[Federal Register: March 20, 1998 (Volume 63, Number 54)]
[Proposed Rules]               
[Page 13566-13568]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr20mr98-36]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-NM-59-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 an inspection to determine the 
material type of the stop support fittings of the main entry doors. The 
proposed AD also would require repetitive visual inspections to detect 
cracks of certain stop support fittings of the main entry doors, and 
replacement of any cracked stop support fitting with a certain new stop 
support fitting. This proposal is prompted by reports that stress 
corrosion cracking was found on certain stop support fittings of the 
main entry doors. The actions specified by the proposed AD are intended 
to detect and correct such stress corrosion cracking, which could lead 
to failure of the stop support fittings. Failure of the stop support 
fittings could result in loss of a main entry door and consequent rapid 
decompression of the airplane.

DATES: Comments must be received by May 4, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport

[[Page 13567]]

Airplane Directorate, ANM-114, Attention: Rules Docket No. 97-NM-59-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-59-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-59-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received numerous reports of cracks on the stop support 
fittings (made from either 7079-T651 or 7075-T651 material) of the 
numbers 1, 2, 3, and 4 main entry doors on Boeing Model 747 series 
airplanes. The cause of these cracks has been attributed to stress 
corrosion. The effects of such stress corrosion cracking, if not 
detected and corrected in a timely manner, could lead to failure of the 
stop support fittings. Failure of the stop support fittings could 
result in loss of a main entry door and consequent rapid decompression 
of the airplane.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletin 747-53-
2358, dated August 26, 1993, which describes procedures for performing 
a high frequency eddy current (HFEC) inspection to determine the 
material type of the stop support fittings of the main entry doors. The 
service bulletin also describes procedures for repetitive visual 
inspections to detect cracks of the stop support fitting (not made from 
7075-T73 material) of the main entry doors, and replacement of any 
cracked fitting with a new fitting made from 7075-T73 material. In 
addition, the service bulletin describes procedures for optional 
replacement of the stop support fittings of the main entry doors with 
stop support fittings made from 7075-T73 material, which would 
eliminate the need for repetitive inspections. The new stop support 
fitting is less susceptible to 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 require an HFEC inspection to determine the material 
type of the stop support fittings of the main entry doors. The proposed 
AD also would require repetitive visual inspections to detect cracks of 
the stop support fitting (not made from 7075-T73 material) of the main 
entry doors, and replacement of any cracked fitting with a new fitting 
made from 7075-T73 material. In addition, the proposed AD provides for 
an optional replacement of the stop support fittings of the main entry 
doors with stop support fittings made from 7075-T73 material, which 
would constitute terminating action for the repetitive inspection 
requirements. The actions would be required to be accomplished in 
accordance with the service bulletin described previously.

Differences Between the Proposal and the Relevant Service 
Information

    Operators should note that the proposed compliance time of 18 
months for the repetitive inspections differs from the compliance time 
recommended in the referenced service bulletin. In developing an 
appropriate compliance time for this action, the FAA considered not 
only the degree of urgency associated with addressing the subject 
unsafe condition, but the susceptibility of the subject area to stress 
corrosion cracking. In addition, the FAA finds that a compliance time 
of 18 months will allow the inspection to be performed at a base during 
regularly scheduled maintenance where special equipment and trained 
maintenance personnel will be available, if necessary. In consideration 
of these items, the FAA finds that repetitive visual inspections 
conducted at the proposed compliance time of 18 months will better 
ensure that any detrimental effect associated with stress corrosion 
cracking will be identified and corrected prior to the time that it 
could adversely affect the stop support fittings of the main entry 
doors.
    In addition, unlike the procedures described in the referenced 
service bulletin, this proposed AD would not permit further flight with 
cracking detected in the stop support fittings. The FAA has determined 
that, due to the safety implications and consequences associated with 
such cracking, all stop support fittings that are found to be cracked 
must be replaced prior to further flight.
    Furthermore, the FAA is not proposing to mandate the replacement of 
stop support fittings for several reasons:
    1. Accessing the stop support fittings for inspection is easily 
accomplished.
    2. The cracked stop support fittings are easily detectable by means 
of a visual inspection.
    3. The visual inspection will preclude the occurrence of multiple 
failed stop support fittings, which could result in a catastrophic 
failure.
    The FAA also is not including the option for inspection at an 
initial compliance time of 6 years since date of manufacture of the 
airplane, as recommended by the referenced service bulletin. The FAA 
has determined that all affected airplanes are older than 6 years since 
date of manufacture of the airplane.

[[Page 13568]]

Other Relevant Rulemaking

    The FAA has previously issued AD 92-02-01, amendment 39-8137 (57 FR 
5373, February 14, 1992), which addresses cracking of certain support 
fittings on Boeing Model 747 series airplanes having line numbers 001 
through 113 inclusive. That AD currently requires repetitive 
inspections for cracking of the doorstop support fittings at the 
forward edge of the number 5 main entry door, and replacement, if 
necessary.

Cost Impact

    There are approximately 515 Boeing Model 747 series airplanes of 
the affected design in the worldwide fleet. The FAA estimates that 164 
airplanes of U.S. registry would be affected by this proposed AD.
    It would take approximately 1 work hour per door 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 HFEC inspection 
proposed by this AD on U.S. operators is estimated to be $60 per door.
    Should an operator be required to accomplish the proposed visual 
inspection, it would take approximately 2 work hours per door to 
accomplish the proposed actions, at an average labor rate of $60 per 
work hour. Based on these figures, the cost impact of the visual 
inspection proposed by this AD on U.S. operators is estimated to be 
$120 per door.
    Should an operator elect to accomplish the optional terminating 
action that would be provided by this proposed AD action, the number of 
hours required to accomplish it would be approximately 124 work hours 
per door, at an average labor rate of $60 per work hour. Required parts 
would cost approximately $13,000 per door. Based on these figures, the 
cost impact of the optional terminating action on U.S. operators is 
estimated to be $20,440 per door.
    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 97-NM-59-AD.

    Applicability: Model 747-100, -100B, -200, -200B, -200C, -300, -
400, and 747SR series airplanes, having line numbers 1 through 830 
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 (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 stress corrosion cracking of the stop 
support fittings of the main entry doors and the resultant failure 
of the stop support fittings, which could result in loss of a main 
entry door and consequent rapid decompression of the airplane, 
accomplish the following:
    (a) Within 18 months after the effective date of this AD, 
perform a high frequency eddy current inspection to determine the 
material type of the stop support fittings of the main entry doors, 
in accordance with the Accomplishment Instructions of Boeing Service 
Bulletin 747-53-2358, dated August 26, 1993.
    (1) If the fitting is made from 7075-T73 material, no further 
action is required by this AD.
    (2) If the fitting is NOT made from 7075-T73 material, prior to 
further flight, perform a visual inspection to detect cracks of the 
stop support fitting of the main entry doors, in accordance with the 
service bulletin.
    (i) If no crack is detected, repeat the visual inspection 
thereafter at intervals not to exceed 18 months.
    (ii) If any crack is detected, prior to further flight, replace 
the fitting with a stop support fitting made from 7075-T73 material, 
in accordance with the service bulletin.
    (b) Replacement of the stop support fitting of the main entry 
doors with a stop support fitting made from 7075-T73 material, in 
accordance with Boeing Service Bulletin 747-53-2358, dated August 
26, 1993, constitutes terminating action for the repetitive 
inspection requirements of this AD for the replaced fitting.
    (c) As of the effective date of this AD, no person shall install 
a stop support fitting made from either 7079-T651 or 7075-T651 
material 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 2: 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 March 13, 1998.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 98-7228 Filed 3-19-98; 8:45 am]
BILLING CODE 4910-13-U