Airworthiness Directives; Boeing Model 747 Series Airplanes

[Federal Register Volume 62, Number 85 (Friday, May 2, 1997)]
[Rules and Regulations]
[Pages 24022-24024]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-11199]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-NM-52-AD; Amendment 39-10009; AD 97-09-13]
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 
a one-time inspection to detect corrosion and cracking of the upper 
deck floor beam at station 980, and repair, if necessary. This 
amendment is prompted by reports of extensive corrosion found at 
station 980. Analysis of the corrosion indicated that fatigue cracking 
of the floor beam at this area could occur and cause the beam to break. 
The actions specified by this AD are intended to detect and correct 
such corrosion and/or cracking, which could cause the floor beam to 
break and result in extensive damage to adjacent structure and possible 
rapid decompression of the airplane.

DATES: Effective June 6, 1997.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of June 6, 1997.

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: Bob Breneman, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington; telephone (206) 227-2776; 
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 November 18, 1996 
(61 FR 58667). That action proposed to require a one-time detailed 
visual inspection to detect corrosion and/or fatigue cracking of the 
upper deck floor beam at station 980 with the cart lift threshold 
removed, and repair, if necessary. That action also proposed to provide 
an alternative inspection method for older airplanes, which includes a 
detailed visual inspection to detect corrosion and/or fatigue cracking 
of the upper deck floor beam at station 980 with the cart lift 
threshold installed, followed later by an inspection with the cart lift 
threshold removed, 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.

Support for the Proposal

    Four commenters support the proposal.

Request to Revise the Initial Compliance Time for Certain Airplanes

    One commenter requests that the initial inspection threshold be 
revised for airplanes that have been modified in accordance with Boeing 
Service Bulletin 747-53-2327. The commenter requests that the 
compliance time be changed from the proposed ``within 6 years after the 
effective date of the AD'' to ``within 6 years after the accomplishment 
of the actions described in Boeing Service Bulletin 747-53-2327.'' The 
commenter notes that the actions described in that service bulletin 
include a modification to install a new increased thickness shear plate 
at the stairway cutout and cart lift cutout. The commenter asserts that 
the modification reduces the stress levels by approximately 25%, and 
increases the tolerance to corrosion damage. In addition, the commenter 
notes that Boeing Service Bulletin 747-53-2327 also includes a 
description of procedures to perform a detailed visual inspection for 
corrosion and treatment of the affected area with corrosion 
preventative compound BMS 3-23.
    The FAA concurs with the commenter's request to revise the proposed 
compliance time. The FAA has determined that existing corrosion would 
be detected and corrected in accordance with Boeing Service Bulletin 
747-53-2327. The FAA also acknowledges that the installation of an

[[Page 24023]]

increased thickness shear plate will reduce the stress level of the 
floor beam upper chord; however, corrosion of the upper chord of the 
station 980 upper deck floor beam is primarily dependent on 
environmental conditions and time-in-service, not the stress level. 
Nevertheless, since the existing corrosion would be detected and 
corrected in accordance with that service bulletin, paragraph (a) of 
the final rule has been revised to specify that the initial inspection 
requirement of this AD may be accomplished within 6 years after the 
accomplishment of the actions specified in Boeing Service Bulletin 747-
53-2327.

Request to Consider Previously Accomplished Service Information

    Two commenters request that the FAA consider accomplishment of 
Boeing Service Bulletin 747-53-2327, Revision 1, (which includes the 
application of faying surface sealant between the threshold and the 
floor beam chord) as an alternative method of compliance for the 
requirements of the proposed AD. The commenters did not explain why 
accomplishment of Revision 1 should be considered as an alternative 
method of compliance.
    The FAA does not concur. The FAA finds that the procedures 
described in Boeing Service Bulletin 747-53-2327, Revision 1, do not 
provide adequate instructions for applying faying surface sealant 
between the cart lift threshold and floor beam during the modification. 
In light of this, the FAA has determined that there is no assurance 
that operators will install the faying surface sealant during the 
modification. However, under the provisions of paragraph (c) of the 
final rule, the FAA may approve requests for an alternative method of 
compliance if sufficient justification is presented to the FAA.

Request To Exclude Certain Airplanes From the Requirements of the 
AD

    One commenter, the airplane manufacturer, requests that four Model 
747-400 series airplanes that were modified to include a cart lift 
system in accordance with Boeing Service Bulletin 747-25-3108, be 
excluded from the applicability of this AD. The manufacturer states 
that the subject modification provides adequate instructions for the 
installation of faying surface sealant between the cart lift threshold 
and the existing station 980 floor beam.
    The FAA acknowledges that the modification described in Boeing 
Service Bulletin 747-25-3108 provides adequate instructions for the 
installation of faying surface sealant between the cart lift threshold 
and the existing station 980 floor beam. However, the four airplanes 
listed in the effectivity listing of that service bulletin range 
between line positions 891 and 927. The FAA points out that the 
applicability for this AD expressly states ``for Model 747-300 and -400 
series airplanes having line numbers up to and including 843.'' 
Therefore, no change to the final rule is necessary.

Clarification of the Reinstallation Requirements of the AD

    In paragraph (a) of this AD, to clarify the FAA's intent that, 
after the one-time detailed visual inspection and any necessary repair, 
the cart lift threshold should be reinstalled in accordance with the 
alert service bulletin, the FAA has added the words ``then reinstall.'' 
To further clarify this intent, in paragraph (c)(1) of this AD, the FAA 
has added the words ``and reinstall; in accordance with the alert 
service bulletin.''

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 195 Model 747 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 28 
airplanes of U.S. registry will be affected by this AD, that it will 
take approximately 19 work hours per airplane to accomplish the 
required actions, 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 $31,920, or $1,140 per airplane.
    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.

Regulatory Impact

    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. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

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

97-09-13  Boeing: Amendment 39-10009. Docket 96-NM-52-AD.

    Applicability: Model 747-300 and -400 series airplanes having 
line numbers up to and including 843, and Model 747 series airplanes 
modified to a stretched upper deck configuration; on which an upper 
deck cart lift has been installed at station 980; certificated in 
any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
otherwise 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 (d) 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.


[[Page 24024]]


    Compliance: Required as indicated, unless accomplished 
previously.
    To detect and correct corrosion and consequent fatigue cracking 
of the upper deck floor beam at station 980, which could cause the 
floor beam to break and, consequently, result in extensive damage to 
adjacent structure and possible rapid decompression of the airplane, 
accomplish the following:
    (a) Perform a one-time detailed visual inspection to detect 
corrosion and/or fatigue cracking of the upper deck floor beam at 
station 980 with the cart lift threshold removed, then reinstall; in 
accordance with Boeing Alert Service Bulletin 747-53A2400, dated 
December 21, 1995, at the time specified in paragraph (a)(1), 
(a)(2), or (a)(3) of this AD, as applicable.

    Note 2: Boeing Alert Service Bulletin 747-53A2400, dated 
December 21, 1995, specifies that the inspection described in the 
alert service bulletin need not be accomplished on airplanes on 
which the actions described in Boeing Service Bulletin 747-53-2327 
have been accomplished. However, this AD requires that, for 
airplanes on which the actions described in Boeing Service Bulletin 
747-53-2327 have been accomplished, the initial inspection required 
by this AD (in accordance with Boeing Alert Service Bulletin 747-
53A2400) may be accomplished within 6 years after the accomplishment 
of those actions specified in Boeing Service Bulletin 747-53-2327. 
Where there are differences between this AD and the alert service 
bulletin, the requirements of the AD prevail.

    (1) For airplanes that, as of the effective date of this AD, 
have accumulated less than 6 years since date of delivery of the 
airplane, or since installation of a stretched upper deck (SUD), or 
since the accomplishment of Boeing Service Bulletin 747-53-2327: 
Accomplish the inspection at the later of the times specified in 
paragraphs (a)(1)(i) and (a)(1)(ii) of this AD.
    (i) Within 6 years since date of delivery of the airplane, or 
since installation of a SUD, or within 6 years since the 
accomplishment of Boeing Service Bulletin 747-53-2327; whichever 
occurs later. Or
    (ii) Within 1,500 flight cycles after the effective date of this 
AD.
    (2) For airplanes that, as of the effective date of this AD, 
have accumulated 6 or more years, but less than 10 years, since date 
of delivery of the airplane or since installation of a SUD: 
Accomplish the inspection within 1,500 flight cycles or 18 months 
after the effective date of this AD, whichever occurs first.
    (3) For airplanes that, as of the effective date of this AD, 
have accumulated 10 or more years of service since the time of 
initial delivery, or since the time of installation of the SUD: 
Except as provided by paragraph (c) of this AD, accomplish the 
inspection within 9 months or within 750 flight cycles after the 
effective date of this AD, whichever occurs first.
    (b) If any corrosion or cracking is detected during the 
inspection required by paragraph (a) of this AD: Prior to further 
flight, repair the corrosion and/or cracking, and apply sealant 
between the threshold and the upper deck floor beam at station 980, 
in accordance with Boeing Alert Service Bulletin 747-53A2400, dated 
December 21, 1995.
    (c) For airplanes that, as of the effective date of this AD, 
have accumulated 10 or more years of service since the time of 
initial delivery, or 10 or more years of service since the 
installation of a SUD: In lieu of accomplishing the requirements of 
paragraph (a) of this AD, within 9 months after the effective date 
of this AD, perform a one-time detailed visual inspection to detect 
corrosion of the upper deck floor beam at station 980 with the cart 
lift threshold installed, in accordance with Boeing Alert Service 
Bulletin 747-53A2400, dated December 21, 1995.
    (1) If no corrosion or cracking is detected: Within 18 months or 
1,500 flight cycles after the effective date of this AD, whichever 
occurs first, remove the cart lift threshold, perform a visual 
inspection to detect any corrosion or cracking of the upper deck 
floor beam at station 980, and reinstall; in accordance with the 
alert service bulletin. If any corrosion or cracking is detected, 
prior to further flight, repair the corrosion and/or cracking, and 
apply sealant between the threshold and the upper deck floor beam at 
station 980; in accordance with the alert service bulletin.
    (2) If any corrosion or cracking is detected: Prior to further 
flight, remove the cart lift threshold and perform a detailed visual 
inspection to detect any corrosion or cracking of the upper deck 
floor beam at station 980; repair any corrosion and/or cracking 
detected; and apply sealant between the threshold and the upper deck 
floor beam at station 980; in accordance with the alert service 
bulletin.
    (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 3: 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 actions shall be done in accordance with Boeing Alert 
Service Bulletin 747-53A2400, dated December 21, 1995. 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 June 6, 1997.

    Issued in Renton, Washington, on April 24, 1997.
Neil D. Schalekamp,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-11199 Filed 5-1-97; 8:45 am]
BILLING CODE 4910-13-U

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