[Federal Register Volume 64, Number 214 (Friday, November 5, 1999)]
[Proposed Rules]
[Pages 60386-60388]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-29056]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-231-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 all Boeing Model 747 series 
airplanes. This proposal would require repetitive inspections to detect 
cracking of the forward and aft inner chords and the splice fitting of 
the forward inner chord of the station 2598 bulkhead, and repair, if 
necessary. This proposal is prompted by reports of fatigue cracking 
found in those areas. The actions specified by the proposed AD are 
intended to detect and correct such cracking, which could result in 
reduced structural capability of the bulkhead and the inability of the 
structure to carry horizontal stabilizer flight loads.

DATES: Comments must be received by December 20, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 99-NM-231-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 99-NM-231-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. 99-NM-231-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received reports indicating that fatigue cracking has 
been detected in the forward and aft inner chords and the splice 
fitting of the forward inner chord of the station 2598 bulkhead on 
Boeing Model 747 series airplanes. The horizontal stabilizer hinge 
fittings are attached to the station

[[Page 60387]]

2598 bulkhead. The bulkhead includes a large cutout that gives access 
to the rear spar of the horizontal stabilizer. The reports indicate 
that the cracking was detected around the upper corners of the cutout. 
In addition, a recent report indicates that a fatigue crack was 
detected in the station 2598 splice fitting where it attaches to the 
upper and lower sections of the bulkhead forward inner chord. Such 
cracking, if not detected and corrected, could result in reduced 
structural capability of the bulkhead and the inability of the 
structure to carry horizontal stabilizer flight loads.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Alert Service Bulletin 
747-53A2427, dated December 17, 1998, which describes procedures for a 
one-time high frequency eddy current (HFEC) inspection and repetitive 
detailed visual inspections to detect cracking of the forward and aft 
inner chords of the station 2598 bulkhead, and repair, if necessary.

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 a one-time HFEC inspection and repetitive 
detailed visual inspections to detect cracking of the forward and aft 
inner chords of the station 2598 bulkhead, and repair, if necessary. 
These actions would be required to be accomplished in accordance with 
the alert service bulletin described previously, except as discussed 
below. The proposed AD also would require a one-time HFEC inspection 
and repetitive detailed visual inspections to detect cracking of the 
splice fitting of the forward inner chord of the station 2598 bulkhead. 
Such inspections of the splice fitting of the forward inner chord would 
be required to be accomplished in accordance with procedures included 
in paragraphs (a)(2) and (b)(2) of this AD. If any cracking is found 
during such inspections, repair would be required to be accomplished in 
accordance with a method approved by the FAA, as specified in paragraph 
(d) of this proposed AD.

Differences Between Proposed Rule and Alert Service Bulletin

    Operators should note that, although the alert service bulletin 
specifies that the manufacturer may be contacted for disposition of 
certain repair conditions, this proposed AD would require 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.
    Operators also should note that, as described previously, this 
proposed AD would require a one-time HFEC inspection and repetitive 
detailed visual inspections to detect cracking of the splice fitting of 
the forward inner chord of the station 2598 bulkhead. The alert service 
bulletin does not specify such inspections of the splice fitting. Also, 
though this inspection area is shown in Figure 2, Detail A, and Figure 
3, Detail A, of the alert service bulletin, the inspection area is not 
highlighted in those figures.

Interim Action

    This is considered to be interim action. The manufacturer has 
advised that it currently is developing a modification that will 
positively address the unsafe condition addressed by this AD. Once this 
modification is developed, approved, and available, the FAA may 
consider additional rulemaking.

Cost Impact

    There are approximately 1,301 airplanes of the affected design in 
the worldwide fleet. The FAA estimates that 260 airplanes of U.S. 
registry would be affected by this proposed AD.
    It would take approximately 2 work hours per airplane to accomplish 
the proposed HFEC inspection, at an average labor rate of $60 per work 
hour. Based on these figures, the cost impact of the proposed 
inspection on U.S. operators is estimated to be $31,200, or $120 per 
airplane.
    It would take approximately 2 work hours per airplane to accomplish 
the proposed detailed visual inspections, at an average labor rate of 
$60 per work hour. Based on these figures, the cost impact of the 
proposed inspections on U.S. operators is estimated to be $31,200, or 
$120 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 99-NM-231-AD.

    Applicability: All Model 747 series airplanes, 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

[[Page 60388]]

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 forward and aft inner 
chords and the splice fitting of the forward inner chord of the 
station 2598 bulkhead, which could result in reduced structural 
capability of the bulkhead and the inability of the structure to 
carry horizontal stabilizer flight loads, accomplish the following:

Initial Inspection

    (a) Prior to the accumulation of 13,000 total flight cycles, or 
within 1,000 flight cycles after the effective date of this AD, 
whichever occurs later: Accomplish the requirements specified in 
paragraphs (a)(1) and (a)(2) of this AD.
    (1) Perform a high frequency eddy current inspection (HFEC) to 
detect cracking of the forward and aft inner chords of the station 
2598 bulkhead, in accordance with Boeing Alert Service Bulletin 747-
53A2427, dated December 17, 1998.
    (2) Perform an HFEC inspection to detect cracking of the splice 
fitting along the upper and lower attachment to the forward inner 
chord of the station 2598 bulkhead, as shown in Figure 2, Detail A, 
of Boeing Alert Service Bulletin 747-53A2427, dated December 17, 
1998.

    Note 2: Operators should note that the inspection area specified 
in paragraph (a)(2) of this AD is NOT highlighted in Figure 2, 
Detail A, of Boeing Alert Service Bulletin 747-53A2427, dated 
December 17, 1998.

Repetitive Inspections

    (b) Within 3,000 flight cycles after accomplishment of the 
inspections required by paragraph (a) of this AD: Accomplish the 
inspections specified in paragraphs (b)(1) and (b)(2) of this AD. 
Repeat the inspection thereafter at intervals not to exceed 3,000 
flight cycles.
    (1) Perform a detailed visual inspection to detect cracking of 
the forward and aft inner chords of the station 2598 bulkhead, in 
accordance with Boeing Alert Service Bulletin 747-53A2427, dated 
December 17, 1998.

    Note 3: 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.''

    (2) Perform a detailed visual inspection to detect cracking of 
the splice fitting along the upper and lower attachment to the 
forward inner chord of the station 2598 bulkhead, as shown in Figure 
3, Detail A, of Boeing Alert Service Bulletin 747-53A2427, dated 
December 17, 1998.

    Note 4: Operators should note that the inspection area specified 
in paragraph (b)(2) of this AD is NOT highlighted in Figure 3, 
Detail A, of Boeing Alert Service Bulletin 747-53A2427, dated 
December 17, 1998.

Repair

    (c) If any cracking is detected during the inspections required 
by paragraph (a)(1) or (b)(1) of this AD, prior to further flight, 
repair in accordance with Boeing Alert Service Bulletin 747-53A2427, 
dated December 17, 1998, except as provided by paragraph (d) of this 
AD.
    (d) If any cracking is detected during the inspections required 
by paragraph (a)(2) or (b)(2) of this AD, or where the alert service 
bulletin specifies that the manufacturer may be contacted for 
disposition of certain repair conditions, 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 (DER) 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, or a Boeing DER, 
as required by this paragraph, the approval letter must specifically 
reference this AD.

Alternative Methods of Compliance

    (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 5: 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. Issued in Renton, 
Washington, on November 1, 1999.
D. L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 99-29056 Filed 11-4-99; 8:45 am]
BILLING CODE 4910-13-U