# AD 78-09-07 R3: Magnetos - Type: Airworthiness directive - Status: Historical - Products: Bendix Magnetos - Effective: January 17, 1983 - Superseded by: [AD 96-12-07](https://openairdocs.org/ad/96-12-07) - Product type: Appliance - Amendment: 39-4538 - FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/1918BF5D5435D94186256A32006004C5.0001 - DRS record last changed: August 7, 2025 - Page: https://openairdocs.org/ad/78-09-07-R3 ## The airworthiness directive 78-09-07 R3 BENDIX: Amendment 39-3205 as amended by Amendments 39-3252 and 39-3963 is further amended by Amendment 39-4538. Applies to Bendix S-20 series, S-1200 series, D-2000 series, and D-3000 series magnetos incorporating impulse couplings. Compliance required as indicated unless previously accomplished. To preclude magneto or engine failure resulting from magneto impulse coupling failure, accomplish the following: a. On magnetos having less than 475 hours time in service since new or overhaul, accomplish the provisions of paragraphs "c" and "d" of this AD prior to 500 hours time in service and thereafter at intervals not to exceed 500 hours time in service from the last inspection. b. On magnetos having 475 or more hours in service since new or overhaul, accomplish the provisions of paragraphs "c" and "d" of this AD within the next 25 hours time in service and thereafter at intervals not to exceed 500 hours time in service from the last inspection. c. Inspect and replace, if necessary, impulse coupling components in accordance with the paragraph titled "Detailed Instructions" contained in Bendix Engine Products Division Service Bulletin Number 599B or an FAA approved equivalent. d. After accomplishing paragraph "c" of this AD, make a logbook entry showing the compliance time. Include the magneto make, model, and serial number. (Note: Except for new or zero time overhauled magnetos, any magneto not accompanied by a record of operating time must be in compliance with paragraph "c" upon installation on an approved engine.) e. Equivalent inspections and procedures must be approved by the Manager, New York Aircraft Certification Office, Room 202, 181 South Franklin Avenue, Valley Stream, New York 11581. f. As permitted by Federal Aviation Regulations (FARs) 21.197 and 21.199, aircraft may be flown to a base where maintenance required by this AD can be accomplished. Amendment 39-3205 was effective May 9, 1978. Amendment 39-3252 amended Amendment 39-3205 effective July 3, 1978. Amendment 39-3963 amended Amendments 39-3205 and 39-3252 effective November 3, 1980. This Amendment 39-4538 is effective on January 17, 1983. ## Registered aircraft it may apply to (OpenAirDocs) No registered aircraft matched the models it names. ## Related documents - [AD 96-12-07](https://openairdocs.org/ad/96-12-07) (historical): Magnetos · Teledyne Continental Motors Magnetos. Effective Jul 18, 1996. Supersedes this AD Its text cites no advisory circulars or STCs. ## NTSB investigations that cite this AD (11) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB ERA10LA475](https://openairdocs.org/ntsb/ERA10LA475), Sep 10, 2010: Cessna 150 (N7922E), Fayetteville, WV, substantial damage. Probable cause: A loss of engine power due to the failure of the left magneto system’s distributor gear as a result of the improper maintenance of the magnetos by maintenance personnel. - [NTSB FTW99LA027](https://openairdocs.org/ntsb/FTW99LA027), Nov 17, 1998: Mooney M20J (N201QK), San Angelo, TX, substantial damage. Probable cause: The total loss of engine power due to the magneto failure resulting from oil contamination when the bearing plate retainer screw fractured due to improper manufacturing. Factors were the lack of… - [NTSB CHI94LA121](https://openairdocs.org/ntsb/CHI94LA121), Mar 21, 1994: Piper PA-32-300 (N5251S), Ellsworth, NE, substantial damage. Probable cause: the jammed impulse coupling on the left magneto which caused the crankshaft drive gear to shear from the crankshaft. - [NTSB FTW90FA119](https://openairdocs.org/ntsb/FTW90FA119), Jun 18, 1990: Piper PA-28-140 (N6767W), Bossier City, LA, destroyed, 2 fatal. Probable cause: LOSS OF ENGINE POWER FOR AN UNKNOWN REASON. - [NTSB LAX89FA014](https://openairdocs.org/ntsb/LAX89FA014), Oct 16, 1988: Piper PA-32-300 (N4113R), Sedona, AZ, destroyed, 5 fatal. Probable cause: TOTAL FAILURE OF THE MAGNETO'S IMPULSE COUPLING WHICH RESULTED IN A SHEARING OF THE CRANKSHAFT'S IDLER GEAR TEETH AND THE CRANKSHAFT DOWEL PIN. - [NTSB ATL88FA055](https://openairdocs.org/ntsb/ATL88FA055), Dec 6, 1987: Piper PA-32-260 (N5587J), Lagrange, GA, destroyed, 4 fatal - [NTSB ATL85LA024](https://openairdocs.org/ntsb/ATL85LA024), Oct 30, 1984: Piper PA-25-235 (N9855P), Lincoln, TN, substantial damage - [NTSB MKC80FCG31](https://openairdocs.org/ntsb/MKC80FCG31), Jun 28, 1980: Aero Comdr A-9B (N8025V), Cameron, MO, substantial damage - [NTSB FTW80FA020](https://openairdocs.org/ntsb/FTW80FA020), Dec 5, 1979: Piper PA-32 (N4097R), Harrah, OK, destroyed - [NTSB MIA80FKT17](https://openairdocs.org/ntsb/MIA80FKT17), Nov 28, 1979: Piper PA-32 (N3762W), Miami, FL, destroyed - [NTSB MIA79FLA14](https://openairdocs.org/ntsb/MIA79FLA14), Jan 3, 1979: Piper PA-32 (N3705W), Cross City, FL, substantial damage --- From OpenAirDocs.org, an independent open copy of FAA and NTSB data. 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