Strange prop and engine gauge behavior

[iangrant1981]

I'm experiencing some odd propeller behavior as well as some suspect indications on the gauges.

The main issue is the prop kind of has a mind of its own. Trying to set climb power the rpm would consistently jump back up about 75 rpm a few moments after I pulled it back. For example, I pulled it back to 2000 only to have it rise back up to about 2070 a second later. The next time it rose back up to around 2050. It took me a while to finally get it to settle on 2000 rpm. During descent it began acting up again in response to my power changes. Unless I am completely mistaken, I believe the prop rpm should more or less stay right around where it is set on a PT6 (or just about any turboprop for that matter) unless there are dramatic power changes or extremely low power settings, in both cases the governor would have troubles maintaining the rpm set. I can assure you that this is not a control calibration issue.

Other oddities I found was what I thought to be a lack of expected torque rise when decreasing prop rpm at a given power setting. This may be model specific and just how this particular aircraft is but it was something I thought peculiar. Far more peculiar, however, was the behavior of the small needle on the %Ng gauge. It seemed to have no correlation to the main needle what so ever (it should be indicating the same thing, just down to a single percent). It often would give completely erroneous readings. For example, it would point to 2 when the large needle was indicating roughly 86%. Stranger still is that it would move in the opposite direction from what it should have. Making a small power decrease of just a few percent the needle actually spun in the wrong direction indicating an increase!

I uninstalled and reinstalled the aircraft to no avail. UAC set, ran as admin and AV turned off so that's not it. The problem persisted exactly as before.

I love everything else about this plane so I'm not trying to lambaste it or anything. I love the start up/shut down simulation, the sounds and everything else. ITT seems to be very well modeled too indicating appropriate rises in temps as you climb and so on- well done there! I just can't figure what's going on with the prop setting and other engine indications during the rest of my flight.

[Krazycolin]

have you read the section about friction controls?

[Taguilo]

Hi,

"The main issue is the prop kind of has a mind of its own."

Propeller operation is custom coded, hence very sensitive to controllers' noise. I believe that is your case, so I recommend you use the friction rod and adjust lever to around 55 %, should work fine then.

"lack of expected torque rise when decreasing prop rpm at a given power setting"

There is indeed an increase in torque with prop reduction, between 2.5 - 3.0 psi between 2200 and 2000 RPM. Full governor range is ~ 8 psi.

"Far more peculiar, however, was the behavior of the small needle on the %Ng gauge"

The small needle is currently disconfigured, gauge error (like it sometimes happens in RL). Left ex-profeso for release, we will probably fix it in a service pack.

Thanks!
Tomas

[iangrant1981]

Thanks for the replies!

Re: Propeller behavior
Setting the friction lock to 50-55 doesn't fix the problem as such but it does mitigate the effect but slowing the propeller control input to a rate in which the aircraft (i.e. custom propeller logic) can keep up. I assume this is actually the intended effect and kudos to you guys for building in a way to fine tune that. I had in fact missed that in the manual so thanks for pointing it out.

Re: Torque response
About 2.5psi is exactly what I noted when dropping from 2000 to 1800 rpm. It just seemed slight to me based on other aircraft. There also seems to be little or no 'torque bloom' on take off run which caught me out. Again, I am really not familiar with this particular PT6 installation so I was open to the notion that it's correct behavior on this plane. I'm glad to hear you've got the range all figured out and it seems to respond appropriately as you've described it.

Re: The 'one's needle'
That make sense. It does kind of wander around as it pleases. It dropped 5% on it's own accord during cruise while I hadn't touched the throttle! Honestly' it's easy enough to ignore as the main needle gets you close enough to the setting you need. I was more worried it was indicative of something not working correctly on my end when taken in account with the jumpy prop rpms. Knowing that it is essentially supposed to be inop and isn't a symptom of the other issues I had is a good enough explanation for me!

Cheers guys, thanks for the hard work on this one!

[Taguilo]

There also seems to be little or no 'torque bloom' on take off run which caught me out.

From the aicraft's original manual:

NOTES:
1. Torque increases approximately 0.5 PSI from zero to 70 MPH.

That's what you get, with a max increase of ~ 1.5 psi at 100 mph.

Thanks!

Tomas

[iangrant1981]

NOTES:
1. Torque increases approximately 0.5 PSI from zero to 70 MPH.

That's what you get, with a max increase of ~ 1.5 psi at 100 mph.

You guys got it spot on then! It seems like a very small amount when compared to other aircraft both real and simulated is all.

Seriously, thanks for the quick replies and help. I appreciate it very much!

[Taguilo]

You guys got it spot on then! It seems like a very small amount when compared to other aircraft both real and simulated is all.

Yes, seems really small. For example, compared to PT6A-60A in KA350, which is ~ 2 % at 70 mph (aprox) or ~ 1.2 psi using T.Otter units.
Bear in mind the engine is overpowered for this aircraft so I guess all riggins are set to keep it safety controllable.

Tomas