1.Without a comprehensive King Air C90 reference in front of me, it's the best I can do...but you can pull back the prop speed to about 1800 and the FF/power stays generally consistent....

 

1. That sounds very nice. Can you confirm that the torque increases with decreasing prop rpm?

 

1.I decided to use your pencil and paper method...just to make sure my results that I got in my head matched the results I got on pencil and paper. Very interesting results. Still non-linear on all counts

2.I won't comment on what I found out about FSX's engine model

 

1.That only proves that you don't know to plot even the most basic things and/or how to use a ruler.

2.You can't comment on that due to your apparent lack of knowledge concerning FSX. Everything needed to adjust thrust and spoolrate is in the airfile.

1.That only proves that you don't know to plot even the most basic things and/or how to use a ruler.

2.You can't comment on that due to your apparent lack of knowledge concerning FSX.

I do get offended because you are comparing apples and oranges. Point is that there's everything needed in the airfile in FSX to adjust thrust and spoolrate as much as you like.

You made a statement and were proven wrong by me. You are now evading that by rambling about pencils, papers, rulers, and "near" linearity along with a personal attack by saying I don't know how to use a pencil and ruler. I never insulted you. All I asked for was proof. If you are actually right in your opinion, then proving your opinion should be very easy. Without the attacks or pointless arguments.

Bernt, give up. The engine model in X Plane is non linear. It doesn't get much simpler than that. I gave you figures for comparison. What figures did you provide? None.

I proved you wrong with those figures and now you're trying to prove yourself right by talking about pencils and papers and rulers and asking me to plot it. Well, I did. Prove me wrong by showing me your evidence that X Planes engine model is non linear. You're the one trying to prove a negative. Only do it with something other than suggestions and opinions.

1. That sounds very nice. Can you confirm that the torque increases with decreasing prop rpm?

 

Yes it does, more or less. I set the power lever to @ 300HP and reduced the prop speed in 1000 rpm increments. See below

 

HP TQE RPM FF

----------------------------------------

311 778 2100 122.1

309 810 2000 120.3

303 839 1900 116

295 862 1800 110

 

All those above are for a fixed power lever settting, only adjusting prop speed Now it seems somewhat reasonable to me, that at some point, you will reduce power (and thus fuel flow) with reduced RPM of the prop...I mean at 100 RPM, you're not going to maintain 310 HP, however, I have no what happens in reality. I mean..at what prop RPM will the FF begin to reduce...there is a limit to the prop pitch of course and I'd assume it's once the prop has reached it's max pitch to try and maintain the power setting. I'd be intrigued as to see a real PT-6 graph of power vs. torque vs. fuel flow vs prop pitch...all the goodies. What is a typical operating prop speed range in a King Air C90 anyhow?

Basically during a wide range of RPM variation on a free-running turbine we should see no variation in FF.

 

You can get the ELITE v8.6 demo from here and then test the B200. Since we can't use a throttle quad with it, the Insert/Delete, Home/End and PgUp/PgDwn keys can be used to control throttle, rpm and condition. Use CTRL-M to place the aircraft at cruise and then run your tests...

 

It is the closest to real, from the engine mngmt and model pov, you can get on a PC-based sim :-)

 

 

 

Yes it does, more or less. I set the power lever to @ 300HP and reduced the prop speed in 1000 rpm increments. See below

 

HP TQE RPM FF

----------------------------------------

311 778 2100 122.1

309 810 2000 120.3

303 839 1900 116

295 862 1800 110

 

All those above are for a fixed power lever settting, only adjusting prop speed Now it seems somewhat reasonable to me, that at some point, you will reduce power (and thus fuel flow) with reduced RPM of the prop...I mean at 100 RPM, you're not going to maintain 310 HP, however, I have no what happens in reality. I mean..at what prop RPM will the FF begin to reduce...there is a limit to the prop pitch of course and I'd assume it's once the prop has reached it's max pitch to try and maintain the power setting. I'd be intrigued as to see a real PT-6 graph of power vs. torque vs. fuel flow vs prop pitch...all the goodies. What is a typical operating prop speed range in a King Air C90 anyhow?

You made a statement and were proven wrong by me

 

Goran... I've read this entire thread... and I'll be completely honest. You didn't actually prove Bernt wrong at all. You failed to actually understand the information that was being presented and why it was a fundamental flaw in the base engine simulation process.

 

Bernt's statement stands as factual and has been proved in the other thread as well. I'd say you owe him an apology... (yes he probably owes you one as well).

Hey, what can I say...communication breakdown? Maybe.

As for an apology? Well, we all know how he feels about those.

Hey, what can I say...communication breakdown? Maybe.

As for an apology? Well, we all know how he feels about those.

 

Does it matter "how he feels about those" when it's still the right thing to do? Really??

Does it matter "how he feels about those" when it's still the right thing to do? Really??

That's something between him and me and really has nothing to do with you.

Thanks for your concern, though.

That's something between him and me and really has nothing to do with you.

Thanks for your concern, though.

 

I'd also like to know................who's correct? Private PM's don't answer anything.

I'd also like to know................who's correct? Private PM's don't answer anything.

 

Make up your own mind...

http://forum.avsim.n...r/#entry2315204

By all means, read the whole thread after you read that post.

Really sick of derailed topics with this "perceived" FSX/XPlane rivalry crap...would you guys please take it somewhere else?

 

I have a B200 manual with performance charts for fuel flow at various power settings and did some testing...and also did a lot of research on PT-6s in general. The first thing I came up with is that the terms "basically" and "wide range" don't really specify any measurable behavior...sorry jcomm. I'm on a Mac so I'm not using the Elite simulator either and even if I did, I wouldn't necessarily trust it. On our ixeg 737 project...we routinely rent level-D simulator time and compare that against our simulation and also against real flying experience by our consultant. Here's what we found....we're more accurate than the level-D on some areas...and many things are simulated "approximately". Also we found that pilot observation is fallable. This comes from our consultant..8000 hours+ and 737 captain. We'd ask quesitons about values down to the 1/10th of a value and he wouldn't know cause he never scrutinized the behavior before.

 

So all that to say that given what to me is a "narrow range" vs. a wide range...ie.. 1800 - 2000 RPM.....that fuel flow is "basically" constant in the model I have now. If you're going exact by the floating point numbers, there is a small reduction in power and fuel flow with reducing prop RPM but it's barely noticable on the needle...the kind of "barely noticable" that a pilot probably wouldn't notice because he's too busy with other stuff on his mind so he'd probably say it was constant. To say that x-plane has a "fundamental flaw" is, without rigorous assessment, flawed thinking. Is it perfect? of course not, it's a general purpose model....but is it good enough for a desktop simulation? I certainly think so. If a 35 million dollar level-D sim can "fudge a little" here and there, I'm pretty sure a little fudge in a 80.00 simulator is acceptable. so to recap...here's what I'm seeing in the C90 for the next update.

 

reduction in prop speed increases torque...fuel flow stays "basically" constant....this through the "wide range" of 1800-2000 rpm. The performance charts I referenced on the B200 only go from 1700-1900 so dont' be arguing outside the 200 rpm range without data to support it. I'll claim ignorance outside this range without a thorough testing of torque / FF / lever settings / RPM through full range of motion at standard increments...which I doubt anybody will do because it'd probaby burn up 100+ bucks of fuel doing it. ...and any A & P who worked on them that I asked would probably think I'm a terrorist anyhow and report me. (Yea, that's happened). Anyhow...after the next update, I'll be happy to take more observations.

 

A question for C90 pilots though (or similar aircraft with the same engine). What are typical prop RPM values at low idle and high idle with power levers fully retarded?

 

Tom Kyler

Laminar

V10 aircraft

V10 scenery

Typical C90 prop RPM value is around 1100 with engine anti-ice on and 1200 with engine anti-ice off. This is irrespective of whether the prop levers are full forward or brought back to the detent in front of the feather... as long as the power levers are at idle.

Tom!!!!

 

This is indeed GREAT NEWS!!! Looking forward for it! Thanks!

 

tkyler[/color]' timestamp='1335532840' post='2352896']

So all that to say that given what to me is a "narrow range" vs. a wide range...ie.. 1800 - 2000 RPM.....that fuel flow is "basically" constant in the model I have now. If you're going exact by the floating point numbers, there is a small reduction in power and fuel flow with reducing prop RPM but it's barely noticable on the needle...

Typical C90 prop RPM value is around 1100 with engine anti-ice on and 1200 with engine anti-ice off

 

And these values are the same for both lo idle and hi idle lever settings? I've read a few posts by PT-6 pilots that say some don't have lo/hi...and on some that did...they said they never used the hi idle setting...basically using the condition lever as a fuel on / fuel off lever.

And these values are the same for both lo idle and hi idle lever settings? I've read a few posts by PT-6 pilots that say some don't have lo/hi...and on some that did...they said they never used the hi idle setting...basically using the condition lever as a fuel on / fuel off lever.

 

It should remain relatively unchanged, within around 100 RPM. According to the POH the minimum RPM at low idle is 1100... here's an excerpt from a C90 POH regarding prop RPMs:

 

Stabilized propeller operation on the ground between 500 and 1100 rpm is prohibited. Operation in this range can generate high propeller stresses, which can cause propeller damage and result in propeller failure and loss of control of the airplane. The propeller may be operated when feathered at or below 500 rpm.