[Federal Register Volume 61, Number 223 (Monday, November 18, 1996)]
[Proposed Rules]
[Pages 58667-58669]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-29418]


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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-NM-52-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Boeing Model 747 series 
airplanes. This proposal would require a one-time inspection to detect 
corrosion and cracking of the upper deck floor beam at station 980, and 
repair, if necessary. This proposal 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 the proposed 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: Comments must be received by December 30, 1996.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 96-NM-52-AD, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056. Comments may be inspected at this location 
between 9:00 a.m. and 3:00 p.m., Monday through Friday, except Federal 
holidays.
    The service information referenced in the proposed rule may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington.

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:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 96-NM-52-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-103, Attention: Rules 
Docket No. 96-NM-52-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received reports of corrosion found under the threshold 
attached to the floor beam at the cart lift cutout in the upper deck 
floor at station 980 on several Boeing Model 747-300 and -400 series 
airplanes. The corrosion occurred where the stainless steel threshold 
contacts the aluminum floor structure. Analysis of an extensively 
corroded section of the station 980 floor beam, which had been removed 
from a 7-year old Model 747-400 series airplane, revealed that fatigue 
cracking could initiate at the corroded area and could propagate. The 
analysis further indicated that the floor beam could break at 
approximately 1,500 flight cycles after cracking was initiated. At

[[Page 58668]]

this time, the FAA has not received any reports of cracking of the 
floor beam due to corrosion at station 980. However, such corrosion and 
potential cracking, if not detected and corrected in a timely manner, 
could cause the upper deck floor beam at station 980 to break, and 
would result in extensive damage to adjacent structure and possible 
rapid decompression of the airplane.

Similar Models Subject to the Unsafe Condition

    Upper deck cart lifts installed at station 980 on Boeing Model 747-
300 and -400 series airplanes are identical to those cart lifts 
installed at station 980 on other Model 747 series airplanes; 
therefore, all of these models may be subject to this same unsafe 
condition.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Alert Service Bulletin 
747-53A2400, dated December 21, 1995, which describes procedures for 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. For older airplanes, the 
alert service bulletin describes alternative procedures that include 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 a detailed visual inspection 
with the cart lift threshold removed; and repair, if necessary.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would 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. The proposed AD also would 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. The actions would be required to be accomplished 
in accordance with the alert service bulletin described previously.

Difference Between the Proposed AD and Referenced Service Bulletin

    Operators should note that Boeing Alert Service Bulletin 747-
53A2400, dated December 21, 1995, advises that, if an operator has 
performed the modification work and has applied sealant under the cart 
lift threshold as specified in Boeing Service Bulletin 747-53-2327, the 
inspection described in Boeing Alert Service Bulletin 747-53A2400 is 
not necessary. However, the FAA has determined that Boeing Service 
Bulletin 747-53-2327 does not provide adequate instructions to apply 
sealant under the threshold. Therefore, the FAA does not consider the 
accomplishment of Boeing Service Bulletin 747-53-2327 to be an 
alternative to the requirements of this proposed 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 would be affected by this proposed AD, that 
it would take approximately 19 work hours per airplane to accomplish 
the proposed actions, and that the average labor rate is $60 per work 
hour. Based on these figures, the cost impact of the proposed 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 proposed 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 proposed herein would 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 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, 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 copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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:

Boeing: 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.

    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, in accordance with 
Boeing Alert Service Bulletin 747-53A2400, dated

[[Page 58669]]

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 the 
inspection described in the alert service bulletin be accomplished 
regardless of accomplishment of the 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 
prevails.

    (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): 
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, whichever occurs first. 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 and perform a visual 
inspection to detect any corrosion or cracking of the upper deck 
floor beam at station 980. 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.

    Issued in Renton, Washington, on November 8, 1996.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 96-29418 Filed 11-15-96; 8:45 am]
BILLING CODE 4910-13-U