Rotax shutdown issues

[ab3198]

Hi all, I have a roko via with the 912 rotax. Since we bought it (it had 100hrs when purchased last year and have put on 50 since) i have had intermittent problems with being able to shutdown the engine. When the key is turned to off the engine continues to run and can only be stopped by turning off the fuel. I replaced the ignition switch but this didn't help. At the last inspection I asked the Lame to check it again but as with any intermittent issue it shutdown with no problems and they could not identify the fault.

 

Has anyone else experienced this? Any suggestions?

 

Cheers, Andrew

 

 

[kasper]

Had similar issue on the 912 on the raven at 180hrs - its was a break in the earth wires inside the plastic at the point the wires exit from the ignition box ... intermittent in experience as the ends of the broken wire either worked or not to ground out the circuit depending on how warm the wire was or if the ends touched long enough to kill.

 

The fix was expensive - replace the ignition box as the break was at the wire as it exited the sealed end of the box.

 

 

[rick morawski]

I had same fault symptoms and was broken kill switch wire same as Kasper, except mine was about 15mm away from the ignition box so I just had enough wire left to do a repair. Lucky me.

 

 

[kasper]

I had same fault symptoms and was broken kill switch wire same as Kasper, except mine was about 15mm away from the ignition box so I just had enough wire left to do a repair. Lucky me.

Yeah lucky you - not lucky me:crying:

 

 

[ab3198]

Thanks Kasper and Rick, I spoke to Bert Floods yesterday who said they can do a bench test on the modules, I just need to send them down. Hopefully that might show an easy (cheap) fix. I would find it hard to take that I would need to spend $1300 to replace each module on a near new engine...

 

 

[pylon500]

And while the 912 does not have any form of 'impulse' magneto, you should be aware that if this condition exists (broken wires /hard to stop), then you technically have a 'live' engine.

 

I would be very hesitant to turn a 'warm' engine in this condition.

 

 

[storchy neil]

what you blokes are describing was discussed here by maj RIPmate and others some time ago that is the reason that I do a maggi check every time I shut down and use only one maggi on shut down

 

 

[Geoff_H]

Wires that have been soldered will fatigue and break, maybe the wire was soldered to a lug. Ensure that all wires have crimped fittings.

 

This is a rule for GA aircraft LAMES.

 

Cheers

 

Geoff

 

 

[facthunter]

Copper has a bad habit of work hardening and breaking. Nev

 

 

[Geoff_H]

Sure this is the mechanism of final failure, a soldered joint is ridgid and has little support which increases the stress on the copper that is held at the sharp soldered joint. A crimped joint is allowed to flex with less stress where the copper leaves the shroud. Hence crimpping gives a better life, provided a crimp is done correctly with the proper tool, one should never use pliars or similar. The cable is actually held by the insulation and the copper

 

is galvanically crimped but does not carry the wire load.

 

 

[facthunter]

An uninsulated bare wire will fail at the end of the solder build up. Support the wire further up where insulated ( covered) add a shrunk on support. I don't fully trust crimps but you occasionally find dry soldered joints too. Nev

 

 

[Geoff_H]

A properly done crimp joint will have a galvanic connection pressure greater than 30,000 psi. Above the pressure at which oxygen can infiltrate and cause corrosion and high resistance. But it must be done properly, an improperly done joint will cause problems and as most people don't have a crimping tool that ensures that the crimp is compete before letting go then the heat shrink with solder would be better, but I would not use it. All connections of electrical power are crimped and bolted, never soldered owing to long term degradation of solder.

 

 

[Geoff_H]

Electrical power in the poles and wires from the power station to your local transformer that is. I spent 42 years in this industry. We always crimped.

 

 

[Geoff13]

The never ending argument of crimp or solder always seems to leave out the option of wire wrapping. ????

 

Just putting this out there for consideration.

 

 

[Ayecapt]

Problem with most hand made automotive crimps is that they are not done properly , this follows onto aircraft as well .

 

true galvanic crimps as used in power cabling and if sectioned will be invisable to the naked eye. This will not be the case with auto type crimp lugs.

 

As to not shutting down to stop the engine both magnetos need to be grounded. Thats both... So its unlikly that your ign packs are both faulty . I would inspect all ground connections to the engine, firewall,engine to firewall and ensure they are tight and clean.

 

 

[tailspin]

Thank you all for the imfo on crimping always had the feeling solder was the way to go, as they say you are never too old to learn