AD 96-24-09 Airworthiness Directives; Allison Engine Company Model 250-C47B Turboshaft Engines

Models named: 250-C47B turboshaft, 407. Read the applicability below — it usually turns on serial or part numbers too.

Allison Engine Company Model 250-C47B turboshaft engines, installed on but not limited to BHTC Model 407 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 (h) 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.

Required prior to further flight, unless accomplished previously. To prevent uncommanded inflight engine shutdowns, which can result in autorotation, forced landing, and possible loss of the helicopter, accomplish the following: (a) Replace the engine main electrical harness assembly, Part Number (P/N) 23062796, with an improved assembly, P/N 23065805, in accordance with Allison Engine Company Alert Commercial Engine Bulletin (CEB) CEB-A-73-6010, dated October 15, 1996. (b) Disable the overspeed solenoid in accordance with Allison Engine Company CEB-A-73-6011, dated October 31, 1996. (c) Inspect the electronic control unit (ECU) internal PW10 voltage to determine electrical noise characteristics, and replace ECUs not considered serviceable, in accordance with Allison Engine Company CEB-A-73-6012, dated October 31, 1996. (d) Install the following placard on the instrument panel near the overspeed test switch, notifying the pilot that the engine overspeed protection system is disabled, ``OVSPD SYSTEM INOP''. 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 2 inches in height, but not greater than 6 inches in height. Additionally, the color of lettering must contrast with the background (color of placard material) such that it is legible. (e) Remove the placard required by AD 96-21-12, which states, ``Flight Of This Helicopter Is Prohibited''. (f) Revise the FAA-approved Rotorcraft Flight Manual (RFM) by incorporating Appendix 1 of this AD in the Normal Procedures. This may be accomplished by inserting a copy of Appendix 1 of this AD in the RFM: Appendix 1 Note: Operators must initiate action to notify and ensure that flight crewmembers are appraised of this change. (1) Revise the FAA approved Rotorcraft Flight Manual (RFM) by incorporating the following Limitation placard to page 1-14A/14B. ----------------------------------------------------------------------- OVSPD SYSTEM INOP ----------------------------------------------------------------------- Location: Instrument panel near overspeed test switch (2) Revise the FAA-approved RFM by incorporating the following to the Normal Procedures. Section 2-4. INTERIOR AND PRESTART CHECK * * * * * 18. Caution lights--ENG OUT, XMSN OIL PRESS, RPM, HYDRAULIC SYSTEM, GEN FAIL, FADEC DEGRADED, FADEC FAULT, L/FUEL BOOST, R/FUEL BOOST, L/FUEL XFR, and R/FUEL XFR will be illuminated. NOTE L/FUEL XFR and R/FUEL XFR will not be illuminated when forward fuel tank is empty. 18a. Throttle--Idle position. NOTE GPU or battery cart power, if being used, must be cycled when the BATT switch is OFF. 18b. BATT switch--Cycle OFF, ON. NOTE Observations of Step 16 will be repeated. FADEC DEGRADED and FADEC FAULT lights, that are due to the overspeed system being inoperative, will be extinguished. 18c. Throttle--Closed position. 18d. Horn Mute button--Press to mute. * * * * * Section 2-11. ENGINE SHUTDOWN * * * * * 14. Delete * * * * * 23. BATT switch--OFF. CAUTION Applicable maintenance action must be performed prior to further flight if a FADEC light has illuminated during the flight or on engine shutdown. (3) Revise the FAA approved RFM by incorporating the following to the Emergency/Malfunction Procedures. Section 3-3-J. DRIVE SHAFT FAILURE * * * * * 7. Delete PROCEDURE: 1. Maintain heading and attitude control. 1a. Throttle--idle * * * * * 3-3-K. FADEC FAILURE NOTE Takeoff power may not be available in the MANUAL mode. Maximum continuous power will be available for all ambient conditions. INDICATIONS: 1. FADEC fail audio activated. 2. FADEC FAIL warning light illuminated. PROCEDURE: WARNING Raising or lowering of the collective during a FADEC fail condition will result in rotor droop or engine overspeed, respectively. If increasing the collective when the failure occurs, smoothly lower collective to eliminate the NR/NP droop while simultaneously retarding the throttle to the 90% bezel position. If reducing the collective when the failure occurs, smoothly increase the collective to correct the overspeed while simultaneously retarding the throttle to the 90% bezel position. 1. Collective--Maintain position. (if steady state flight condition) WARNING Within 2 to 7 seconds after the FADEC FAIL warning, NR/NP may increase very rapidly, requiring positive movements of collective to control NR/NP. 2. Throttle--Immediately retard to approximately 90% bezel position. (if not previously accomplished) [[Page 59831]] 3. FADEC MODE switch--Depress one time. NOTE Initial engine response to manual control of fuel flow with throttle may take up to 7 seconds. 4. NR/NP--Maintain 95 to 100% with the throttle and collective. 5. Land as soon as practical. NOTE It may be necessary to use FUEL VALVE switch to shutdown engine after landing. 6. Normal shutdown if possible. NOTE When throttle is repositioned to the idle stop (during engine shutdown) the PMA will go off-line and engine may flameout. (g) After accomplishing all the actions of this AD, operators may resume flight operations of the BHTC Model 407 helicopter. (h) An alternative method of compliance that provides an acceptable level of safety may be used if approved by the Manager, Chicago Aircraft Certification Office. The request should be forwarded through an appropriate FAA 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, if any, may be obtained from the Chicago Aircraft Certification Office. (i) The actions required by this AD shall be accomplished in accordance with the following Allison Engine Company Alert CEBs: ------------------------------------------------------------------------ Document No. Page Revision Date ------------------------------------------------------------------------ CEB-A-73-6010.................. 1-7 Original..... Oct. 15, 1996. Total pages: 7. CEB-A-73-6011.................. 1-12 Original..... Oct. 31, 1996. Total pages: 12. CEB-A-73-6012.................. 1-11 Original..... Oct. 31, 1996. Total pages: 11. ------------------------------------------------------------------------ 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 P-40A, Indianapolis, IN 46206-0420; telephone (317) 230-2720, fax (317) 230-3381. 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 supersedes priority letter AD 96-21- 12, issued October 11, 1996. (k) This amendment becomes effective November 25, 1996, except effective upon receipt to all persons receiving a copy of this AD directly from the FAA. Issued in Burlington, Massachusetts, on November 15, 1996. Jay J. Pardee, Manager, Engine and Propeller Directorate, Aircraft Certification Service. [FR Doc. 96-29861 Filed 11-21-96; 12:14 pm] BILLING CODE 4910-13-U