[Federal Register Volume 64, Number 55 (Tuesday, March 23, 1999)]
[Rules and Regulations]
[Pages 13884-13886]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-6828]
[[Page 13884]]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 97-NM-296-AD; Amendment 39-11085; AD 99-07-03]
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
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 AD also provides for optional terminating action for
the repetitive inspections. This amendment 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 this AD are intended to detect and
correct such fatigue cracking, which could result in rapid
decompression of the airplane.
DATES: Effective April 27, 1999.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of April 27, 1999.
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, 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: 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 July 15, 1998 (63 FR
38118). That action proposed to 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. That action also proposed
to provide for optional terminating action for the repetitive
inspections.
Comments Received
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 Proposed Rule
Two commenters support the proposed rule.
Request to Re-Evaluate Repetitive Inspection Intervals
One commenter requests that the FAA re-evaluate the repetitive
inspection intervals of the proposed AD. The commenter suggests that
the FAA give consideration to the expected crack growth rate, so that
there is full confidence that crack detection will occur before the
cracks are able to cause a rapid decompression failure. The commenter
states that the reports discussed in the Discussion section of the
proposed AD indicate that in-service loads on the frame are
significantly different from those experienced in testing. This
difference could be due to repeated door operations, flight loads, and
exposure to various other environmental stresses.
The FAA does not concur with the commenter's request to re-evaluate
the repetitive inspection intervals. The FAA based the inspection
threshold and repetitive inspection intervals upon physical analysis
that determined the crack growth rate of the cracked structure, as well
as on damage tolerance and residual strength analytical methods that
provide conservative predications. The FAA has confidence that
accomplishment of the inspection at the defined thresholds and
repetitive intervals will provide an acceptable level of safety for the
affected airplanes. The FAA considered not only those safety issues in
developing an appropriate compliance time for this action, but the
recommendations of the manufacturer, the availability of any necessary
repair parts, and the practical aspect of accomplishing the required
inspection within an interval of time that parallels normal scheduled
maintenance for the majority of affected operators. Therefore, the FAA
finds that no change to the final rule is necessary.
Request to Clarify Differential Pressure Adjustment Factor
One commenter states that flight cycles below 2.0 pounds per square
inch (psi) differential pressure should not be counted when determining
the number of flight cycles on an airplane. Boeing provided
substantiating data that showed flight cycles accumulated at less than
2.0 psi cabin differential pressure has an insignificant effect on
fatigue life of the subject structure. From this comment, the FAA
infers that the commenter is requesting that a NOTE be added to
paragraph (a) of the AD to clarify this point. The FAA concurs. Based
on the manufacturer's substantiating data, the FAA has determined that
for this specific structure the effect of cabin differential pressure
at or below 2.0 psi is insignificant. Therefore, for the purposes of
this AD, the cabin differential pressure cycles at or below 2.0 psi may
be discounted from the total number of flight cycles of the airplane.
The FAA has added a new NOTE to the final rule to clarify this point.
Explanation of Additional Change
The FAA has revised paragraph (c) of the final rule to allow repair
of any crack in the subject area to be accomplished in accordance with
a method approved by the FAA, or in accordance with data meeting the
type certification basis of the airplane approved by a Boeing Company
Designated Engineering Representative who has been authorized by the
FAA to make such findings.
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 685 Model 747 series airplanes of the
affected design in the worldwide fleet. The FAA estimates that 211
airplanes of U.S. registry will be affected by this AD.
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 will take approximately 2 work hours per airplane to accomplish
the required inspection, and that the average labor rate is $60 per
work hour. Based on these figures, the cost impact of the
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inspection required 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 will
take approximately 1 work hour per airplane to accomplish the required
inspection, and that the average labor rate is $60 per work hour. Based
on these figures, the cost impact of the inspection required 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 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 is 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 this optional terminating action would be $2,400 per
airplane.
Should an operator of Group 2 airplanes elect to accomplish the
optional terminating action that is 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 this optional terminating action would be $1,200 per
airplane.
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:
99-07-03 Boeing: Amendment 39-11085. 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:
Inspection
(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.
Note 2: For the purposes of this AD, it is not necessary to
count flight cycles accumulated at 2.0 pounds per square inch (psi)
or less cabin differential pressure.
(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
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.
Repetitive Inspections
(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.
Corrective Action
(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; or in accordance with data meeting the type
certification basis of the airplane approved by a Boeing Company
Designated Engineering Representative who has been authorized by the
Manager, Seattle Aircraft Certification Office (ACO), to make such
findings.
Note 3: 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.
Optional Terminating Repair/Modification
(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.
Alternative Methods of Compliance
(e) An alternative method of compliance or adjustment of the
compliance time that
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provides an acceptable level of safety may be used if approved by
the Manager, Seattle 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 4: Information concerning the existence of approved
alternative methods of compliance with this AD, if any, may be
obtained from the Seattle ACO.
Special Flight Permits
(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.
Incorporation by Reference
(g) Except as provided by paragraphs (c) and (d) of this AD, the
actions shall be done in accordance with Boeing Alert Service
Bulletin 747-53A2414, dated August 7, 1997. 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.
(h) This amendment becomes effective on April 27, 1999.
Issued in Renton, Washington, on March 15, 1999.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 99-6828 Filed 3-22-99; 8:45 am]
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