[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: ``9-ane-
[email protected]''. 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