04-14945. Airworthiness Directives; Rolls-Royce Corporation (Formerly Allison Engine Company, Allison Gas Turbine Division, and Detroit Diesel Allison) 250-B and 250-C Series Turbofan and Turboshaft Engines

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to adopt a new airworthiness directive (AD) for Rolls-Royce Corporation (RRC) 250-B and 250-C series turbofan and turboshaft engines with certain part numbers (PNs) of compressor adaptor couplings manufactured by Alcor Engine Company (Alcor), EXTEX Ltd. (EXTEX), RRC, and Superior Air Parts (SAP) installed. This proposed AD would require operators to remove from service affected compressor adaptor couplings. This proposed AD results from nine reports of engine shutdown caused by compressor adaptor coupling failure. We are proposing this AD to reduce the risk of failure of the compressor adaptor coupling and subsequent loss of all engine power.

DATES:

We must receive any comments on this proposed AD by August 30, 2004.

ADDRESSES:

Use one of the following addresses to submit comments 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 20590-001.
• 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:

Robert Baitoo, Aerospace Engineer, Los Angeles Aircraft Certification Office, FAA, Transport Airplane Directorate, 3960 Paramount Blvd., Lakewood, CA 90712-4137; telephone: [phone], fax: [phone], for questions about Alcor, EXTEX, or SAP compressor adaptor couplings; and John Tallarovic, Aerospace Engineer, Chicago Aircraft Certification Office, FAA, 2300 East Devon Avenue, Des Plaines, IL 60018-4696; telephone [phone]; fax [phone], for questions about RRC compressor adaptor couplings.

SUPPLEMENTARY INFORMATION:

Docket Management System (DMS)

We have implemented new procedures for maintaining AD dockets electronically. As of May 17, 2004, we posted new AD actions on the DMS and assigned a DMS docket number. We track each action and assign a corresponding Directorate identifier. The DMS docket No. is in the form “Docket No. FAA-200X-XXXXX.” Each DMS docket also lists the Directorate identifier (“Old Docket Number”) as a cross-reference for searching purposes.

Comments Invited

We invite you to submit any written relevant data, views, or arguments regarding this proposal. Send your comments to an address listed under ADDRESSES. Include “Docket No. FAA-2004-18515; Directorate Identifier 2004-NE-12-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 DMS Web site, anyone can find and read the comments in any of our dockets, including 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.

We are reviewing the writing style we currently use in regulatory documents. We are interested in your comments on whether the style of this document is clear, and your suggestions to improve the clarity of our communications that affect you. You can get more information about plain language at http://www.faa.gov/​language and http://www.plainlanguage.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 Offices 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

The FAA has received reports of nine RRC 250-B and 250-C series turbofan and turboshaft engines that have experienced failure of the compressor adaptor coupling in service. Each failure has resulted in total loss of engine power, with three of the events resulting in accidents. The engines are installed in mostly single-engine helicopters, along with several turboprop airplanes. Alcor, EXTEX, and SAP each independently manufactured compressor adaptor couplings, under Parts Manufacturer Approval (PMA) authority. RRC manufactured compressor adaptor couplings under type and production certificate authority.

While the precise mechanism of coupling failure is still under investigation, enough evidence has been collected to conclude that the four individual part designs could have unsatisfactory rates of failure in service, and should be removed from service as recommended and substantiated by each individual part manufacturer.

Each of the four manufacturers is responsible for its own independent component design, design substantiation, component manufacture, and development of a field management plan for its fleet. EXTEX is handling field management of affected couplings made by SAP, under an agreement between the two manufacturers.

Compliance requirements in this proposed AD have been developed based on the FAA's consideration of those individual field management plans and corresponding substantiation. The condition described previously, if not corrected, could result in failure of the compressor adaptor coupling and subsequent loss of all engine power.

With respect to the field management plans, design and production approval holders are expected to have a comprehensive understanding of the system that the component is installed in and the consequences of failure of that specific component design. Also, design and production approval holders are expected to effectively collect and review service data and assess risk to support continued operational safety of their components in service. The different manufacturers of compressor adaptor couplings have conducted their own independent data reviews and risk assessments, with varying outcomes. These varying outcomes have generated different compliance requirements in this proposed AD, for users of each manufacturer's compressor adaptor coupling.

FAA's Determination and Requirements of the Proposed AD

We have evaluated all pertinent information available from field reports and from the four manufacturers' safety assessments and have identified an unsafe condition that is likely to exist or develop in other RRC 250-B17, -B17B, -B17C, -B17D, -B17E, 250-C20, -C20B, -C20F, -C20J, -C20S, and -C20W series turbofan and turboshaft engines that have any of the following compressor adaptor couplings installed:

• Alcor: P/Ns 23039791AL and 23039791AL-1/-2/-3.
• EXTEX: P/Ns A23039791, E23039791, E23039791-1/-2/-3, EH23039791, and EH23039791-1/-2/-3.
• RRC: P/Ns 23039791-1/-2/-3.
• SAP: P/N A23039791.

We are proposing this AD, which would:

• Remove from service affected Alcor compressor adaptor couplings using the schedule specified in the compliance section of this proposed AD. The related Alcor safety assessment and recommendations are based on a significant number of service part inspections and engineering judgment.
• Remove from service affected EXTEX and SAP compressor adaptor couplings using the schedule specified in the compliance section of this proposed AD. The related EXTEX and SAP safety assessments and recommendations are based on a significant number of service part inspections and engineering judgment.
• Remove from service affected RRC compressor adaptor couplings using the schedule specified in the compliance section of this proposed AD. The related RRC safety assessment and recommendations are based on a significant number of service part inspections, component tests, and manufacturing and overhaul assembly analysis, and engineering analysis.

Costs of Compliance

There are about 9,000 RRC 250-B and 250-C series turbofan and turboshaft engines of the affected design in the worldwide fleet. We estimate that 6,000 engines installed on helicopters and airplanes of U.S. registry would be affected by this proposed AD. We also estimate that it would take about 3 work hours per engine to perform the proposed actions when done at time of rotor disassembly, and that the average labor rate is $65 per work hour. Required parts would cost about $1,601 per engine. Based on these figures, we estimate the total cost of the proposed AD to U.S. operators to be $10,776,000.

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 summary of the costs to comply with this proposal and placed it in the AD Docket. You may get a copy of this summary at the address listed under ADDRESSES.

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:

Rolls-Royce Corporation (formerly Allison Engine Company, Allison Gas Turbine Division, and Detroit Diesel Allison): Docket No. FAA-2004-18515; Directorate Identifier 2004-NE-12-AD.

Comments Due Date

(a) The Federal Aviation Administration (FAA) must receive comments on this airworthiness directive (AD) action by August 30, 2004.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Rolls-Royce Corporation (formerly Allison Engine Company, Allison Gas Turbine Division, and Detroit Diesel Allison) 250-B17, -B17B, -B17C, -B17D, -B17E, 250-C20, -C20B, -C20F, -C20J, -C20S, and -C20W series turbofan and turboshaft engines with the compressor adaptor couplings installed listed in the following Table 1:

Table 1.—Affected Compressor Adaptor Couplings

Manufacturer	Affected part numbers
Alcor Engine Company (Alcor)	P/Ns 23039791AL; 23039791AL-1/-2/-3;
EXTEX Ltd. (EXTEX)	A23039791; E23039791; E23039791-1/-2/-3; EH23039791; EH23039791-1/-2/-3.
Rolls-Royce Corporation (RRC)	23039791-1/-2/-3
Superior Air Parts (SAP)	A23039791

These engines are installed on, but not limited to, the aircraft in the following Table 2:

Helicopters

Agusta Models

A109, A109A, A109A II Bell Models

206A, 207B, 206L Enstrom Models

TH-28, 480, 480B Eurocopter France Models

AS355E, AS355F, AS355F1, AS355F2

Eurocopter Deutschland Models

BO-105C, BO-105S

MDHI Models

369D, 369E, 369H, 369HM, 369HS, 369HE

Schweizer Model 269D

Airplanes

B-N Group Ltd. Model

BN-2T

Unsafe Condition

(d) This AD results from nine reports of engine shutdown caused by compressor adaptor coupling failure.

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.

Alcor Compressor Adaptor Couplings

(f) Remove Alcor compressor adaptor couplings, P/Ns 23039791AL, 23039791AL-1, -2, and -3 from service as follows:

(1) For couplings with 600 or more operating hours-since-new as of the effective date of this AD, or the operating hours are unknown and cannot be determined, remove couplings from service at next access but not to exceed 50 additional operating hours.

(2) For couplings with fewer than 600 operating hours-since-new on the effective date of this AD, remove couplings from service at next access but not to exceed 649 operating hours-since-new.

EXTEX and SAP Compressor Adaptor Couplings

(g) Remove EXTEX and SAP compressor adaptor couplings, P/Ns A23039791, E23039791, E23039791-1, -2, and -3, EH23039791, and EH23039791-1, -2, and -3, from service as follows:

(1) For couplings with operating hours that are unknown and cannot be determined, remove couplings from service at next access but not to exceed 50 additional operating hours.

(2) For couplings with 600 or more operating hours-since-new as of the effective date of this AD, remove couplings from service at next access but not to exceed 100 additional operating hours.

(3) For couplings with fewer than 600 operating hours-since-new on the effective date of this AD, remove couplings from service at next access but not to exceed 150 additional operating hours.

RRC Compressor Adaptor Couplings

(h) Remove RRC compressor adaptor couplings, P/Ns 23039791-1, -2, and -3 from service at next access but not later than March 1, 2012.

Installation Requirements for Compressor Adaptor Couplings

(i) Machine the compressor impeller as follows:

(1) Machine the inside diameter (ID) to accept the next larger size outside diameter (OD) compressor adaptor coupling.

(2) For example, if a −1 coupling was removed, a −2 coupling must be installed.

(3) If a −3 coupling is removed, a new impeller is required.

(4) A fit of 0.0000 to −0.0018 inch must be achieved. No fretting is allowed on the impeller after machining.

(5) Due to previous fretting, an impeller with a −1 coupling removed might have to be machined for a −3 coupling. Plating of the impeller ID is not allowed.

(6) Fluorescent penetrant inspect the impeller.

(7) Install a new compressor adaptor coupling, P/N 23076559-2 or -3; or

(8) If a new impeller is installed, then install compressor adaptor coupling, P/N 23076559-1.

(9) Heating of the impeller per the engine overhaul manual is required to install the coupling to achieve the target fit specified in the following Table 3:

Table 3.—Impeller-to-Coupling Target Fit

Impeller ID	New Adaptor	Adaptor OD	Fit (Interference)
(i) 0.900 to 0.899 inch	23076559-1	0.9000 to 0.9008 inch	0.0000 to −0.0018 inch.
(ii) 0.902 to 0.901 inch	23076559-2	0.9020 to 0.9028 inch	0.0000 to −0.0018 inch.
(iii) 0.904 to 0.903 inch	23076559-3	0.9040 to 0.9048 inch	0.0000 to −0.0018 inch.

Definition

(j) For the purposes of this AD, next access is defined as when the compressor module is separated from the engine and disassembled for any reason.

Alternative Methods of Compliance

(k) The Manager, Los Angeles Aircraft Certification Office, has the authority to approve alternative methods of compliance for Alcor, EXTEX, and SAP adaptor couplings addressed in this AD if requested using the procedures found in 14 CFR 39.19. The Manager, Chicago Aircraft Certification Office, has the authority to approve alternative methods of compliance for RRC adaptor couplings addressed in this AD if requested using the procedures found in 14 CFR 39.19.

Material Incorporated by Reference

(l) None.

Related Information

(m) Alcor SLB No. 814-3-1, Revision C, dated April 28, 2004, EXTEX Alert Service Bulletin T-081, Revision B, dated May 4, 2004, and RRC CEB-A-1392 and CEB-A-1334, dated September 9, 2003, pertain to the subject of this AD.

Issued in Burlington, Massachusetts, on June 25, 2004.

Jay J. Pardee,

Manager, Engine and Propeller Directorate, Aircraft Certification Service.