MT Governor and IMC

Heres a good one for you engine/prop/governor gurus.

IO-360-M1B with an MT P-860-4 driving a Hartzell BA. Approx 500hrs over 5.5 yrs

Of late I've noticed that when flying in and out of IMC, that I get a slight RPM drift. In clear air its rock solid all day. In and out of the CU though, I get a +/- 10-20 RPM. Enough to feel, so its not a sender issue.

Ive looked over all the linkages and theres no obvious sign of play. I spoke to MT and they said that the current P-860-4 is a rev-G governor now with slightly higher operating pressure and pumping capacity than the rev F version currently installed.

Given that its only a few months away from 72 mth TBO, and the cost of overhaul here is more than a new one, I think I know what the resolution is. Just curious as to whether anyone has had experience with this.

Cheers

Richard


.

No answer here but what RPM were you at when you experienced the RPM shift?

It would seem to me that the engine power output is changing slightly with the weather conditions. If the prop is already at the (internal) stop when the engine suddenly makes a bit more power, then you get more rpm, no?

Bevan

Hi Richard,

Sorry to drift your thread, but what do you expect the overhaul to cost you?

I am curious because I'd really like to install a constant speed prop and want to get my head around operating costs?

Cheers

Hi Bevan,
I usually run 2400 and WOT or thereabouts in the cruise. Sometimes up to 2500 if a bit higher. So well within governing range.

Hi Eddie, around AUD 1450 as an initial estimate. More if requires extra bits. A new one is USD 1250 from Vans.

Cheers

Richard Connell said:

...flying in and out of IMC...

Click to expand...

I've noticed that engines always run worse in IMC. Doesn't matter if they're turbine or there's more than one. I've heard it called "auto-rough".
It's not that I don't believe you, but maybe your paying much more attention to the engine when in IMC vs VMC?

Richard Connell said:

Of late I've noticed that when flying in and out of IMC, that I get a slight RPM drift. In clear air its rock solid all day. In and out of the CU though, I get a +/- 10-20 RPM. Enough to feel, so its not a sender issue.

Click to expand...

If you're really serious about going through CU (cumulous), you're probably hitting a reasonable amount of turbulence. I wouldn't be surprised to see 10RPM drift as a result. The fact that you are IMC is not the issue, rather it might be the turbulence.

just a curious side note, what other things are you forced to overhaul at given times or calendar limits down under that we on this side of the globe are not forced to?


bob burns
rv-4 N82RB

I didn't know that there is a overhaul requirement or even recommended for the governer if all is working OK? Does that apply to only MT governer or Hartzel as well?

ChiefPilot said:

If you're really serious about going through CU (cumulous), you're probably hitting a reasonable amount of turbulence. I wouldn't be surprised to see 10RPM drift as a result. The fact that you are IMC is not the issue, rather it might be the turbulence.

Click to expand...

Yes I think this may be part of the issue. I'm not talking about penetrating serious wx. More like in and out of SCT or BKN CU. So there is a little bit of minor turbulence associated with it. I haven't analysed the normal or lateral acceleration vs RPM drift on the last few flights but its on the list to tick off.

I don't particularly want to debate the manufacturer TBO WRT local legislation in AUS given recent threads. FWIW MT specifies a 2000hr or 72m TBO for the P-860-4.

cheers