[Federal Register Volume 59, Number 156 (Monday, August 15, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-19480]


[[Page Unknown]]

[Federal Register: August 15, 1994]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 93-NM-204-AD; Amendment 39-8996; AD 94-17-01]

 

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 the upper row of fasteners in the 
lower lobe of the fuselage skin lap joints, and repair, if necessary. 
This amendment is prompted by reports of incidents involving fatigue 
cracking and corrosion in transport category airplanes that are 
approaching or have exceeded their design life goal. The actions 
specified by this AD are intended to prevent separation of the fuselage 
skin and rapid loss of pressure in the airplane. This AD also relates 
to the recommendations of the Airworthiness Assurance Working Group 
assigned to review Model 747 series airplanes, which indicate that, to 
assure long term continued operational safety, various structural 
inspections should be accomplished.

DATES: Effective September 14, 1994.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of September 14, 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 14, 1994 (59 
FR 11733). That action proposed to require repetitive external high 
frequency eddy current inspections (HFEC) to detect cracking in the 
upper row of fasteners in the lower lobe of the 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 requests that the requirements of the proposal be 
revised to coincide with the actions specified in the service bulletin 
that is referenced in the proposal as the appropriate source of service 
information. The commenter states that Boeing Service Bulletin 747-
53A2267, Revision 3, dated March 26, 1992, excludes airplanes on which 
lap joints are thicker than 0.071 inch. The FAA does not concur. The 
FAA finds that the requirements of the AD and the actions specified in 
Revision 3 of the service bulletin include inspection of areas at the 
upper row of fasteners in the lap joint on which the thickness of the 
skin is 0.090 inch or less (where protruding head fasteners are 
required). As such, airplanes on which the skin of the lap joints is 
thicker than 0.071 inch are not exempt from the requirements of the AD 
or the actions specified in the referenced service bulletin.
    One commenter questions the justification for including the 
airplane having line position 1 in the applicability of the proposal 
since it is not included in the effectivity of Boeing Service Bulletin 
747-53A2267, Revision 3, dated March 26, 1992, which is referenced in 
the proposal as the appropriate source of service information. From 
this comment, the FAA infers that the commenter requests that this 
airplane be deleted from the applicability of the proposal. The FAA 
does not concur. The FAA intentionally included airplane having line 
position 1 in the applicability of the rule since it, too, is subject 
to the same unsafe condition as those airplanes listed in the 
referenced service bulletin. Therefore, no change to the final rule is 
necessary.
    One commenter requests that the proposal be revised to include 
specific procedures to accomplish the inspection required by paragraph 
(a) for airplanes that have been modified to install a main deck side 
cargo door (MDSCD) in accordance with a supplemental type certificate 
(STC). The commenter states that, as a result of the STC modification, 
the MDSCD doublers cover the lap joints. The FAA does not concur. The 
FAA's intent is not to address in this rule every conceivable airplane 
configuration for every operator. Consequently, paragraph (d) of this 
AD provides for FAA approval of alternative methods of compliance to 
address unique circumstances. Until such time that the FAA approves of 
such alternative methods of compliance, operators are required to 
remove the doublers that cover the lap joints to accomplish the 
required inspection. Therefore, no change to the final rule is 
necessary.
    One commenter requests correction of typographical errors in the 
applicability statements of proposed paragraphs (a)(2) and (a)(3). The 
commenter notes that the correct date for the original issue of Boeing 
Service Bulletin 747-53A2267 is March 28, 1986, rather than March 8, 
1986, as erroneously referenced in paragraph (a)(2) of the proposal. 
This commenter also points out that the optional modification 
referenced in the applicability statement of proposed paragraph (a)(3) 
is in error. The optional modification was not introduced until 
Revision 2 of the service bulletin; therefore, the reference to the 
original issue and Revision 1 of the service bulletin in proposed 
paragraph (a)(3) is erroneous. The FAA concurs. Paragraphs (a)(2) and 
(a)(3) of the final rule have been revised accordingly.
    One commenter requests clarification of the requirement in proposed 
paragraph (c) to inspect following repair of the lap joint in 
accordance with the 747 Structural Repair Manual (SRM) since the SRM 
specifies various repairs depending upon the extent of damage to the 
lap joint. The FAA concurs that clarification is warranted. The FAA 
finds that if the damage to the lap joint is such that the repair 
specified in the SRM includes removing the lap joint and the upper row 
of countersunk fasteners, then the inspection required by paragraph (a) 
of the final rule does not have to be repeated following such repairs. 
Paragraph (c) of the final rule has been revised accordingly.
    One commenter requests that detailed visual inspections of the lap 
joints to detect corrosion be included in the proposal, in light of the 
consequences of crack propagation due to corrosion in lap joints. The 
commenter notes that these inspections are specified in Boeing Service 
Bulletin 747-53A2267, which is referenced in the proposal as the 
appropriate source of service information. The FAA concurs, in part. 
The FAA acknowledges the criticality of inspecting to detect corrosion. 
However, as stated in the proposal, these inspections are currently 
required by AD 90-25-05, Amendment 39-6790 (55 FR 49268, November 27, 
1990), which requires inspections to detect fatigue cracking due to 
corrosion. Therefore, no change to the final rule is necessary.
    Another commenter, a non-U.S. operator, requests 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 considers it inappropriate to 
include various provisions in an AD applicable to a single operator's 
unique use of an affected airplane. Paragraph (d) of this AD provides 
for the approval of alternative methods of compliance to address these 
types of unique circumstances. 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.
    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 changes previously 
described. The FAA has determined that these changes will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.
    There are approximately 200 Model 747 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 118 
airplanes of U.S. registry will be affected by this AD, that it will 
take approximately 124 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 $804,760, or $6,820 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 FAA recognizes that the required inspections will require a 
large number of work hours to accomplish. However, the compliance times 
specified in paragraph (a) of this AD should allow ample time for the 
inspections to be accomplished coincidentally with scheduled major 
airplane inspection and maintenance activities, thereby minimizing the 
costs associated with special airplane scheduling.
    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:

94-17-01 Boeing: Amendment 39-8996. Docket 93-NM-204-AD.

    Applicability: Model 747 series airplanes having line positions 
1 through 200 inclusive, certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent separation of fuselage skin and rapid loss of 
pressure in the airplane, accomplish the following:
    (a) Perform an external high frequency eddy current inspection 
to detect cracks in the upper row of fasteners in the modified lap 
joints in accordance with Boeing Service Bulletin 747-53A2267, 
Revision 3, dated March 26, 1992, at the time specified in paragraph 
(a)(1) or (a)(2) or (a)(3) of this AD, as applicable.
    (1) For airplanes on which the full modification required by AD 
90-06-06, Amendment 39-6490, has been accomplished in accordance 
with Revision 2 of Boeing Service Bulletin 747-53A2267, dated March 
29, 1990, or Revision 3, dated March 26, 1992: Prior to the 
accumulation of 10,000 flight cycles after accomplishment of the 
full modification.
    (2) For airplanes on which the full modification required by AD 
90-06-06, Amendment 39-6490, has been accomplished in accordance 
with Boeing Service Bulletin 747-53A2267, dated March 28, 1986, or 
Revision 1, dated September 25, 1986: Prior to the accumulation of 
7,000 flight cycles after accomplishment of the full modification.
    (3) For airplanes on which the optional modification has been 
accomplished in accordance with Boeing Service Bulletin 747-53A2267, 
Revision 2, dated March 29, 1990; or Revision 3, dated March 26, 
1992: Prior to the accumulation of 7,000 flight cycles after 
accomplishment of the optional modification.
    (b) If no cracking is detected, repeat the inspection required 
by paragraph (a) of this AD thereafter at intervals not to exceed 
3,000 flight cycles.
    (c) If any cracking is detected, prior to further flight, repair 
in accordance with the Section 53-30-03 of the 747 Structural Repair 
Manual (SRM), and repeat the inspections required by paragraph (a) 
of this AD.
    (1) If the repair specified in the 747 SRM does not include 
removing the lap joint and the upper row of countersunk fasteners, 
thereafter at intervals not to exceed 3,000 flight cycles.
    (2) If the repair specified in the 747 SRM includes removing the 
lap joint and the upper row of countersunk fasteners, such repair 
constitutes terminating action for the inspection requirements of 
this AD.
    (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 shall be done in accordance with Boeing 
Service Bulletin 747-53A2267, Revision 3, dated March 26, 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 14, 1994.

    Issued in Renton, Washington, on August 4, 1994.
James V. Devany,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-19480 Filed 8-12-94; 8:45 am]
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