[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]



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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]
BILLING CODE 4910-13-U