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Les Parson

FSX Turboprop ITT Comparison

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Greetings,

 

I prepared a brief, unscientific comparison of ITT performance between a variety of aircraft. At issue is if ITT increases or decreases with altitude due to thinner air.

Only the Flight 1 B200 ITT increased with altitude. I assume this is a FSX limitation.

 

1.) Carenado B200

2.) RealAir B60 Turbine Duke

3.) Milviz B350i (ALPHA)*

4.) Flight 1 B200

 

*Note - The Milviz B350i remains in Alpha mode without documentation.

FSX TURBOPROP ITT COMPARISON            

          1.) CARENADO B200  PT6A-42     ALT OAT C TQ ITT RPM 10000 9 2093 713 1907 15000 -3 1959 667 1908 FL180 -8 1842 647 1906 FL200 -12 1738 634 1906 FL220 -16 1628 622 1908 FL240 -20 1519 611 1908

 

          2.) REALAIR B60 TURBINE DUKE PT6A-35   ALT OAT C TQ ITT RPM 10000 11 713 747 1906 15000 -2 879 764 1906 FL180 -9 881 756 1906 FL200 -12 886 735 1906 FL220 -16 888 715 1906 FL240 -20 887 688 1906

 

          3.) MILVIZ B350i PT6A-60A (ALPHA)   ALT OAT C TQ ITT RPM 10000 12 63.9 717 1627 15000 -1 64.1 682 1627 FL180 -8 63.7 663 1627 FL200 -11 63.3 654 1627 FL220 -15 64.2 656 1627 FL240 -19 63.5 643 1627

 

          4.) FLIGHT 1 B200 PT6A-52     ALT OAT C TQ ITT RPM 10000 12 2040 704 1805 15000 -2 1935 703 1805 FL180 -8 2077 724 1805 FL200 -12 2064 731 1805 FL220 -16 2064 739 1805 FL240 -20 2055 754 1805

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Carenado PC-12 with the Engine mod from Autogyro fixes this bug in the Carenado PC-12. No other Carenado models it properly. It is an issue with the fsx engine.

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There is more to the story than ITT. More important issues to me are whether torque increases when you lower RPM and does the drag of the prop at beta or when you go to props full forward come into play. The Realair Duke Turbine V2 and the Twotter Extended from Aerosoft model these perfectly.

 

Donald

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What about on a Pt-6 the FF not varying with RPM adjustments ?

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Nice test!! I like this kind of stuff. Yes ITT isn't modelled correctly in most add-ons bar a couple.

 

Did I read that right and see that the Duke'ss ITT drops with altitude?

 

 

Are you able to run a test for me with the Flight 1 B200?

 

At ISA + 20 FL260 Normal cruise TQ 1700 rpm?

 

Also FL270 TQ 1550 1700 RPM

OAT -22 C.

 

I have some real word numbers and want to see how close it is.

I'll see what I can do.

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King_Air Fan:

 

How's this?

 

FL250, ISA +10

ITT - 748

TQ - 2029

RPM - 1704

FF - 342

IAS 201

TAS - 297

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Did I read that right and see that the Duke'ss ITT drops with altitude?

 

 

Actually it both rises AND falls, as it should. ITT in turboprops tends to rise up to a certain level all other things being equal, and then drops when getting into super-cooled air masses. 

 

On the other hand there are wonderful things to enjoy in life apart from being glued to an ITT gauge to check it is "correct".

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With an altitude increase for a given torque setting both N1 and ITT will increase for a free, gas coupled turbine such as the PT6. At higher altitudes available torque will be limited when N1 and ITT reach their respective limits.

.

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Sad to know that the Milviz 350i not give the correct model to the PT6, I have all hope for that, the team of milviz will have a PT6 correctly and we'll done. Carenado all know that they don't modeled the turboprop correctly. Real air I don't know that they can't done that too, well I hope that milviz make the garrett of they Moooooooo well done, a geared turbine it's a goal, only PMDG in their JS42 has done that in the garrett turboprop. The people of flysimware are others that can't done the garrett in their 2 planes correctly.

Milviz please

........ Moo garrett well modeled!!

Redgard

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Actually it both rises AND falls, as it should. ITT in turboprops tends to rise up to a certain level all other things being equal, and then drops when getting into super-cooled air masses. 

 

On the other hand there are wonderful things to enjoy in life apart from being glued to an ITT gauge to check it is "correct".

 

Yes indeed!!!

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Pretty much this. At high OAT temps torque will be reducd which is why of course the torque charts for ISA+20 show less torque then ISA OAT.

 

What doesn't get mentioned is the ITT becomes a limiting factor on the climb. As mentioned above, N1 and ITT rise. And at high OAT, the ITT limit - depending on aircraft and engines, cruise climb ITT is less then Max continuous - so the pilot reduces torque to keep the ITT from exceeding any limits.

 

And since company limits can be and are often less again, correct ITT indications ARE an important part of MSFS aircraft indications and should be modelled.

 

The engine mod for the Carenado PC-12 has turned it into a new plane, you really have to look out for the temps on climb and on hot days.

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The engine (and ITT) control system isn't even IN the alpha that was put out.

 

Hence the reason it's called ALPHA... 

 

We're working hard in close conjunction with Tomas and he's got THAT end totally covered.

 

Worry not, it will do as it's supposed to do.

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In some engines in some conditions you'll actually reach the N1 limit first. One kingair I flew has the -21(-20 front end and a -27 back end) and at altitude one of the engines would reach the N1 limit of 101.5% while the ITT was just under max limit. Of course available torque was way reduced.

Interesting thread. FSX and P3D have their limits in modelling engines. That said some flight sim aircraft producers get much closer to the real thing than others.

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The engine mod for the Carenado PC-12 has turned it into a new plane, you really have to look out for the temps on climb and on hot days.

Do you think it may be possible for a Carenado C90 mod? Should I/we reach out to "Autogyro"?

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Do you think it may be possible for a Carenado C90 mod? Should I/we reach out to "Autogyro"?

 

Here is the engine mod topic

 

http://www.avsim.com/topic/461589-pc12-overhaul-mod-v10-and-n594wa-repaint-released/

 

I'd ask him, he's been away from updating the mod for a few months but said hed be back. Couldn't hurt to ask. I don't own the C90 but have their C200 and would like the mod for that too. But it looks like a lot of work.

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Here is the engine mod topic

 

http://www.avsim.com/topic/461589-pc12-overhaul-mod-v10-and-n594wa-repaint-released/

 

I'd ask him, he's been away from updating the mod for a few months but said hed be back. Couldn't hurt to ask. I don't own the C90 but have their C200 and would like the mod for that too. But it looks like a lot of work.

 

Thanks, I sent him an email a few hours ago.

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Hi guys just came across this thread thanks to LDP's email.

 

Ostensibly yes it can be done to any and all aircraft; all I did was to brute force it in a way.

 

The current turboprop simulation in the base FSX game is all sorts of wrong for the PT6A engines.

 

No doubt your professional modellers from RealAir and Milviz will do a bang up job with ITT modelling.

 

Unfortunately these days I'm short on time so I'm hesitant to make promises I can't keep - although I wish I had the time to help everyone.

 

The current ITT output is mostly affected by the torque output only and drops too much with altitude. What I did in the PC12 is to:

 

Determine what the realistic ITT values are in relation to various flight regimes based on POH.

 

Correct ITT values with altitude at ISA conditions. In retrospect I should not have made the ITT values a function of altitude but air pressure or inverse air pressure as it gave me more work to do later on.

 

Correct ITT values with temperature for a fixed altitude based on POH.

 

Correct ITT vs torque. I found it was not sensitive enough to torque changes at various altitudes and temperatures.

 

Correct fuel use to be an approximate average to real world use at near cruising conditions based on POH.

 

The corrections are basic maths, you just take what you output and you write formulae to correct it and set it as close to a trend as you can.

 

Cleverer people than I would write better functions and use better input parameters. A better starting point than the FSX ITT model would also help.

 

In the end though, my ######ised model does its job well enough to be a more realistic approximation of the PC12 torque and ITT relationship than anything the base gauge would output or what you could do with the .air file, and I'd argue is the most realistic PC12 simulation available at the moment.

 

As for the C90, the theory would be the same, if anybody wants to give it a go. I'm more than happy to help but I can't devote that much time (or it would take me months to do it) to do it myself anymore.

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The engine (and ITT) control system isn't even IN the alpha that was put out.

 

Hence the reason it's called ALPHA... 

 

We're working hard in close conjunction with Tomas and he's got THAT end totally covered.

 

Worry not, it will do as it's supposed to do.

 

Colin is right, the incoming engine system for the KA 350i models ITT in every aspect possible, bypassing FSX limitations.

 

BTW, there is a simple test that can be done in a King Air turboprop to detect whether engine parameters are right:

 

Position the aircraft at El Alto Airport, La Paz, Bolivia (13000+ ft.), with 28 °C temperature, no head winds, at or near MTOW, and try to take off and maintain a climb attitude. 

 

If the aircraft fails the test, engine parameters are well modeled; otherwise they are not.

 

Tom

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Hi guys just came across this thread thanks to LDP's email.

 

Ostensibly yes it can be done to any and all aircraft; all I did was to brute force it in a way.

 

The current turboprop simulation in the base FSX game is all sorts of wrong for the PT6A engines.

 

No doubt your professional modellers from RealAir and Milviz will do a bang up job with ITT modelling.

 

Unfortunately these days I'm short on time so I'm hesitant to make promises I can't keep - although I wish I had the time to help everyone.

 

The current ITT output is mostly affected by the torque output only and drops too much with altitude. What I did in the PC12 is to:

 

Determine what the realistic ITT values are in relation to various flight regimes based on POH.

 

Correct ITT values with altitude at ISA conditions. In retrospect I should not have made the ITT values a function of altitude but air pressure or inverse air pressure as it gave me more work to do later on.

 

Correct ITT values with temperature for a fixed altitude based on POH.

 

Correct ITT vs torque. I found it was not sensitive enough to torque changes at various altitudes and temperatures.

 

Correct fuel use to be an approximate average to real world use at near cruising conditions based on POH.

 

The corrections are basic maths, you just take what you output and you write formulae to correct it and set it as close to a trend as you can.

 

Cleverer people than I would write better functions and use better input parameters. A better starting point than the FSX ITT model would also help.

 

In the end though, my ######ised model does its job well enough to be a more realistic approximation of the PC12 torque and ITT relationship than anything the base gauge would output or what you could do with the .air file, and I'd argue is the most realistic PC12 simulation available at the moment.

 

As for the C90, the theory would be the same, if anybody wants to give it a go. I'm more than happy to help but I can't devote that much time (or it would take me months to do it) to do it myself anymore.

I have the time and the C90 POH for the -21 engine. However, I don't have the expertise nor the Carenado PC-12. Thanks for all this valuable info. I will PM you.

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You can make ITT do almost anything you wish, if you code some xml or C++ gauges which over-ride the default behaviour. But all that is doing is creating something artificial on top of something else that is also artificial. By its very nature, everything in simulation is about hacking other stuff that is also hacked. I think there are more important things to be concerned about first. For example, lots of sim products have gauges which read more or less completely "correct" but that doesn't necessarily make the feel of what you are flying any more convincing. 

 

I remember a very well known developer hacking a big piston tail dragger aircraft he was creating, and to get the steering to work better on the ground he had to create a dummy nosewheel 20 feet in front of the aircraft, unseen, so the tail behaved reasonably to his satisfaction, 40 feet behind his hacked notional landing gear. Essentially this model was in fact steering from the front while appearing to steer from the tail wheel. It did the trick and no-one was the wiser for it. This kind of hacking is really quite routine. There's nothing much wrong with it because all it does is try to create an impression that is satisfying for the end user. As long as you know that very little of this stuff is more than an illusion layered upon another illusion. 

 

It's well known that turboprop modelling in FSX is not the greatest achievement, so all sorts of tricks have to be conjured to create a better impression. It is not proper modelling in the sense that some might feel is happening. It is just finding tricks to negotiate a way around a flawed core system. I have no doubt that exactly the same things happen with the most expensive motion sims too. In fact I know that is the case because motion sim designers have exactly the same hurdles to clear.

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