[Federal Register Volume 62, Number 238 (Thursday, December 11, 1997)]
[Proposed Rules]
[Pages 65233-65235]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-32427]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 97-NM-47-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 supersedure of an existing
airworthiness directive (AD), applicable to certain Boeing Model 747
series airplanes, that
[[Page 65234]]
currently requires repetitive high frequency eddy current (HFEC)
inspections to detect cracking on all surfaces of the upper recesses in
certain latch support fittings of the cargo doorway, and replacement of
cracked fittings with new fittings. That AD also provides for optional
terminating action for the repetitive inspections. This proposal would
require accomplishment of the previously optional terminating action.
This proposal is prompted by reports indicating that the repetitive
inspections required by the existing AD may not detect cracked fittings
in a timely manner. The actions specified by the proposed AD are
intended to prevent the cargo door from opening while the airplane is
in flight, which could result in rapid decompression of the airplane.
DATES: Comments must be received by January 26, 1998.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-103,
Attention: Rules Docket No. 97-NM-47-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: Robert Breneman, Aerospace Engineer,
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office,
1601 Lind Avenue, SW., Renton, Washington; telephone (425) 227-2776;
fax (425) 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 97-NM-47-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. 97-NM-47-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
On February 12, 1993, the FAA issued AD 93-02-16, amendment 39-8500
(58 FR 11190, February 24, 1993), applicable to certain Boeing Model
747 series airplanes, to require repetitive high frequency eddy current
(HFEC) inspections to detect cracking on all surfaces of the upper
recess in each 7079-T6 aluminum latch support fitting of the cargo
doorway, and replacement of cracked fittings with new fittings. That
action was prompted by reports of cracked fittings on two Model 747
series airplanes. The requirements of that AD are intended to prevent
the cargo door from opening while the airplane is in flight, which
could result in rapid decompression of the airplane.
Actions Since Issuance of Previous Rule
Since the issuance of AD 93-02-16, the FAA has received reports
indicating that the inspections required by that AD may not adequately
detect stress corrosion cracking in 7079-T6 aluminum latch support
fittings. Three operators reported that, during HFEC inspections, five
cracked latch support fittings were detected on four airplanes that had
accumulated between 11,555 and 18,252 flight cycles. That AD requires
that an operator conduct repetitive HFEC inspections of latch support
fittings at intervals not to exceed 18 months. One operator reported
that it performed an HFEC inspection on the same airplane twice during
a 6-month period and that during the first inspection, no cracks were
detected. However, during the second inspection that was conducted 6
months later, an 8-inch crack was detected in one of the latch support
fittings for the aft door.
Findings indicate that cracks in these fittings may occur at such
an unpredictable rate that repetitive HFEC inspections are not
sufficient to detect cracking in a timely manner.
Explanation of Relevant Service Information
The FAA has reviewed and approved Boeing Service Bulletin 747-
53A2377, Revision 2, dated October 6, 1994, which describes procedures
for repetitive HFEC inspections to detect stress corrosion cracking on
the surfaces of the upper recess in each 7079-T6 aluminum latch support
fitting, and replacement of cracked fittings with new 7075-T73 fittings
that are not susceptible to stress corrosion cracking. Such replacement
would eliminate the need for repetitive HFEC inspections and prevent
the development and propagation of stress corrosion cracking.
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 supersede AD 93-02-16 to continue to require HFEC
inspections of all 7079-T6 latch support fittings of the cargo doorway,
and replacement of cracked fittings with new fittings. In addition,
this proposed AD would require the eventual replacement of all 7079-T6
latch support fittings with new 7075-T73 fittings, which would
constitute terminating action for the repetitive inspection
requirements.
These actions would be required to be accomplished in accordance
with the service bulletin described previously.
Cost Impact
There are approximately 200 airplanes of the affected design in the
worldwide fleet. The FAA estimates that 115 airplanes of U.S. registry
would be affected by this proposed AD.
The inspections that are currently required by AD 93-02-16, and
retained in this proposed AD, take approximately 31 work hours per
airplane, per inspection cycle, to accomplish, at an average labor rate
of $60 per work hour. Based on these figures, the cost impact of
currently required inspections on U.S. operators is estimated to be
$213,900, per inspection cycle, or $1,860 per airplane, per inspection
cycle.
The replacement, as proposed in this new AD action, would take
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approximately 1,019 work hours per airplane to accomplish, at an
average labor rate of $60 per work hour. Required parts would cost
approximately $20,917 per airplane ($12,888 for all aft door fittings;
$8,029 for all forward door fittings). Based on these figures, the cost
impact of the proposed replacement of this AD on U.S. operators is
estimated to be $9,436,555, or $82,057 per airplane.
The cost impact figures discussed above are based on assumptions
that no operator has yet accomplished any of the current or 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 removing amendment 39-8500 (58 FR
11190, February 24, 1993), and by adding a new airworthiness directive
(AD), to read as follows:
Boeing: Docket 97-NM-47-AD. Supersedes AD 93-02-16, Amendment 39-
8500.
Applicability: Model 747 airplanes, line numbers 1 through 200
inclusive; having 7079-T6 aluminum latch support fittings;
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 prevent the cargo door from opening while the airplane is in
flight, which could result in rapid decompression of the airplane,
accomplish the following:
Restatement of the Requirements of AD 93-02-16
(a) Within 60 days after March 11, 1993 (the effective date of
AD 93-02-16, amendment 39-8500), perform a high frequency eddy
current (HFEC) inspection to detect cracking on all surfaces of the
upper recess in each 7079-T6 aluminum latch support fitting of the
cargo doorway, in accordance with Boeing Service Bulletin 747-
53A2377, Revision 1, dated January 28, 1993, or Revision 2, dated
October 6, 1994. After the effective date of this AD, only Revision
2 of the service bulletin shall be used.
Note 2: Boeing Service Bulletin 747-53A2377, Revision 2, dated
October 6, 1994, references Boeing Service Bulletin 747-53-2200,
Revision 1, dated November 16, 1979, as an additional source of
service information for the replacement of these fittings.
(1) If any cracking is found on any fitting, prior to further
flight, replace the cracked fitting with a new 7075-T73 aluminum
latch support fitting in accordance with Boeing Service Bulletin
747-53A2377, Revision 1, dated January 28, 1993, or Revision 2,
dated October 6, 1994. After the effective date of this AD, only
Revision 2 of the service bulletin shall be used.
(2) If no cracking is found on any fitting, repeat the HFEC
inspection thereafter at intervals not to exceed 18 months until the
requirements of paragraph (b) of this AD are accomplished.
New Requirements of This AD
(b) Within 18 months after the effective date of this AD,
replace all 7079-T6 aluminum latch support fittings with new 7075-
T73 fittings in accordance with Boeing Service Bulletin 747-53A2377,
Revision 2, dated October 6, 1994. Replacement of all latch support
fittings constitutes terminating action for the inspection
requirements of this AD.
(c) As of the effective date of this AD, no operator shall
install any 7079-T6 aluminum latch support fitting of the cargo door
on any airplane.
(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 December 5, 1997.
John J. Hickey,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 97-32427 Filed 12-10-97; 8:45 am]
BILLING CODE 4910-13-U
