[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
