[Federal Register Volume 65, Number 22 (Wednesday, February 2, 2000)]
[Proposed Rules]
[Pages 4906-4909]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-2226]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-NM-285-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 supersedure of an existing 
airworthiness directive (AD), applicable to certain Boeing Model 747 
series airplanes, that currently requires repetitive inspections for 
damage or cracking of the aft pressure bulkhead, and repair, if 
necessary. That action also removes certain repetitive inspections for 
cracking of the bulkhead web to Y-ring lap joint area, but retains the 
initial inspection for cracking in that area. That action also adds a 
one-time detailed visual inspection from the forward side of the 
bulkhead to detect fatigue cracking of the upper segment of the 
bulkhead web, and follow-on corrective actions, if necessary. This 
action would require that the one-time inspection be accomplished 
repetitively, and would add additional repetitive inspections. The 
actions specified by the proposed AD are intended to detect and correct 
fatigue cracking of the bulkhead web, which could result in rapid 
depressurization of the airplane, and consequent reduced 
controllability of the airplane.

DATES:  Comments must be received by March 20, 2000.

ADDRESSES:  Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 98-NM-285-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:  Rick Kawaguchi, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (425) 227-1153; 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 98-NM-285-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-285-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On September 14, 1998, the FAA issued AD 98-20-20, amendment 39-
10786 (63 FR 50495, September 22, 1998), applicable to certain Boeing 
747 series airplanes, to require certain repetitive inspections for 
damage or cracking of the aft pressure bulkhead, and repair, if 
necessary. In addition, that AD removes repetitive detailed visual 
inspections for cracking of the bulkhead web to Y-ring lap joint area, 
but retains the initial inspection for cracking in that area. That AD 
also adds a one-time detailed visual inspection from the forward side 
of the bulkhead to detect fatigue cracking of the upper segment of the 
bulkhead web, and follow-on corrective actions, if necessary. That 
action was prompted by reports indicating that the inspections required 
by AD 87-23-10, amendment 39-5758 (52 FR 41551, October 29, 1987), may 
not detect cracking of the bulkhead web in a timely manner. The 
requirements of AD 98-20-20 are intended to detect and correct fatigue 
cracking of the upper segment of the bulkhead web, which could result 
in rapid depressurization of the airplane, and consequent reduced 
controllability of the airplane.

Actions Since Issuance of Previous Rule

    In the preamble of AD 98-20-20, the FAA specified that the actions 
required by that AD were considered to be interim action. The FAA 
indicated that it may consider further rulemaking action to require 
repetitive detailed visual inspections and surface probe high frequency 
eddy current (HFEC) inspections to detect cracking of the upper and 
lower segments of the aft pressure bulkhead web, and repair if 
necessary. The FAA has determined that further rulemaking is indeed 
necessary; this proposed AD follows from that determination.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Alert Service Bulletin 
747-53A2275, Revision 6, dated August 27, 1998, which describes 
procedures for, among other things, repetitive inspections from the 
forward side of the bulkhead web at body station (BS) 2360 to detect 
cracking. The inspections to detect cracking include a detailed visual 
inspection of the upper half of the bulkhead and a surface probe HFEC 
inspection of the upper and lower segments of the bulkhead. 
Accomplishment of the actions specified in the service bulletin is 
intended to adequately address the identified unsafe condition.

[[Page 4907]]

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 supersede AD 98-20-20 to continue to require the 
actions specified in that AD. This action also would require that the 
one-time detailed visual inspection required by AD 98-20-20 be 
accomplished repetitively, and would add repetitive surface probe HFEC 
inspections, and repair, if necessary. The actions would be required to 
be accomplished in accordance with the service bulletin described 
previously, except as discussed below.

Differences Between Proposed AD and Service Bulletin

    Operators should note that, although the service bulletin specifies 
that the manufacturer may be contacted for disposition of certain 
cracking conditions, this proposal would require the repair of those 
conditions to be accomplished in accordance with a method approved by 
the FAA.

Clarification of Proposed Requirement

    The FAA has been advised that the manufacturer's intent of the 
surface probe HFEC inspection, as described in Figure 15 of the service 
bulletin, is that accomplishment of a surface probe HFEC inspection 
implies concurrent accomplishment of a detailed visual inspection, as 
described in Figure 14 of the service bulletin. This proposed rule 
clarifies the manufacturer's intent, in that it would explicitly 
require accomplishment of the repetitive detailed visual inspections at 
intervals not to exceed 1,500 flight cycles, and repetitive surface 
probe HFEC inspections at intervals not to exceed 3,000 flight cycles.

Cost Impact

    There are approximately 671 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 149 airplanes of U.S. registry 
would be affected by this proposed AD.
    The actions that are currently required by AD 98-20-20 and retained 
in this proposed AD, take approximately 360 work hours per airplane to 
accomplish, at an average labor rate of $60 per work hour. Based on 
these figures, the cost impact of the currently required actions on 
U.S. operators is estimated to be $3,218,400, or $21,600 per airplane, 
per inspection cycle.
    The new repetitive detailed visual inspections that are proposed in 
this AD action would take approximately 4 work hours per airplane to 
accomplish, at an average labor rate of $60 per work hour. Based on 
these figures, the cost impact of the proposed requirements of this AD 
on U.S. operators is estimated to be $35,760, or $240 per airplane, per 
inspection cycle.
    The new repetitive HFEC inspections that are proposed in this AD 
action would take approximately 48 work hours per airplane to 
accomplish, at an average labor rate of $60 per work hour. Based on 
these figures, the cost impact of the proposed requirements of this AD 
on U.S. operators is estimated to be $429,120, or $2,880 per airplane, 
per inspection cycle.
    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the current or 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 removing amendment 39-10786 (63 FR 
50495, September 22, 1998), and by adding a new airworthiness directive 
(AD), to read as follows:

Boeing: Docket 98-NM-285-AD. Supersedes AD 98-20-20, Amendment 39-
10786.
    Applicability: Model 747 series airplanes, line positions 1 
through 671 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 (j)(1) 
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 cracking of the bulkhead web, 
which could result in rapid depressurization of the airplane, and 
consequent reduced controllability of the airplane, accomplish the 
following:

Restatement of Actions Required by AD 98-20-20, Amendment 39-10786

    (a) Within 750 landings after December 10, 1987 (the effective 
date for AD 87-23-10, amendment 39-5758), unless accomplished within 
the last 1,250 landings [for airplanes subject to a 2,000-landing 
repeat inspection interval in accordance with paragraph (b) of this 
AD], or unless accomplished within the last 250 landings [for 
airplanes subject to a 1,000-landing repeat inspection interval in 
accordance with paragraph (b) of this AD], perform a detailed visual 
inspection; in accordance with Boeing Service Bulletin 747-53-2275, 
dated March 26, 1987, Revision 1, dated August 13, 1987, Revision 2, 
dated March 31, 1988, Revision 3, dated March 29, 1990, Revision 4, 
dated March 26, 1992, or Revision 5, dated January 16, 1997, or 
Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 
27, 1998; of the aft side of the entire Body Station (BS) 2360 aft 
pressure bulkhead for damage such as dents, tears, nicks, gouges, or 
scratches; and cracks at splices and doublers, and around the 
Auxiliary Power Unit pressure pan cutout; and, for Group 4 airplanes 
only, inspect from the forward side, the area adjacent to the window 
cutout for damage or cracks.



[[Page 4908]]


    Note 2:  Notwithstanding provisions to the contrary in AD 87-23-
10, and in Boeing Service Bulletin 747-53-2275, dated March 26, 
1987, Revision 1, dated August 13, 1987, Revision 2, dated March 31, 
1988, Revision 3, dated March 29, 1990, Revision 4, dated March 26, 
1992, and Revision 5, dated January 16, 1997: For Model 747SR 
airplanes operating at a cabin pressure differential lower than 8.6 
pounds-per-square-inch (psi), an adjustment factor of 1.2 shall not 
be used after October 7, 1998 (the effective date for AD 98-20-20), 
as a multiplier for inspection thresholds and intervals specified in 
this AD.


    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.''


    (b) After initial compliance with paragraph (a) of this AD, 
continue to inspect as follows:
    (1) For Group 1 airplanes, repeat the inspections required by 
paragraph (a) of this AD, at intervals not to exceed 2,000 landings.
    (2) For Groups 2 and 3 airplanes, repeat the inspections 
required by paragraph (a) of this AD, at intervals not to exceed 
1,000 landings; or optionally, at the applicable time specified in 
paragraph (b)(2)(i) or (b)(2)(ii) of this AD.
    (i) For Group 2 airplanes that operate the entire interval with 
aft lavatory complexes or galleys adjacent to bulkheads, repeat the 
inspections required by paragraph (a) of this AD at intervals not to 
exceed 2,000 landings.
    (ii) For Groups 2 and 3 airplanes that operate the entire 
interval with an intact protective shield on the lower half of the 
forward side of the bulkhead, repeat the inspections required by 
paragraph (a) of this AD at intervals not to exceed 2,000 landings; 
and perform a detailed visual inspection of the protective shield 
for damage in accordance with Boeing Service Bulletin 747-53-2275, 
dated March 26, 1987, Revision 1, dated August 13, 1987, Revision 2, 
dated March 31, 1988, Revision 3, dated March 29, 1990, Revision 4, 
dated March 26, 1992, or Revision 5, dated January 16, 1997, or 
Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 
27, 1998, at intervals not to exceed 1,000 landings. If damage is 
found to the protective shield that exceeds the limits indicated in 
the service bulletin, prior to further flight, repeat the inspection 
required by paragraph (a) of this AD.
    (3) For Group 4 airplanes, repeat the inspections required by 
paragraph (a) of this AD at intervals not to exceed 1,000 landings.
    (c) Within 750 landings after December 10, 1987, or prior to the 
accumulation of 20,000 total landings, whichever occurs later, 
unless accomplished within the last 3,250 landings; and at intervals 
thereafter not to exceed 4,000 landings; perform eddy current, 
ultrasonic, and X-ray inspections of the aft side of the BS 2360 aft 
pressure bulkhead for cracks; in accordance with Boeing Service 
Bulletin 747-53-2275, dated March 26, 1987, Revision 1, dated August 
13, 1987, Revision 2, dated March 31, 1988, Revision 3, dated March 
29, 1990, Revision 4, dated March 26, 1992, or Revision 5, dated 
January 16, 1997, or Boeing Alert Service Bulletin 747-53A2275, 
Revision 6, dated August 27, 1998.
    (d) Within 750 landings after December 10, 1987, or prior to the 
accumulation of 20,000 total landings, whichever occurs later, 
unless accomplished within the last 6,250 landings; and thereafter 
at intervals not to exceed 7,000 landings until the inspection 
required by paragraph (g) of this AD is accomplished: Perform a 
detailed visual inspection to detect cracking of the BS 2360 aft 
pressure bulkhead web to Y-ring lap joint area between radial 
stiffeners from the forward side of the bulkhead, in accordance with 
Boeing Service Bulletin 747-53-2275, dated March 26, 1987, Revision 
1, dated August 13, 1987, Revision 2, dated March 31, 1988, Revision 
3, dated March 29, 1990, Revision 4, dated March 26, 1992, or 
Revision 5, dated January 16, 1997, or Boeing Alert Service Bulletin 
747-53A2275, Revision 6, dated August 27, 1998.
    (e) If any cracking or damage is found during any inspection 
required by paragraph (a), (b), (c), or (d) of this AD, repair prior 
to further flight in accordance with Boeing Service Bulletin 747-53-
2275, dated March 26, 1987, Revision 1, dated August 13, 1987, 
Revision 2, dated March 31, 1988, Revision 3, dated March 29, 1990, 
Revision 4, dated March 26, 1992, or Revision 5, dated January 16, 
1997, or Boeing Alert Service Bulletin 747-53A2275, Revision 6, 
dated August 27, 1998.
    (f) For the purpose of complying with this AD, the number of 
landings may be determined to equal the number of pressurization 
cycles where the cabin pressure differential was greater than 2.0 
psi.
    (g) Perform a detailed visual inspection from the forward side 
of the bulkhead of the upper segment of the bulkhead web at BS 2360 
to detect cracking, in accordance with Boeing Alert Service Bulletin 
747-53A2275, Revision 6, dated August 27, 1998, at the earlier of 
the times specified in paragraphs (g)(1) and (g)(2) of this AD. 
Accomplishment of this inspection terminates the repetitive 
inspection requirement of paragraph (d) of this AD.
    (1) Within 7,000 landings after the most recent detailed visual 
inspection accomplished in accordance with paragraph (d) of this AD.
    (2) At the latest of the times specified in paragraphs 
(g)(2)(i), (g)(2)(ii), and (g)(2)(iii) of this AD.
    (i) Prior to the accumulation of 20,000 total landings.
    (ii) Within 1,500 landings after the most recent detailed visual 
inspection accomplished in accordance with paragraph (d) of this AD.
    (iii) Within 90 days after October 7, 1998 (the effective date 
of AD 98-20-20).
    (h) If any cracking is detected during the detailed visual 
inspections required by paragraph (g) of this AD, prior to further 
flight, accomplish a surface probe high frequency eddy current 
(HFEC) inspection from the forward side of the bulkhead to detect 
cracking of the upper and lower segments of the bulkhead web around 
the fasteners that attach the web to the outer chord of the Y-ring, 
in accordance with Boeing Alert Service Bulletin 747-53A2275, 
Revision 6, dated August 27, 1998. Repair any cracking, prior to 
further flight, 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.

New Requirements of This AD

    (i) If no cracking is detected during the detailed visual 
inspection required by paragraph (g) of this AD, within 1,500 flight 
cycles after accomplishment of that inspection or within 250 flight 
cycles after the effective date of this AD, whichever occurs later: 
Repeat the detailed visual inspection, as specified in paragraph 
(g); and perform a surface probe HFEC inspection from the forward 
side of the bulkhead to detect cracking of the upper and lower 
segments of the bulkhead web, in accordance with Figure 15 of Boeing

[[Page 4909]]

Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 
1998.
    (1) If no cracking is detected, repeat the detailed visual 
inspection thereafter at intervals not to exceed 1,500 flight 
cycles; and repeat the surface probe HFEC inspection thereafter at 
intervals not to exceed 3,000 flight cycles.
    (2) If any cracking is detected, prior to further flight, repair 
in accordance with a method approved by the Manager, Seattle 
Aircraft Certification Office (ACO), FAA, Transport Airplane 
Directorate, or a Boeing Company Designated Engineering 
Representative who has been authorized by the FAA 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

    (j)(1) 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.
    (2) Alternative methods of compliance, approved previously in 
accordance with AD 98-20-20, amendment 39-10786, are approved as 
alternative methods of compliance with this AD.

    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

    (k) 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 January 27, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-2226 Filed 2-1-00; 8:45 am]
BILLING CODE 4910-13-U