[Federal Register Volume 59, Number 148 (Wednesday, August 3, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-18453]


[[Page Unknown]]

[Federal Register: August 3, 1994]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 93-NM-212-AD; Amendment 39-8988; AD 94-15-17]

 

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 of certain fuselage longitudinal lap 
joints, repair of any cracking found, and replacement of the 
countersunk fasteners in those lap joints with protruding head 
fasteners. This amendment is prompted by a structural reassessment of 
Model 747 series airplanes. The actions specified by this AD are 
intended to prevent skin cracking in the longitudinal lap joints of 
certain stringers, which can lead to rapid decompression of the 
airplane.

DATES: Effective September 2, 1994.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of September 2, 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 March 4, 1994 (59 FR 
10338). That action proposed to require repetitive external high 
frequency eddy current inspections to detect cracking of the skin 
around the fasteners in the upper row of the longitudinal lap joints of 
Stringer (S)-12L and S-12R from station 520 to station 741.1, repair of 
any cracking found, and replacement of the countersunk fasteners in 
those lap joints with protruding head fasteners.
    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.
    One commenter requests that the compliance time specified in 
proposed paragraph (b) for accomplishing the replacement of the 
countersunk fasteners be reduced from the proposed ``20,000 total 
flight cycles or within 4 years after the effective date of the AD, 
whichever occurs later,'' to ``20,000 total flight cycles or within 2 
years after the effective date of the AD, whichever occurs later.'' The 
commenter states that this suggested shorter compliance time would make 
the compliance time requirements of the proposed AD commensurate with 
the compliance time of AD 94-12-09, amendment 39-8937 (59 FR 30285, 
June 13, 1994), which requires modification of certain skin panel lap 
joints in this same area.
    The FAA does not concur. After consideration of all the available 
information, the FAA cannot conclude that a reduction of the proposed 
compliance time, without prior notice and opportunity for public 
comment, is warranted. In developing an appropriate compliance time, 
the FAA considered the safety implications, parts availability, and 
normal maintenance schedules for timely accomplishment of replacement 
of the fasteners. Further, the proposed compliance time was arrived at 
with operator, manufacturer, and FAA concurrence. In consideration of 
all of these factors, the FAA determined that the compliance time, as 
proposed, represents an appropriate interval in which replacement of 
the fasteners can be accomplished in a timely manner within the fleet 
and still maintain an adequate level of safety. Operators are always 
permitted to accomplish the requirements of an AD at a time earlier 
than that specified as the compliance time; therefore, if an operator 
elects to accomplish the fastener replacement prior to the accumulation 
of 20,000 total flight cycles or 2 years after the effective date of 
this AD, whichever is later (in order to accomplish the replacement 
concurrently with an action required by another AD), it is that 
operator's prerogative to do so. If additional data are presented that 
would justify a shorter compliance time, the FAA may consider further 
rulemaking on this issue.
    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 30 Model 747 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 12 
airplanes of U.S. registry will be affected by this AD, that it will 
take approximately 17 work hours per airplane to accomplish the 
required inspections, and that the average labor rate is $55 per work 
hour. Based on these figures, the total cost impact of the required 
inspections on U.S. operators is estimated to be $11,220, or $935 per 
airplane.
    The FAA estimates that it will take approximately 302 work hours 
per airplane to accomplish the requirement to replace fasteners, and 
that the average labor rate is $55 per work hour. Required parts will 
be nominal in cost. Based on these figures, the total cost impact of 
the requirement to replace fasteners on U.S. operators is estimated to 
be $199,320, or $16,610 per airplane.
    Based on the figures, above, the total cost impact of the required 
actions (cost of inspections added to the cost of replacement of 
fasteners) on U.S. operators is estimated to be $210,540, or $17,545 
per airplane.
    The FAA recognizes that the replacement of fasteners would require 
a large number of work hours to accomplish. However, the 4-year 
compliance time specified in paragraph (b) of this AD should allow 
ample time for the replacement of the fasteners to be accomplished 
coincidentally with scheduled major airplane inspection and maintenance 
activities, thereby minimizing the costs associated with special 
airplane scheduling.
    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:

    94-15-17 Boeing: Amendment 39-8988. Docket 93-NM-212-AD.

    Applicability: Model 747 series airplanes, having line numbers 
201 through 230 inclusive; certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent rapid decompression of the airplane, accomplish the 
following:
    (a) Prior to the accumulation of 15,000 total flight cycles or 
within 1,000 flight cycles after the effective date of this AD, 
whichever occurs later, perform an external high frequency eddy 
current (HFEC) inspection to detect cracking of the skin at the 
upper row of countersunk fasteners in the longitudinal lap joints of 
Stringer (S-)12L and S-12R from station 520 to station 741.1, in 
accordance with Boeing Service Bulletin 747-53-2366, dated August 6, 
1992.
    (1) If no cracking is found, repeat the inspection thereafter at 
intervals not to exceed 4,000 flight cycles until the replacement of 
fasteners required by paragraph (b) of this AD is accomplished.
    (2) If any cracking is found, prior to further flight, repair in 
accordance with the 747 Structural Repair Manual. After repair, 
repeat the inspection at intervals not to exceed 4,000 flight cycles 
until the replacement of fasteners required by paragraph (b) of this 
AD is accomplished.
    (b) Prior to the accumulation of 20,000 total flight cycles or 
within 4 years after the effective date of this AD, whichever occurs 
later, replace the countersunk fasteners in the upper row of the 
longitudinal lap joints of S-12L and S-12R from station 520 to 
station 741.1 with protruding head fasteners, in accordance with 
Boeing Service Bulletin 747-53-2366, dated August 6, 1992. 
Replacement of these fasteners constitutes terminating action for 
the repetitive inspections required by paragraph (a) of this AD.
    (c) Prior to the accumulation of 10,000 total flight cycles 
after replacement of the countersunk fasteners required by paragraph 
(b) of this AD, perform an external HFEC inspection to detect 
cracking of the skin at the upper row of protruding head fasteners 
in the longitudinal lap joints of S-12L and S-12R from station 520 
to station 741.1, in accordance with Boeing Service Bulletin 747-53-
2366, dated August 6, 1992.
    (1) If no cracking is found, repeat the inspection thereafter at 
intervals not to exceed 3,000 flight cycles.
    (2) If any cracking is found, prior to further flight, repair in 
accordance with the 747 Structural Repair Manual. After repair, 
repeat the inspection at intervals not to exceed 3,000 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 
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.
    (f) The inspections and replacement shall be done in accordance 
with Boeing Service Bulletin 747-53-2366, including the ``ADDENDUM,'' 
dated August 6, 1992. 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 September 2, 1994.

    Issued in Renton, Washington, on July 22, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-18453 Filed 8-2-94; 8:45 am]
BILLING CODE 4910-13-U