Engine issues

[severniae]

Hi, 

Sorry - me again! 

Again on 11.50 - Beta 11 now. I've noticed a few more oddities that I thought I would mention - I hope you don't mind.. Some things I'm sure are my understanding of how Xplane works, so please forgive me if I am stating the obvious..

1. Engine NG at low idle - I noticed in low idle when turning on all the lights, the engine NG lowers by a good 10(ish)%. to sit at around 30 something - When switching them on again, the engine RPM only rises once the strobe has been switched off. I've noticed that the effect is there at high idle also, but to a lesser extent.

2. Engine start up - once the engine spools up to around 49% it stabilises there but the starter stays on. If I advance the condition lever through low idle a little ways in between low & high it then automatically disengages. If I don't move the condition lever, I have to manually disengage the starter. Could you advise if this is intended behaviour, or should I be doing something different?

3. Again on startup, sometimes after disengaging the starter after the engine stabilising at 49%, as soon as the starter is disengaged the engine RPM drops to around 34-38%. This seems reasonably intermittent and I wonder if it is somehow related to the lights I mentioned earlier.

4. Just as a general note, wow this thing is fast!! It's got some legs too, I got up to 380KTS TAS (ok, my altitude was a little higher than the demonstrated maximum!) and I estimated that at the fuel burn (max throttle at FL370) I could have stayed up for 4 hours, serious range! The only thing I did notice was that at that height, and power setting IRL I would expect a PT6 to be pushing, if not exceeding the temp limits, though perhaps the additional airflow at such speeds is playing quite a part here. I've of course tried it at the normal Flight levels also and it still seems to be a little on the cool side.

All the above I've been able to repeat with xplane plugins on, and also with all off except for the ones necessary for the PR.

Thanks for your time again, I hope my questions aren't becoming annoying.

Regards,

James

EDIT - attached image that shows ITT at altitude - in a PT6 I'd expect to be temp limited here, but it seems that I'm torque limited instead?

EDIT - 

 

Edited June 18, 2020 by severniae

[Coop]

2 hours ago, severniae said:

1. Engine NG at low idle - I noticed in low idle when turning on all the lights, the engine NG lowers by a good 10(ish)%. to sit at around 30 something - When switching them on again, the engine RPM only rises once the strobe has been switched off. I've noticed that the effect is there at high idle also, but to a lesser extent.

2. Engine start up - once the engine spools up to around 49% it stabilises there but the starter stays on. If I advance the condition lever through low idle a little ways in between low & high it then automatically disengages. If I don't move the condition lever, I have to manually disengage the starter. Could you advise if this is intended behaviour, or should I be doing something different?

3. Again on startup, sometimes after disengaging the starter after the engine stabilising at 49%, as soon as the starter is disengaged the engine RPM drops to around 34-38%. This seems reasonably intermittent and I wonder if it is somehow related to the lights I mentioned earlier.

4. Just as a general note, wow this thing is fast!! It's got some legs too, I got up to 380KTS TAS (ok, my altitude was a little higher than the demonstrated maximum!) and I estimated that at the fuel burn (max throttle at FL370) I could have stayed up for 4 hours, serious range! The only thing I did notice was that at that height, and power setting IRL I would expect a PT6 to be pushing, if not exceeding the temp limits, though perhaps the additional airflow at such speeds is playing quite a part here. I've of course tried it at the normal Flight levels also and it still seems to be a little on the cool side.

1. That is an interesting behavior. I sure haven't seen that, but we are using the base X-Plane PT-6 engine model. We have quite a few tuning tweaks coming soon that might fix weird issues like this
2. Hm, it should disengage automatically. Is the prop full forward or at feather?
3. Same as 1, plus some of the quirks of X-Plane's engine model in general
4. ITT tuning will be tweaked a bit in the same coming update, the ITT tuning is a careful balance of compromises between low altitude and high altitude behaviors.

Thanks for the reports  

[severniae]

Thanks @Coop - After I posted earlier I did a quick test to see what the engine does in 'strange' conditions - I was able to maintain full torque until around 25,000 feet (Is this a 680HP engine or one that has a higher SHP rating and is flat rated down?) Temperature never really left the 400s.

I then for laughs wondered how high I could go - I gave up at around FL550 - Torque was way down but the temp was around 530 on the ITT, it was great fun but I imagine IRL the engine would have well and truly melted by that point. 

I might take a look at some engine performance documents for the Piper Cheyenne II, which uses the same engine (Am I right thinking you modelled a PT6A-28?) - IIRC that aircraft has some poke to it but I don't recall its performance limits, of course the fancy prop on the rocket will give it somewhat of an advantage too.

Edit: BTW - regarding point 1 above, take a look at this link https://developer.x-plane.com/2016/12/fight-model-improvements-done-for-x-plane-11-00/

It looks like somewhere along the way austin modelled in this behavour in order to make it match his real life PT6 equipped Lancair. 

Edit2: Sorry forgot to mention - I've tried the start with prop full forward and at feather, same behaviour.

Edited June 18, 2020 by severniae

[OuterMarker]

On 6/18/2020 at 5:17 AM, Coop said:

1. That is an interesting behavior. I sure haven't seen that, but we are using the base X-Plane PT-6 engine model. We have quite a few tuning tweaks coming soon that might fix weird issues like this
2. Hm, it should disengage automatically. Is the prop full forward or at feather?
3. Same as 1, plus some of the quirks of X-Plane's engine model in general
4. ITT tuning will be tweaked a bit in the same coming update, the ITT tuning is a careful balance of compromises between low altitude and high altitude behaviors.

Thanks for the reports  

Hi Coop, is that update still planned?
Thanks

[Coop]

23 hours ago, OuterMarker said:

Hi Coop, is that update still planned?
Thanks

Yes, it is being worked on currently

[OuterMarker]

52 minutes ago, Coop said:

Yes, it is being worked on currently

Great news, thanks :-) Haven't flown it in a while but the Pocket Rocket is still one of my favorites