[Federal Register Volume 59, Number 122 (Monday, June 27, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-14903]


[[Page Unknown]]

[Federal Register: June 27, 1994]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 93-NM-189-AD; Amendment 39-8946; AD 94-13-06]

 

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 
inspections to detect cracking in certain fuselage upper deck tension 
ties, and repair or modification of any cracked tension ties. This 
amendment is prompted by reports of fatigue cracking in tension ties. 
The actions specified by this AD are intended to prevent failure of two 
or more tension ties and the resultant rapid decompression of the 
airplane.

DATES: Effective July 27, 1994.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of July 27, 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 (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to certain Boeing Model 747 series 
airplanes was published in the Federal Register on January 24, 1994 (59 
FR 3527). That action proposed to require inspections to detect 
cracking in certain fuselage upper deck tension ties, and repair or 
modification of any cracked tension ties.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.
    Two commenters support the proposed rule.
    Several commenters request that the proposed 1,000-flight cycle 
compliance time for low-time airplanes be revised to require that the 
inspection be performed ``upon the accumulation of 20,000 total flight 
cycles or within 1,000 flight cycles after the effective date of this 
AD, whichever comes later.'' The FAA does not concur. Since cracking 
has been found on airplanes that had accumulated less than 20,000 
flight cycles, the FAA reasoned that requiring inspection of all 
airplanes within 1,000 flight cycles, regardless of the total number of 
flight cycles, would be prudent to preclude the propagation of cracks 
in airplanes in the Model 747 fleet.
    Two commenters request that the proposed rule be revised to include 
a provision specifying that pressurization cycles of 2.0 psi or less 
need not be counted as a flight cycle when determining the number of 
flight cycles relative to the proposed compliance thresholds. 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. 
The FAA does not consider it appropriate to include various provisions 
in an AD applicable to a single operator's unique use of an affected 
airplane. Further, this commenter does not compile data for each of its 
airplanes so that an individual airplane's pressurization cycles could 
be determined; instead, it uses a fleet average to calculate the 
equivalent number of pressurization cycles. The FAA does not consider 
it appropriate to use approximations for determining compliance with 
this AD. Furthermore, 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 (c) of the final rule.
    One commenter requests that the FAA and Boeing review the 
requirement for inspections contained in AD 93-06-01, amendment 39-8526 
(58 FR 19571, April 15, 1993), which requires that the FAA-approved 
maintenance inspection program include inspections that will give no 
less than the required damage tolerance rating (DTR) for each 
Structural Significant Item (SSI). This commenter states that the 
proposed inspection of the tension ties may be included in the 
requirement for inspections contained in AD 93-06-01. The FAA concurs 
and has reviewed the requirement for inspections contained in AD 93-06-
01. This AD was prompted by reports of fatigue cracks that were 
detected while performing inspections specified by the Supplemental 
Structural Inspection Document (SSID) program, which was required to be 
implemented by AD 93-06-01. The purpose of that AD is to implement an 
inspection program of a sample number of airplanes, which will detect 
the potential for cracking in specific areas of the airplane that are 
critical for safety of flight. Whenever cracks are found in an SSI 
during an inspection in accordance with the SSID program, the FAA takes 
rulemaking action to correct these findings of an unsafe condition 
within the applicable fleet. This AD is issued in response to such a 
finding. Therefore, the FAA will, in a separate rulemaking action, 
revise AD 93-06-01 to remove the requirement to inspect the tension 
ties.
    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 as proposed.
    There are approximately 203 Model 747 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 113 
airplanes of U.S. registry will be affected by this AD, that it will 
take approximately 5 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 $31,075, or $275 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 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. 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:

94-13-06 Boeing: Amendment 39-8946. 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 in accordance with 
paragraph (a)(2) of this AD, 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 
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, repair, and modification shall be done in 
accordance with Boeing Service Bulletin 747-53-2371, including the 
``ADDENDUM,'' dated July 29, 1993. 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 July 27, 1994.

    Issued in Renton, Washington, on June 14, 1994.
Robert C. McCracken,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-14903 Filed 6-24-94; 8:45 am]
BILLING CODE 4910-13-U