Frequently asked questions about magnetos
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TCM/Bendix
for all models (S-20/S-200, D-2000/D-3000, S-1200) applies:
- 500 hrs inspection – after an operating time of 500 hrs
- Overhaul – latest after 4 years in use or 5 years on shelf
- Overhaul – in case of Overspeed, Sudden Stoppage and motor-overhaul an overhaul is necessary
- (With SB643A TCM does not require an interval inspection only on the magnetos but also on the harness, ignition switch and starter vibrator).
For S-20/S-200 und S-1200 gilt zusätzlich
- Magnetos with serial number after June 2015 need to be overhauled „only“ after 12 years in service. Older magnetos must be overhauled after 4 years in service.
- (in case of factory overhauled magnetos, the serial number stays the same, therefore this change only applies for factory new TCM magnetos).
Slick
for alle Modelle (4200/6200 & 4300/6300)
- 100 hrs inspection – performed on the motor
- 250 hrs/2 years inspection – on engines with single ignition (motor gliders) & pressurized magnetos
- 500hrs inspection – for all engines with double ignition system
Additionally for new style models (series 4300/6300)
- Overhaul – general overhaul after 12 years
Additionally for older style models (series 4200/6200)
- 1000 hrs inspection
- Overhaul – general overhaul together with the engine
What is the overhaul interval of magnetos?
My magnetos reached the TBO but run without any problem, why should they be inspected?
In the aerospace industry we often talk about inspection and not repair. It is like it should be part of every inspection. The FBO should inspect if every part is still working properly, and ensure that axels or bearings run smoothly, get new grease and oil.
Several smaller defects don not occur at first. The shrinking power is more often not recognized because it develops rather slowly. Other problems occur right at the start of the engine or they cause a higher consumption.
Yes, there are regulations and airworthiness directives.
A major problem of the general aviation is the short time in service of the aircraft engines and aggregates. A lot of parts wear more because of rust. An inspection is always recommended.
My magnetos did only run a few hours in the past years, should they be checked?
What is checked at a 500 hrs/4 years inspection?
This question has to be answered separately for the two main magnetos Unison/Slick and TCM/Bendix.
Unison/Slick
The magneto is going to be mostly disassembled and cleaned. All parts are proved for applicable SB’s (Service Bulletin) The ignition coil and the condenser are tested for their electrical tolerances and with a separate tester for hardware defects. The distributor block and the distributor gear electrode are cleaned from contaminants. All parts are visually – if needed with a 3D microscope – checked. The main contact, cam, screws of the main contact and gaskets for pressurized magnetos are replaced. After the assembly the magneto is tested with different speeds on our magneto bench.
Every part of our control is written down at a detailed maintenance report including all tolerances required. You will receive an EASA FORM ONE with every inspected magneto.
TCM/ Bendix
The magneto is completely disassembled and cleaned. All parts are checked for SB’s and LTA’S (German airworthiness directives). The housings are sandblasted and newly varnished (priming & varnishing) if they are in bad conditions. The ignition coil and the condenser are also tested for their electrical tolerances and with a separate tester for hardware defects. The distributor block and the distributor gear electrode are cleaned from contaminants.
Die elektrischen und mechanischen Bauteile werden auf ihre Sollwerte/ Toleranzen geprüft. Die Verteilerkappe und der Verteilerläufer werden von Abbrand gereinigt. Daraufhin wird die VAfterwards the distributor block will be deoiled, cleaned and oil again at 100 degree Celsius (the oiling takes one hour in the oven). Depending on the material of the distributor block it will receive new doping. All other components are cleaned in an ultrasonic wash-basin. Replaced are the main contact, felt strip and –washer, self-locking screws and the spring for the impulse coupling. Newly lubricated the magneto will be assembled. After the assembly the magneto is tested with different speeds on our magneto bench.
Every part of our control is written down at a detailed maintenance report including all tolerances required. You will receive an EASA FORM ONE with every inspected magneto.
