements of that AD.
    (b) Prior to the accumulation of 10,000 flight cycles following 
repair or modification of any tension tie, perform a detailed visual 
inspection to detect cracking of the repaired or modified outboard 
end tension tie in accordance with Boeing Service Bulletin 747-53-
2371, dated July 29, 1993.
    (1) If no cracking is detected, repeat this inspection 
thereafter at intervals not to exceed 6,000 flight cycles.
    (2) If any cracking is detected, prior to further flight, repair 
or modify in accordance with the service bulletin, and repeat the 
inspection required by paragraph (b) 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 FAR 
21.197 and 21.199 to operate the airplane to a location where the 
requirements of this AD can be accomplished.

    Issued in Renton, Washington, on January 18, 1994.
John J. Hickey,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-1542 Filed 1-21-94; 10:00 am]
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