[Federal Register Volume 64, Number 63 (Friday, April 2, 1999)]
[Rules and Regulations]
[Pages 15920-15922]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-8133]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 99-NM-38-AD; Amendment 39-11107; AD 99-08-03]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 737-600, -700, and -800
Series Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule; request for comments.
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SUMMARY: This amendment adopts a new airworthiness directive (AD) that
is applicable to all Boeing Model 737-600, -700, and -800 series
airplanes. This action requires an inspection of the power distribution
panels (PDP) to verify proper installation of the power feeder
terminals and associated hardware, and corrective actions, if
necessary. This action also requires repetitive torque checks of the
terminal attachment screws. This amendment is prompted by reports
indicating the loss of electrical power from the engine-driven
generators or the auxiliary power unit due to overheating, melting, and
subsequent failure of the power feeder terminals. The actions specified
in this AD are intended to prevent such conditions, which could result
in increased risk of fire and the loss of electrical power from the
associated alternating current power source.
DATES: Effective April 19, 1999.
Comments for inclusion in the Rules Docket must be received on or
before June 1, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 99-NM-38-AD, 1601 Lind Avenue, SW., Renton,
Washington 98055-4056.
Information pertaining to this amendment may be obtained from or
examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue,
SW., Renton, Washington.
FOR FURTHER INFORMATION CONTACT: Stephen S. Oshiro, Aerospace Engineer,
Systems and Equipment Branch, ANM-130S, FAA, Transport Airplane
Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue,
SW., Renton, Washington 98055-4056; telephone (425) 227-2793; fax (425)
227-1181.
SUPPLEMENTARY INFORMATION: The FAA has recently received several
reports indicating the loss of electrical power from the engine-driven
generators or the auxiliary power unit on Boeing Model 737 series
airplanes, due to failure of the power feeder terminals located in
power distribution panels (PDP) P91 and P92. This failure is attributed
to an overheat condition caused by loosening of the screws that fasten
the power feeder terminals to the PDP rigid bus assembly. Investigation
revealed that inadequate support of the power feeder terminal allows
movement of the terminal during the power feeder wire installation and
removal procedures. The consequent loosening of the screws may result
in increased electrical resistance and the generation of heat between
the power feeder terminal and the rigid busbar at the terminal-to-
busbar interface. This condition, if not corrected, may cause
overheating and melting of the power feeder terminals, which could
result in increased risk of fire and the loss of electrical power from
the associated alternating current (AC) power source.
Explanation of the Requirements of the Rule
Since an unsafe condition has been identified that is likely to
exist or develop on other Boeing Model 737-600, -700, and -800 series
airplanes of the same type design, this AD is being issued to prevent
overheating, melting, and subsequent failure of the power feeder
terminals, which could result in increased risk of fire and the loss of
electrical power from the associated AC power source. This AD requires
an inspection of the PDP's to verify proper installation of the power
feeder terminals and associated hardware, and corrective actions, if
necessary. This action also requires repetitive torque checks of the
terminal attachment screws.
[[Page 15921]]
Interim Action
This is considered to be interim action. The FAA is currently
considering further rulemaking action to supersede this AD to require
repetitive replacement of the PDP rigid bus assembly for all Boeing
Model 737-600, -700, and -800 series airplanes. However, the planned
compliance time for the repetitive replacement is sufficiently long so
that notice and opportunity for prior public comment will be
practicable.
Determination of Rule's Effective Date
Since a situation exists that requires the immediate adoption of
this regulation, it is found that notice and opportunity for prior
public comment hereon are impracticable, and that good cause exists for
making this amendment effective in less than 30 days.
Comments Invited
Although this action is in the form of a final rule that involves
requirements affecting flight safety and, thus, was not preceded by
notice and an opportunity for public comment, comments are invited on
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All
communications received on or before the closing date for comments will
be considered, and this rule may be amended in light of the comments
received. Factual information that supports the commenter's ideas and
suggestions is extremely helpful in evaluating the effectiveness of the
AD action and determining whether additional rulemaking action would be
needed.
Comments are specifically invited on the overall regulatory,
economic, environmental, and energy aspects of the rule that might
suggest a need to modify the 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 that
summarizes each FAA-public contact concerned with the substance of this
AD will be filed in the Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments
submitted in response to this rule must submit a self-addressed,
stamped postcard on which the following statement is made: ``Comments
to Docket Number 99-NM-38-AD.'' The postcard will be date stamped and
returned to the commenter.
Regulatory Impact
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.
The FAA has determined that this regulation is an emergency
regulation that must be issued immediately to correct an unsafe
condition in aircraft, and that it is not a ``significant regulatory
action'' under Executive Order 12866. It has been determined further
that this action involves an emergency regulation under DOT Regulatory
Policies and Procedures (44 FR 11034, February 26, 1979). If it is
determined that this emergency regulation otherwise would be
significant under DOT Regulatory Policies and Procedures, a final
regulatory evaluation will be prepared and placed in the Rules Docket.
A copy of it, if filed, 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.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration amends 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:
99-08-03 Boeing: Amendment 39-11107. Docket 99-NM-38-AD.
Applicability: All Boeing Model 737-600, -700, and -800 series
airplanes; 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 (c) 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 overheating, melting, and subsequent failure of the
power feeder terminals, which could result in increased risk of fire
and the loss of electrical power from the associated alternating
current (AC) power source, accomplish the following:
Initial Inspection
(a) Within 90 days after the effective date of this AD: Perform
a one-time general visual inspection to verify proper installation
of the power feeder terminals and associated hardware located in
power distribution panels (PDP) P91 and P92, in accordance with the
following procedures.
Using a flashlight, inspect each of the six power feeder
terminals by looking into the access holes located in the plastic
cover of the rigid bus assembly. The holes are located on the aft
face of PDP's P91 and P92. [Refer to the Boeing 737-600, -700, -800,
-900 Airplane Maintenance Manual (AMM), Section 24-21-71/401, Figure
401 (Sheet 1), for the location of PDP P91 and P92.] On PDP P91, the
holes are adjacent to terminal blocks TB5001 and TB5002. On PDP P92,
the holes are adjacent to terminal blocks TB5005 and TB5006. There
are a total of six holes per PDP. [Refer to the Boeing 737-600, -
700, -800, -900 AMM, Section 24-21-71/401, Figure 401 (Sheet 2), for
the location of the access holes on the PDP's.] Note that although
each PDP has nine power feeder terminals, only the six terminals
adjacent to the access holes require inspection. Verify that the
power feeder terminal is properly installed and held in place on the
busbar by the No. 8 socket head cap screw, and verify that the cap
screw is inserted into the hole in the terminal. For the proper
power feeder terminal and screw buildup, refer to the Boeing 737-
600, -700, -800, -900 AMM, Chapter 24-21-71/401, Figure 401 (Sheet
4). The subject power feeder terminal is identified as item [7] and
the cap screw as item [12]. This visual inspection does not require
loosening or removing any fasteners. The inspection may require
looking through the access hole at a slight angle to see the
terminal clearly. The terminal can be identified by its shiny metal
finish; the current transformer behind the terminal block is made of
plastic with a flat black finish. If the power feeder terminal and
No. 8 socket head cap screw are not assembled as shown in Boeing
737-600, -700, -800, -900 AMM, Section 24-21-71/401, Figure 401
(Sheet 4): Prior to further flight, replace the rigid bus assembly
with a new assembly, in accordance with the procedures specified in
Boeing 737-600, -700, -800, -900 AMM, Section 24-21-22.
[[Page 15922]]
Repetitive Torque Check
(b) Concurrent with the accomplishment of the requirements of
paragraph (a) of this AD: Perform a torque check of the attachment
screws of the power feeder terminals in accordance with the
procedures specified in Boeing Maintenance Tip 737 MT 24-003, dated
May 14, 1998. Repeat the torque check thereafter at intervals not to
exceed 1,000 flight hours, in accordance with the maintenance tip.
Alternative Methods of Compliance
(c) 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.
Special Flight Permits
(d) 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.
(e) This amendment becomes effective on April 19, 1999.
Issued in Renton, Washington, on March 29, 1999.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 99-8133 Filed 4-1-99; 8:45 am]
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