79-12-07: Magnetos

79-12-07 BENDIX: Amendment 39-3495. Applies to Bendix Model D-2000/D-2200 series (green distributor block only) six-and-eight-cylinder magnetos identified as follows: Magneto Model Part No. D6LN-2031 10-382560-53 D8LN-2200 10-382620-51 D6LN-2230 10-382910-53 D8LN-2200 10-382920-51 D6RN-2230 10-382910-58 D6RN-2230 10-382910-12 D6LN-2230 10-382910-17 D6LN-2230 10-382610-53 These magnetos are installed on but not limited to the following aircraft engines or aircraft engine/aircraft combinations: AVCO Lycoming Engines Installations TIO-540-R2AD TIO-540-F2BD TIO-540-N2BD IO-720-B1BD IO-720-D1CD IO-720-D1CD Piper, PA-36-375 IO-720-D1CD Cessna 414 IO-720-B1BD per Riley STC SA2680-SW IO-720-B1BD Rockwell 500S, 560S, and 680S modified by STC SA2691WE IO-720-B1BD Rockwell 680F, 680FL and 680FLP modified by STC SA2891WE To detect loose distributor block bushings, accomplish the following within the next 10 hours in service after the effective date of this A.D. unless previously accomplished, and every 25 hours thereafter until green distributor blocks are replaced by comparable black distributor blocks with part numbers as follows: P/N 10-382978 by 10-382998 and P/N 10-382976 by 10-382972, or equivalent FAA approved parts and procedures. a. Remove the ventilator plugs, threaded bushing, or solid plug from both ends of the magneto housing, as applicable. b. Remove gear axle retaining ring P/N 10-92815-37, plain washer P/N 10-50753, and felt washer P/N 10-50752 from both distributor gear axle positions. c. Fabricate a 1/4 in. round probe of non-metallic material, preferably wood dowel rod, approximately six inches long, with one end approximately 1/8 in. wide by 1/8 in. thick by 1 in. long to resemble a screw driver blade. d. Insert the formed end of the tool thru the inspection hole at one end of the magneto housing and between two teeth of the distributor gear.Gently so as not to damage the gear teeth, attempt to push the gear back and forth sideways, while observing the corresponding bronze bushing in the distributor block. If there is no movement between the bushing and the block, insert the tool under the flat surface of the gear on its outside diameter. Exert pressure on the end of the tool to lift the gear towards the distributor block. Inspect for movement between the bushing and the block. If no bushing movement is detected by either of these two inspections, repeat the procedures at the gear bushing location at the opposite end of the magneto. e. If no movement is detected, reassemble the magneto per maintenance and overhaul instructions listed in Bendix publications L-928-1 and L-945 or other approved procedures. f. If bushing movement is detected at either end, the distributor block must be replaced prior to further flight. When replacing distributor block, center the block relative to any lateral movement of block. g. Tighten distributor block screws to a torque value of 25 to 30 inch lbs. Reassemble the magneto according to applicable instructions in D-2000/D-2200 series magneto overhaul publication, Bendix Form L-945 and tighten the magneto cover screws to a torque value of 30-35 in. lb for black magnetos and 40-45 in. lb for gray magnetos. h. If replacing the green distributor block with a black distributor block, reidentify the magneto system P/N and magneto P/N by stamping the numeral 1 over the first digit of the dash number suffixes. For example: System P/N -201 becomes -101 Magneto P/N -51 becomes -11 Record magneto serial number in aircraft engine log. Equivalent methods of compliance must be approved by the Chief, Engineering and Manufacturing Branch, FAA Eastern Region. As permitted by FAR 21.197, aircraft may be flown to a base where maintenance required by this airworthiness directive can be accomplished. Bendix Service Bulletin No. 606 pertains to this problem. This amendment is effective June 19, 1979, except for those persons to whom it was made effective by emergency airmail letter dated April 19, 1979.