[Federal Register Volume 62, Number 238 (Thursday, December 11, 1997)]
[Proposed Rules]
[Pages 65233-65235]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-32427]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-47-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

[[Page 65234]]

currently requires repetitive high frequency eddy current (HFEC) 
inspections to detect cracking on all surfaces of the upper recesses in 
certain latch support fittings of the cargo doorway, and replacement of 
cracked fittings with new fittings. That AD also provides for optional 
terminating action for the repetitive inspections. This proposal would 
require accomplishment of the previously optional terminating action. 
This proposal is prompted by reports indicating that the repetitive 
inspections required by the existing AD may not detect cracked fittings 
in a timely manner. The actions specified by the proposed AD are 
intended to prevent the cargo door from opening while the airplane is 
in flight, which could result in rapid decompression of the airplane.

DATES: Comments must be received by January 26, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 97-NM-47-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, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington; 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-47-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-103, Attention: Rules 
Docket No. 97-NM-47-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    On February 12, 1993, the FAA issued AD 93-02-16, amendment 39-8500 
(58 FR 11190, February 24, 1993), applicable to certain Boeing Model 
747 series airplanes, to require repetitive high frequency eddy current 
(HFEC) inspections to detect cracking on all surfaces of the upper 
recess in each 7079-T6 aluminum latch support fitting of the cargo 
doorway, and replacement of cracked fittings with new fittings. That 
action was prompted by reports of cracked fittings on two Model 747 
series airplanes. The requirements of that AD are intended to prevent 
the cargo door from opening while the airplane is in flight, which 
could result in rapid decompression of the airplane.

Actions Since Issuance of Previous Rule

    Since the issuance of AD 93-02-16, the FAA has received reports 
indicating that the inspections required by that AD may not adequately 
detect stress corrosion cracking in 7079-T6 aluminum latch support 
fittings. Three operators reported that, during HFEC inspections, five 
cracked latch support fittings were detected on four airplanes that had 
accumulated between 11,555 and 18,252 flight cycles. That AD requires 
that an operator conduct repetitive HFEC inspections of latch support 
fittings at intervals not to exceed 18 months. One operator reported 
that it performed an HFEC inspection on the same airplane twice during 
a 6-month period and that during the first inspection, no cracks were 
detected. However, during the second inspection that was conducted 6 
months later, an 8-inch crack was detected in one of the latch support 
fittings for the aft door.
    Findings indicate that cracks in these fittings may occur at such 
an unpredictable rate that repetitive HFEC inspections are not 
sufficient to detect cracking in a timely manner.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 747-
53A2377, Revision 2, dated October 6, 1994, which describes procedures 
for repetitive HFEC inspections to detect stress corrosion cracking on 
the surfaces of the upper recess in each 7079-T6 aluminum latch support 
fitting, and replacement of cracked fittings with new 7075-T73 fittings 
that are not susceptible to stress corrosion cracking. Such replacement 
would eliminate the need for repetitive HFEC inspections and prevent 
the development and propagation of stress corrosion cracking.

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 93-02-16 to continue to require HFEC 
inspections of all 7079-T6 latch support fittings of the cargo doorway, 
and replacement of cracked fittings with new fittings. In addition, 
this proposed AD would require the eventual replacement of all 7079-T6 
latch support fittings with new 7075-T73 fittings, which would 
constitute terminating action for the repetitive inspection 
requirements.
    These actions would be required to be accomplished in accordance 
with the service bulletin described previously.

Cost Impact

    There are approximately 200 airplanes of the affected design in the 
worldwide fleet. The FAA estimates that 115 airplanes of U.S. registry 
would be affected by this proposed AD.
    The inspections that are currently required by AD 93-02-16, and 
retained in this proposed AD, take approximately 31 work hours per 
airplane, per inspection cycle, to accomplish, at an average labor rate 
of $60 per work hour. Based on these figures, the cost impact of 
currently required inspections on U.S. operators is estimated to be 
$213,900, per inspection cycle, or $1,860 per airplane, per inspection 
cycle.
    The replacement, as proposed in this new AD action, would take

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approximately 1,019 work hours per airplane to accomplish, at an 
average labor rate of $60 per work hour. Required parts would cost 
approximately $20,917 per airplane ($12,888 for all aft door fittings; 
$8,029 for all forward door fittings). Based on these figures, the cost 
impact of the proposed replacement of this AD on U.S. operators is 
estimated to be $9,436,555, or $82,057 per airplane.
    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 39-8500 (58 FR 
11190, February 24, 1993), and by adding a new airworthiness directive 
(AD), to read as follows:
Boeing: Docket 97-NM-47-AD. Supersedes AD 93-02-16, Amendment 39-
8500.

    Applicability: Model 747 airplanes, line numbers 1 through 200 
inclusive; having 7079-T6 aluminum latch support fittings; 
certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
otherwise 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 prevent the cargo door from opening while the airplane is in 
flight, which could result in rapid decompression of the airplane, 
accomplish the following:

Restatement of the Requirements of AD 93-02-16

    (a) Within 60 days after March 11, 1993 (the effective date of 
AD 93-02-16, amendment 39-8500), perform a high frequency eddy 
current (HFEC) inspection to detect cracking on all surfaces of the 
upper recess in each 7079-T6 aluminum latch support fitting of the 
cargo doorway, in accordance with Boeing Service Bulletin 747-
53A2377, Revision 1, dated January 28, 1993, or Revision 2, dated 
October 6, 1994. After the effective date of this AD, only Revision 
2 of the service bulletin shall be used.

    Note 2: Boeing Service Bulletin 747-53A2377, Revision 2, dated 
October 6, 1994, references Boeing Service Bulletin 747-53-2200, 
Revision 1, dated November 16, 1979, as an additional source of 
service information for the replacement of these fittings.

    (1) If any cracking is found on any fitting, prior to further 
flight, replace the cracked fitting with a new 7075-T73 aluminum 
latch support fitting in accordance with Boeing Service Bulletin 
747-53A2377, Revision 1, dated January 28, 1993, or Revision 2, 
dated October 6, 1994. After the effective date of this AD, only 
Revision 2 of the service bulletin shall be used.
    (2) If no cracking is found on any fitting, repeat the HFEC 
inspection thereafter at intervals not to exceed 18 months until the 
requirements of paragraph (b) of this AD are accomplished.

New Requirements of This AD

    (b) Within 18 months after the effective date of this AD, 
replace all 7079-T6 aluminum latch support fittings with new 7075-
T73 fittings in accordance with Boeing Service Bulletin 747-53A2377, 
Revision 2, dated October 6, 1994. Replacement of all latch support 
fittings constitutes terminating action for the inspection 
requirements of this AD.
    (c) As of the effective date of this AD, no operator shall 
install any 7079-T6 aluminum latch support fitting of the cargo door 
on any airplane.
    (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 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.

    (e) 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 December 5, 1997.
John J. Hickey,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-32427 Filed 12-10-97; 8:45 am]
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