02-7416. Airworthiness Directives; Hamilton Sundstrand Power Systems (Formerly Sundstrand Power Systems, Turbomach, and Solar) T-62T Series Auxiliary Power Units

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The Federal Aviation Administration (FAA) proposes to adopt a new airworthiness directive (AD) that is applicable to Hamilton Sundstrand Power Systems (formerly Sundstrand Power Systems, Turbomach, and Solar) T-62T series auxiliary power units (APU's) with compressor wheel part number (P/N) 100636-1 installed. This proposal would require the replacement of compressor wheels P/N 100636-1. This proposal is prompted by a manufacturer's stress analysis that indicates stress levels high enough to initiate and drive crack growth in these compressor wheels. The actions specified by the proposed AD are intended to mandate the replacement of the affected compressor wheels, which if not replaced, could result in uncontained compressor wheel failure and damage to the airplane.

DATES:

Comments must be received by May 28, 2002.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 2002-NE-01-AD, 12 New England Executive Park, Burlington, MA 01803-5299. Comments may be inspected at this location, by appointment, between 8:00 a.m. and 4:30 p.m., Monday through Friday, except Federal holidays. Comments may also be sent via the Internet using the following address: “[e-mail]”. Comments sent via the Internet must contain the docket number in the subject line.

The service information referenced in the proposed rule may be obtained from Hamilton Sundstrand Power Systems, Technical Publications Department, P.O. Box 7002, Rockford, IL, 61125-7002; telephone [phone]; fax [phone]. This information may be examined, by appointment, 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 [phone], fax [phone].

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 action 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 action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2002-NE-01-AD.” The postcard will be date stamped and returned to the commenter.

Availability of NPRM's

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. 2002-NE-01-AD, 12 New England Executive Park, Burlington, MA 01803-5299.

Discussion

Hamilton Sundstrand Power Systems recently informed the FAA that models T-62T-2C, T-62T-25, T-62T-29, and T-62T-39 APU's with compressor wheel P/N 100636-1 installed, have high probability of uncontained compressor wheel failure caused by low-cycle fatigue. Several low-cycle fatigue failures of compressor wheels on the larger, Hamilton Sundstrand Power Systems model T-62T-40C APU, triggered the manufacturer to perform analysis of the geometrically similar compressor wheel P/N 100636-1. Although no uncontained failures of compressor wheel P/N 100636-1 have been known to occur in APU's installed on airplanes of U.S. registry, inspections of some compressor wheels during maintenance revealed cracks in attachment holes that are a precursor to failure. The manufacturer is aware also that four compressor wheels of the affected P/N have failed in APU's installed on U.S. military aircraft. This condition, if not corrected, could result in uncontained compressor wheel failure and damage to the airplane.

FAA's Determination of an Unsafe Condition and Proposed Actions

Since an unsafe condition has been identified that is likely to exist or develop on other aircraft with Hamilton Sundstrand Power Systems (formerly Sundstrand Power Systems, Turbomach, and Solar) models T-62T-2C, T-62T-25, T-62T-29, and T-62T-39 APU's installed, the proposed AD would require replacement at new reduced cycle life limits of compressor wheels P/N 100636-1, with compressor wheel P/N 4503164, 4504174, or M4504174. Two manufactured types of compressor wheel P/N 100636-1 exist. One type is a cast steel compressor wheel, identifiable by a four-digit casting lot vendor identification number, used as a prefix to the serial number. The other type is a wrought steel compressor wheel, identifiable by a serial number beginning with the letter W.

Cast steel compressor wheel replacement schedule:

• Replace compressor wheels with 2,350 or greater cycles-since-new (CSN) on the effective date of the proposed AD within 250 cycles-in-service (CIS) after the effective date of the proposed AD.
• Replace compressor wheels with less than 2,350 CSN on the effective date of the proposed AD before accumulating 2,600 CSN.

Wrought steel compressor wheel replacement schedule:

• Replace compressor wheels with 3,600 or greater CSN on the effective date of the proposed AD within 500 CIS after the effective date of the proposed AD.
• Replace compressor wheels with less than 3,600 CSN on the effective date of the proposed AD before accumulating 4,100 CSN.

Economic Analysis

There are approximately 492 Hamilton Sundstrand Power Systems (formerly Sundstrand Power Systems, Turbomach, and Solar) models T-62T-2C, T-62T-25, T-62T-29, and T-62T-39 APU's of the affected design in the worldwide fleet. The FAA estimates that 337 APU's installed on airplanes of U.S. registry would be affected by this proposed AD. The FAA also estimates that it would take approximately 40 work hours per APU to do the proposed actions, and that the average labor rate is $60 per work hour. The cost of a replacement compressor wheel is estimated to be $16,799. Based on these figures, the total cost of the proposed AD on U.S. operators is estimated to be $6,470,063.

Regulatory Analysis

This proposed rule does not have federalism implications, as defined in Executive Order 13132, because it 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. Accordingly, the FAA has not consulted with state authorities prior to publication of this proposed rule.

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.

§ 39.13

[Amended]

2. Section 39.13 is amended by adding the following new airworthiness directive:

Hamilton Sundstrand Power Systems: Docket No. 2002-NE-01-AD.

Applicability: This airworthiness directive (AD) is applicable to aircraft with Hamilton Sundstrand Power Systems (formerly Sundstrand Power Systems, Turbomach, and Solar) models T-62T-2C, T-62T-25, T-62T-29, and T-62T-39 auxiliary power units (APU's) installed that have compressor wheel part number (P/N) 100636-1 installed. These APU's are installed on, but not limited to, Fairchild FH-227, Dassault Falcon 20, Lockheed 1329 series (Jetstar), British Aerospace Jetstream 3101, Raytheon Aircraft HS125-600,—700,—800, and Sabreliner Corporation 60 and 80 aircraft, and Boeing Defense & Space Group 234 Series Helicopters.

Note 1:

This 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 APU's 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, alteration, or repair of 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: Compliance with this AD is required as indicated, unless already done.

To replace affected compressor wheels P/N 100636-1, which if not replaced, could result in uncontained compressor wheel failure and damage to the airplane, do the following.

Cast Steel Compressor Wheel Replacement

(a) For compressor wheels, P/N 100636-1, made of cast steel, identifiable by a four-digit casting lot vendor identification number used as a prefix to the serial number, replace compressor wheels with compressor wheel P/N 4503164, 4504174, or M4504174 as follows:

(1) Replace cast steel compressor wheels with 2,350 or greater cycles-since-new (CSN) on the effective date of this AD within 250 cycles-in-service (CIS) after the effective date of this AD.

(2) Replace cast steel compressor wheels with less than 2,350 CSN on the effective date of this AD before accumulating 2,600 CSN.

Wrought Steel Compressor Wheel Replacement

(b) For compressor wheels, P/N 100636-1 made of wrought steel, identifiable by a serial number beginning with the letter W, replace compressor wheels with compressor wheel P/N 4503164, 4504174, or M4504174 as follows:

(1) Replace wrought steel compressor wheels with 3,600 or greater CSN on the effective date of this AD within 500 CIS after the effective date of this AD.

(2) Replace wrought steel compressor wheels with less than 3,600 CSN on the effective date of this AD before accumulating 4,100 CSN.

(c) Information on procedures for replacing compressor wheel P/N 100636-1 may be found in Hamilton Sundstrand Power Systems service bulletin No. SB-T-62T-49-148, Revision 1, dated December 20, 2001.

Reduced Life Limits

(d) This AD establishes new cyclic life limits for compressor wheels P/N 100636-1, of 2,600 CSN for cast steel compressor wheels and 4,100 CSN for wrought steel compressor wheels. Except as provided in paragraph (e) of this AD, no alternate life limits for these parts may be approved.

Alternative Methods of Compliance

(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 (ACO). Operators must submit their request through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Los Angeles ACO.

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 ACO.

Special Flight Permits

(f) Special flight permits may be issued in accordance with §§ 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the aircraft to a location where the requirements of this AD can be done.

Issued in Burlington, Massachusetts, on March 20, 2002.

Francis A. Favara,

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