Trying to find a way to adjust prop drag on MU-2

#1
Hey folks, not really a dev....just wanted to see if there was anyway I could adjust the prop drag somewhat on the MU-2

Flysimware Mu-2 to be exact. I believe Mark has done the best with FSX/P3d4.x parameters available. Flying a Marquise in real life,
I can say without a doubt, the prop drag and or reverse drag is fairly off. In the real plane, if you come to beta to reverse, that
plane will stop on a dime. Really, you don't even need to use reverse that often, beta will slow you fairly quickly.

On the Flysimware MU-2, there essentially is no beta range, just idle and reverse for ground ops. Airborne, when reducing torque,
takes a bit to slow down. In the real plane, if you pull back torque to around 40%, level flight will slow down fairly quickly.

Is there any way to modify any parameter on this MU-2 to try and increase my prop drag somewhat. I have airwrench if I need that as well.

Thanks for any insight. I realize this is made even more difficult, as were talking about a TPE331 engine, as opposed to the PT6.

Thanks for your valuable time and insight.
Best,
David
 
#2
Open the aircraft.cfg go to section [propeller] Look for minimum_on_ground_beta = 4 and change to -4 or -6 seems good. You will hear the reverser sound slightly but after all it is beta. So after you stop move the throttle slightly forward.
I will ask my tech guy why we don't have this as when i tested it i really like it. He might not know i can setup the beta range like this. Keep me posted.
 
#3
Thank You delivery guy(Mark), I'll give it a try. That seems to cover me on ground. Any ideas of increasing prop drag airborne?
Mark, just wanted to say, after getting checked out in the "Marquise" this year, I really enjoy your MU-2. The place I was taught uses FF a lot. The MU-2 numbers of FF vs Torque are quite a bit off. However, I know you are limited on
turboprop behavior in flightsim. I utilize a LUA file to try and keep from getting the condition levers max sound while taxiing.
It works OK, it will prevent the torque from exceeding 30% when the sound changes, so a little more realistic with my Saitek stuff.
I even tried to see if I could create a beta sound on taxi, but it looks like it's all tied into a dll or something. I know you said you are done with any updates or changes to the "Mits", but perhaps someday
you'll revisit the beautiful plane again. Glad your Falcon 50 is almost ready for release, looks great. ON down line, would you give consideration to a Falcon 10/20 if accessible.
What a beautiful "hotrod" the Falcon 10 is to fly.
Thanks again for the "Mits"
Best,
David
 
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Roy Holmes

Resource contributor
#4
Any ideas of increasing prop drag airborne?
When you are in the air the situation is different from on the ground because you have no direct control of prop pitch angle.
It is controlled by the constant speed mechanism. Normally you will not get negative prop thrust and the pitch will not go negative.
It is possible to adjust the N1 and shaft torque relationship so that your idle setting torque will change but not by a lot.
That in turn will adjust prop thrust. I managed to get an increase in the drag to thrust ratio which slowed the thing down quicker.

I'm only talking about what is possible without using external programs such as simconnect etc. With them you can do what you want.

The problem with turboprops in the sim is that power is proportional to the N1 RPM so it basically assumes a free turbine engine. For a single stage engine like yours you have to pretend that the gas generator does not exist while you actually use it for control. A real single stage turbine responds to fuel input rate variations for power variation with monitoring by the TIT. However in the sim fuel rate and TIT are display variables, not control inputs. Yes you can vary the fuel rate by writing to it directly from an external input and you can control power to some extent by controlling the mixture but in the end you affect N1 which then controls the power.

Basically the turboprop is far more tricky to control than a turbojet.
Roy
 
#5
"It is possible to adjust the N1 and shaft torque relationship so that your idle setting torque will change but not by a lot.
That in turn will adjust prop thrust. I managed to get an increase in the drag to thrust ratio which slowed the thing down quicker."

Hello Roy, Thanks for the info. Based on the above statement. Were you referencing the MU-2? Or just a turboprop in general.

I can try either way. Is this an aircraft.cfg setting? Airfile? Or both. At anyrate, can you point in the right direction for variables to adjust and try performance afterwards?

Thank You, for your valuable time.
Best,
David
 

Roy Holmes

Resource contributor
#6
I'm referring to the Grumman C-2/E-2. I started work on the FDE in February. The first Beta was released a fortnight ago and as a result of excellent feedback from former pilots of the type I'm still working on one or two aspects. The advantage of such feedback is that pilots know things that are not covered in the flight manuals.
I have not worked continuously on this project, but my performance spreadsheet has over 1000 lines of calculations in it. Unlike turbojets where sim performance is easily calculated so that a lot of trial and error is avoided, turboprops are less of an open book as far as how performance is achieved in the sim. I have more than 100 hours of test flights in the sim for these models. At every turn a small change to one parameter causes changes elsewhere in more than one area so it is a question of flying taking data changing flight condition taking more data etc. When I say data I'm talking about all the parameters that are not available from cockpit instruments

What all that is about is that there is no one sim variable or aircraft.cfg entry or air file coefficient that you can adjust and try performance afterwards. It is, unfortunately more complex than that.
To give but one example, prop thrust is a complex function of shaft torque and propeller efficiency. Propeller efficiency varies with prop pitch angle, airplane speed, propeller diameter and propeller PRM. Propeller RPM is generally kept constant once in flight by varying prop pitch angle according to the power absorbed by the prop which is a function of power coefficient, pitch angle, airplane speed and prop RPM. Torque is a function of Shaft horsepower and air density and PLA setting. So far so good, but what happens with reverse thrust? The prop tables have no values for a negative pitch propeller. More research is needed and the most recent document I could find on the subject was a 1933 NACA report!.

So not much that I have done would help with a quite different set up such as the MU-2.

Finally, as I mentioned above, I have not gone beyond what is built into the sim for performance tuning. I'm told that using external inputs you can faithfully model all aspects of engine performance. However my brief was to keep it simple, which is a great challenge but a rewarding one.
Roy
 
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