Maintenance Powerplant; Maintenance Airframe
Maintenance Lead Technician 30
Troubleshooting; Human-Machine Interface
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Maintenance
Flight Crew Inflight Shutdown; Flight Crew Landed in Emergency Condition; General Maintenance Action
Incorrect / Not Installed / Unavailable Part; Procedure; Human Factors; Aircraft
Our maintenance organization is based overseas. We had encountered 6 serviceable magneto failures - the latest was a twin mag failure - the pilot landed the aircraft just short of a runway and no damage to the aircraft and the pilot. Upon examination of the records I discovered that the aircraft engine had 30 hours since major overhaul - in theory the mags are new. Examining the other mag failure of the previous incidents demonstrated that those failures had taken place well within time life limits of the components.  Looking into those facts it appeared to me that the mag failure is attributed to heat - we removed 2 perfectly airworthy mags and requested a magneto shop to run them for few hours- the first mag failed after an hour or so and the second failed 5 min later. Corresponding to the flight time of the twin mag failure aircraft.  It appears that once the mag reach certain temperature a breakdown of the internal insulation take place - further investigation of records show that whilst the mags are new in the context of unused - yet they are old Russian military stock. I presume that calendar life of the materials used had been exceeded.  The aircraft Yak 52 is an old Russian military trainer that can perform basic aerobatic and has the appearance of a war bird hence its attractiveness - it is used by the owners generally for short duration flight (up to an hour or so)- hence the low reporting - the mags don't get hot enough for the breakdown to surface.  We raised a report with the UK CAA - and requested them to alert the industry- the above constitutes a real risk to human life - so far they had failed to notify the international community. As many Yak 52 aircraft are flying globally and under different registration including the N reg - and as the risk to life is real could you please advise us as how to progress our attempt to inform the global GA community on your platform.
Technician reported several instances of magneto failure causing engine shutdowns.