Erratic Oil Pressure and CHT display readings

[hhobbit]

D180 in 2007 CTSW bought secondhand w/c65hrs Hobbs in Jan 2009, instrument functioning fine all the time AFAIK.  Now there’s approx 290hrs on Hobbs.

Occasionally I noticed a few wild CHT excursions, at maybe 175 on the Hobbs; subsequent tightening of the spade connector made a useful improvement in that behaviour.

But in the last few flying hours, I notice the Oil Pressure maxing out off the scale intermittently, and of course displaying an alarm message.   This behaviour appears to have been increasing in frequency of occurrence over recent flights.  

On Saturday last, over the sea between Scotland and Ireland, the problem reappeared and in addition with the two CHTs going all the way down, no indicator bar length on show.

I played about with the engine RPMs in an effort to understand if vibration level had anything to do with it.  Sometimes it restored the correct readings, other times it did not.

So I conclude there is a vibration related fault appearing, where that may be is the clue I hope to get from the forum.  Or is it something else I haven’t considered?

Thanks in advance,
John

 

[dynonsupport]

The short story is that there are two different oil pressure sensors that Rotax has used. The newer one was supposed to help with sensor failures, but they're both prone to vibration-induced failure. Rotax's default sensor installation recommendation location is on the engine, which doesn't help things either. In some CTs it's relocated to the firewall, which we've heard helps things, but this is a question for your CT representative.

It's probably the pressure sensor, in any case. That particular sensor comes with the engine, so you may want to go through your Flight Design support channels to get it looked at.

 

[hhobbit]

What about the two erratic CHTs? It appears they are a further symptom of the same problem. Is it possible that this faulty Oil Pressure sensor can cause other temp sensors to go haywire? I don't suppose the cost of replacing the sensor is a big deal, but am I to replace the CHTs also?

 

[Roger_Lee]

Hi Hobbit,

If you have a CT, I guarantee you have a bad ground if you are having more than one gauge bouncing around. Hobbit go on back the CT forum. The answers are there. You have 5 grounds that need to be tightened. remember we have a plastic plane so keeping the grounds tight are important.

 

[hhobbit]

Hi Roger
I was n fact expecting Dynon to say just that. Three gauges all going out at once suggests a wiring rather than a sensor problem. In the meantime I'll have a look where you suggest, thanks.
John