[Federal Register Volume 59, Number 55 (Tuesday, March 22, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-6068]


[[Page Unknown]]

[Federal Register: March 22, 1994]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 93-NM-146-AD; Amendment 39-8858; AD 94-06-11]

 

Airworthiness Directives; Boeing Model 737-300, -400, and -500 
Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain Boeing Model 737-300, -400, and -500 series 
airplanes, that requires modification of the leading edge slat access 
panel and internal structure at Front Spar Station (FSS) 250.663. This 
amendment is prompted by reports that fuel leaking from the fuel line 
at FSS 250.663 flowed through a drain hole in a slat access panel and 
leaked into the turbine exhaust area. The actions specified by this AD 
are intended to prevent drainage from such a fuel leak into the turbine 
exhaust area, which could cause an external fire under the wing.

DATES: Effective April 21, 1994.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of April 21, 1994.

ADDRESSES: The service information referenced in this AD may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the Federal 
Aviation Administration (FAA), Transport Airplane Directorate, Rules 
Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of 
the Federal Register, 800 North Capitol Street, NW., suite 700, 
Washington, DC.

FOR FURTHER INFORMATION CONTACT: Stephen Bray, Aerospace Engineer, 
Propulsion Branch, ANM-140S, FAA, Transport Airplane Directorate, 
Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (206) 227-2681; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations to include an airworthiness directive (AD) that is 
applicable to certain Boeing Model 737-300, -400, and -500 series 
airplanes was published in the Federal Register on November 16, 1993 
(58 FR 60415). That action proposed to require modification of the 
leading edge slat access panel and internal structure at Front Spar 
Station (FSS) 250.663.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.
    One commenter supports the proposal.
    Another commenter suggests that certain wording used in the 
preamble to the notice to describe the unsafe condition be clarified. 
This commenter notes that the preamble described the proposed actions 
as intended to ``prevent such a fuel leak [from causing an external 
fire under the wing];'' however, the actual intent of the proposed 
actions is to ``prevent drainage from such a fuel leak into the turbine 
exhaust area [which could cause an external fire under the wing].'' The 
FAA concurs with the commenter' suggestion and has revised certain 
wording in the preamble to this final rule accordingly.
    This commenter also suggests that the preamble to the notice 
contained an inaccurate statement in the Discussion section, which 
indicated that ``* * *. The resultant fire could spread from the 
turbine exhaust area to the strut and, subsequently, could ignite fuel 
within the strut.'' The commenter points out that the strut drain 
system would route leakage clear of the exhaust area and, therefore, 
the strut would not contain fuel to be ignited. The commenter suggests 
that condition being addressed is the result of fuel leakage draining 
from the wing leading edge slat access panel outboard of the strut. The 
proposed corrective modification involves closing the slat access panel 
drain and rerouting the drainage from this area into the strut drain 
system, which will ensure that the drainage is discharged clear of the 
turbine exhaust area. The FAA does not concur that this statement was 
totally inaccurate. However, in order to provide some clarification of 
this issue, the FAA considers that a more precise description of the 
situation prompting the addressed unsafe condition is ``* * *. The 
resultant fire could spread from the turbine exhaust area to the wing 
leading edge slat, and subsequently spread to the wing front spar at 
FSS 250.663.''
    This same commenter requests that the FAA delay issuance of the 
rule until a revised version of the referenced service bulletin is 
issued in mid-April. This revised service bulletin will include 
procedures for an optional method of closing the drain hole in the slat 
access panel. The FAA does not concur that delaying issuance of this 
rule, for the reasons cited by the commenter, is appropriate. If a 
revised service bulletin is released sometime in the future, the use of 
it as an alternative method for complying with this rule may be 
requested under the provisions of paragraph (b) of this final rule.
    Several commenters request that the proposed compliance time of 12 
months be extended to 60 months, so that the modification can be 
accomplished during a regularly scheduled ``heavy'' maintenance 
interval when the airplane is brought to the main maintenance base for 
an extended hold. These commenters point out that adoption of the 
proposed 12-month compliance time would require affected operators to 
schedule special times for the accomplishment of this modification, at 
significant additional expense. These commenters consider that such an 
extension is justified since a fuel leak of the type addressed by the 
proposed AD is limited to ground operations after the engines have been 
shut down; the risk of injury to personnel under this scenario is 
considerably less than a potential fire threat during airborne 
operations. The FAA concurs that the compliance time can be extended 
somewhat. Upon reconsideration, the FAA finds that the proposed 12-
month compliance time may impose an undue economic burden on affected 
operators. The FAA has determined that extending the compliance time 
for modification to 24 months will not compromise safety. In addition, 
it will allow operators to accomplish the modification during a 
regularly scheduled ``C'' check maintenance interval at a main base, 
where special equipment and trained maintenance personnel will be 
available, if required. Paragraph (a) of the final rule has been 
revised accordingly.
    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with the changes previously 
described. The FAA has determined that these changes will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.
    There are approximately 950 Model 737-300, -400, and -500 series 
airplanes of the affected design in the worldwide fleet. The FAA 
estimates that 400 airplanes of U.S. registry will be affected by this 
AD, that it will take approximately 10 work hours per airplane to 
accomplish the required actions, and that the average labor rate is $55 
per work hour. The cost of required parts is expected to be negligible. 
Based on these figures, the total cost impact of the AD on U.S. 
operators is estimated to be $220,000, or $550 per airplane.
    The total cost impact figure discussed above is based on 
assumptions that no operator has yet accomplished any of the 
requirements of this AD action, and that no operator would accomplish 
those actions in the future if this AD were not adopted.
    The regulations adopted herein will 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 final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it may be obtained 
from the Rules Docket at the location provided under the caption 
ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends 14 CFR part 
39 of the Federal Aviation Regulations as follows:

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

94-06-11 Boeing: Amendment 39-8858. Docket 93-NM-146-AD.

    Applicability: Model 737-300, -400, and -500 series airplanes, 
line position 1001 through 1976 inclusive, 1978 through 2183 
inclusive, 2185 through 2186 inclusive, and 2188 through 2193 
inclusive; certificated in any category.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent drainage from a fuel line leak within the wing 
leading edge from entering the turbine exhaust area, which could 
cause an external fire under the wing, accomplish the following:
    (a) Within 24 months after the effective date of this AD, modify 
the leading edge slat access panel and internal structure at Front 
Spar Station (FSS) 250.663 in accordance with Boeing Service 
Bulletin 737-57-1221, dated August 6, 1992.
    (b) 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: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (c) Special flight permits may be issued in accordance with 
Federal Aviation Regulations (FAR) 21.197 and 21.199 to operate the 
airplane to a location where the requirements of this AD can be 
accomplished.
    (d) The modification shall be done in accordance with Boeing 
Service Bulletin 737-57-1221, dated August 6, 1992. This 
incorporation by reference was approved by the Director of the 
Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 
51. Copies may be obtained from Boeing Commercial Airplane Group, 
P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be 
inspected at the FAA, Transport Airplane Directorate, 1601 Lind 
Avenue, SW., Renton, Washington; or at the Office of the Federal 
Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
    (e) This amendment becomes effective on April 21, 1994.

    Issued in Renton, Washington, on March 10, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-6068 Filed 3-21-94; 8:45 am]
BILLING CODE 4910-13-U