Airworthiness Directives; Boeing Model 747 Series Airplanes

[Federal Register Volume 66, Number 134 (Thursday, July 12, 2001)]
[Rules and Regulations]
[Pages 36443-36445]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-17119]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-251-AD; Amendment 39-12318; AD 2001-14-07]
RIN 2120-AA64


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 
repetitive high frequency eddy current inspections to find cracking of 
the bulkhead frame support at body station 2598 under the hinge support 
fittings of the horizontal stabilizer, and repair if cracking is found. 
These actions are necessary to find and fix fatigue cracking in the 
frame support, which could result in inability of the structure to 
carry horizontal stabilizer flight loads and reduced controllability of 
the horizontal stabilizer. This action is intended to address the 
identified unsafe condition.

DATES: Effective August 16, 2001.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of August 16, 2001.

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: Rick Kawaguchi, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
227-1153; fax (425) 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 all Boeing Model 747 series 
airplanes was published in the Federal Register on February 21, 2001 
(66 FR 10974). That action proposed to require repetitive high 
frequency eddy current inspections to find cracking of the bulkhead 
frame support at body station 2598 under the hinge support fittings of 
the horizontal stabilizer, and repair if cracking is found.

Comments

    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Revised Service Information

    Two commenters ask that the FAA approve Boeing Service Bulletin 
747-53A2449, Revision 1, dated May 24, 2001, as another source of 
service information for doing the actions specified in the proposed 
rule. The proposed rule cited Boeing Alert Service Bulletin 747-
53A2449, dated June 8, 2000, as the proper source of service 
information for doing the specified actions.
    One commenter, the manufacturer, states that the revised service 
bulletin changes the airplane effectivity by limiting the affected 
airplanes to line numbers (L/N) 1 through 1307, inclusive. Airplanes 
delivered after L/N 1307 have been redesigned to reduce the possibility 
of early cracking of the bulkhead in the subject area. The revised 
bulletin also corrects the bolt torque values specified in the original 
issue of the service bulletin. The commenter adds that using the torque 
values in the original issue could lead to over-torque of the bolts 
during installation.
    Another commenter suggests that, when a revised service bulletin is 
released, it should specify the correct torque values for the shear 
bolts, or reference the Structural Repair Manual, Chapter 51-30-04 or 
51-40-04. The commenter adds that the manufacturer informed the 
commenter by telex that, if the shear bolts are torqued per the service 
bulletin specified in the proposed rule, they will be over-torqued. The 
commenter does not intend to do the inspections until a revised service 
bulletin is issued, in order to minimize the risk of over-torquing the 
shear bolts and to avoid the need to rework and replace the bolts.
    The FAA concurs with the commenters and has reviewed and approved 
Boeing Service Bulletin 747-53A2449, Revision 1, dated May 24, 2001; 
which is referenced in the final rule as the proper source of service 
information for doing the actions specified. Accordingly, the 
applicability section has been changed to specify Model 747 series 
airplanes, as listed in Revision 1 of the service bulletin; the number 
of airplanes, as well as the number of work hours, which were increased 
in Revision 1 of the service bulletin, have been changed in the cost 
impact section; and a new Note 2 has been added to specify that actions 
done before the effective date of this AD, per the original issue of 
the service bulletin, are acceptable for compliance with paragraph (a) 
of the final rule.
    Although the torque values have been corrected in the revised 
service bulletin, operators who used the incorrect torque values during 
re-installation of the bolts can wait until the next repeat inspection 
to use the correct torque values. We have determined that over-torqued 
bolts will not compromise safety, as long as the bolts are properly 
torqued during the next repeat inspection.

[[Page 36444]]

Extend Compliance Time

    One commenter asks that the compliance time for the proposed rule 
be extended from before the accumulation of 10,000 total flight cycles, 
or within 1,000 flight cycles after the effective date of this AD, 
whichever occurs later; to before the accumulation of 10,000 total 
flight cycles, or within 1,200 flight cycles after the effective date 
of this AD, whichever occurs later. The commenter states that its 
recommendation will allow the accomplishment of the initial inspection 
during its regularly scheduled heavy maintenance checks, while still 
maintaining an equivalent level of safety.
    The FAA does not concur with the commenter's request because the 
cracking of the bulkhead frame support is caused by fatigue, which is 
contingent on the number of accumulated flight cycles. In developing an 
appropriate compliance time for this action, we considered not only the 
degree of urgency associated with addressing the subject unsafe 
condition, but the manufacturer's recommendation as to an appropriate 
compliance time, and the practical aspect of accomplishing the required 
inspection within an interval of time that parallels normal scheduled 
maintenance for the majority of affected operators. We have determined 
that before the accumulation of 10,000 total flight cycles, or within 
1,000 flight cycles after the effective date of this AD, whichever 
occurs later, represents an appropriate compliance time allowable for 
the initial inspection to be accomplished during scheduled maintenance 
intervals. However, under the provisions of paragraph (c) of the final 
rule, we may approve requests for adjustments to the compliance time if 
data are submitted to substantiate that such an adjustment would 
provide an acceptable level of safety.

Terminating Action

    One commenter asks that a terminating action, such as oversizing 
the subject fastener holes, be provided by the manufacturer. The 
commenter states that this would alleviate potential structural damage 
caused by the repeated fastener and sealant removal, and installation 
at a critical joint. The FAA agrees with the intent of the comment, but 
until the manufacturer provides adequate service information giving 
procedures for a terminating action, such action cannot be added. If 
terminating action becomes available in the future, we may consider 
additional rulemaking. No change to the final rule is necessary in this 
regard.

Conclusion

    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.

Cost Impact

    There are approximately 1,147 airplanes of the affected design in 
the worldwide fleet. The FAA estimates that 261 airplanes of U.S. 
registry will be affected by this AD, that it will take approximately 
18 work hours (9 work hours per side) per airplane to accomplish the 
required inspections, and that the average labor rate is $60 per work 
hour. Based on these figures, the cost impact of the AD on U.S. 
operators is estimated to be $281,880, or $1,080 per airplane, per 
inspection cycle.
    The 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 cost impact figures discussed 
in AD rulemaking actions represent only the time necessary to perform 
the specific actions actually required by the AD. These figures 
typically do not include incidental costs, such as the time required to 
gain access and close up, planning time, or time necessitated by other 
administrative actions.

Regulatory Impact

    The regulations adopted herein will not have a substantial direct 
effect 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, it 
is determined that this final rule does not have federalism 
implications under Executive Order 13132.
    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. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

2001-14-07  Boeing: Amendment 39-12318. Docket 2000-NM-251-AD.

    Applicability: Model 747 series airplanes, as listed in Boeing 
Service Bulletin 747-53A2449, Revision 1, dated May 24, 2001, 
certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
modified, altered, or repaired in the area subject to the 
requirements of this AD. For airplanes that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (c) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To find and fix fatigue cracking in the bulkhead frame support 
at body station (BS) 2598 under the hinge support fittings of the 
horizontal stabilizer, which could result in inability of the 
structure to carry horizontal stabilizer flight loads and reduced 
controllability of the horizontal stabilizer, accomplish the 
following:

Repetitive High Frequency Eddy Current (HFEC) Inspections

    (a) Before the accumulation of 10,000 total flight cycles, or 
within 1,000 flight cycles after the effective date of this AD, 
whichever occurs later: Do an open-hole HFEC inspection to find 
cracking of the bulkhead frame support under the hinge support 
fittings of the horizontal stabilizer on the left and right sides at 
BS 2598, per Figure 2 of

[[Page 36445]]

the Accomplishment Instructions of Boeing Service Bulletin 747-
53A2449, Revision 1, dated May 24, 2001. Repeat the inspection after 
that at intervals not to exceed 3,000 flight cycles.

    Note 2: Inspections accomplished before the effective date of 
this AD per Boeing Alert Service Bulletin 747-53A2449, dated June 8, 
2000, are considered acceptable for compliance with the applicable 
inspection specified in paragraph (a) of this AD.

Repair

    (b) If any cracking is found during any inspection required by 
paragraph (a) of this AD, before further flight, repair per a method 
approved by the Manager, Seattle Aircraft Certification Office 
(ACO), FAA; or per data meeting the type certification basis of the 
airplane approved by a Boeing Company Designated Engineering 
Representative who has been authorized by the Manager, Seattle ACO, 
to make such findings. For a repair method to be approved by the 
Manager, Seattle ACO, as required by this paragraph, the approval 
letter must specifically reference this AD.

Alternative Methods of Compliance

    (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 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.

Special Flight Permits

    (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.

Incorporation by Reference

    (e) Except as provided by paragraph (b) of this AD, the actions 
shall be done per Boeing Service Bulletin 747-53A2449, Revision 1, 
dated May 24, 2001. 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.

Effective Date

    (f) This amendment becomes effective on August 16, 2001.

    Issued in Renton, Washington, on July 2, 2001.
Vi L. Lipski,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 01-17119 Filed 7-11-01; 8:45 am]
BILLING CODE 4910-13-U

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