[Federal Register Volume 64, Number 112 (Friday, June 11, 1999)]
[Proposed Rules]
[Pages 31518-31520]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-14817]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 99-NM-62-AD]
RIN 2120-AA64
Airworthiness Directives; Boeing Model 737-600, -700, and -800
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 all Boeing Model 737-600, -
700, and -800 series airplanes, that currently 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. That AD also requires repetitive torque checks
of the terminal attachment screws. This action would add a requirement
for repetitive replacement of the PDP rigid bus assembly with a new
assembly. This proposal is prompted by reports of 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 by the proposed 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: Comments must be received by July 26, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), Transport Airplane Directorate, ANM-114,
Attention: Rules Docket No. 99-NM-62-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.
Information pertaining to this amendment may be obtained from or
examined at the FAA, Transport
[[Page 31519]]
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:
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 99-NM-62-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. 99-NM-62-AD, 1601 Lind Avenue, SW., Renton, Washington
98055-4056.
Discussion
On March 29, 1999, the FAA issued AD 99-08-03, amendment 39-11107
(64 FR 15920, April 2, 1999), applicable to all Boeing Model 737-600, -
700, and -800 series airplanes, to require 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. That action also requires repetitive torque checks of the
terminal attachment screws. That action was prompted by reports of 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 requirements of that 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.
Actions Since Issuance of Previous Rule
In the preamble to AD 99-08-03, the FAA specified that the actions
required by that AD were considered ``interim action'' and that the FAA
was considering further rulemaking action to supersede that AD to
require repetitive replacement of the PDP rigid bus assembly with a new
assembly for all Boeing Model 737-600, -700, and -800 series airplanes.
The FAA has determined that further rulemaking is indeed necessary;
this proposed AD follows from that determination.
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 99-08-03 to continue to require 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 would continue to require repetitive torque
checks of the terminal attachment screws. This proposed AD would add a
requirement for repetitive replacement of the PDP rigid bus assembly
with a new assembly.
Interim Action
This is considered to be interim action. The manufacturer has
advised that it currently is developing a modification that will
positively address the unsafe condition addressed by this AD. Once this
modification is developed, approved, and available, the FAA may
consider additional rulemaking.
Cost Impact
There are approximately 153 airplanes of the affected design in the
worldwide fleet. The FAA estimates that 56 airplanes of U.S. registry
would be affected by this proposed AD.
The actions that are currently required by AD 99-08-03 take
approximately 2 work hours per airplane to accomplish, at an average
labor rate of $60 per work hour. Based on these figures, the cost
impact of the currently required actions on U.S. operators is estimated
to be $6,720, or $120 per airplane.
The new replacement that is proposed in this AD action would take
approximately 6 work hours per airplane to accomplish, at an average
labor rate of $60 per work hour. Required parts would be provided by
the manufacturer at no cost to the operators. Based on these figures,
the cost impact of the replacement proposed by this AD on U.S.
operators is estimated to be $20,160, or $360 per airplane, per
replacement cycle.
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:
[[Page 31520]]
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 39-11107 (64 FR
15920, April 2, 1999), and by adding a new airworthiness directive
(AD), to read as follows:
Boeing: Docket 99-NM-62-AD. Supersedes AD 99-08-03, Amendment 39-
11107.
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 (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 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:
Restatement of Requirements of AD 99-08-03, Amendment 39-11107:
Initial Inspection
(a) Within 90 days after April 19, 1999 (the effective date of
AD 99-08-03, amendment 39-11107): 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.
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.
New Requirements of This AD
Repetitive Replacement
(c) Within 1,000 flight hours after accomplishment of the eighth
torque check required by paragraph (b) of this AD: Replace the PDP
rigid bus assembly with a new assembly, in accordance with the
procedures specified in Boeing 737-600, -700, -800, -900 AMM,
Chapter 24-21-22. Repeat the replacement thereafter at intervals not
to exceed 1,000 flight hours after every eighth torque check in
accordance with the procedures specified in the AMM.
Alternative Methods of Compliance
(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.
Special Flight Permits
(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 June 4, 1999.
Vi L. Lipski,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 99-14817 Filed 6-10-99; 8:45 am]
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