[Federal Register Volume 64, Number 161 (Friday, August 20, 1999)]
[Proposed Rules]
[Pages 45466-45468]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-21693]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-282-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 
broken fasteners and cracking of the forward edge frame for main entry 
door number 3, and repair, if necessary. This proposal is prompted by 
reports of fatigue cracks at the inner chord and web of the body 
station 1265 edge frame between stringers 23 and 27. The actions 
specified by the proposed AD are intended to detect and correct such 
cracking, which could result in rapid depressurization of the airplane.

DATES: Comments must be received by October 4, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-282-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: Robert 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.

[[Page 45467]]

    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 98-NM-282-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. 98-NM-282-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received reports indicating that fatigue cracking has 
been detected in the frame web and frame inner chord at stringer 26 at 
body station 1265. In addition, one report indicates that, on one 
airplane, the fuselage frame web and frame inner chord had severed 
above stringer 24 near the top of a frame inner chord reinforcement 
strap. This frame is the forward edge frame for main entry door number 
3. Such fatigue cracking, if not detected and corrected in a timely 
manner, could result in rapid depressurization of the airplane.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Alert Service Bulletin 
747-53A2416, Revision 1, dated May 6, 1999, which describes procedures 
for repetitive inspections to detect broken fasteners and cracking of 
the forward edge frame for main entry door number 3, and repair, if 
necessary. The inspection of the frames at the floor intercostal 
includes a detailed visual inspection for broken fasteners, an open 
hole high frequency eddy current (HFEC) inspection of certain fasteners 
in the frame inner chord to detect cracking, and a surface HFEC 
inspection of the frame web to detect cracking. For certain airplanes, 
the service bulletin recommends a surface HFEC inspection and an open 
hole HFEC inspection of the frames at the top of the inner chord 
reinforcement strap to detect cracking. Accomplishment of the actions 
specified in the alert service bulletin is 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 actions specified in 
the alert service bulletin described previously, except as discussed 
below.

Differences Between Alert Service Bulletin and This AD

    Operators should note that, although the alert service bulletin 
specifies that the manufacturer may be contacted for repair data for 
cracking conditions, this AD requires the repair of those conditions 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.
    The alert service bulletin also indicates that a modification to 
the frame and lateral intercostal can be made that will increase the 
interval between frame inspections, and that the procedures for such a 
modification will be included in a subsequent revision to the alert 
service bulletin. Any modification incorporated to increase the 
interval between inspections or as terminating action for the 
inspections must be approved as an alternative method of compliance in 
accordance with paragraph (d) of this AD.

Cost Impact

    There are approximately 1,182 airplanes of the affected design in 
the worldwide fleet. The FAA estimates that 251 airplanes of U.S. 
registry would be affected by this proposed AD.
    It would take approximately 1 work hour per airplane to accomplish 
the proposed inspection of the frames at the floor intercostal, at an 
average labor rate of $60 per work hour. Based on these figures, the 
cost impact of this proposed inspection on U.S. operators is estimated 
to be $15,060, or $60 per airplane, per inspection cycle.
    The FAA estimates that the proposed inspection of the frames at the 
top of the inner chord reinforcement strap would be required to be 
accomplished on 103 U.S.-registered airplanes. It would take 
approximately 1 work hour per airplane to accomplish the proposed 
inspection, at an average labor rate of $60 per work hour. Based on 
these figures, the cost impact of this proposed inspection on U.S. 
operators is estimated to be $6,180, 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.

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 98-NM-282-AD.
    Applicability: Model 747 series airplanes, as listed in Boeing 
Alert Service Bulletin 747-53A2416, Revision 1, dated May 6, 1999; 
certificated in any category.

    Note 1: This AD applies to airplanes that have been converted 
from a passenger configuration to a special freighter configuration.

    Note 2: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been

[[Page 45468]]

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 (d) 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 cracking of the inner chord and web of the 
body station 1265 edge frame between stringers 23 and 27, which 
could result in rapid depressurization of the airplane, accomplish 
the following:

Inspections

    (a) Accomplish the flight safety inspections of the frames at 
the floor intercostal to detect broken fasteners and cracking, in 
accordance with Figure 5 of Boeing Alert Service Bulletin 747-
53A2416, Revision 1, dated May 6, 1999, at the applicable time 
specified in paragraph (a)(1), (a)(2), or (a)(3) of this AD. Repeat 
the inspection thereafter at intervals not to exceed 3,000 flight 
cycles.

    Note 3: Figure 5 of the alert service bulletin includes a 
detailed visual inspection for broken fasteners, an open hole high 
frequency eddy current (HFEC) inspection of certain fasteners in the 
frame inner chord to detect cracking, and a surface HFEC inspection 
of the frame web to detect cracking.

    Note 4: For the purposes of this AD, a detailed visual 
inspection is defined as: ``An intensive visual examination of a 
specific structural area, system, installation, or assembly to 
detect damage, failure, or irregularity. Available lighting is 
normally supplemented with a direct source of good lighting at 
intensity deemed appropriate by the inspector. Inspection aids such 
as mirror, magnifying lenses, etc., may be used. Surface cleaning 
and elaborate access procedures may be required.''

    Note 5: The alert service bulletin gives instructions to perform 
an open hole inspection, but does not give instructions to oversize 
the fastener hole after the inspection. This will keep sufficient 
material to oversize the hole at a later date when the modification 
work is accomplished.

    (1) For airplanes that have accumulated fewer than 10,000 total 
flight cycles as of the effective date of this AD: Inspect prior to 
the accumulation of 10,000 total flight cycles, or within 1,000 
flight cycles after the effective date of this AD, whichever occurs 
later.
    (2) For airplanes that have accumulated between 10,000 and 
20,000 total flight cycles as of the effective date of this AD: 
Inspect prior to the accumulation of 11,000 total flight cycles, or 
within 750 flight cycles after the effective date of this AD, 
whichever occurs later.
    (3) For airplanes that have accumulated more than 20,000 total 
flight cycles as of the effective date of this AD: Inspect prior to 
the accumulation of 20,750 total flight cycles, or within 500 flight 
cycles after the effective date of this AD, whichever occurs later.
    (b) For Group 1 airplanes, as identified in Boeing Alert Service 
Bulletin 747-53A2416, Revision 1, dated May 6, 1999, on which the 
extended chord reinforcement strap modification specified in Boeing 
Service Bulletin 747-53-2066, dated June 28, 1972, has not been 
accomplished or on which the extended chord reinforcement strap 
modification was accomplished after the accumulation of 10,000 total 
flight cycles: Accomplish the surface HFEC inspection and the open 
hole HFEC inspection, as applicable, of the frames at the top of the 
inner chord reinforcement strap to detect cracking, in accordance 
with Figure 6 of the alert service bulletin at the applicable time 
specified in either paragraph (b)(1) or (b)(2) of this AD. Repeat 
the inspection thereafter at intervals not to exceed 800 flight 
cycles.
    (1) For airplanes that have accumulated 20,000 total flight 
cycles or fewer as of the effective date of this AD: Inspect prior 
to the accumulation of 16,000 total flight cycles, or within 500 
flight cycles after the effective date of this AD, whichever occurs 
later.
    (2) For airplanes that have accumulated more than 20,000 total 
flight cycles as of the effective date of this AD: Inspect prior to 
the accumulation of 20,500 total flight cycles, or within 250 flight 
cycles after the effective date of this AD, whichever occurs later.

Repair

    (c) If any broken fastener or cracking is detected during the 
inspections required by paragraph (a) or (b) of this AD, prior to 
further flight, repair in accordance with a method approved by the 
Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport 
Airplane Directorate; 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 ACO, to make such findings. For a repair method to 
be approved by the Manager, Seattle ACO, as required by this 
paragraph, the Manager's approval letter must specifically reference 
this AD.

Alternative Methods of Compliance

    (d) 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 6: 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

    (e) Special flight permits may be issued in accordance with 
Secs. 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 August 16, 1999.
D. L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-21693 Filed 8-19-99; 8:45 am]
BILLING CODE 4910-13-P