[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

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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