Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Krusty on October 11, 2009, 01:05:19 PM
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I fly the B-25H once in a while... I'm terrible with the big gun. Have tried it on bombers, GVs, CVs, etc... Never noticed any speed loss, any vibrations, and backward motion.
Seems to have no recoil.
I saw this today:
http://www.youtube.com/watch?v=zpi11_iS8Nk&feature=related
B-25H test fire of the cannon. The entire airframe rocks backwards on its wheels. Looks like they TIED IT DOWN, which is surprising.
Maybe AH2's B-25H doesn't have enough kick?? :O
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Get very slight forward motion on the runway, fire the gun and see if you stop or get pushed backwards. I got one aircraft, N1K2-J or Il-2 I think, up to about 20mph backwards using the guns as thrusters.
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This is a myth that persists today with the A-10 Thunderbolt II. Due to conservation of momentum, there is no change in the forward velocity of an airborne aircraft during weapons fire of any kind.
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This is a myth that persists today with the A-10 Thunderbolt II. Due to conservation of momentum, there is no change in the forward velocity of an airborne aircraft during weapons fire of any kind.
Go to offline practice, set your ammo load to infinite, take up any airplane you like, full throttle and auto level, and hold down the trigger. You will loose airspeed. So if it is a myth, it is a myth that is modeled into AHII.
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This is a myth that persists today with the A-10 Thunderbolt II. Due to conservation of momentum, there is no change in the forward velocity of an airborne aircraft during weapons fire of any kind.
It is NOT a myth. Even the pilots in Korea knew this. One told a story of how a MiG was just outside of his Saber's gun range, and he knew if he took a shot it would slow him down even further, but the MiG was getting away so he sprayed a burst anyways, then turned back for home.
EDIT: The myth may be that you fall out of the sky or fly backwards or something. You DO slow down, that's a fact.
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This is a myth that persists today with the A-10 Thunderbolt II. Due to conservation of momentum, there is no change in the forward velocity of an airborne aircraft during weapons fire of any kind.
Really? Newton's Third Law seems to dictate the idea that there would be lose in speed, the only way to avoid this would be ways of dispersing the recoil of the gun through dampeners or something of that sort.
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What IS a myth is the stories that the recoil would cause the B-25 to immediately stop in mid-air, or be thrown backwards by the recoil.
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What IS a myth is the stories that the recoil would cause the B-25 to immediately stop in mid-air, or be thrown backwards by the recoil.
Assuming I did it right, a B-25 weighing 15,200Kg moving at 300MPH would have the Kinetic Energy of 136693816.9344 Joules, no aircraft mounted gun is going to stop that midair from recoil.
Not to say you were implying this of course.
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This is a myth that persists today with the A-10 Thunderbolt II. Due to conservation of momentum, there is no change in the forward velocity of an airborne aircraft during weapons fire of any kind.
sorry but... :rofl
The recoil of that 30 mm cannon you mention, is about equal to the thrust of one of the A10's engines. It's like hitting a brick wall, very rapid deceleration. Conservation of momentum, ehhh? :huh
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The recoil of that 30 mm cannon you mention, is about equal to the thrust of one of the A10's engines. It's like hitting a brick wall, very rapid deceleration. Conservation of momentum, ehhh? :huh
Which is exactly how A-10 pilots describe it.....
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:frown:
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:frown:
It's ok, it is well documented that "the myth" you presented, exists.
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Maybe AH2's B-25H doesn't have enough kick?? :O
I found this interesting so I went and tested it. It appears the AH aircraft have their brakes locked when sitting still and no throttle is applied (take planes on the CV for example, they sit still unless you add very little thottle, in which they will roll backwards).
I put the b25 so it was moving slightly forward, and when I fired the 75mm, it went from 1mph to 2mph (backwards using E6B). It looked almost exactly like the video you posted, except in AH you have to be moving slightly for it to take effect.
It appears the 75mm has the same recoil affect as all of the 50 cals on the b25.
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I think you have to test it in the air. Doing the same thing in a P47 you can get -10mph of speed up. It's not a matter of constant firing, it's how much 1 shot will slow ya down, that I'm wondering about. I usually slow down as much as I can so that I can milk as many shots on a single target as I can, and have never had problems with my nose dropping, or stalling out, or needing to goose the throttles, or anything in-game.
So it makes me wonder.
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I think you have to test it in the air. Doing the same thing in a P47 you can get -10mph of speed up. It's not a matter of constant firing, it's how much 1 shot will slow ya down, that I'm wondering about. I usually slow down as much as I can so that I can milk as many shots on a single target as I can, and have never had problems with my nose dropping, or stalling out, or needing to goose the throttles, or anything in-game.
So it makes me wonder.
For the most part you would already going down hill with the B-25H when attacking. Gravity helps keep airspeed up. Heck, even with throttles closed you have to be cautions of alt before nosing over. Those elevators come off real easy.
As for trying to snipe buffs... you'd have to have it firewalled just to keep up with any other buff.
As to the recoil itself it does push the nose around, difficult to get multiple shots off on a tank.
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Which is exactly how A-10 pilots describe it.....
I was reading this thread, and saw the post about the A-10, I was interested so I called my cousin, who used to fly them.
Firing the cannon on it DID induce deceleration, not enough to cause the plane to STOP or stall in any way, but it WAS noticiable. The other thing was that when they fired, the smoke from the gun, would be ingested by the engines, reducing thrust, and if fired for too long continuously (approx 3 seconds) it could even cause a flameout!
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Noobs
do not fire your guns ingame to try for overshoot......just saying...
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A long time ago I read something on an AC-47 nicknamed Puff the Magic Dragon. She had 3 massive gatlin guns each capable of firing 6000 rounds a second out one of her sides, able to cover a football field in just over 3 seconds of fire. But the reason I bring it up (unfortunately I couldn't locate anything for or against to post as well) is I remember it saying that if she fired all her guns at once for too long it would cause her to slow enough to stall and drop from the sky. If anyone could confirm or deny this, please, as like I said, I can't remember where, just the name and the story. :airplane:
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A long time ago I read something on an AC-47 nicknamed Puff the Magic Dragon. She had 3 massive gatlin guns each capable of firing 6000 rounds a second out one of her sides, able to cover a football field in just over 3 seconds of fire. But the reason I bring it up (unfortunately I couldn't locate anything for or against to post as well) is I remember it saying that if she fired all her guns at once for too long it would cause her to slow enough to stall and drop from the sky. If anyone could confirm or deny this, please, as like I said, I can't remember where, just the name and the story. :airplane:
Spooky
http://en.wikipedia.org/wiki/AC-47_Spooky
Since it fired out the side...hard to slow it down. Now push it sideways?
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The sideway push can (and probably will) slow it down because of the added drag. If that'd be enough to stall the aircraft I don't know, but consider that it must fly in a wide circle and bank to get guns on target in the first place. So the pushing motion would be outwards and upwards in the turn. The C47 isn't very fast, nor has it very powerful engines, so I can believe there would be a stall if the guns were fired continuously as the aircraft is very heavy laden with the guns and ordnance on board.
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I can certainly admit to being wrong, but I just can't get my head around this. Any physics geeks out there who can better explain the forces at work?
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http://www.youtube.com/watch?v=iH48Lc7wq0U
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Thanks for the video.
So, the kinetic energy generated by the fired projectile acts against the forward movement of the aircraft? Let's look at the numbers.
The A-10 Thunderbolt II has an average loaded weight of 42,000 pounds (as listed on Wikipedia for anti-armor missions). At 340 mph (cruise speed, approx. 500 fps), this translates into about 163.2 million foot-pounds of energy (Weight in grains times velocity in fps squared divided by 450,240).
The GAU 8/A generates approximately 178,482 foot-pounds of energy with each shot (6560 grain projectile at 3500 fps). This is about 0.00109 the kinetic energy of the aircraft. Added together, this makes a 1 second burst (65 rounds) from the GAU 8/A about 11.6 million foot-pounds, or about 0.071 the kinetic energy of the aircraft.
So according to my calculations (please check my math), a one second burst from the cannon translates into a 7.1% loss in the forward velocity of the aircraft. One can presume longer bursts have a greater effect, but at some point the continued thrust of the engines would have to mitigate the effect of the cannon.
I should have crunched the numbers first and saved myself the embarrassment.
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Ok I've not checked the numbers on this so this won't be exact. However, consider that the entry speed on the attack run is not 'cruise speed' but full throttle and as much speed as you can get. So I'm assuming that'd be closer to 500 mph than 340. Then, a burst with the GAU would be against a group of vehicles perhaps a couple seconds long. Again using your numbers of 7.1% speed loss per second, that's 14.2% of 500 mph in 2 seconds which add up to just over 70 mph in 2 seconds. Now tell me that decrease in speed will not be noticeable in the cockpit. It's a deceleration more violent than what most stock cars can perform on the strip in acceleration.
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Making strafing runs at maximum speed is contrary to accuracy, aim, stability, and plane control.
Would be silly to assume it's flying 500mph or so, especially when the A-10 loiters at cruising speed (sometimes shutting off 1 engine?) waiting for a call to come in.
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Also, you're not just looking at the projectile, it's the giant jet of expanding gasses that project the shell as well. A space shuttle is extremely massive, and heavy, but it only takes a tiny burst of jets (thrusters) to move it about. A plane flying in-air can be slowed by the gasses shooting forward from gun barrels.
A giant cargo plane can be launched from a standstill to takeoff speed in a split second by a few (small diameter) rockets on its side [ED: I'm thinking Blue Angels C-130 here, but many other instances apply]
Don't discount firing super-high-caliber guns while flying at slow speeds as a means for slowing/impeding forward speed.
The question is: How much does it do in-game already on our B-25H?
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Making strafing runs at maximum speed is contrary to accuracy, aim, stability, and plane control.
Would be silly to assume it's flying 500mph or so, especially when the A-10 loiters at cruising speed (sometimes shutting off 1 engine?) waiting for a call to come in.
Coming in hot with the possibility of taking return fire, I don't know about you but I'd want to move as fast as possible. The loss in accuracy is a moot point as the cannon on the A10 was never known to be a precision weapon. If you want precision, drop laser guided munitions from 20,000 feet.
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Speaking from game play experience, when you fire the B25's cannon you can sometimes notice the speedometer "shaking" abit from the shot. However the recoil is not enough to have any real affect on the aircraft as the B25's gun fires far to slowly for this.
On a side note though, and as stated earlier in the tread, if you "unlock" your wheels and fire the B25's guns on the runway it will start rolling backwards. But again this is true for any plane with a large gun package.
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Used to fly H2H a lot, and with their silly ammo loadouts, jug would have like 15 THOUSAND rounds, and consequently handle even more poorly than normal. Keeping trigger held down for 2-3 min on climbout would drain lots of excess ammo, but it REALLY impeded acceleration
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That's a misconception.
When ammo multiplier is turned UP, the ammo does not weigh more than the standard ammo loadout would weigh. Otherwise you'd have P-47s weighing in at 150,000lbs and never go anywhere.
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That's a misconception.
When ammo multiplier is turned UP, the ammo does not weigh more than the standard ammo loadout would weigh. Otherwise you'd have P-47s weighing in at 150,000lbs and never go anywhere.
Yep you right, has it always been that way?
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Always.
HTH rooms since day one were running a million x ammo multipliers, flies like "1x weight" onboard.
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Spooky
http://en.wikipedia.org/wiki/AC-47_Spooky
Since it fired out the side...hard to slow it down. Now push it sideways?
She was at Thunder Over Michigan in July. My pop, son and I walked through her. Gatling Guns still attached and looking as badass as ever.
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Not this is scientific data, but my neighbor (Passed away 2 months ago at 85 :salute) worked on the B-25H main guns (along with turrets). In a discussion he mentioned the the recoil on the 25H in level flight was enough to slow the plane down. He also said, and I quote "That son of a Biscuit would shake the whole Flipping plane, you'd swear the damn wings were going to rip off". Little cleaned up, but you get the picture.
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Also, you're not just looking at the projectile, it's the giant jet of expanding gasses that project the shell as well. A space shuttle is extremely massive, and heavy, but it only takes a tiny burst of jets (thrusters) to move it about. A plane flying in-air can be slowed by the gasses shooting forward from gun barrels.
The space shuttle only takes a tiny burst of jets to move around because there is no air resistance in space. Due to conservation of angular momentum, the shuttle will spin unimpeded although its velocity vector would be approximately the same. This is why "dogfighting" in any type of real space combat would be pretty boring - every spacecraft could essentially point its nose at you at will (though the velocity vector may take quite some time to change).
As far as the giant jet of expanding gases - the whole point of those gases is to transfer momentum from the gun platform (the aircraft) to the projectile. Assuming those gases transfer momentum at 100% efficiency and ignoring possible drag effects, you do not need to consider the gases AT ALL, as conservation of momentum then insures that all that momentum went from the plane into the projectile.
Of course it's not possible that momentum is transferred 100% efficiently, but even so, I doubt the momentum loss from an inefficient propellant mechanism can be significant enough to throw the deceleration estimate off too much. This part I'm not sure on, as I'm not familiar with the actual details of projectile cartridges and how efficiently momentum is transferred, but I'm guessing gunmakers have made it a point to refine their designs over the years so as to transfer momentum as efficiently as possible. More oompf from the same amount of chemical.
But to make an analogy to the space shuttle turning using thrusters is just absolutely faulty.
Edit: As to your original question - you can get a basic idea by just multiplying the projectile speed and projectile mass. This will give you momentum transferred. Then just divide the momentum by the airplane mass to get the instantaneous loss in airspeed. Since the B25H doesn't fire its big gun continuously, you don't need to consider thrust or gravity - you will instantly lose that amount of airspeed. The thrust/gravity aspects only matter insofar as how quickly you gain that speed back.
Even with HTC's advanced physics modeling, I doubt they model the jet of gases, so you can probably just ignore that part. If they do model it, then it only matters assuming the jet was actually significant due to an inefficient firing mechanism, which I again doubt.
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Expanding gases coming out of the gun barrel is just a side effect, of sorts. All the acceleration of the projectile that will occur, is while the projectile go down the barrel toward the muzzle and once outside the barrel it will hit v0 and decelerate from there on. The deceleration of the plane is because of the acceleration of the proj forward, and the expanding gases escaping the barrel muzzle at high velocity, also directed forward. If you want to be exact about it, it's not the plane accelerating the projectile forward, but the expanding gases in the barrel. These gases work both ways directed by the barrel forward against the projectile and backwards toward the weapon itself (don't know the english term) and the aircraft it's fixed in.
The conservation of momentum in the case of the space shuttle is because it operates in vacuum, airplanes do not. So the space shuttle can burn thrusters for 0.1 second and still rotate a full 360 degrees since there is no atmosphere slowing down the continuous motion. The space shuttle is at "rest" with the gravitational pull equal to the acceleration force by the orbital trajectory it's in. An aircraft travelling through the earth's atmosphere will rarely achieve a true state of equillibrium, but will always have a number of forces pulling it to either direction be it turbulence, drag, thrust, lift, gravity or any type of control surface output to alter the flight path. So an aircraft is not comparable to the space shuttle as they operate in completely different conditions.
Just trying to clarify what boomer said. Not that I felt it is really needed but for the sake of clarity.
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We must be the nerds of our squad, Turner. :lol
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Not that this brings up anything to the discussion but look how cramped the B-25H was. It must have been terribly uncomfortable being the tail gunner, having to rest on your knees like that. I didn't know that the waist gunner manned both waist guns, thought both positions were fully crewed.
(http://www.historyflight.com/images/content_aircraft/b25h_cutaway_color.jpg)
ack-ack
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All I know is that if you get an Me262 up to maximum sustained speed in AH and then fire all the guns, it slows down quite a lot.