Corner Velocities

[AKEagle+]

Does anyone know where I can get information as to the corner velocities for the different AH planes?

Yeh, I can get a stop watch and figure it out, but I'd rather spend the time on line serving as a target drone

AKEagle+

[funkedup]

A modern definition of the corner speed for an aircraft, would be the lowest speed that the aircraft can reach its g limit. In Aces High there isn't a g limit. Some of the aircraft have structural or placard limits, at the point where they suffer damage under load, but the important limit for BFM in AH is the physiological limit. That's because you will black out above 6g and so higher loads aren't practical because generally speaking, if you lose sight, you lose the fight.

So, if you consider the corner velocity in AH to be the lowest speed at which 6g is still available to you, it is easy to calculate because it is just the 6g stall speed and can be found if you know the 1g stall speed. You just need to multiply the 1g stall speed by the square root of 6g. The square root of 6 is 2.45 so just multiply by that.

For example, if an aircraft has a stall speed of 85 mph then its corner speed would be 2.45 * 85 = 208 mph.

Hope that helps.

Badboy

[funkedup]

So find the stall speed in level flight, multiply times 2.45, and you have a great estimate of the effective corner speed.

[AKEagle+]

Thanks, I guess I don't know what corner velocity means. LOL

I am looking for the turning speed that gives you the fastest sustained turn.  If you turn to tight, you actually turn slower than if you kept your speed a bit higher.  Too high a speed and of course you turn slower again.

I guess my question should be "What is that optimal turning speed called? And is it posted somewheres?"

AKEagle+

[funkedup]

We are talking about a condition where your plane is at full power and is making a coordinated turn at a constant altitude, and it is turning as hard as it can (right on the edge of stall).

Corner speed is the lowest speed at which you can pull your maximum amount of G's (limited by lift, blackout, or structural limit).  So it's the best compromise between turn rate and turn radius.

If you go above corner speed your radius gets bigger, but you can't pull any more G's because you are already at the limit.  So you just make bigger circles.

If you go below corner speed, you can't pull the as many G's as you can at corner speed, so your turn rate (degrees per second) will drop.  Your take longer to get around the circle.

Unfortunately none of these WWII planes have enough power to stay at corner speed while pulling max G's, unless they are descending.  So you might start at corner speed but if you turn enough you'll probably end up well below it.  

But corner speed still tells you what the best speed is for instantaneous maneuverability.

[AKEagle+]

Getting lots of good info here thanks!

I never though of doing a decending spiral to turn faster!

Anything to keep the bogey from gettin a firing solution.  Another 5 secs may be just the time needed for your wingie to turn the bogey into buzzard bait !

AK(I need all the help I can get)Eagle+

[drgondog]

Corner Speed has a specific definition -

The equation for Corner Velopcity is Vc=K*sqrt{2*Nmax*W/(rho*CLmax*S)

where K= conversion factor = 1/1.467 to convert feet per second to mph
Nmax= Limit load factor for the airframe for a specific Gross Weight
Rho = .0023769 slugs*Rho@altitude/Rho@SL
W= weight in pounds
CLmax=stall speed maximum Lift Coefficient
S=Wing Area

For the P-51D the S=233.2, CLmax ~ 1.6, Nmax = 8 for 8000 pounds GW, W= 8000 pounds..

if the GW modelled is 9600 pounds, then Nmax = 64000/ 9600=6.66 G

The Manuever Point on the V-n diagram is the highest possible velocity at Nmax and represents the smallest possible turn radius and fastest possible turn rate for the airplane and also represents the point at which for holding max G steady any increase to velocity will 'bend the airplane' or exceed the Limit Load

The Vcorner for 6.66G in a 9600 pound Mustang is 259mph. Dropping the velocity at this point while holding the 6.66 G will put it into an accelerated stall. Increasing the G will holding the velocity steady will also cause an accelerated stall

If someone can tell me how to post an image I will post the V-n diagram for a P-51D at 8000 pounds GW at Sea Level

[dtango]

Holy necro_thread Batman!

[FLS]

Welcome to the BB drgndog. There are more recent posts on corner velocity and EM diagrams if you're interested. Generally anything by Badboy is a good read.

[drgondog]

Does anyone know where I can get information as to the corner velocities for the different AH planes?

Yeh, I can get a stop watch and figure it out, but I'd rather spend the time on line serving as a target drone

AKEagle+

You can solve for each one given the Nmax, the GW, the Wing Area, the CLmax and the altitude you wish to solve for.
     Vcorner=K*sqrt{[(2*Nmax)/(Rho*CLmax)]}(W/S)}

K=1/1.467 to convert fps to mph, Rho=.0023769 slugs*(Rho@alt/Rho@SL); Nmax = max Limit Load, CLmax=1.6, W= Gross weight used, S=Area.
For a P-51D at 8000 pounds at SL and pulling 8G, the Vcorner = ~259mph - which is very close to the presented value in the Handbook. For a 9600 pound GW, 259mph speed puts the airframe in the bend mode. 

Note: P-51D at 9600 pounds and a CLmax=1.6, Area=233.2 ft>>2  -------> Nmax= 8G*8000/9600= 6.67  (the original design weight for XP-51 was 8000 and the Limit Load was 8G).  As the airplane grew in GW then the corresponding Nmax shrank s well as Vcorner. 

[drgondog]

We are talking about a condition where your plane is at full power and is making a coordinated turn at a constant altitude, and it is turning as hard as it can (right on the edge of stall).

Correct - but the V-n diagrame also applies to any manuever about a central point including a dive pullout, a descending or ascending spiral or remotely - a loop - in which the AoA increases to increase CL toward CLmax - so in reality it is also an expression of the bad things that can happen at Limit Load/High Lift on the airframe.  Strictly speaking it has nothing to do per se with Power if we recognize that a high speed pullout with a dead engine could conceivably place you on the accelerated stall or structural deformation side of the diagram.

Corner speed is the lowest speed at which you can pull your maximum amount of G's (limited by lift, blackout, or structural limit).  So it's the best compromise between turn rate and turn radius.

IIRC the Manuever Point which is at the top of the G curve (at the Limit Load) is Corner Velocity point and has two interesting 'things'.  First it is the Highest G and lowest velocity for that G. occuring at CLmax, Radius minimum, and turn rate maximum plus it is the highest possible speed at that G load in which you will not bend the airframe.

Also at this point, and all along the curve, any drop in velocity for that G will put you into an accelerated stall as CLmax has already reached max  and the wing will stall at that bank angle

Unfortunately none of these WWII planes have enough power to stay at corner speed while pulling max G's, unless they are descending.  So you might start at corner speed but if you turn enough you'll probably end up well below it.  

But corner speed still tells you what the best speed is for instantaneous maneuverability.

IIRC most WWII fighters were in the 3G+- ..5G was pretty much tops for a sustained altitude 360 circular turn manuever.

[drgondog]

Welcome to the BB drgndog. There are more recent posts on corner velocity and EM diagrams if you're interested. Generally anything by Badboy is a good read.

I am interested - I hang out a lot on WWIIaircraft and have been immersing myself in the Aero I sudied and practised a long time ago... and always ready to be corrected on faulty memory.

[hitech]

Life is much simpler, go fast pull stick to black out edge.

If stall horn not blaring on edge raise nose.

If stalling lower nose.

No need to really know corner speed except for initial engagement in which case you just glance at your speed once when holding corner for the next fight.

HiTech

[MiloMorai]

What? Gaston has not shown up yet and posted his words of aeronautical expertise.

[uptown]

Life is much simpler, go fast pull stick to black out edge.

If stall horn not blaring on edge raise nose.

If stalling lower nose.

No need to really know corner speed except for initial engagement in which case you just glance at your speed once when holding corner for the next fight.

HiTech

That's how us country boys do it.