How To Reduce Power At Idle ?

Mick

Mick

SOH-CM-2025
I have a plane, piston powered, that has too much power at idle. It's almost impossible to lose altitude on approach and it's difficult to stop when taxiing despite adequate braking power.

I suppose it's just a matter of adjusting some figure or other in the aircraft.cfg file, but I don't see anything that looks like the obvious choice.

I'm sure someone here knows what needs to be done...
 
You likely need to adjust something in the air file and you need some special program to open the air file. I looked for one once and the only one I found cost $30. Maybe someone knows of a freebie available somewhere.
 
Thanks for the reply, Rich.

You're thinking of AirEd, a freeware AIR file editor that's been around since FS98, if not earlier.

I have it, have had it for as long as I've dabbled in FS, but I don't know where to make the adjustment, whether it be in the Aircraft.cfg file or the AIR file.

If it comes to that, I may just adapt the flight model from another aircraft.
 
Sounds like the Default DH.88 Comet

We once tested and the Comet is easier to land gear up then to land gear down. It will come to a stop quicker. :biggrin-new:

No matter what plane it is to edit the airfile use AAM 1.0 for FS9 http://www.aero.sors.fr/fsairfile.html

It sounds like it needs more drag at zero lift. It does not sound like a power issue.

Keep in mind editing the airfile can give undesired results as some times simple changes to one entry affect the flight model in unexpected ways. Back up the .air file before adjusting.
 
You can chase your tail here, but I adjust the .air files for items 508,509,511 & 511, to get near the correct thrust. I visualise the graphs in Herve Sors AAM V2.2, but change the values in AirEd because I find it easier as it only updates those particular items. One can also download Herve's AFSD which can show engine HP as well as thrust whilst flying FS9. You can also of course copy & paste those items from a known good model .air file, but they do not always transfer well to another model. Approach speed can also be affected by the value of induced drag in the .cfg flight tuning section.
There are other simple changes one can try in the .cfg; reduce the thrust &/or the power coefficient as well as trying the min throttle limit, but those can cause start problems.
HTH
Keith
 
Mick said:
I have a plane, piston powered, that has too much power at idle. It's almost impossible to lose altitude on approach and it's difficult to stop when taxiing despite adequate braking power.

I suppose it's just a matter of adjusting some figure or other in the aircraft.cfg file, but I don't see anything that looks like the obvious choice.

I'm sure someone here knows what needs to be done...
Click to expand...


Mick,

You do not specify the aircraft so I can only guess at some possible easy fixes. It sounds like it may be a turboprop with the taxi issue.

1) If it is a TP engine, ensure you are pulling your prop condition lever back to ground fine for ground ops. This would be your mixture lever on a piston aircraft.

2) Assuming it's a variable pitch prop, ensure that the min_beta in the propeller section is 15 or less. If 15, drop it o 12 and try that.

3) If that does not help, look in the cfg flight tuning section and raise the value of the drag parameters by .1 at a time; SP a 1.0 becomes a 1.1, etc.
Recognize that this will also decrease your top speed so its not the best option, just easier.

4) You can also increase idle friction in the tuning section to lower your idle speed, again .1 (10%) at a time.

5) Also ensure that when descending, you pull the prop back as far as specs allow. TP can be pulled all the way back to flight idle. Pistons must maintain a minimum MAP to prevent shock cooling or carb freeze.

Not at home so I cannot be more specific.

Hope this helps.
 
If it's one of the recent Connies, they're actually pretty accurate. You can't just wait for ATC to tell you to descend. You'll want to request a lower altitude quite a bit sooner. Do like Milton said and watch your MAP. But before you fly, read through the manual and take a few notes. Write down the max speed for each flap setting, and the instant you cross under one of those speeds, drop that notch of flaps - it will help with bleeding off speed. You also have accurately modeled speed brake in the form of the main gear.

Of course, if you're talking about a different plane, just ignore the above ramblings... :dizzy:
 
Thanks to all who replied.

I knew I should mention what plane it was and I intended to, but somehow I managed to neglect putting it into my post.

The plane is F. Giuli's Bell P-39 Airacobra. It didn't want to lose altitude on approach, and it didn't want to stop once it was on the ground. I had to shut the engine off to land it.

I decided on a quick fix and adapted the flight model from Akemi's P-39. Shoulda done that right from the start and not bothered you guys.

I appreciate the suggestions, and I learned something from them even though I didn't put that knowledge into practice on this particular plane. I've kept notes, and I'm sure I'll make use of the info in the future. If it happens again, there might not be another model of the same aircraft that I can copy the flight model from.
 
The FS-KBT P-3 is a fine aircraft, its' only problem is the absolute charge it does in my FS9 down the taxiway at 60 or 70 knots even with the throttle pulled all the way back. Using the "Groundhandling" add-on and setting the taxiing speed to 10 kts results in a series of head-bows until arriving at the EOR. In the [propeller] section I've set the beta_min (hopefully, that's what I'm supposed to adjust) as low as 6.000 and still experience this. There isn't a condition lever setup on the panel I have, just thrust levers. I can fine-adjust pitch using ctrl-F2/F3, it does slow things down a slight amount at that spot just before the props flatten out, but only by a few kts. The only seeming fix I've found, in conjunction with the Groundhandling add-on, is to turn on the deicing switch on the panel, which brings things down speed-wise but results in a higher power setting to taxi.
 
Interesting - and complicated! Sounds like it's pretty specific to that plane. The need for new software means that I won't be trying it. Adapting another flight model did the trick quite well and saved me a lot of trouble.
 
I installed both P-39s in FS9 and did not have the problem you describe with either one.

CFS2 mdl by SimTech: Orig Cfg & Air files dated 6/12/2003 (CFS)
FSX conversion ('p39_airacobra.zip') by A.F. Scrub

FS9 version ('giup39_n.zip') by F.Giuli: Used SimTech Cfg (dated 6/12/2003)
but an 'unknown' Air File.

I installed Giuli's model in FS9 and it all worked fine. Please note that Giuli used the SimTech aircraft config file (the same one Scrub used). Values, etc are identical. The Giuli air file is from unknown model. The contact points were all wrong (too far backwards-which tells me the original model had different ref datum setting (ie: 2.000, 0.000, 0.000 and now is 0.000, 0.000, 0.000 resulting in mis-placement of cnt pts). But, mods to cfg requires also move/re-positioning of fuel tanks, and engine. But, it all depends on individual's needs and/or expectations. Some see it (tweaking) as a waste of time and just jam down runway and as long as it lifts off they have it made. Landing is optional (obviously). Not me. But to be fair, to land on main wheels I need +20.0 of pitch trim. So it's not perfect. Gives me something to 'work on' tomorrow (heehee).
Chuck B
Napamule
 
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