Sudden thrust BUG – from stopped to barely moving

[Martyson]

"Nope not a default aircraft."

I looked at the link you provided.
This is a freeware aircraft for FSX that you are using to test this problem .. correct?

Did it come with an installer for P3D and is it approved for P3D?

Do you also see the problem you reported at default a P3D airport and using a default P3D aircraft?

[alaxus]

"Nope not a default aircraft."

I looked at the link you provided.
This is a freeware aircraft for FSX that you are using to test this problem .. correct?

Not testing per se, just happened to notice the aircraft exhibiting similar behavior to posted issue. I found it rather odd as I have not seen this issue before. And in hindsight after more experimentation, I don't think that it is the same issue rather the aircraft doesn't seem to be able to generate enough thrust to overcome the initial grass friction, hence changing the thrust values seems to have made a difference. It does not have this issue on tarmac.

I tried the default J3 cub as it is a low power aircraft to see if it had the same issue. In this case I could get it to move but it still required a larger amount of power than I thought what would be needed to un-stick it.

Did it come with an installer for P3D and is it approved for P3D?

No just a air file and cfg.

Do you also see the problem you reported at default a P3D airport and using a default P3D aircraft?

Not at any airport (ie sealed, tarmac etc), no. Hence I think the behavior is more akin to being stuck in the mud.
For my problem this points more towards a friction issue rather than a thrust issue as once it is unstuck it move quite freely, until it stops.

[Martyson]

"No just a air file and cfg."
Ok, not a P3D aircraft.

So, after all, no problems with P3D. That is good news.

Have a good flight.

[F_H_S]

Given the fact that whatever change in code P3D got to change direct movement of planes, it created legacy issues for no notcieable benefit, thus I have a sightly different about "good news".

I observed this issue also with a freely avaliable reproduction of a Fokker Dr.I, where an owner of a self built replica tuned the .air and .cfg file to make it fly more according to his plane (with great success!). During the iterations, the plane was almost "free" of the bug, but as soon as ground handling got adjusted (in FSX), suddenly the plane got completely stuck when I checked back in P3D.

Would be nice if there was a better documenation on the inner differences between FSX and P3D, especially when it comes to porting planes. Maybe there is, but I haven't found it.

[Larry_R]

Hi Mike,

Your comments above have been a huge help! I wonder if you could give a rough idea of the mathematical relationship between low_speed_theory_limit, the low_speed_theory_scalar and the final resulting thrust. Based on what I've found, it's not so obvious.

I am putting the final touches on a pilotable WSF ferry, and getting a realistic throttle response has been a problem I have not been able to solve. In a manner similar to what's described in this tread and with the low_speed_theory_limit= 80, if I adjust the power scalar so full throttle is required for the boat to just begin to move, it then accelerates excessively and the top speed is unreasonable, say 50 to 60 knots. And low speed control, critical for docking, is very poor.

Based on your info, I've been playing with these parameters, but the result is opposite to what I had expected. If I lower the low_speed_theory_limit the speed control problem gets worse. A large number of trials with various combinations a lower low_speed_theory_limit, and the low_speed_theory_scalar caused grossly excessive acceleration (for a ferry) once the boat started moving.

However when I *increased* the low_speed_theory_limit from 80 to 100 and then 120 and removed the low_speed_theory_scalar, the result was a vast improvement in low speed controllability. (It's quite reasonable now.) What seems odd is that the boat's cruising speed is say 30 f/sec, which is a long way from even 80 f/sec not to mention 120 f/sec. So it's a puzzle to me.

Larry