SAFETY CONCERN / BACKGROUND
Slick (Champion Aerospace) 4300 series Magneto Impulse Coupler failures.
Over the last several years we have been seeing and hearing reports of Slick Magneto Impulse Coupling failures that caused damage to the Magneto housing, which in turn, causes the Magneto to come out of the Accessory Case, or damages the gearing in the case, the idler gear and the shaft. When this happens, the engine requires disassembling due to metal contamination. This hazard can impact the operation of the engine and result in engine failure.
Of the seven (7) recent failures noted all but one of these magnetos failed in under 500 hours time in service (TIS), since the Overhaul/500hr inspection was complied with. The unit that was over 500hrs TIS, at the time of failure, had approximately 900hrs TIS.
All failures were due to loose rivets, as addressed by the Slick Service Bulletin SB2-19A. The damage caused, exhibits traits and failures as described in AD 99-04-04, with the same parts coming loose from the impulse coupling. AD 99-04-04 only applies to 6-cylinder engines. AD 80-06-05, which did not include the 4300 series Magneto, pertains to parts used as spares, and which must be tested.
The Washington DC Flight Standards District Office (FSDO EA27) is in contact with Aircraft Certification, Aircraft Evaluation Division (AFS-100), and the PMA holder, Hartzell Corporation, to discuss the failure rate, and mode of the unit.
IMPACT STATEMENT
It appears the attached pins are bending and loosening in the 5-piece impulse coupling made by Champion Aerospace. (See attachments and M&D report). The magnetos in this case are part number 4371 and 4373 for 4-cylinder engines. The couplings are also failing prior to the inspection called for by the Service Bulletin. Some of the impulse couplings do not have part or serial numbers on them which makes tracking very difficult.
All failures were due to loose rivets, addressed by Slick SB 2-19A. The damage caused, exhibits traits and failures as described in AD 99-04-04, with the same parts coming loose from the impulse coupling. AD 99-04-04 only applies to 6-cylinder engines.
RECOMMENDATION(S)
Based on the available data, FSDO EA27 is recommending an expansion of AD 99-04-04 to include all four-cylinder engines with the five-piece impulse coupling installed. Specifically, this would apply to all Champion Aerospace Magnetos (Slick) 4300 series impulse couplings, that have the 5-piece impulse couplings installed. The inspection would consist of looking for loose rivets or pins, bending or missing parts within the next 100 hours or next annual whichever comes first. The inspection should recur every 100 hours until replacement with a one-piece unit.
If any defects are noted during Magneto Inspections, please report those findings within the Service Difficulty Reporting (SDR) ;system, on the malfunction /defect side of the program.
LINK TO SUPPORTING ATTACHMENT:
https://www.faasafety.gov/files/notices/2026/May/Mag_Failure_Pictures.pdf
CONTACT INFORMATION:
Ramon Smeltz: FSDO EA27 Aviation Safety Inspector
E-MAIL: Ramon.Smeltz@faa.gov
Telephone: 703-488-8228
