[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
