Author Topic: Glide slopes (Read 1048 times)

Raptor · « **Reply #15 on:** May 27, 2007, 07:18:15 PM »

Perk the Thermals!

CFYA · « **Reply #16 on:** May 27, 2007, 07:33:29 PM »

Any chance I could get them on demand? They would come in right handy when I lose the engine!:D

Ryan

Benny Moore · « **Reply #17 on:** May 27, 2007, 10:57:53 PM »

The 15:1 glide ratio (thank you) for the P-51 comes from Jeff Ethell, of the Roaring Glory warbird videos. He flew more warbirds than any other civilian pilot, besides being a commercial pilot. His father flew P-38s in the war with multiple kills.

Benny Moore · « **Reply #18 on:** May 27, 2007, 11:08:27 PM »

Quote

Originally posted by DAVENRINO
The multi-engine planes in AH don't require any rudder input to compensate for asymetrical thrust when an engine quits. I don't think dogfighting in a P38 would be much fun in RL with an engine out.

But they do. Not only do they require some input at high speed, but massive input at slow speeds. Near a stall, you need full rudder and even then if you hold it in the stall, it's not enough.

That corresponds exactly to test pilot descriptions. A real P-38 could be rolled and looped on one engine, and even stalled straight forward on one engine (though not held in the stall). Again, all this is also possible in Aces High, and rudder input is quite necessary. I urge you to test this out.

Also remember that Aces High II automatically feathers the dead engine. The famous engine failure on takeoff problem wasn't just due to the engine failing, it was due to the engine failing and the pilot failing to feather the propeller.

DAVENRINO · « **Reply #19 on:** May 27, 2007, 11:26:33 PM »

Quote

Originally posted by Benny Moore
The 15:1 glide ratio (thank you) for the P-51 comes from Jeff Ethell, of the Roaring Glory warbird videos. He flew more warbirds than any other civilian pilot, besides being a commercial pilot. His father flew P-38s in the war with multiple kills.

I didn't say you were incorrect, just that I find it hard to believe.

DAVENRINO · « **Reply #20 on:** May 27, 2007, 11:36:19 PM »

Quote

Originally posted by Benny Moore
But they do. Not only do they require some input at high speed, but massive input at slow speeds. Near a stall, you need full rudder and even then if you hold it in the stall, it's not enough.

That corresponds exactly to test pilot descriptions. A real P-38 could be rolled and looped on one engine, and even stalled straight forward on one engine (though not held in the stall). Again, all this is also possible in Aces High, and rudder input is quite necessary. I urge you to test this out.

Also remember that Aces High II automatically feathers the dead engine. The famous engine failure on takeoff problem wasn't just due to the engine failing, it was due to the engine failing and the pilot failing to feather the propeller.

I haven't flown P38s much in AH lately, but I don't recall any yaw when advancing to full power from idle with one engine caged. I will try it when I get back from vacation. I certainly understand the prop feathering advantages after giving several hundred hours of multi-engine training as a CFI in prop planes.

Bronk · « **Reply #21 on:** May 28, 2007, 07:00:31 AM »

Quote

Originally posted by DAVENRINO
I haven't flown P38s much in AH lately, but I don't recall any yaw when advancing to full power from idle with one engine caged. I will try it when I get back from vacation. I certainly understand the prop feathering advantages after giving several hundred hours of multi-engine training as a CFI in prop planes.

Umm dave. Have an engine shot out, hit auto lvl and watch trim gauges. Not only will it trim in the direction needed. It's still not enough and you will drift in the direction of the dead engine.

To really notice the effect of yaw on a dead engine take combat trim off.

Bronk

bj229r · « **Reply #22 on:** May 28, 2007, 07:23:04 AM »

Minor drift and yaw aren't really the same thing. B17 with 1 engine out will drift

DAVENRINO · « **Reply #23 on:** May 28, 2007, 07:32:57 AM »

Quote

Originally posted by Bronk
Umm dave. Have an engine shot out, hit auto lvl and watch trim gauges. Not only will it trim in the direction needed. It's still not enough and you will drift in the direction of the dead engine.

To really notice the effect of yaw on a dead engine take combat trim off.

Bronk

I could be wrong. I don't fly P38 much and am guilty of using combat trim more than I should. I wasn't aware that Combat trim also trimmed rudders as well as elevators. What happens if you close the throttle on the good engine for a bit and then firewall it? I am leaving Japan tommorow night and will test it myself when I get home.

Bronk · « **Reply #24 on:** May 28, 2007, 07:43:01 AM »

Quote

Originally posted by bj229r
Minor drift and yaw aren't really the same thing. B17 with 1 engine out will drift

Umm yea the slip indicator begs to differ with you.

Bronk

Bronk · « **Reply #25 on:** May 28, 2007, 07:44:03 AM »

Quote

Originally posted by DAVENRINO
I could be wrong. I don't fly P38 much and am guilty of using combat trim more than I should. I wasn't aware that Combat trim also trimmed rudders as well as elevators. What happens if you close the throttle on the good engine for a bit and then firewall it? I am leaving Japan tommorow night and will test it myself when I get home.

Gimme a min and I'll post pic with engine off and indicator pegged to the side.

Bronk

Lusche · « **Reply #26 on:** May 28, 2007, 07:52:56 AM »

There is a simple formula to calculate max. gilding distance after engine breakdown for all planes in game:

Distance = (Range to closest friendly runway) - 10 ft

Bronk · « **Reply #27 on:** May 28, 2007, 08:00:37 AM »

Power off with 1 dead engine.

Power on with 1 dead engine.

Tried to keep controls neutral for the picks.

Like I said slip indicator differs with bj229r.

Bronk

Benny Moore · « **Reply #28 on:** May 28, 2007, 08:34:55 AM »

Good pictures. Notice that these were taken at about 200 M.P.H.; at slower speeds than this, applying power on one side can cause an instant flat spin.

All of these effects are much more drastic if the propeller isn't feathered. Since Aces High II automatically feathers the propeller if the engine is dead, the only way to see how it works with non-feathered propellers is to keep the engine idle.

bozon · « **Reply #29 on:** May 28, 2007, 10:39:25 AM »

What sets the glide angle is the aerodynamic efficiency which is total drag to total lift ratio. If your airspeed (v) is constant, the rate of decent is v*sinx, where x is the glide angle.

The rate of energy loss to drag (P=d*v) is compensated by potential energy loss (P=mg*v*sinx):
d*v = mg*v*sinx.

Since the rate of decent is constant it requires that the lift balance the weight:
L = mg

Therefore, we plug this to the 1st equation and cancel out the "v":
d=L*sinx

or

sinx = d/L

(I cheated a little with the angles for simplicity, but this holds well for small angles)

Weight: we see that weight is not directly involved. It is indirectly involved by increasing the induced drag contribution to the total drag.

Now, for gliders you do not necessarily need the best glide angle. For souring on vertical winds, what you need is a slow rate of decent - slower then the velocity of the rising air, not the best angle. So your angle might be poor, but it is achieved at a very low velocity. This is how para-gliders work. They just want to sour, not cover a distance. An aerodynamically efficient fighter can have a shallow glide angle, but at very high velocity, which also mean very high rate of decent.

And one final note: Frontal area has little to do with the drag. Its not even a rough indicator, unless you are just talking about scaling up an identical smaller model.