Simviation Forums

I have found that quite a number of my downloaded aircraft stall at speeds markedly lower than the 'advertised' values.     Can anyone suggest where the .cfg or .air files may be tweaked to adjust the stall speed values?

I can understand the problem if the actual stall speed were higher than specified rather than lower. I have downloaded several aircraft. The only one I've checked is a Harvard with Canadian markings. In the .cfg file, there is a group of reference speeds near the bottom of the list:

[Reference Speeds]
flaps_up_stall_speed= 62.000
full_flaps_stall_speed= 49.600
cruise_speed= 140.000
max_indicated_speed= 209.180

If your aircraft have similar lists of reference speeds, check to see if they are unusually high or low compared to similar system aircraft.

Jim

Thank you JJH.     Most of my downloaded aircraft are near or near-about the performance specifications given the built-in deficiencies of the basic FS9 engine.     A little 'tweaking' here and there and they can be made to perform not so far off the specs.      Except for stall speeds.     Recently, I downloaded a F8 Crusader which got down to below 60K with still no sign of a power off stall.      I've tried playing with the stall angle in the .air file but without any success.      I'm sure that there must be some parameter which controls stall speed but, so far, I haven't been able to track it down.      Thank you for taking the trouble to reply.

Well, as long as your aircraft are ending up on the runway and not plowing furrows in the grass, I wouldn't worry too much about a low stall speed.

Let me know from whence the F8 Crusader came, and I'll poke around and see if I can find some reason for the phenomenon.

Thank you JJH.     I try to 'tweak' my aircraft to get them as close as I can to the performance specs.       Not much point having a simulator if it doesn't simulate with at least some degree of accuracy.   The Crusader is the F8E model from Alphasim.       And it's not alone in this very low stall speed phenomenon.

I couldn't find the F8E Crusader in AlphaSim's Freeware.  There must be one in there somewhere because there is a a reworked model in SimV Military Page 48:- "This aircraft is a composite of three textures from the Alphasim f-8 e crusader. Reworked air and aircraft.cfg files so that it now flys more like the real one. It will now reach maximim speed. Added an afterburner and put in a modified F-86 panel Bob Chicilo. 4.5MB" That may contain some clues to your speed problems. Suggest you download that one and compare the air and aircraft.cfg files to the one you have. You said you are having similar problems with other aircraft. Are those aircraft all from the same or from various sources?

A technicality.... but stalling has little to do with speed

Well, Anxyous, I guess I've been living under a misconception for all these years.    

[quote]Well, Anxyous, I guess I've been living under a misconception for all these years.

A technicality.... but stalling has little to do with speed

It has a lot to do with angle of attack, correct?

Thank you for your interest Homebrewer.     And, yes, you are quite right.     In the case of the 1g, unaccelerated, power off condition, the stalling speed (IAS) is directly related to the wing angle of attack.    Other factors do impinge - mach effects and Reynolds Number effects - but below about 10,000 feet these effects are negligible.       My problem is that quite a number of my aircraft stall at speeds appreciably higher than the advertised stall speeds in the .cfg files.    I could attempt to rectify this by playing about with the wing lift coefficient, but I was interested to canvass other views before I started to mess about with th .air files.

A technicality.... but stalling has little to do with speed

It has a lot to do with angle of attack, correct?

A of A and airspeed. The A of A has to be within limits for that airspeed, and vice versa.  Technically, you can stall any (stall-able) airplane at any airspeed, in any attitude relative to the ground... all you need to do is pitch up or down beyond the limits for that airspeed (or slow down/speed up beyond the limits of a given angle).

Naturally, as soon as you change the A of A, the airspeed will change, but if you pitch up or down abruptly enough, you could stall a plane at, say, its normal cruising speed.
 This is the secret behind the snap roll, which is sort of a horizontal spin. Entry is usually well above the normal stall speed, but abrupt elevator input breaks the airflow over the wing as the A of A increases rapidly,  causing a stall (first of one wing) at an indicated  airspeed you will not find in the book as a stalling speed.  

Aside from aerobatic stuff, or drastic maneuvers like Rotty mentions.. it's all about INDICATED airspeed. Your indicated airspeed IS your AoA.

Remember, the pitot tube is fixed, and oriented as something near an incidence of zero. If the pitot tubes "sees" an IAS above stall speed, the wing is flying.

Then there's the increase in indicated stalling speed due to load factor...

Then there's the increase in indicated stalling speed due to load factor...

Oh yeah.. there are a bunch of variables...

The concept that really needs to be understood, is the accelerated stall..

I got into a big argument with an instructor over that... It was my