05-13134. Airworthiness Directives; Hamilton Sundstrand Power Systems (formerly Sundstrand Power Systems) Auxiliary Power Units Models T-62T-46C2, T-62T-46C2A, T-62T-46C3, T-62T-46C7, and T-62T-46C7A

AGENCY:

Federal Aviation Administration (FAA), Department of Transportation (DOT).

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD). The new AD is for Hamilton Sundstrand Power Systems (formerly Sundstrand Power Systems) auxiliary power units (APUs) models T-62T-46C2, T-62T-46C2A, T-62T-46C3, T-62T-46C7, and T-62T-46C7A, with compressor impeller assembly, part number (P/N) 4502020 or 4502020A, installed. This proposed AD would require removal from service of those compressor impeller assemblies at reduced service life limits. This proposed AD results from two reports of uncontained failures of compressor impeller assemblies. We are proposing this AD to prevent an uncontained APU failure and damage to the airplane.

DATES:

We must receive any comments on this proposed AD by September 6, 2005.

ADDRESSES:

Use one of the following addresses to comment on this proposed AD.

• DOT Docket Web site: Go to http://dms.dot.gov and follow the instructions for sending your comments electronically.
• Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically.
• Mail: Docket Management Facility; U.S. Department of Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, Washington, DC 20590-0001.
• Fax: [phone].
• Hand Delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

You may examine the comments on this proposed AD in the AD docket on the Internet at http://dms.dot.gov.

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 [phone], fax [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send us any written relevant data, views, or arguments regarding this proposal. Send your comments to an address listed under ADDRESSES. Include “Docket No. FAA-2005-21719; Directorate Identifier 2005-NE-19-AD” in the subject line of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments received by the closing date and may amend the proposed AD in light of those comments.

We will post all comments we receive, without change, to http://dms.dot.gov,, including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this proposed AD. Using the search function of the Docket Management System (DMS) Web site, anyone can find and read the comments in any of our dockets. The Web site includes the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You may review the DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78) or you may visit http://dms.dot.gov.

Examining the AD Docket

You may examine the docket that contains the proposal, any comments received and, any final disposition in person at the DMS Docket Office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Office (telephone [phone]) is located on the plaza level of the Department of Transportation Nassif Building at the street address stated in ADDRESSES. Comments will be available in the AD docket shortly after the DMS receives them.

Discussion

We received two reports of uncontained failures of compressor impeller assemblies installed in Hamilton Sundstrand Power Systems model T-62T-46C3 APUs. One report was of a compressor impeller failing in the field, at 17,680 cycles-since-new (CSN). The other report was of a compressor impeller failing at the manufacturer's site. Hamilton Sundstrand has determined that these failures were caused by low-cycle-fatigue (LCF) cracking. The LCF cracking starts on the compressor impeller back face radius, and grows circumferentially to failure, over a high number of cycles. This condition, if not corrected, could result in uncontained APU failure and damage to the airplane.

FAA's Determination and Requirements of the Proposed AD

We have evaluated all pertinent information and identified an unsafe condition that is likely to exist or develop on other products of this same type design. We are proposing this AD, which, for Hamilton Sundstrand Power Systems model T-62T APUs with compressor impeller assembly P/N 4502020 or 4502020A installed, would require:

• For APUs with compressor impeller assemblies that have 12,000 or more CSN on the effective date of the proposed AD, removal from service before accumulating 500 additional cycles; and
• For APUs with compressor impeller assemblies that have fewer than 12,000 CSN on the effective date of the proposed AD, removal from service at or before accumulating 12,500 CSN.

Costs of Compliance

There are about 50 Hamilton Sundstrand Power Systems model T-62T APUs of the affected design in the worldwide fleet. We estimate that eight APUs installed on airplanes of U.S. registry would be affected by this proposed AD. We also estimate that it would take about 8 work hours to remove and install an APU, and that the average labor rate is $65 per work hour. A new or serviceable compressor impeller assembly, P/N 4502020 or 4502020A, may be installed provided it meets the cycles-since-new criteria in the compliance section of this proposed AD. It would take about 55.5 hours to remove and replace affected compressor impeller assembly parts. New configuration replacement parts for each APU would cost approximately $36,587. Based on these figures, we estimate the total cost of the proposed AD to U.S. operators, to remove, upgrade, and install the APUs to be $325,716.

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, Section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, “General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

Regulatory Findings

We have determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would not have a substantial direct effect 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.

For the reasons discussed above, I certify that the 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. Would not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

We prepared a regulatory evaluation of the estimated costs to comply with this proposed AD. See the ADDRESSES section for a location to examine the regulatory evaluation.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Under the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 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.

§ 39.13

[Amended]

2. The FAA amends § 39.13 by adding the following new airworthiness directive:

Hamilton Sundstrand: Docket No. FAA-2005-21719; Directorate Identifier 2005-NE-19-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this airworthiness directive (AD) action by September 6, 2005.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Hamilton Sundstrand Power Systems (formerly Sundstrand Power Systems) auxiliary power units (APUs) models T-62T-46C2, T-62T-46C2A, T-62T-46C3, T-62T-46C7, and T-62T-46C7A, with compressor impeller assembly, part number (P/N) 4502020 or 4502020A installed. These APUs are installed on, but not limited to, BAE Systems AVRO 146, Fokker 50, Saab 2000, and Saab 340 airplanes.

Unsafe Condition

(d) This AD results from two reports of uncontained failures of compressor impeller assemblies. We are issuing this AD to prevent an uncontained APU failure and damage to the airplane.

Compliance

(e) You are responsible for having the actions required by this AD performed within the compliance times specified unless the actions have already been done.

(f) For APUs with compressor impeller assemblies that have 12,000 or more cycles-since-new (CSN) accumulated on the effective date of this AD, remove compressor impeller assemblies from service before accumulating 500 additional cycles.

(g) For APUs with compressor impeller assemblies that have fewer than 12,000 CSN on the effective date of this AD, remove compressor impeller assemblies from service at or before accumulating 12,500 CSN.

Alternative Methods of Compliance

(h) The Manager, Los Angeles Aircraft Certification Office, has the authority to approve alternative methods of compliance for this AD if requested using the procedures found in 14 CFR 39.19.

Related Information

(i) Hamilton Sundstrand Service Bulletins No. 4500090-49-33, dated January 6, 2005, No. 4500482-49-33, dated January 6, 2005, No. 4501578-49-22, dated January 13, 2005, No. 4501690-49-47, dated November 19, 2004, and No. 4501909-49-16, dated January 13, 2005, pertain to the subject of this AD.

Issued in Burlington, Massachusetts, on June 28, 2005.

Diane S. Romanosky,

Acting Manager, Engine and Propeller Directorate, Aircraft Certification Service.