Another "aircraft tweaking" question
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Quixoticish
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Another "aircraft tweaking" question
I've been playing around with a freeware SAAB Gripen but I've ran into a few problems and I was hoping some of the more talented aircraft-developing types on here would be able to point me in the right direct. I've managed to get the aircraft up to the correct top speed but the stupid thing now has too much thrust and will creep on the ground and accelerate at idle throttle, even in the air. Is there any way (in the air file or the aircraft.cfg) to fix this? Some way of keeping the top speed as it is but stopping this seemingly large amount of thrust while the throttle is at idle without touching the thrust when the throttle is at 100%?
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Quixoticish
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bigred1970
- Victor
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Quixoticish
- Concorde
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- Joined: 15 Oct 2005, 15:16
- Location: York
AIRED is probably the best, with an updated INI file for FS2004.
You can grab them both over on the left hand side of this site:
http://perso.orange.fr/hsors/FS_Soft/fsairfile.html
You can grab them both over on the left hand side of this site:
http://perso.orange.fr/hsors/FS_Soft/fsairfile.html
Chris,
A few general thoughts about this problem:
It's important to fix something at the outset and keep it reasonably constant as a reference. What I mean is that it's very possible to get wrapped around the axle trying to vary the thrust profile, while assuming the drag profile to be correct, then finding that it isn't and go around the loop again.
You're probably doing the right thing, but you need to remember that you've a few other parameters to play with - intake area is important for drag at speed, for example, and getting the "dynamic-pressure-limited" top speed at low-level is as important as getting the "Mach-number-limited" top speed at altitude correct: this means paying as much attention to the various drag parameters as to the thrust ones - although the excess thrust at idle is obviously not that!
Lift matters, too - lift-induced drag at low speeds, e.g. landing approach, will make a significant contribution to the thrust required as the speed falls.
Finally, it is well worth taking a good, hard look at the original 'air' and 'aircraft' files to be sure that they are worth modifying, as opposed to starting again with a 'clean' file. Quite often, designers will pinch the basic M$ Learjet 'air' file and then hack about the 'aircraft' file to get something 'fighter-like'. This can take as long to unravel as starting again, so do consider it. Alternatively, take a look at the 'tuning' section of the 'aircraft' file - if you see factors less than 0.7 or more than 1.3, it's a hack - ideally, the numbers should all be 1.0, as everything there can be modified in the 'air file.
I hope that this is of some help - sometimes it's useful to step back from the detail
Cheers,
Kevin
A few general thoughts about this problem:
It's important to fix something at the outset and keep it reasonably constant as a reference. What I mean is that it's very possible to get wrapped around the axle trying to vary the thrust profile, while assuming the drag profile to be correct, then finding that it isn't and go around the loop again.
You're probably doing the right thing, but you need to remember that you've a few other parameters to play with - intake area is important for drag at speed, for example, and getting the "dynamic-pressure-limited" top speed at low-level is as important as getting the "Mach-number-limited" top speed at altitude correct: this means paying as much attention to the various drag parameters as to the thrust ones - although the excess thrust at idle is obviously not that!
Lift matters, too - lift-induced drag at low speeds, e.g. landing approach, will make a significant contribution to the thrust required as the speed falls.
Finally, it is well worth taking a good, hard look at the original 'air' and 'aircraft' files to be sure that they are worth modifying, as opposed to starting again with a 'clean' file. Quite often, designers will pinch the basic M$ Learjet 'air' file and then hack about the 'aircraft' file to get something 'fighter-like'. This can take as long to unravel as starting again, so do consider it. Alternatively, take a look at the 'tuning' section of the 'aircraft' file - if you see factors less than 0.7 or more than 1.3, it's a hack - ideally, the numbers should all be 1.0, as everything there can be modified in the 'air file.
I hope that this is of some help - sometimes it's useful to step back from the detail
Cheers,
Kevin