AD 94-11-11

This amendment supersedes an existing airworthiness directive (AD), applicable to Pratt & Whitney Canada PW100 series turboprop engines, that currently requires rework or replacement of the intercompressor case (ICC), and replacement of the low pressure rotor speed (NL) sensor port sealing tube and the external air tube connecting the P2.5/P3 switching valve to the rear inlet case. This amendment additionally requires installation of an airflow deflector bracket nozzle assembly, or modification of the No. 5 bearing pressure air system. Finally, this action requires installation of a No. 5 bearing vent tube assembly and allows extension of the compliance interval for reworking or replacing the ICC. This amendment is prompted by the development of additional hardware that will further reduce the risk of internal oil fires in the ICC. The actions specified by this AD are intended to prevent fire in the engine ICC and nacelle cavities, inflight engine shutdown, and aircraft damage.

Final rule.

94-11-11 Pratt & Whitney Canada: Amendment 39-8927. Docket 93-ANE-47. Supersedes AD 92-22-01, Amendment 39-8387.
Applicability: Pratt & Whitney Canada (PWC) PW118A, PW123, PW124B, PW125B, and PW126A turboprop engines installed on but not limited to Embraer EMB-120, DeHavilland Dash 8 Series 300, Aerospatiale ATR 72, Fokker 50, and British Aerospace ATP aircraft.
Compliance: Required as indicated, unless accomplished previously.
To prevent fire in the engine intercompressor case (ICC) and nacelle cavities, inflight engine shutdown, and aircraft damage, accomplish the following:
(a) Replace the low pressure rotor speed (NL) sensor port sealing tube and the external air tube connecting the P2.5/P3 switching valve to the rear inlet case at the next engine shop visit, but not later than October 21, 1994, as follows:
(1) For PW118A engines, in accordance with PWC Service Bulletin (SB) No. 21112, dated February 13, 1992, and SB No. 20914, Revision 3, dated October 15, 1991.
(2) For PW123 engines, in accordance with PWC SB No. 21113, Revision 1, dated May 4, 1992.
(3) For PW124B engines, in accordance with PWC SB No. 21111, Revision 1, dated June 22, 1992.
(4) For PW125B engines, in accordance with PWC SB No. 21088, Revision 1, dated November 12, 1991.
(5) For PW126A engines, in accordance with PWC SB No. 21097, dated November 8, 1991.
(b) Install an airflow deflector bracket nozzle assembly in accordance with PWC SB No. 21065, Revision 4, dated February 1, 1993, or modify the No. 5 bearing pressure air system in accordance with SB 21211, dated January 28, 1993, at the next engine shop visit, but not later than December 31, 1995.
(c) Install a No. 5 bearing vent tube assembly in accordance with PWC SB No. 21053, Revision 2, dated December 9, 1991, at the next engine shop visit, but not later than December 31, 1995.
(d) For engines incorporating the modifications specified by any revision level of PWC SB No. 20237, rework the existing 2 hole internal air passage ICC to a 19 hole design, or replace the existing ICC, in accordance with PWC SB No. 20957, Revision 5, dated August 10, 1992, or PWC SB No. 20962, Revision 4, dated August 10, 1992, at the next engine shop visit, but not later than December 31, 1995.
(e) For the purpose of this AD, an engine shop visit is defined as when any major module is separated.
(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. The request should be forwarded through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Engine Certification Office. NOTE 1: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Engine Certification Office. NOTE 2: PWC has issued PW100 Service Information Letter (SIL) No. PW-281 that lists those SB's and revision levels that constitute acceptable methods of compliance to the requirements of this AD.
(g) Special flight permits may be issued in accordance with 14 CFR 21.197 and 21.199 to operate the aircraft to a location where the requirements of this AD can be accomplished.
(h) The replacement and modifications shall be done in accordance with the following service bulletins:

Document No.
Pages
Revision
Date
PWC SB No. 21053R2
1-12
2
December 9, 1991
Total pages: 12.

PWC SB No. 21113R1
1-14
1
May 4, 1992
Total pages: 14.

PWC SB No. 21112
1-6
Original
February 13, 1992
Total pages: 6.

PWC SB No. 21111R1
1-13
1
June 22, 1992
Total pages: 13.

PWC SB No. 21088R1
1-18
1
November 12, 1991
Total pages: 18.

PWC SB No. 21065R4
1-18
4
February 1, 1993
Total pages: 18.

PWC SB No. 21097
1-11
Original
November 8, 1991
Total pages: 11.PWC SB No. 20957R5
1-8
5
August 10, 1992
Total pages: 8.

PWC SB No. 20962R4
1-4
4
August 10, 1992
Total pages: 4.

PWC SB No. 20914R3
1-13
3
October 15, 1991
Total pages: 13.

PWC SB No. 21211
1-44
Original
January 28, 1993
Total pages: 44.

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, Technical Publications Department, 1000 Marie Victorin, Longueuil, Quebec J4G 1A1. Copies may be inspected at the FAA, New England Region, Office of the Assistant Chief 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.
(i) This amendment becomes effective on July 25, 1994.

Transport Canada, which is the airworthiness authority for Canada, recently notified the Federal Aviation Administration (FAA) that an unsafe condition may exist on Pratt & Whitney Canada (PWC) PW118A, PW123, PW124B, PW125B, and PW126A turboprop engines. Transport Canada advises that they have received reports of internal oil fires in the intercompressor case (ICC). There have been 13 ICC fire events due to ignition of oil that had accumulated in the P2.5 air cavity. The ICC fire melts the brazing on the external air-tube connected to the P2.5/P3 switching-valve, and on the low pressure rotor speed (NL) sensor port sealing tube, allowing both to disengage. The ICC fire then migrates into the engine nacelle cavity resulting in inflight engine shutdown and potential aircraft damage.
On December 14, 1992, the FAA issued AD 92-22-01, Amendment 39-8387 (58 FR 6191, January 27, 1993), to require rework or replacement of the existing ICC and replacement of the NL sensor port sealing tube and the external air tube connecting the P2.5/P3 switching valve to the rear inlet case.
Since the issuance of that AD, the manufacturer has developed additional hardware that will further reduce the risk of internal oil fires in the ICC.
A proposal to supersede AD 92-22-01 was published in the Federal Register on November 3, 1993 (58 FR 58669). That action proposed to retain the requirements for rework or replacement of the existing ICC and replacement of the NL sensor port sealing tube and the external air tube connecting the P2.5/P3 switching valve to the rear inlet case. That action also proposed to extend the compliance end date for rework or replacement of the December 31, 1995, based upon fleet utilization rates and parts availability. In addition, that action proposed to require installation of an airflow deflector bracket nozzle assembly, or modification of the No. 5 bearing pressure air system. Finally, that action proposed to requireinstallation of a No. 5 bearing vent tube assembly.
PWC has issued the following service bulletins (SB): SB No. 21112, dated February 13, 1992; SB No. 20914, Revision 3, dated October 15, 1991; SB No. 21113, Revision 1, dated May 4, 1992; SB No. 21111, Revision 1, dated June 22, 1992; SB No. 21088, Revision 1, dated November 12, 1991; and SB No. 21097, dated November 8, 1991. These SB's describe procedures for replacing the NL sensor port sealing tube and the external air tube connecting the P2.5/P3 switching valve to the rear inlet case.
In addition, PWC has issued the following SB's: SB No. 20957, Revision 5, dated August 10, 1992, and SB No. 20962, Revision 4, dated August 10, 1992, that describe procedures for reworking the existing 2 hole internal air passage ICC to a 19 hole design.
PWC has also issued the following SB's: SB No. 21065, Revision 4, dated February 1, 1993, that describes procedures for installing an airflow deflector bracket nozzle assembly; SB No. 21211, dated January 28, 1993, that describes procedures for modifying the No. 5 bearing pressure air system; and SB No. 21053, Revision 2, dated December 9, 1991, that describes procedures for installing a No. 5 bearing vent tube assembly.
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 and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, Transport Canada has kept the FAA informed of the situation described above. Transport Canada issued AD's No. CF-91-26R1, CF-92-03R1, and CF-92-06, mandating the accomplishment of the above service bulletins. The FAA has 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.
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.
One commenter offered no objection to the proposed rule.
One commenter states that earlier revisions to the SB's listed in the proposed rule should be acceptable for compliance, as the revisions were minor and did not materially affect the AD's requirements. The FAA concurs. PWC has issued PW100 Service Information Letter (SIL) No. PW-281 that lists those SB's and revision levels that constitute acceptable methods of compliance to the actions required by this AD. The FAA has added a note to paragraph (f) of the AD to provide further guidance to operators on those acceptable alternate methods of compliance.
One commenter states that the economic analysis in the proposed rule significantly underestimated costs to operators, by not including the costs for premature engine removal, added inspections and parts replacement not required by the proposed rulebut required by the applicable maintenance manuals, and for life limited parts not suitable for reinstallation. The FAA does not concur. While other costs may be involved, they represent costs that will be borne by the operators eventually anyway. The economic analysis examines only those costs directly related to the actions required by the proposed rule. Although the AD may result in a hot section inspection at a time earlier than the operator originally scheduled, the costs of that inspection are not directly related to the requirements of the AD, and therefore are not a result of the AD. In addition, those costs will vary significantly for each engine, and, may not be accurate if extrapolated to a fleet-wide estimate based on a small sampling.
After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the change described previously. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD.
The FAA estimates that 85 engines installed on aircraft of U.S. registry will be affected by this AD, that it will take approximately 8 work hours per engine to accomplish the required actions, and that the average labor rate is $55 per work hour. The manufacturer advises the FAA that required parts will be supplied at no cost to the operator. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $37,400.
The regulations adopted herein will not have substantial direct effects 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. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.
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 DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) 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 from the Rules Docket at the location provided under the caption "ADDRESSES." List of Subjects in 14 CFR Part 39
Air 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 14 CFR part 39 of the Federal Aviation Regulations as follows: PART 39 - AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. 39.13 - [AMENDED]
2. Section 39.13 is amended by removing amendment 39-8387 (58 FR 6191, January 27, 1993) and by adding a new airworthiness directive, Amendment 39-8927, to read as follows: