[Federal Register Volume 63, Number 135 (Wednesday, July 15, 1998)]
[Proposed Rules]
[Pages 38118-38120]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-18778]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 97-NM-296-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 repetitive inspections to detect
cracks in the edge frame web and doubler of the number 1 main entry
door cutout; and repair, if necessary. This proposed AD also provides
for optional terminating action for the repetitive inspections. This
proposal is prompted by reports indicating that fatigue cracks were
found in the edge frame web and doubler at the door stop number 1 of
the number 1 main entry door cutout. The actions specified by the
proposed AD are intended to detect and correct such fatigue cracking,
which could result in rapid decompression of the airplane.
DATES: Comments must be received by August 31, 1998.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No.97-NM-296-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, Transport Airplane Directorate, Seattle
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056; 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-296-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-114, Attention: Rules
Docket No. 97-NM-296-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
The FAA has received reports indicating that, while replacing the
inner chord of the frame on Boeing Model 747 series airplanes, cracks
were found in the edge frame web and doubler of the number 1 main entry
door cutout at station 488, between stringers 25 and 26 (door stop
number 1). The edge frame web in each incident was almost completely
severed. These airplanes had accumulated as few as 18,502 total flight
cycles. In addition, the FAA has received a report indicating that,
during fatigue testing on a Boeing Model 747SR test article, cracking
occurred in the edge frame web at 27,500 total pressure cycles and in
the inner chord at 30,750 total pressure cycles. The cause of such
cracking in all incidents has been attributed to fatigue. This
condition, if not detected and corrected, could result in rapid
decompression of the airplane.
Explanation of Relevant Service Information
The FAA has reviewed and approved Boeing Alert Service Bulletin
747-53A2414, dated August 7, 1997. This alert service bulletin
describes procedures for repetitive high frequency eddy current (HFEC)
inspections to detect cracks in both the aft side of the edge frame web
along the lower edge of the backup structure attachment at the stop
fitting number 1, and the forward side of the doubler at the lower edge
of door stop number 1 of the number 1 main entry door cutout; and
repair, if necessary.
The alert service bulletin specifies that operators of Group 1
airplanes are to perform those inspections of the subject areas on both
the left and right sides of the airplane; whereas, operators of Group 2
airplanes are to perform those inspections of the subject areas on the
left side only of the airplane. Group 1 airplanes are those Model 747
series airplanes that have a number 1 main entry door on both the left
and right sides of the airplane. Group 2 airplanes are those Model 747
series airplanes that only have a number 1 main entry door on the left
side of the airplane.
This alert service bulletin also describes procedures for a
preventative modification of the edge frame web and doubler, which
involves trimming the lower portion of the subject web; removing the
trimmed web and the doubler; and installing a new web, doubler, and
splice plate. For airplanes on which the inner chord of the edge frame
is not being replaced concurrently with the repair specified in the
alert service bulletin, the procedures also include an open hole HFEC
inspection of the inner chord of the edge frame. Accomplishment of the
preventative modification would eliminate the need for the repetitive
inspections. Accomplishment of the actions specified in the alert
service bulletin is
[[Page 38119]]
intended to adequately address the identified unsafe condition.
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 accomplishment of the inspections and repair,
if necessary, specified in the alert service bulletin described
previously. The proposed AD also provides for optional terminating
action, which, if accomplished, would terminate the repetitive
inspections.
The FAA considers three criteria for those situations where
repetitive inspections of a crack-prone area, such as in this proposed
AD, may be permitted to continue indefinitely, even though a positive
fix to the problem exists: (1) the area is easily accessible, (2) the
cracking is easily detectable, and (3) the consequences of the cracking
are not likely to be catastrophic. In consideration of the cracking
that may occur at the edge frame web and doubler at station 488, the
FAA has determined that the circumstances warranting continual
repetitive inspections meet these three criteria.
Cost Impact
There are approximately 685 airplanes of the affected design in the
worldwide fleet. The FAA estimates that 211 airplanes of U.S. registry
would be affected by this proposed AD, and that the average labor rate
is $60 per work hour.
The FAA estimates that 191 airplanes are equipped with a number 1
main entry door on both the left and right sides (Group 1 airplanes),
that it would take approximately 2 work hours per airplane to
accomplish the proposed inspection, and that the average labor rate is
$60 per work hour. Based on these figures, the cost impact of the
inspection proposed by this AD on U.S. operators of these airplanes is
estimated to be $22,920, or $120 per airplane, per inspection cycle.
The FAA estimates that 20 airplanes are equipped with a number 1
main entry door on the left side only (Group 2 airplanes), that it
would take approximately 1 work hour per airplane to accomplish the
proposed inspection, and that the average labor rate is $60 per work
hour. Based on these figures, the cost impact of the inspection
proposed by this AD on U.S. operators of these airplanes is estimated
to be $1,200, or $60 per airplane, per inspection cycle.
The cost impact figures discussed above are 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.
Should an operator of Group 1 airplanes elect to accomplish the
optional terminating action that would be provided by this AD action,
it would take approximately 40 work hours to accomplish it, at an
average labor rate of $60 per work hour. Based on these figures, the
cost impact of the optional terminating action would be $2,400 per
airplane.
Should an operator of Group 2 airplanes elect to accomplish the
optional terminating action that would be provided by this AD action,
it would take approximately 20 work hours to accomplish it, at an
average labor rate of $60 per work hour. Based on these figures, the
cost impact of the optional terminating action would be $1,200 per
airplane.
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 97-NM-296-AD.
Applicability: Model 747 series airplanes, line numbers 1
through 685 inclusive, 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 (e) 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 fatigue cracks in the edge frame web and
doubler of the number 1 main entry door cutout, which could result
in rapid decompression of the airplane, accomplish the following:
(a) Perform a high frequency eddy current (HFEC) (pencil probe
eddy current) inspection to detect cracks in both the aft side of
the lower edge frame web and the forward side of the edge frame web
doubler at station 488, between stringers 25 and 26 (door stop
number 1), of the number 1 main entry door cutout; in accordance
with Boeing Alert Service Bulletin 747-53A2414, dated August 7,
1997; at the time specified in paragraph (a)(1), (a)(2), (a)(3), or
(a)(4) of this AD, as applicable. For Group 1 airplanes (as
identified in the alert service bulletin), the inspection shall be
accomplished on both the left and right sides of the airplane. For
Group 2 airplanes (as identified in the alert service bulletin), the
inspection shall be accomplished only on the left side of the
airplane.
(1) For airplanes that have accumulated less than 16,000 total
flight cycles as of the effective date of this AD: Inspect prior to
the accumulation of 16,000 total flight cycles, or within 1,500
flight cycles after the effective date of this AD, whichever occurs
later.
(2) For airplanes that have accumulated 16,000 or more total
flight cycles but less than 20,000 total flight cycles as of the
effective date of this AD: Inspect prior to the accumulation of
21,000 total flight cycles, or within 1,500 flight cycles after the
effective date of this AD, whichever occurs first.
(3) For airplanes that have accumulated 20,000 or more total
flight cycles but less than 25,000 total flight cycles as of the
[[Page 38120]]
effective date of this AD: Inspect prior to the accumulation of
25,500 total flight cycles, or within 1,000 flight cycles after the
effective date of this AD, whichever occurs first.
(4) For airplanes that have accumulated 25,000 or more total
flight cycles as of the effective date of this AD: Inspect within
500 flight cycles after the effective date of this AD.
(b) If no crack is detected during any inspection required by
paragraph (a) of this AD, repeat the HFEC inspection thereafter at
intervals not to exceed 3,000 flight cycles.
(c) If any crack is detected during any inspection required by
paragraph (a) of this AD, prior to further flight, repair in
accordance with Boeing Alert Service Bulletin 747-53A2414, dated
August 7, 1997.
Note 2: The alert service bulletin emphasizes the importance of
performing an open hole HFEC inspection of the inner chord of the
frame within 6.0 inches of the web or doubler crack (as applicable),
if the inner chord of the frame is not replaced concurrently with
the web and doubler repair.
(d) Accomplishment of the repair or preventative modification
specified in Boeing Alert Service Bulletin 747-53A2414, dated August
7, 1997, constitutes terminating action for the repetitive
inspection requirements of this AD for that repaired/modified edge
frame web and doubler.
(e) 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.
(f) 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 July 8, 1998.
S.R. Miller,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 98-18778 Filed 7-14-98; 8:45 am]
BILLING CODE 4910-13-U
