97-25-09: Helical Power Takeoff Gearshaft Assembly

97-25-09 Allison Engine Company: Amendment 39-10233. Docket 97-ANE-31-AD. Applicability: Allison Engine Company Model 250-C40B turboshaft engines, with engines, gearboxes, and gears identified by serial number (S/N) in Allison Alert Commercial Engine Bulletin (CEB) No. A-72-5009, dated May 21, 1997. The 250-C40B engine is installed on and limited to the twin-engine Bell Helicopter Textron 430 series helicopters. Note 1: This airworthiness directive (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 (g) 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 should include specific proposed actions to address it. Compliance: Required as indicated, unless accomplished previously. To prevent fatigue failure of the helical power takeoff gearshaft assembly, which could result in a loss of engine power and inflight engine shutdown, accomplish the following for part number (P/N) 23056617, identified by S/N in Allison Alert CEB No. A-72-5009, dated May 21, 1997: (a) Prior to further flight, install the following placard on the instrument panel in clear view of the pilot, "RECORD TORQUE AND TIME ABOVE 86% ENGINE TORQUE." The placard shall be manufactured of a material that cannot be easily defaced or erased, and the lettering shall be block-style and at least 1/8 inches in height. Additionally, the color and lettering must contrast with the background (color of placard material) such that it is legible. (b)Remove from service affected helical power takeoff gearshaft assemblies, P/N 23056617, and replace with serviceable parts, in accordance with Allison Alert CEB No. A-72-5009, dated May 21, 1997, when the first of the following conditions exists: (1) At the time of turbine overhaul; or (2) During gearbox disassembly for any reason; or (3) If any of the operational restrictions listed in paragraph (c) of this AD are exceeded; or (4) No later than December 31, 2000. (c) After the effective date of this AD, observe the following operational restrictions at all times, until paragraph (b) of this AD is complied with by installing serviceable helical power takeoff gearshaft assemblies: (1) Total operational time accumulated on the suspect helical power takeoff gearshaft assemblies may not exceed 1,750 hours time in service (TIS). Engines are to be operated in the torque sharing mode only. (2) Operation of the engine at power between 86% torque and 93% torque is limited to one hour prior to reaching 1,750 hours TIS. (3) Operation of the engine above 93% torque will require replacement of the helical power takeoff gearshaft assemblies. Any previously recorded time (Electronic Control Unit (ECU), Integrated Instrument Display System (IIDS) or Log Book) must be accounted for. Operators will be allowed four hours of operation at torque levels less than 86% torque to ferry the aircraft to a maintenance facility for replacement of the assembly unless any of the following have been exceeded: (i) Operation of the engine between 93% torque and 105% torque for more than six minutes requires replacement of the assembly before further flight. (ii) Operation of the engine between 105% torque and 110% torque for more than ninety seconds requires replacement of the assembly before further flight. (d) Revise the limitations section of the FAA-approved Rotorcraft Flight Manual (RFM) by inserting a copy of this AD. Thereafter, except as provided in paragraph (g) of this AD, no alternative limitations may be approved for affected helical power takeoff gearshaft assemblies, P/N 23056617. (e) After replacing parts in accordance with paragraph (b) of this AD, remove the placard and the AD required by paragraphs (a) and (d) of this AD. (f) For the purposes of this AD, a serviceable helical power takeoff gearshaft assembly is one not identified by S/N in Allison Alert CEB No. A-72-5009, dated May 21, 1997. (g) 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, Chicago Aircraft Certification Office. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Chicago Aircraft Certification Office. Note 2: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, ifany, may be obtained from the Chicago Aircraft Certification Office. (h) Special flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) and paragraph (c)(3) of this AD to operate the aircraft to a location where the requirements of this AD can be accomplished. (i) The actions required by this AD shall be done in accordance with the following Allison Alert CEB: Document No. Pages Date A-72-5009 1-5 May 21, 1997 Total pages: 5. 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 Allison Engine Company, P.O. Box 420, Speed Code U-15, Indianapolis, IN 46206-0420; telephone: (317) 230-6674. 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. (j) This amendment becomes effective on December 23, 1997.