[Federal Register Volume 63, Number 63 (Thursday, April 2, 1998)]
[Rules and Regulations]
[Pages 16098-16100]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-8349]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 96-NM-245-AD; Amendment 39-10435; AD 98-07-15]
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
an internal visual inspection to detect cracks of the skin and internal
doublers above main entry door 1 at body station 460, and various
follow-on actions. This amendment is prompted by reports indicating
that multiple fatigue cracks were found in both internal skin doublers.
The actions specified by this AD are intended to detect and correct
such fatigue cracking, which could result in reduced structural
integrity of the fuselage and consequent rapid depressurization of the
cabin.
DATES: Effective May 7, 1998.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of May 7, 1998.
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), ransport 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, Seattle Aircraft Certification Office,
1601 Lind Avenue, SW., Renton, Washington; telephone (206) 227-2776;
fax (206) 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 April 25, 1997 (62
FR 20132). That action proposed to require an internal visual
inspection to detect cracks of the skin and internal doublers above
main entry door 1 at body station 460, and various follow-on actions.
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 Proposal
One commenter supports the proposed rule.
Request to Revise Method of Counting Accumulated Flight Cycles
One commenter, the manufacturer, requests that the FAA expand the
definition of the term ``flight cycles'' as used in the compliance
times for this proposed AD. The manufacturer requests that the FAA
specify that, for the purposes of this AD, flight cycles that occur
while operating with a cabin differential pressure of 2.0 pounds per
square inch (psi) or less need not be considered or counted as a flight
cycle when determining the number of flight cycles relative to the
proposed compliance thresholds. The manufacturer states that the
fuselage skin in the upper forward portion of the airplane is almost
exclusively subjected to pressure loading, and there are no data to
support counting all flight cycles for fatigue or crack growth.
The manufacturer further states that finite element data indicate
that more than 97 percent of the loading in this area is directly due
to cabin differential pressure. Similarly, strain gages installed
common to an adjacent lap splice indicated that ground loading and
flight loading are insignificant when compared to pressurization
loading.
Additionally, the manufacturer states that if the provision to
eliminate counting flight cycles that occur while operating with a
cabin differential pressure of 2.0 psi or less is not permitted,
several operators that use non-pressurized touch-and-go cycles for crew
training will be adversely affected. The manufacturer also points out
that if operators are required to count all flight cycles for this
rule, some of these airplanes could be approaching the 13,000 cycle
threshold, yet actually have less than 2,700 flight cycles that are
actually pressurized.
The FAA concurs that, in this case, flight cycles shall be defined
as flight cycles that have a cabin differential pressure of more than
2.0 psi. The FAA has reviewed substantiating data submitted by the
manufacturer and has determined that the primary fatigue loading at the
subject location (on Boeing Model 747 series airplanes) is due to cabin
differential pressure cycles
[[Page 16099]]
with an insignificant contribution from ground and flight loads.
Therefore, the FAA has added a provision to the final rule that
specifies the definition of flight cycles for the purposes of this AD.
Request to Shorten the Compliance Time
One group of commenters requests that the FAA shorten the
compliance time for the initial internal visual inspection to detect
cracks of the skin and internal doublers from 18 months to 9 months in
order to ensure the safety of the flying public. The commenters believe
that shortening the compliance time will make the AD process more
effective and will prevent an event similar to that which occurred in
April 1988 on a Model 737 series airplane.
The FAA does not concur that a shorter compliance time is needed.
After consideration of all the available information, the FAA concludes
that a reduction of the proposed compliance time, without prior notice
and opportunity for public comment, is not warranted. In developing an
appropriate compliance time, the FAA considered the safety implications
and normal maintenance schedules for accomplishment of the various
inspections and determined that 18 months was the most cost-effective
compliance time. Further, the proposed compliance time of 18 months was
arrived at with operator, manufacturer, and FAA concurrence. To reduce
the compliance time of the proposal would necessitate (under the
provisions of the Administrative Procedure Act) reissuing the notice,
reopening the period for public comment, considering additional
comments received, and eventually issuing a final rule; the time
required for that procedure may be as long as four additional months.
In comparing the actual compliance date of the final rule after
completing such a procedure to the compliance date of this final rule
as issued, the increment in time is minimal. In light of this, and in
consideration of the amount of time that has already elapsed since
issuance of the original notice, the FAA has determined that further
delay of this final rule action is not appropriate. However, if
additional data are presented that would justify a short compliance
time, the FAA may consider further rulemaking on this issue.
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 change previously
described. The FAA has determined that this change will neither
increase the economic burden on any operator nor increase the scope of
the AD.
Cost Impact
There are approximately 880 Boeing Model 747 series airplanes of
the affected design in the worldwide fleet. The FAA estimates that 143
airplanes of U.S. registry will be affected by this AD. Each of these
airplanes has a left- and right-side main entry door 1.
It will take approximately 76 work hours per airplane to accomplish
the required internal visual inspection, at an average labor rate is
$60 per work hour. Based on these figures, the cost impact of the
internal visual inspection required by this AD on U.S. operators is
estimated to be $652,080, or $4,560 per airplane.
Should an operator be required to accomplish the specified
preventative modification, it will take approximately 100 work hours
per airplane to accomplish, at an average labor rate of $60 per work
hour. Required parts will cost approximately $1,094 per airplane. Based
on these figures, the cost impact of the preventative modification (if
accomplished) specified in this AD on U.S. operators is estimated to be
$1,014,442, or $7,094 per airplane.
It will take approximately 40 work hours per airplane to accomplish
the required high frequency eddy current (HFEC) or low frequency eddy
current (LFEC) inspection (i.e., post-modification), at an average
labor rate of $60 per work hour. Based on these figures, the cost
impact of the HFEC or LFEC inspection required by this AD on U.S.
operators is estimated to be $343,200, or $2,400 per airplane, per
inspection cycle.
Should an operator be required to accomplish the specified repair,
it will take approximately 212 work hours per airplane to accomplish,
at an average labor rate of $60 per work hour. Required parts will cost
approximately $2,602 per airplane. Based on these figures, the cost
impact of the repair (if accomplished) specified by this AD on U.S.
operators is estimated to be $2,191,046, or $15,322 per airplane.
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.
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:
98-07-15 Boeing: Amendment 39-10435. Docket 96-NM-245-AD.
Applicability: Model 747 series airplanes, having line numbers
207 through 1088 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
[[Page 16100]]
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 cracking in the internal skin
doublers, which could result in reduced structural integrity of the
fuselage and consequent rapid depressurization of the cabin,
accomplish the following:
(a) For airplanes identified as Groups 1 through 10, inclusive,
in Boeing Service Bulletin 747-53A2396, Revision 1, dated February
22, 1996: Prior to the accumulation of 13,000 flight cycles, or
within 18 months after the effective date of this AD, whichever
occurs later, perform an internal visual inspection to detect cracks
of the skin and internal doublers above main entry door 1 at body
station (STA) 460, in accordance with Part 2--Inspection of the
Accomplishment Instructions of Boeing Service Bulletin 747-53A2396,
Revision 1, dated February 22, 1996. For the purposes of this AD,
the number of flight cycles in which cabin differential pressure
occurs at 2.0 pounds per square inch (psi) or less need not be
counted when determining the number of flight cycles that have
occurred on the airplane.
(1) If no crack is detected during the internal visual
inspection required by paragraph (a) of this AD, prior to further
flight, perform an open hole high frequency eddy current (HFEC)
inspection to detect cracks of the skin and internal doublers above
main entry door 1, in accordance with Figure 10 of the service
bulletin.
(i) If no crack is detected during the open hole HFEC inspection
required by paragraph (a)(1) of this AD, prior to further flight,
install an external doubler in accordance with Part 4--Modification
of the Accomplishment Instructions of the service bulletin.
(ii) If any crack is detected during the open hole HFEC
inspection, prior to further flight, perform a visual inspection to
detect damage of the adjacent structure within 20 inches of the
cracks, in accordance with Part 3--Repair of the Accomplishment
Instructions of the service bulletin. If any damage is detected,
prior to further flight, repair it in accordance with Part 3--
Repair, or the Note specified in paragraph G. of Part 2--Inspection
of the Accomplishment Instructions of the service bulletin.
(2) If any crack is detected during the internal visual
inspection required by paragraph (a) of this AD, prior to further
flight, perform a visual inspection to detect damage of the adjacent
structure within 20 inches of the cracks, in accordance with Part
3--Repair of the Accomplishment Instructions of the service
bulletin. Prior to further flight following accomplishment of this
visual inspection, repair any cracked skin or internal doublers,
and/or repair adjacent damaged structure, in accordance with Part
3--Repair of the Accomplishment Instructions of the service
bulletin.
(b) Perform either an internal surface HFEC or external low
frequency eddy current (LFEC) inspection to detect damage of the
repaired or modified area, in accordance with Part 6--After-Repair
or After-Modification Inspection Program of the Accomplishment
Instructions of Boeing Service Bulletin 747-53A2396, Revision 1,
dated February 22, 1996; at the time specified in paragraph (b)(1)
or (b)(2) of this AD, as applicable.
(1) For airplanes identified as Groups 1 through 10, inclusive,
in Boeing Service Bulletin 747-53A2396, Revision 1, dated February
22, 1996: Inspect within 15,000 flight cycles following
accomplishment of either paragraph (a)(1) or (a)(2) of this AD.
(2) For airplanes identified as Group 11 in Boeing Service
Bulletin 747-53A2396, Revision 1, dated February 22, 1996: Inspect
prior to the accumulation of 15,000 total flight cycles.
(c) If no damage is detected during any inspection required by
paragraph (b) of this AD, repeat the inspections required by
paragraph (b) of this AD at the following intervals:
(1) If the immediately preceding inspection was conducted using
HFEC techniques, conduct the next inspection within 6,000 flight
cycles.
(2) If the immediately preceding inspection was conducted using
LFEC techniques, conduct the next inspection within 3,000 flight
cycles.
(d) If any damage is detected during any inspection required by
paragraph (b) of this AD, prior to further flight, repair it in
accordance with a method approved by the Manager, Seattle Aircraft
Certification Office (ACO), FAA, Transport Airplane Directorate.
(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 ACO. 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 2: 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.
(g) The actions shall be done in accordance with Boeing Service
Bulletin 747-53A2396, Revision 1, dated February 22, 1996. 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, ransport 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 May 7, 1998.
Issued in Renton, Washington, on March 25, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 98-8349 Filed 4-1-98; 8:45 am]
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