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Inspection of magnetos

Why make periodic inspections?

Most aircrafts do have system redundancy in the primary systems. This redundancy is made for the case that a system is not working properly or fails completely. In this case a safe operation would still be possible.

The ignition system of small aircrafts with piston engines is essential for a safe operation. Therefor the system is redundant, two magnetos are attached to each engine. Only exception are motor gliders with only one magneto. They are called single ignition systems.

Periodic maintenance reduces the possibility of ignition failure

Good reasons for a regular inspection interval

Following some good reasons for the inspection, not at least to sensitize you – our customers!

Motor gliders
If a failure of the ignition system should occur while flying, the engine will stop to fire. You will be able to glide quite a while without it. The stoppage of the engine should nevertheless be seen as critical. Depending on your aircraft you will have more or less minutes left in the air. Shouldn´t you be able to find a good landing possibility nearby within this time range, a crash-landing will be the result. Motor gliders are depending on their single ignition system. Take care of it!

Ozone

With increasing height, the air density and the insulating resistance are decreasing. The ignition spark can jump uncontrolled within the distributor block. To counter this the magnetos are pressurized. Means that air from the turbo is used for the magneto.

The small hole in the magneto housing is regularly 2mm, to keep the pressure in the housing for pressurized magnetos this hole is only 0,6mm big. If this small hole is closes (because of dirt), air and more important ozone cannot get out.

Ozone is a very aggressive molecule. It’s corrosive! Plastic material can get weak, metal corrodes and the contact points can have excessive wearing until they stop to open. At this point - at last –the magneto fails. If you plan to make long distance flights with pressurized magnetos check their timing. If you have to time the magneto towards the engine quite often or too much, it could be caused by a worn contact point.

For pressurized magnetos it is important to check this hole at the 50h inspection. Check if it is not blocked – check if air comes out!

Should you notice that there is no air we recommend that you inspect the magneto internally.


What does an inspection at WMT include?

All actual Service Bulletins (SB’s) and Airworthiness Directives (AD’s) are checked and carried out.