A friend of mine at our local airfield had encountered increasing difficulty in starting a Tecnam P92 equipped with Rotax 912 ULS, culminating with the inability to start the engine.
The causes had been identified in the absence of voltage to the spark plugs.
Due to a good advice from a rotax expert user my friend immediately inspected the ground cable from the ignition modules(the black wire that go from m5 allen screw fixing modules itself to the m6 bolt on the intake manifold - fig. 74-23 item n°10 , pag. 36 of Rotax heavy maintenance manual).
The connections on intake manifold side were slow and strongly oxidized. On the same bolt on the intake mainfold are wired the grounds of the ignition coils. After the restoration of conductivity the engine has started perfectly. Ex post My friend do not know if the problem was in the ignition or in the coil grounding.
My friend was told that this problem, together with the lack of fuel and / or lubricant is one of the few that can cause failure of the Rotax 912.
Now we can admit that lack of fuel and lubrication problems (the latter very rare to my knowledge) can stop an engine. But but a wire and / or broken or loose wire terminals may cause a total failure in a well-designed and electrical redundant engine seems very strange.
Rotax manual requires fixing allen screws and cable end bolts with Loctite 221 and seems to have updated new engine specifics from one to two ground terminal points on the intake manifolds , perhaps to introduce redundancy (two points for ignition coils of circuit A and B ).
I'd love to hear from anyone who has had experience of the phenomenon because to think that A SINGLE POINT OF FAILURE could jeopardize an engine ignition system with double ignition module, coils, pickups and separate power gens/ lines seems very strange.
Greetings
Nicola Biase
The causes had been identified in the absence of voltage to the spark plugs.
Due to a good advice from a rotax expert user my friend immediately inspected the ground cable from the ignition modules(the black wire that go from m5 allen screw fixing modules itself to the m6 bolt on the intake manifold - fig. 74-23 item n°10 , pag. 36 of Rotax heavy maintenance manual).
The connections on intake manifold side were slow and strongly oxidized. On the same bolt on the intake mainfold are wired the grounds of the ignition coils. After the restoration of conductivity the engine has started perfectly. Ex post My friend do not know if the problem was in the ignition or in the coil grounding.
My friend was told that this problem, together with the lack of fuel and / or lubricant is one of the few that can cause failure of the Rotax 912.
Now we can admit that lack of fuel and lubrication problems (the latter very rare to my knowledge) can stop an engine. But but a wire and / or broken or loose wire terminals may cause a total failure in a well-designed and electrical redundant engine seems very strange.
Rotax manual requires fixing allen screws and cable end bolts with Loctite 221 and seems to have updated new engine specifics from one to two ground terminal points on the intake manifolds , perhaps to introduce redundancy (two points for ignition coils of circuit A and B ).
I'd love to hear from anyone who has had experience of the phenomenon because to think that A SINGLE POINT OF FAILURE could jeopardize an engine ignition system with double ignition module, coils, pickups and separate power gens/ lines seems very strange.
Greetings
Nicola Biase
