Aces High Bulletin Board
General Forums => Aces High General Discussion => Topic started by: Benny Moore on May 26, 2007, 09:32:16 AM
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Why does it seem that the heavy fighters glide much better than the light ones? In heavy fighters I tend to overshoot a little on landing, while in light fighters my tendency is to fall short of the runway. It feels like light fighters drop like a stone. Logically, I would assume that heavy fighters glide worse, if their drag profiles were the same as a lighter one. But I'm sure I'm missing half a dozen factors. Discuss.
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Whatever the wieght of fighters they tend to have similiar size engines or with difference of power that does not correspond with the wieght difference.
Heavier planes tend to have bigger wings and more lift rather than just jacking up the power with ridiculosly sized engines guzzling enourmous amounts of fuel. so when ther's no engine power heavier planes tend to have a better lift to wieght ratio than lighter planes which rely a lot more on thier engines for their lift.
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More to the point a heavy fighter has more kinetic energy for same alt/speed. Therefor its harder to bleed that energy off all things being equal.
Cfya
Ryan
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For whatever reason, I submit that the P47's glide scope is far more generous in here than in RL:)
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Originally posted by bj229r
For whatever reason, I submit that the P47's glide scope is far more generous in here than in RL:)
I think that is true of most fighters in AH. Most glided like anvils in RL. My next door neighbor in Oregon had a beautiful Hellcat that he flew from his private runway until the engine quit at 1000' and he stalled it in over the trees. He said it bout ripped out his shoulder harness when that big old prop turned into an airbrake. He was lucky to survive and the Hellcat didn't.
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It's not at all true that the glide slopes are wrong in Aces High (at least for the ones that I've tested), or that real World War Two-era fighters glided like anvils. In reality, warbirds had much, much better glide slopes than you'd expect; in fact, they had comparable glide slopes to modern gliders (much better than modern civilian aircraft with engines). The P-51 was 15 to 1 and the P-38 was about the same. In fact over strong thermals a dead-stick P-38 could soar until the sun went down (literally), with propellers feathered. That's how good it could glide. The thing would have made a fantastic glider with the engines and accompanying equipment removed.
Having an engine quit at 1000 feet—facing away from and some distance from the runway—is going to put any airplane, no matter what kind of glide slope, into a sticky spot. I'd say it's impossible for any powerless aircraft to make a 360 degree turn at that altitude and still have enough speed to make it to the runway and land safely. This is especially true because from the sound of your description, your neighbor did not minimize his R.P.M., which would nearly feather the propellers and extend the glide slope. But as I said I doubt even a glider released in that position could make it safely to the runway.
What I want to know is why the heavier ones seem to do better than light ones (both here and in reality); the four factors of flight are lift, weight, thrust, and drag. With thrust out of the equation, it's up to lift, weight, and drag. The more the weight, the worse the airplane will glide (while I'm no physicist, I am certain that the belief that mass will help an airplane glide due to kinetic energy is a myth; mass will only help anything go earthwards, and hinder at all else).
Laurie must be right; in order to compensate for that weight, heavy fighters were designed with greater lift and often less drag than light fighters. I just didn't think that it would be enough to actually allow them to glide better than lighter fighters. Still, that would explain why American heavies could out-maneuver fighters half of their size and weight.
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OK, first the correct terminology is "glide ratio". Second, some of the gliders I have have flown have a 40 to 1 glide ratio and I have done 180 degree turns from 400' with a simulated rope break to a landing on the runway with room to spare. I don't have any RL warbird time but I find your 15:1 glide in a P-51 hard to believe. My neighbor certainly didn't convey that experience with his Hellcat. He said he didn't have time to do anything but find a place to crash and he is a very experienced pilot. I didn't say his engine quit on takeoff. He was cruising at 1000' returning from the Evergreen airshow with my other neighbor flying a Bearcat and put it down in a field near our home.
I have flown aver 18,000 RL hours since 1969, including 14,000 in jet transports and also have a Commercial Glider rating. I flew DC-10s for 14 years and can attest that a heavy one is much harder to get down than a light one. We call it "smash" and kinetic energy does play a huge role in descent planning. I can also assure you that a high wing loaded airplane like a P-51 built for speed does not have a high lift wing.
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Could it be that the heavy aircraft in AH have a higher stall speed? The lighter aircraft, like the Zero, are going so slow at stall that they practically fall out of the sky and give no chance for recovery at low alt where as the heavy iron won't go as slow even stalled...
As for glide ratio, I'll put my money on the A6M2 over any heavy iron in this game at the same alt.
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I expect HT tries to find happy medium between a true flight-sim, and arcade fun. (which it WOULDN'T be for most folks if they clamped down on such things as glide ability)
DJ you still doing the Guam run? Such a life:aok
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Originally posted by bj229r
I expect HT tries to find happy medium between a true flight-sim, and arcade fun. (which it WOULDN'T be for most folks if they clamped down on such things as glide ability)
I think you are on the right track BJ. IE. 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.
DJ you still doing the Guam run? Such a life:aok [/B]
Yes, and five other islands between there and Hawaii. I get to fly to Midway next week for the first time. Should be fun as long as those big albatrosses stay outa my way. We are on a little vacation in Kyoto right now.
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Kinetic energy has a LOT to do with glide slopes. However glide ratio is the correct term for what you descibe. One of the reasons a P51 may apparently glide so well is the fact that it is extremly aerodynamic. As for glide slope, this is reliant on:
A. Wing drag to lift ratio
B. Frontal area
C. Prop drag (try it with and without prop feathering)
D. Weight
Many planes in AH will glide at a stable air speed with about a 1k decent rate. That translates into about a 12 mph vertical speed which is EASILY found almost in updrafts in all parts of the world. Even a 2k decent rate is still only a 24mph in the vertical speed. They did indeed glide very well.
I have heard of a modern airliner gliding 200 miles from an altitude of 35k after a massive electrical failure.
Hope that makes sense.
Ryan
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Glide slopes are one of the least documented areas of flight performance documentions. Back in WWII/WWI they wanted to know how fast it could get up not down! I will bet most sim developers use some guessing in this area, or let math figure it out based on the other areas of flight which are documented well.
I would assume HTC did his best to make it as real as possible as apposed to more "playable" since he has always strided to make his FM's super realistic for an aircombat game.
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Originally posted by CFYA
I have heard of a modern airliner gliding 200 miles from an altitude of 35k after a massive electrical failure.
Hope that makes sense.
Ryan
Modern airliners usually start and idle thrust descent on a 3:1 ratio at around 280 KIAS. That means about 105 nm from the airport from 35k. The DC10-30 with 10' longer wingspan than the DC10-10 and more residual thrust from it's more powerful engines used a 3:1 plus 20 additional miles and the -10 used an additional 10 miles. (Note the -30 had a 150,000 lb higher max takeoff weight). You could start down an extra mile earlier for each 10kts tailwind. It also took a mile to lose 10 kts of speed in level fight at idle so it took 10 miles at idle to slow from 350 KIAS to make a 250 KIAS speed restriction at 10k if you were already level. Lotta smash.:) Now days we have onboard computers that figure this all out for us. I found the actual glide ratio to be around 2.5:1 or a bit more in modern airliner simulators with all engines flamed out.
The normal "GLIDE SLOPE" to a landing for all civil aircraft is around 3 to 3.5 degrees. The GLIDE SLOPE is specified on instrument approach charts and flown by following a precise electronic beam or GPS calculated path until the visual approach slope indicator lights (VASI or PAPI) are in sight or touchdown in the case of autoland.
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VWE
Up against a 51d youd lose.
CFYA
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Just in case a 51 is to light I tried a 38L. Youd really lose there.
Weight is not the biggest factor gents.
CFYA
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Perk the Thermals!
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Any chance I could get them on demand? They would come in right handy when I lose the engine!:D
Ryan
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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.
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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.
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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.:)
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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.;)
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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
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Minor drift and yaw aren't really the same thing. B17 with 1 engine out will drift
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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.
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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
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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
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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
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Power off with 1 dead engine.
(http://i114.photobucket.com/albums/n277/1bronk1/ahss25.jpg)
Power on with 1 dead engine.
(http://i114.photobucket.com/albums/n277/1bronk1/ahss26.jpg)
Tried to keep controls neutral for the picks.
Like I said slip indicator differs with bj229r.
Bronk
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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.
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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.