[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]
BILLING CODE 4910-13-U