Glide ratio

[F4UDOA]

Niklas,

I think the AH F4U is more like 4:1.
12:1 is just a number I remember reading but I have no proof of where it came from. So it looks like it is off by 2/3 of what it should be. The A/C that are really porked is the P-51 and P-38. They are much worse off in AH as far as my testing goes.

But looking at Wells numbers it seems like there is a window for glide speed to be effective. The P-51 seems to glide well but only at high speed were as the F4U and F6F are better at low speed. I belive this is because of the wing design of the Navy planes being more effective at High AOA.
If I can figure out how Wells did it I will try to see what happens to the P-51 When it slows down. My guess is that it falls like a rock. I need to retest and see how these numbers compare at the A/C best glide speeds.
Numbers like this give you a better Idea of what the A/C range of performance was designed to be. It is no accident that the Navy planes glide best at speeds aproaching their landing speed on a carrier.

Later
F4UDOA

[wells]

DOA, I got between 7-9 glide ratios.  Are you feathering the prop?  Use the keypad_minus key.

Niklas,

I will use 370 mph, 2000 hp, 80% efficiency and 7400 lbs to figure the drag coefficient.  Wing area is 173 sq ft.

1620 lbs thrust
Cd0 = 0.0259
Cdi = 0.0008

For glide, Cdi = Cd0 = 0.0259
If Cdi = Cl^2 / (pi * aspect ratio), then

Cl = sqrt(Cdi * pi * aspect ratio)
Cl = 0.70 (aspect ratio = 6.1)

Then V = 155 mph to produce 7400 lbs of lift

Drag force ~ 551 lbs
Lift/Drag = 7400 / 551 = 13.4

It could be that thrust values in the sim are on the high side, necessitating higher drag to keep top speed and climb in check, but adversely affecting glide.


[This message has been edited by wells (edited 07-14-2000).]

[Redcoat]

Wells had a technical answer but he was right. It's not as simple as picking a speed and seeing which plane has the best L/D. Each plane reaches there best L/D at a specific speed. You can't reasonably compare a Zero to a P51 at 150 mph, just like you can compare them at 400 mph. Each plane is different.

What is important in sailplanes, is a fairly flat polar curve. With L/D on the vertical and speed on the horizontal, the better the glider, the flatter the slope at any given speed. I believe the best L/D is where the minimum sink polar intersects the best glide speed.

Redcoat

[HABICHT]

some glider ratios:
DG-600   1:49 at 119 Km/h (GREAT COOL PLANE)
LS-3a    1:40 at 100 Km/h (i fly usually)
NIMBUS-4 1:60 at 110 Km/h
ASW-22BLW1:62 at 110 Km/h

so pls model me a ASW-22 BLW.
DUCKWING can tow me up in a C47.
would be nice to do some hanggliding at the
AH mountains. ot may be thermals under the
clouds??

HABICHT
XO JG54

[wells]

Just to note the difference between glide for range and glide for endurance.  While something like a P-47 may glide farther than an F4u, the Corsair might be able to stay in the air longer due to it's lower glide speed.

[F4UDOA]

Wells,

I have been testing my glides this way. I haven't however been able to feather the prop on my F4U. I think only certain A/C have that capabilty. First I set my auto speed for /.speed 150 then when speed is stable I kill the throttle. Wait for the decent to stabilize and measure it on the climb/dive meter. The P-47 is the best I've seen so far. I am surprised by it's ability to glide considering it's drag coefficient does not seem significantly lower that the F4U and it is over 2000lbs heavier. The Mustang and P-38 I would expect to glide well due to aspect ratio and the low drag of the P-51. Does the AOA of the wing vary in the equation? I thought that different airfoils also played a role in glide as well.

What do you think of the climb and accelleration of the P-47??

Later
F4UDOA