Airworthiness Directives; Pratt & Whitney Canada PW206A and PW206E Turboshaft Engines

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The FAA proposes to supersede an existing airworthiness directive (AD) for Pratt & Whitney Canada (PWC) PW206A and PW206E turboshaft engines. That AD currently requires initial and repetitive borescope inspections of compressor turbine and power turbine blades for blade axial shift, and replacement of blade retaining rivets and certain rotor air seals as terminating action for the repetitive borescope inspections.

This proposed AD would require the same actions but needs to clarify the extent of engine disassembly that triggers the required part replacements. This proposed AD is prompted by reports of engine shutdowns and emergency landings due to severe vibration, resulting in exhaust gases escaping from the engine-to-exhaust nozzle interface, thereby triggering in-flight engine fire warnings. We are proposing this AD to prevent turbine blade axial shift, which could cause high levels of vibration, loss of engine torque, in-flight engine shutdown, and loss of the airframe exhaust duct.

DATES:

We must receive any comments on this proposed AD by April 20, 2004.

ADDRESSES:

Use one of the following addresses to submit comments on this proposed AD:

• By mail: Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 2003-NE-25-AD, 12 New England Executive Park, Burlington, MA 01803-5299.
• By fax: (781) 238-7055.
• By e-mail: 9-ane-adcomment@faa.gov

You can get the service information identified in this proposed AD from Pratt & Whitney Canada, 1000 Marie-Victorin, Longueuil, Quebec, Canada J4G1A1.

You may examine the AD docket, by appointment, at the FAA, New England Region, Office of the Regional Counsel, 12 New England Executive Park, Burlington, MA.

FOR FURTHER INFORMATION CONTACT:

Ian Dargin, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone (781) 238-7178; fax (781) 238-7199.

SUPPLEMENTARY INFORMATION:

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 “AD Docket No. 2003-NE-25-AD” in the subject line of your comments. If you want us to acknowledge receipt of your mailed comments, send us a self-addressed, stamped postcard with the docket number written on it; we will date-stamp your postcard and mail it back to you. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. If a person contacts us through a nonwritten communication, and that contact relates to a substantive part of this proposed AD, we will summarize the contact and place the summary in the docket. We will consider all comments received by the closing date and may amend the proposed AD in light of those comments.

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 may 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 AD Docket (including any comments and service information), by appointment, between 8 a.m. and 4:30 p.m., Monday through Friday, except Federal holidays. See ADDRESSES for the location.

Discussion

On August 4, 2003, the FAA issued airworthiness directive (AD) 2003-16-10, Amendment 39-13263 (68 FR 48544, August 14, 2003), to require initial and repetitive borescope inspections of compressor turbine and power turbine blades for blade axial shift. That AD also required replacement of blade retaining rivets and certain rotor air seals as terminating action for the repetitive borescope inspections. That action was prompted by reports of engine shutdowns and emergency landings due to severe vibration and drops in engine torque, and an increase in internal engine temperature, triggering in-flight engine fire warnings. That condition, if not corrected, could result in turbine blade axial shift, which could cause high levels of vibration, loss of engine torque, in-flight engine shutdown, and loss of the airframe exhaust duct.

Comments Received Since AD 2003-16-10 Was Issued

Since that final rule; request for comments was issued, we received two comments on that AD. We have considered those comments.

Request To Clarify the Extent of Engine Disassembly Required

One commenter requests clarification in the AD of the extent of engine disassembly that would trigger the part replacements and clarification of the rework specified in the terminating action. The commenter states that more extensive disassembly is required to do the part replacement specified in Part B of PWC SB No. 200-72-28069, Revision 5, dated February 10, 2003, than to do the part rework specified in Part A of that SB. The commenter also states that the triggering event of a shop visit for any reason is too restrictive.

The FAA agrees. We have rewritten the terminating action to be done at the next engine shop visit when access is available to subassembies, such as modules, accessories, and components, or at the next engine overhaul, whichever occurs first, but before accumulating 1,800 flight hours from the effective date of this AD or before December 31, 2009, whichever occurs first.

Request To Clarify the Preamble

One commenter requests clarification of what prompted the AD. The commenter suggests that the words describing the actions prompting this AD be changed to state that the AD is being issued to prevent turbine blade axial shift, leading to high levels of vibration and possible in-flight engine shutdown.

The FAA agrees to the suggested changes to the preamble, which have been incorporated into this document. There have been six emergency landings due to high vibration levels and in-flight engine fire warnings, one incident of the loss of the airframe exhaust duct, one in-flight shutdown, one pilot report of high oil consumption, and one pilot report of loss of torque. To date, there have been no failures that have resulted in uncontained engine failures. The aircraft warning and detection system should preclude uncontained engine failures from occurring. We agree that the loss of the airframe exhaust duct should have been referenced in the preamble to the current AD. Therefore, the preamble of this proposal is written to reference the loss of the airframe exhaust duct.

Correction To Include No. 4 Bearing Rear Rotor Air Seal

The reference to replacing the No. 4 bearing rear rotor air seal was inadvertently omitted from the compliance section of the AD. We have rewritten paragraph (i) of the AD to include replacing of the No. 4 bearing rear rotor air seal.

Relevant Service Information

We have reviewed and approved the technical contents of the following Pratt & Whitney Canada service documents:

• Alert Service Bulletin (ASB) No. PW200-72-A28242, Revision 1, dated October 2, 2002, that describes procedures for borescope inspecting of compressor turbine blades and power turbine blades for axial shift within the disks.
• Service Bulletin (SB) No. PW200-72-28069, Revision 5, dated February 10, 2003, that describes procedures for replacing compressor turbine blade retaining rivets, the No. 3 bearing rotor air seal, and the No. 4 bearing front rotor air seal.
• SB No. PW200-72-28239, Revision 2, dated February 10, 2003, that describes procedures for replacing power turbine blade retaining rivets. Transport Canada, which is the airworthiness authority for Canada, classified these service bulletins as mandatory and issued AD CF-2003-06, dated February 4, 2003, in order to ensure the airworthiness of these PWC PW206A and PW206E turboshaft engines in Canada.

Bilateral Agreement Information

This engine model is manufactured in Canada and is type certificated for operation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Under this bilateral airworthiness agreement, Transport Canada has kept the FAA informed of the situation described above. We have examined the findings of Transport Canada, reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States.

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. Therefore, we are proposing this AD, which would require:

• Initial and repetitive borescope inspections of compressor turbine blades and power turbine blades for blade axial shift within the turbine disks; and
• Replacement of blade retaining rivets, the No. 3 bearing rotor air seal, and the No. 4 bearing front rotor air seal as mandatory terminating action for the repetitive borescope inspections.

You must use the service information described previously to perform the actions required by this AD.

Changes to 14 CFR Part 39—Effect on the Proposed AD

On July 10, 2002, we issued a new version of 14 CFR part 39 (67 FR 47998, July 22, 2002), which governs the FAA's AD system. This regulation now includes material that relates to altered products, special flight permits, and alternative methods of compliance. This material previously was included in each individual AD. Since this material is included in 14 CFR part 39, we will not include it in future AD actions.

Costs of Compliance

There are about 130 PWC PW206A and PW206E turboshaft engines of the affected design in the worldwide fleet. We estimate that 15 engines installed on airplanes of U.S. registry would be affected by this proposed AD. We also estimate that it would take about 0.5 work hours per engine to perform the proposed actions, and that the average labor rate is $65 per work hour. Required parts would cost about $9,077 per engine. Based on these figures, we estimate the total cost of the proposed AD to U.S. operators to be $136,656. The manufacturer has stated that it may provide replacement parts at no cost to operators.

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 by sending a request to us at the address listed under ADDRESSES. Include “AD Docket No. 2003-NE-25-AD” in your request.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Safety

The Proposed Amendment

Accordingly, 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.