AD 2001-20-01

This amendment adopts a new airworthiness directive (AD), applicable to Pratt & Whitney Canada (PWC) PT6A-25C and -114A turboprop engines. This amendment will require initial and repetitive visual inspections, and eventual replacement of the compressor bleed valve assembly, with a redesigned valve assembly for -114A and -25C engines. This amendment is prompted by reports of two occurrences of uncommanded engine power loss. The actions specified by this AD are intended to detect wear in the compressor bleed valve assembly which may cause valve orifice blockage, resulting in a loss of power, an inability to accelerate the engine, and an in-flight shutdown.

Final rule

2001-20-01 Pratt & Whitney Canada: Amendment 39-12447. Docket 2000-NE-26-AD.

Applicability

This airworthiness directive (AD) applies to PT6A-25C and -114A Series turboprop engines, that have incorporated P&WC S.B. 1510, which are installed on but not limited to Pilatus PC-7 and Cessna 208 Caravan airplanes.

Note 1: This AD applies to each engine 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 engines 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 (f) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request shouldinclude specific proposed actions to address it.

Compliance

Compliance with this AD is required as indicated, unless already done.

To detect wear on the compressor bleed valve assembly cover, guide pin shaft, cotter pin, and to detect particles from diaphragm wear, which may cause valve orifice blockage, resulting in a loss of power, an inability to accelerate the engine, and an in-flight shutdown, do following:

Initial and Repetitive Inspections

(a) Perform an initial visual inspection of the compressor bleed valve assembly components within 150 flight hours after the effective date of this AD in accordance with Accomplishment Instructions, Section 3A through 3B of Pratt & Whitney Canada (PWC) Service Bulletin (SB) PT6A-72-1574, Revision 2, dated October 14, 1999.

(b) Thereafter, perform repetitive visual inspections of the compressor bleed valve assembly components within 600 flight hours after the last inspection in accordance with Accomplishment Instructions, Section 3A through 3B of PWC SB PT6A-72-1574, Revision 2, dated October 14, 1999.

Terminating Action

(c) For PT6A-114A series turboprop engines, replacement of compressor bleed valve assemblies at the next shop visit, with the redesigned valve assembly, in accordance with PWC SB PT6A-72-1588, dated February 18, 2000 or PWC SB PT6A-72-1581, Revision 1, dated February 1, 2000, is considered terminating action for the inspection requirements of this AD. This action must be done at the next shop visit but no later than five years from the effective date of this AD.

(d) For PT6A-25C series turboprop engines, replacement of compressor bleed valve assemblies with the redesigned valve assembly, at the next shop visit, in accordance with PWC SB PT6A-72-1589, dated November 1, 2000, is considered terminating action for the inspection requirements of this AD. This action must be done at the next shop visit but no later than five years from the effective date of this AD.

Definition

(e) For the purpose of this AD, a shop visit is defined as when the subassembly (i.e. module, accessories, components or build groups) is disassembled and access is available to the compressor bleed valve assembly.

Alternative Methods of Compliance

(f) 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, Engine Certification Office (ECO). Operators shall submit their request through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, ECO.

Note 2: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the ECO.

Special Flight Permits

(g) 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 toa location where the requirements of this AD can be accomplished.

Documents That Have Been Incorporated by Reference

(h) The inspections and replacement shall be done in accordance with the following Pratt & Whitney Canada service bulletins:

Document No.
Pages
Revision
Date
SB PT6A-72-1574
Total pages:
All
2
Oct. 14, 1999.
3 SB PT6A-72-1581
Total pages: 12
All
1
Feb. 1, 2000.
SB PT6A-72-1588
Total pages:12
All
Original
Feb. 18, 2000.
SB PT6A-72-1589
Total pages: 10
All
Original
Nov. 1, 2000.

This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Pratt & Whitney Canada, 1000 Marie-Victorin, Longueuil, Quebec, Canada J4G1A1. Copies may be inspected at the FAA, New England Region, Office of the Regional Counsel, 12 New England Executive Park, Burlington, MA; or at the Office of the Federal Register, 800 North Capitol Street, NW, suite 700, Washington, DC.

Note 3: The subject of this AD is addressed in Transport Canada Airworthiness Directive CF-99-23, dated September 14, 1999.

Effective Date

(i) This amendment becomes effective on November 5, 2001.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to PWC PT6A-25C and -114A turboprop engines, was published in the Federal Register on September 20, 2000 (65 FR 56819). That action proposed to require initial and repetitive visual inspections, and eventual replacement of the compressor bleed valve assembly, with a redesigned valve assembly for -114A engines, and -25C engines.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

Comments Received Regarding Terminating Action

Three commenters request that the FAA add PWC Service Bulletin (SB) PT6A-72-1581, Revision 1, dated February 1, 2000, as terminating action for the AD. The FAA agrees. The service bulletin referenced in the proposal, PWC SB PT6A-72-1588, and PWC SB PT6A-72-1581, Revision 1, introduce the same part, a new design of compressor bleed valve assembly that eliminates the unsafe condition. Therefore, either PWC SB PT6A-72-1581 or PWC SB PT6A-72-1588, dated February 18, 2000, will serve as terminating action for PT6A-114A to the inspection requirements of this AD.

Comment Regarding the Applicability of the AD

One comment notes that all of the referenced service bulletins apply to the PT6A-25C and PT6A-114A engines only if those engines have incorporated SB PT6A-72-1510. The comment, therefore, asks that the FAA limit the applicability of this AD to just those engines that have incorporated SB PT6A-72-1510.

The FAA agrees. Only those engines that were modified per SB PT6A-72-1510 should be affected by this AD, which has been changed accordingly.

Differences Between the NPRM and AD

Since the publication of the NPRM, Pratt and Whitey has published PWC SB PT6A-72-1589, dated November 1, 2000. This SB provides for inspection and replacement of compressor bleed valve assemblies installed on PT6A-25C series turboprop engines at the next shop visit, but no later than five years from the effective date of this AD. Replacement of the compressor bleed valve assembly is considered terminating action for the inspection requirements of this AD.

Economic Impact

There are about 504 engines of the affected design in the worldwide fleet. The FAA estimates that 353 engines installed on aircraft of U.S. registry would be affected by this AD, that it would take about two work hours per engine to accomplish the initial inspections, and one hour to accomplish the replacement of the valve, and that the average labor rate is $60 per work hour. Required parts would cost about $7,458.00 per engine. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $2,696,214.

Regulatory Impact

This final 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 final rule.

For the reasons discussed above, I certify that this action (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 final evaluation has been prepared for this action and it 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 39Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 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: