[Federal Register Volume 64, Number 173 (Wednesday, September 8, 1999)]
[Proposed Rules]
[Pages 48723-48725]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-23284]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 99-NE-34-AD]
RIN 2120-AA64
Airworthiness Directives; AlliedSignal Inc. 36-300(A), 36-280(B),
and 36-280(D) Series Auxiliary Power Units
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 AlliedSignal Inc. 36-300(A), 36-
280(B), and 36-280(D) series Auxiliary Power Units (APUs). This
proposal would require installation of an external load compressor
containment shield, or installation of a load compressor impeller with
lower stress concentrations. This proposal is prompted by reports of
load compressor impeller failures. The actions specified by the
proposed AD are intended to prevent an uncontained APU failure and
damage to the airplane.
DATES: Comments must be received by November 8, 1999.
ADDRESSES: Submit comments in triplicate to the Federal Aviation
Administration (FAA), New England Region, Office of the Regional
Counsel, Attention: Rules Docket No. 99-NE-34-AD, 12 New England
Executive Park, Burlington, MA 01803-5299. Comments may also be sent
via the Internet using the following address: ``adcomment@faa.gov''. Comments sent via the Internet must contain the
docket number in the subject line. Comments may be inspected at this
location between 8:00 a.m. and 4:30 p.m., Monday through Friday, except
Federal holidays.
The service information referenced in the proposed rule may be
obtained from AlliedSignal Aerospace Services Attn: Data Distribution,
M/S 64-3/2101-201, P.O. Box 29003, Phoenix, AZ 85038-9003; telephone
(602) 365-2493, fax (602) 365-5577. This information may be examined at
the FAA, New England Region, Office of the Regional Counsel, 12 New
England Executive Park, Burlington, MA.
FOR FURTHER INFORMATION CONTACT: Roger Pesuit, Aerospace Engineer, Los
Angeles Aircraft Certification Office, FAA, Transport Airplane
Directorate, 3960 Paramount Blvd., Lakewood, CA 90712-4137; telephone
(562) 627-5251, fax (562) 627-5210.
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 should 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
[[Page 48724]]
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-NE-34-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, New England Region, Office of the Regional Counsel,
Attention: Rules Docket No. 99-NE-34-AD, 12 New England Executive Park,
Burlington, MA 01803-5299.
Discussion
The Federal Aviation Administration (FAA) has received reports of
load compressor impeller cracks on AlliedSignal Inc. 36-300(A), 36-
280(B), and 36-280(D) series Auxiliary Power Units (APUs). In three
incidents, the load compressor impellers separated, resulting in
uncontained APU failures and debris entering the APU compartment.
Uncontained APU failures potentially could damage wiring, control and
fluid lines, and airplane structure. Investigation revealed that the
outboard rim of the load compressor impeller can crack at the damper
ring groove location. Cracks propagate circumferentially, leading to
loss of sections of the rim from the impeller. The load compressor
impeller was designed with a damper ring. The damper ring retention
groove was machined into the impeller with a tight radius at the
corners. The resulting high stress concentrations caused cracking which
progresses circumferentially allowing pieces of the rim to fail
radially outward. The condition is most acute on impellers that were
originally manufactured with a 0.005 inch radius. Some of these parts
were subsequently modified to 0.035 inch radius and carry a 3822270-4
part number (P/N) designation. All of the parts that have failed in
service accumulated a portion of their operating time with the 0.005
inch radius condition. The P/N 3822270-5 configuration was originally
manufactured with the 0.035 inch radius. Although none of the -5 parts
have failed in service, the stress concentration at the 0.035 inch
radius is sufficiently high to initiate low cycle fatigue cracking at
higher service times. Four -5 configuration parts have been tested to
failure by the manufacturer confirming the identical failure modes with
the -4 parts, the difference being initiation time taking longer on the
-5 part. This condition, if not corrected, could result in an
uncontained APU failure and damage to the airplane.
The FAA has reviewed and approved the technical contents of
AlliedSignal Inc. Service Bulletins (SBs) No. GTCP36-49-7471, dated
April 20, 1999, GTCP36-49-7472, dated March 31, 1999, and GTCP36-49-
7473, dated March 31, 1999, that describe procedures for installation
of an external load compressor containment shield.
Since an unsafe condition has been identified that is likely to
exist or develop on other products of the same design, the proposed AD
would require installation of an external load compressor containment
shield at the next shop visit, or 6 months after the effective date of
this AD, whichever occurs first. The 6 month time frame is based upon
engineering assessment of the risk of operating without containment. An
additional compliance option would be installation of a load compressor
impeller, P/N 3822270-5, to extend cyclic service life to 26,000
cycles-since-new (CSN) before mandatory installation of the containment
shield. Operators cannot operate with a load compressor installed, P/N
3822270-5, past 26,000 CSN unless they have installed an external
containment shield. The actions would be required to be accomplished in
accordance with the SBs described previously.
There are approximately 1,044 APUs of the affected design in the
worldwide fleet. The FAA estimates that 465 APUs installed on airplanes
of US registry would be affected by this proposed AD, that it would
take approximately 6 work hours per Model 36-300(A) APU (85 units) to
accomplish the proposed actions, and 8 work hours per Model 36-280(D)
APU (380 units), and that the average labor rate is $60 per work hour.
Required parts would cost approximately $3,103 per APU. Fifteen
installations on domestic Boeing 737 aircraft (Model 36-280(B)) would
require a tube assembly kit, which would cost approximately $1,042. The
manufacturer has informed the FAA that it may offset some of these
costs thereby lowering the total cost to operators. Based on these
figures, the total cost impact of the proposed AD on US operators is
estimated to be $1,725,270.
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:
AlliedSignal Inc.: Docket No. 99-NE-34-AD.
Applicability: AlliedSignal Inc. 36-300(A), 36-280(B), and 36-
280(D) series Auxiliary Power Units (APUs), installed on but not
limited to Airbus Industrie A319, A320, and A321 series; Boeing 737-
300, -400, -500 series; and McDonnell Douglas MD-80 series
airplanes.
Note 1: This airworthiness directive (AD) applies to each APU
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 APUs 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 (e) of this AD. The request should include an assessment
of the effect of the modification,
[[Page 48725]]
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 an uncontained APU failure and damage to the
airplane, accomplish the following:
(a) For APUs with load compressor impellers, part number (P/N)
3822270-4, at the next shop visit, or within 6 months after the
effective date of this AD, whichever occurs first, accomplish either
of the following:
(1) Install an external load compressor containment shield in
accordance with AlliedSignal Inc. Service Bulletins (SBs) No.
GTCP36-49-7471, dated April 20, 1999, GTCP36-49-7472, dated March
31, 1999, and GTCP36-49-7473, dated March 31, 1999, as applicable;
or
(2) Install load compressor impeller, P/N 3822270-5.
(b) For APUs with load compressor impellers, P/N 3822270-5,
install an external load compressor containment shield within 6
months after the effective date of this AD, or prior to exceeding
26,000 cycles-since-new (CSN), whichever occurs later, in accordance
with AlliedSignal Inc. SBs No. GTCP36-49-7471, dated April 20, 1999,
GTCP36-49-7472, dated March 31, 1999, and GTCP36-49-7473, dated
March 31, 1999, as applicable.
(c) Operators cannot operate with a load compressor, P/N
3822270-5, installed, past 26,000 cycles unless they have installed
an improved external containment shield.
(d) For the purpose of this AD, a shop visit is defined as when
the APU is inducted into a shop for any reason.
(e) 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, Los Angeles Aircraft Certification
Office. Operators shall submit their request through an appropriate
FAA Principal Maintenance Inspector, who may add comments and then
send it to the Manager, Los Angeles Aircraft Certification Office.
Note 2: Information concerning the existence of approved
alternative methods of compliance with this airworthiness directive,
if any, may be obtained from the Los Angeles Aircraft Certification
Office.
(f) Special flight permits may be issued in accordance with
Secs. 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 Burlington, Massachusetts, on September 1, 1999.
Jay J. Pardee,
Manager, Engine and Propeller Directorate, Aircraft Certification
Service.
[FR Doc. 99-23284 Filed 9-7-99; 8:45 am]
BILLING CODE 4910-13-U
