What is the corner speed for the P-39Q?

[oboe]

Anybody know?  Or how to determine in AH?

thks

[FLS]

It's about 2.44 times the stall speed.

[RTHolmes]

do a quick search for badboy's "bootstrap calculator"

[Krusty]

If I recall, cornering velocity only helps with instant turns where you have excess speed, and after that you cannot sustain enough speed to stay at corner velocity.

So you use corner velocity when slowing down, then rely on sustained turning performance (which is significantly slower than corner velocity).

At least, that's what I seem to recall from previous discussions along this topic.

[FLS]

Krusty you can stay at corner speed as long as you can trade altitude for airspeed.

[Stoney]

FLS beat me to it.

Article by Badboy explaining the concept fully:  http://www.simhq.com/_air/air_011a.html

[drgondog]

The corner speed is a specifically defined term.  First, a series of questions:

1. What Gross Weight for the P-39 you are analyzing? and what is the design limit G load at that weight for that model P-39?
2. What is the CLmax you are assuming?
3. What is the altitude?
4. What is the wing area?

Vne=sqrt[(W/S)*(2*G)/(rho*CLmax)] where Vne is in ft/sec for rho in slugs, W in pounds, S in sq ft. G=max permissible load limit in 'g' or N (Limit load - not Ultimate)

[Chalenge]

And what does the never exceed speed have to do with corner velocity?

[Greziz]

I fly the p39 almost exclusively if your wanting to turn the best you can always ride the very beginning of the stall buzzer only use flaps at the top of loops and only breifly as they are garbage also chop your throttle to half you will notice that the plane will turn better I suggest you only half throttle when you have excess speed or are on the 6 as the 39 does not gain e very well but bleeds it very well I have no idea why the plane turns so much better at half throttle but it turns like garbage with no throttle and full throttle. I stay full throttle most of the time as i try to use as few hard turns as possible in the plane I prefer to use energy and angles to set up shots but when all else fails and for some reason I am in a tail to tail turn I will cut throttle to half for about 1 turn. all and all just always be aware of your e and your opponents e because if he ever realizes he has e adv he will go up and you will go down.

[drgondog]

And what does the never exceed speed have to do with corner velocity?

Everything - at the Manuever Point.

The equation I gave you enables you to calculate the Manuever point and plot your own V-n for any load condition so long as you also know the GW, the design limit load at some other weight, the altitude, the CLmax and the wing area.

The manuever point on the V-n diagram is the point in the flight envelope that 'n' (or Gmax or Nmax) and CL (CLmax) is simultaneously at their highest possible values. It is at this point on the Positive n versus V plot that the angular velocity is maximum and the radius of turn is at a minimum..If you are slower at Nmax, you stall, if you are faster at Nmax you 'bend', if you are very much faster at N.Nmax you break.

The 'horizontal and parallel' line on the V-n diagram is your Positive Load Limit factor and the vertical boundary at the far right is where the Q load limit exists.


 

[FLS]

Drgndog you don't need the design limit G load because all pilots in Aces High are limited to 6 Gs so corner speed is the minimum speed you can pull 6 Gs without stalling.

[drgondog]

Fair enough although the first part of the 'question' was how to get the corner speed, was it not?

Secondly, is there a load out condition on the P39Q that would lower limit load to under 6G?

Last, if AH sets 6G as an upper limit, then certain fighters with a high CLmax, low wing loading and higher (than 6) Limit Load factor are penalized unduly by setting such limit.

[FLS]

I think we can assume the OP meant the corner speed in AH. I'm not criticizing your more accurate method but in the absence of known lift limits the 6 G limit is convenient.

I don't believe you can exceed a 6 G load limit for the P-39Q. I believe you're correct that some aircraft are penalized by the 6 G limit assuming the pilot could handle the higher G.

[oboe]

Thanks for your responses, all.

I'm just wondering what speed I should be trying to keep the 39Q at when I'm turning - my parameters would be 50% fuel load, no wing guns, and probably at 2500ft altitude (rarely get above 10K in the bird, and most fights are probably anywhere from 0 to 5,000 ft).

I hesitated to refer to it as a velocity since I thought velocity always implied a directional component and the direction is constantly changing when you are turning.  I didn't realize how involved the calculations are- I have no idea what the Airacobra wing's coefficient of maximum lift is.   

I do like the simplicity 2.44 times stall speed-- where did that come from?   I think the 39Q stalls between 90-100 mph, so using 95mph gives me about 230mph - does that sound reasonable?   

I've started to read Badboy's paper and am very impressed.   

Greziz - if you are turning at the edge of a stall, I don't think you are getting around a circle as fast as you could be if you instead kept it at corner velocity.   At least that's my understanding.   

[Stoney]

Greziz - if you are turning at the edge of a stall, I don't think you are getting around a circle as fast as you could be if you instead kept it at corner velocity.   At least that's my understanding.   

You are correct.