[Federal Register Volume 59, Number 65 (Tuesday, April 5, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-7320]


[[Page Unknown]]

[Federal Register: April 5, 1994]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 93-NM-150-AD; Amendment 39-8864; AD 94-07-06]

 

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 cracked or fractured H-11 steel bolts, 
replacement of discrepant bolts with ones made of Inconel 718 material, 
and eventual replacement of all H-11 steel bolts installed at certain 
critical locations with Inconel 718 material bolts. This amendment is 
prompted by reports of cracked and fractured H-11 steel bolts installed 
at certain critical locations of the airframe structure. The actions 
specified by this AD are intended to prevent the failure of attachment 
bolts in critical locations, which could lead to severe airframe 
damage.

DATES: Effective May 5, 1994.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of May 5, 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: Tim Backman, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue SW., Renton, Washington 
98055-4056; telephone (206) 227-2776; 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 15, 1993 (58 FR 65567). That action 
proposed to require inspections to detect cracked or fractured H-11 
steel bolts, replacement of discrepant bolts with ones made of Inconel 
718 material, and eventual replacement of all H-11 steel bolts 
installed at certain critical locations with bolts made of Inconel 718 
material.
    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 proposal.
    Two commenters request that the applicability of the proposal be 
revised to exclude Model 747-400 series airplanes. These commenters 
state, and the manufacturer has confirmed, that these airplanes were 
delivered without H-11 steel bolts installed. The FAA concurs. Since 
issuance of the notice, the FAA has reviewed and approved Boeing 
Service Bulletin 747-51-2048, Revision 1, dated January 27, 1994, which 
excludes Model 747-400 series airplanes from the effectivity listing. 
Since these airplanes were not delivered with H-11 bolts, they are not 
subject to the addressed unsafe condition. The FAA has revised the 
final rule to exclude Model 747-400 series airplanes from the 
applicability, and to reference this latest revision of the service 
bulletin as an additional source of appropriate service information. 
Additionally, the FAA has revised the economic impact information, 
below, to reflect the exclusion of Model 747-400 series airplanes.
    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 60 Model 747 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 7 
airplanes of U.S. registry will be affected by this AD.
    It would take an average of 15 work hours per airplane to 
accomplish the proposed inspection actions, at an average labor rate of 
$55 per work hour. Based on these figures, the total cost impact of the 
proposed inspection action of this AD on U.S. operators is estimated to 
be $5,775, or $825 per airplane, per inspection cycle.
    It would take an average of 240 work hours per airplane to 
accomplish the proposed bolt replacement action, at an average labor 
rate of $55 per work hour. Required parts would cost approximately 
$11,000 per airplane. Based on these figures, the total cost impact of 
the proposed replacement action of this AD on U.S. operators is 
estimated to be $169,400, or $24,200 per airplane. (This estimate 
assumes that H-11 steel bolts are found at all affected locations.) 
Accomplishment of this replacement action terminates the repetitive 
inspection requirement; therefore the accomplishment of the replacement 
will result in a reduction in costs to affected operators of $275 per 
airplane per inspection cycle that will no longer be required.
    The number of required work hours, as indicated above, is presented 
as if the accomplishment of the actions proposed in this AD were to be 
conducted as ``stand alone'' actions. However, in actual practice, 
these actions for the most part would be accomplished coincidentally or 
in combination with normally scheduled airplane inspections and other 
maintenance program tasks. Therefore, the actual number of necessary 
additional work hours would be minimal in many instances. Additionally, 
any costs associated with special airplane scheduling would be minimal.
    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:

94-07-06 Boeing: Amendment 39-8864. Docket 93-NM-150-AD.

    Applicability: Model 747 series airplanes having line numbers 
641 through 708, inclusive, excluding Model 747-400 series 
airplanes; certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent severe structural damage to the airplane due to 
failure of attachment bolts, accomplish the following:
    (a) Prior to the accumulation of 4 years total time-in-service, 
or within 15 months after the effective date of this AD, whichever 
occurs later, perform a visual inspection, in accordance with Boeing 
Service Bulletin 747-51-2048, dated January 14, 1993, or Revision 1, 
dated January 27, 1994, to verify if bolts made of H-11 steel have 
been installed at the following locations:

    Note 1: Not all airplanes need to be inspected at each critical 
location. Operators should refer to the Boeing service bulletin to 
determine which specific locations are to be inspected on which 
airplanes.

    (1) Body landing gear inboard and outboard trunnion vertical 
support attachment.
    (2) Wing landing gear beam upper chord to longeron attachment.
    (3) Wing landing gear beam lower chord to crease beam 
attachment.
    (4) Body Station (BS) 2598 horizontal stabilizer hinge 
attachment.
    (5) BS 2598 longeron splice fitting attachment at stringers 11 
and 23.
    (6) Fin to body attachment.
    (7) Horizontal stabilizer front spar jack screw attachment.
    (b) If no bolt made of H-11 steel is detected, no further action 
is required by this AD.
    (c) If any bolt made of H-11 steel is detected, prior to further 
flight, visually inspect the bolt to detect cracking or fracture, in 
accordance with Boeing Service Bulletin 747-51-2048, dated January 
14, 1993, or Revision 1, dated January 27, 1994.

    Note 2: A bolt made of H-11 steel is considered to be fractured 
if the sealant around the nut or bolthead is broken, or if there are 
gaps between the bolthead or nut and the adjacent structure.

    (1) If no cracking or fracture of the bolt is detected, repeat 
the inspection of that bolt thereafter at intervals not to exceed 18 
months.
    (2) If any cracking or fracture is detected during this 
inspection or during any inspection required by paragraph (c)(1) of 
this AD, prior to further flight, replace the discrepant bolt with a 
bolt made of Inconel 718 material in accordance with the service 
bulletin.
    (d) Within 48 months after the effective date of this AD, 
replace all bolts made of H-11 steel installed at the locations 
specified in paragraph (a) of this AD with bolts made of Inconel 718 
material, in accordance with Boeing Service Bulletin 747-51-2048, 
dated January 14, 1993, or Revision 1, dated January 27, 1994. Such 
replacement constitutes terminating action for the inspection 
requirements of this AD.
    (e) 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). 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 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (f) Special flight permits may be issued in accordance with 
Federal Aviation Regulations (FAR) 21.197 and 21.199 to operate the 
airplane to a location where the requirements of this AD can be 
accomplished.
    (g) The inspection and replacement shall be done in accordance 
with Boeing Service Bulletin 747-51-2048, dated January 14, 1993, or 
Boeing Service Bulletin 747-51-2048, 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.
    (h) This amendment becomes effective on May 5, 1994.

    Issued in Renton, Washington, on March 23, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-7320 Filed 4-4-94; 8:45 am]
BILLING CODE 4910-13-U