92-09-05 BELL HELICOPTER TEXTRON, INC.: Amendment 39-8230. Docket No. 91-ASW-31. \n\n\tApplicability: Model 212 helicopters, serial numbers (S/N) 35001 through 35037, 35039, and 35040; and Model 412 helicopters, S/N 36001 through 36025, and 36027, certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo prevent possible failure of the combining gearbox, which could result in loss of power to the main rotor system, accomplish the following: \n\n\t(a)\tWithin the next 20 hours' time in service after the effective date of this AD, perform an inspection of the torque on the engine-to-driveshaft coupling adapter retaining nut, part number (P/N) 212-040-631-001, as follows: \n\n\t\t(1)\tRemove the engine-to-transmission driveshaft in accordance with the appropriate Bell Helicopter Textron, Inc. Maintenance Manual, being careful not to remove the driveshaft adapter assembly. \n\n\t\t(2)\tCheck the torque of the engine-to-driveshaft adapter retaining nut (see Figure 1). \n\n\t\t\t(i)\tIf the retaining nut rotates before attaining 125 foot-pounds of torque (check torque in locking direction) comply with the remaining portion of this AD. \n\n\t\t\t(ii)\tIf the retaining nut does not rotate before attaining 125 foot-pounds of torque, no further action is required except to reinstall the engine-to-transmission driveshaft in accordance with the appropriate Bell Helicopter Maintenance Manual. \n\n\t(b)\tRemove the engine-to-driveshaft coupling adapter in accordance with the appropriate Bell Helicopter Component Repair and Overhaul Manual for the Model 212 or the appropriate Bell Helicopter Maintenance Manual for the Model 412, and inspect the adapter as follows: \n\n\t\t(1)\tCheck the adapter splines (see Figure 1) for evidence of corrosion fretting. Red dust is an indication of fretting. If fretting is indicated, replace the adapter with a serviceable part before further flight and accomplish the requirements of paragraphs (c) and (d) of this AD. \n\n\t\t(2)\tMeasure the internal splines of the adapter for a maximum dimension between pins of 1.6632 inches. Use 0.1080 inch diameter pins flatted on one side to 0.1040 inches. If the maximum dimension between pins exceeds 1.6632 inches, replace the adapter with a serviceable part prior to further flight and accomplish the requirements of paragraphs (c) and (d) of this AD. \n\n\t(c)\tInspect the engine output drive splines as follows: \n\n\t\t(1)\tInspect the engine output drive splines for evidence of corrosion fretting. Red dust is an indication of corrosion fretting. If fretting is indicated, overhaul the combining gearbox in accordance with the appropriate Pratt and Whitney overhaul manual. \n\n\t\t(2)\tMeasure the engine output splines for a minimum dimension of 1.9565 inches over pins. Use 0.1080 inch diameter pins. If the minimum dimensions over pins is less than 1.9565 inches, overhaul the combining gearbox in accordance with the appropriate Pratt and Whitney overhaul manual. \n\n\t(d)\tInstall the engine-to-driveshaft coupling adapter as follows (see Figure 1): \n\n\t\t(1)\tPosition the adapter on the engine. \n\n\t\t(2)\tInstall the new lock washer. Ensure that the mating face of the lock washer to the adapter is dry. No lubricant is to be used. \n\n\t\t(3)\tLubricate the threads and mating face of the retaining nut (Item number 5 of Figure 1) to the lock washer using grease MIL-G-25537 or MIL-G-81322. \n\n\t\t(4)\tInstall the retaining nut hand tight. Using a suitable marker, mark an index line on the outer lock washer tang and adapter. This will enable verification that the lock washer does not rotate during torquing operation. \n\n\t\t(5)\tPosition the plate on the adapter. Install the nut (Item number 4 of Figure 1). Position the bar in the retaining nut. \n\n\t\t(6)\tTorque the retaining nut to 250 to 275 foot-pounds (339 to 373 newton-meters) for initial torque. Loosen the retaining nut and then torque 125 to 200 foot-pounds (170-271 newton-meters). \n\n\t\t(7)\tRemove the bar and the plate. \n\n\t\t(8)\tInspect the washer to ensure that the tang indexed in paragraph (d)(4) has not rotated. If the inspection reveals that the washer has rotated, repeat the work of paragraphs (d)(2) through (d)(8) using a new lock washer. \n\n\t\t(9)\tBend one tang of the washer into the retaining nut. \n\n\t\t(10)\tInstall the engine-to-transmission driveshaft in accordance with the appropriate Bell Helicopter Maintenance Manual. \n\n\t(e)\tSpecial flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the helicopter to a location where the requirements of this AD can be accomplished. \n\n\t(f)\tCompliance with Bell Helicopter Textron, Inc. Alert Service Bulletin No. 212-91-67, dated 6/24/91, for the Model 212 helicopter, or Alert Service Bulletin No. 412-91-53, dated 6/24/91, for the Model 412 helicopter, constitutes compliance with this AD. \n\n\t(g)\tAn alternative method of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used if approved by the Manager, Rotorcraft Certification Office, ASW-170, Rotorcraft Directorate, Aircraft Certification Service, FAA, Southwest Region, 4400 Blue Mound Road, Fort Worth, Texas, 76193-0170. The request shall be forwarded through an FAA inspector who may concur or comment and then send it to the Manager of the Rotorcraft Certification Office. \n\n\t(h)\tThis amendment becomes effective June 2, 1992. \n\n\n\n\n\t\tNOTES: \n\t\t1.\tInstall T101588-5 plate (7) on adapter (1). \n\t\t\tSecure with nut (4). \n\n\t\t2.\tInsert extension bar (6) into plate (7). Ensure \n\t\t\tthat extension bar (6) is seated all the way into \n\t\t\tnut (5) before attempting to loosen nut (5). \n\n\t\t3\tInstall T103063 plate (7) on adapter (1) \n\t\t\tfor model 412 S/N 36020 and sub. \n\n\t\t\t\t\tFIGURE 1 \n\t\t\t\t AD 92-09-05