How about the recoil?

[billeinstein]

I found an interesting web, calculating the recoil of the P-51.

 

http://www.thermospokenhere.com/wp/05_tsh/E232___P_51/P_51.html

 

I feel the recoil in the sim is a bit small. When firing for a long time on the ground with out brake, the aircraft doesn't move. Failed 3 guns on one side wing and fire in the flight, I feel very little skid in yaw. Even with long burst firing, this skid will not affect the aiming.

 

Wish devs can show some historical date of test or report on that if you have.

[Rotareneg]

That page is laughably wrong as it assumes that the plane somehow expends all the ammunition instantly.

[billeinstein]

That page is laughably wrong as it assumes that the plane somehow expends all the ammunition instantly.

Or you may calculate the dv of first shot of all six guns and the speed recovery before next 6 bullets are fired...:D

 

What we care about is the sim's effect.

[WildBillKelsoe]

the gun cannon balls.... :mad:

[Yo-Yo]

I found an interesting web, calculating the recoil of the P-51.

 

http://www.thermospokenhere.com/wp/05_tsh/E232___P_51/P_51.html

 

I feel the recoil in the sim is a bit small. When firing for a long time on the ground with out brake, the aircraft doesn't move. Failed 3 guns on one side wing and fire in the flight, I feel very little skid in yaw. Even with long burst firing, this skid will not affect the aiming.

 

Wish devs can show some historical date of test or report on that if you have.

 

Rather than to think, you'd better calculate the right recoil using your understanding of right recoil. The article you quated has at least two principal mistakes hidden behind a veil of scientific looking smoke.

[Echo38]

If a 150-lb. person can fire a fully-automatic .308 without being moved (and I know from personal experience that this is true), then I think a 10,000+ lb. airplane can fire a few .50's without being moved. Granted, the person isn't on roller skates, but, if you do the maths, the aircraft has a much higher mass-to-muzzle-energy ratio going on. (Also, the wheel-to-ground friction is many times higher in the case of the aircraft than in the case of the shooter-on-roller-skates scenario, due to the mass.)

[NineLine]

Wouldnt you see recoil movement if any substantial amount was applied in gun camera footage? I would say their isnt much unless each pilot is compensating very well in the footage.

 

[joey45]

That's vibration from the guns.

[NineLine]

That's vibration from the guns.

 

My point was I dont see any large movements when the guns fire that would lead me to believe there is any real noticeable amounts of recoil in the air, highly unscientific analysis by me, but that's what I do :)

[Echo38]

I blame IL-2 for the incorrect impression that some have about gun recoil; it was grossly exaggerated in that game.

 

Also: anyone else notice that the page linked in the O.P. listed the P-51's weight as 5400 lb.?

 

o O

___

[NineLine]

I blame IL-2 for the incorrect impression that some have about gun recoil; it was grossly exaggerated in that game.

 

 

Honestly the only reference I could find to recoil problems was structural damage, I believe it was a Yak (cant remember the variant) would actual be damaged if you fired over the 3 round recommended burst. Most weapons by that time had different forms of recoil buffers, springs, etc. Least from my limited quick search that is what I found.

 

Now if you unloaded your guns all at once there might be some felt, but I doubt that would have ever been done in a combat situation.

[Rotareneg]

Ok, ran some numbers:

 

Assuming an aircraft weight of 9200 pounds,

270 rounds per gun (so they all run empty at the same time,) 800 rpm per gun,

45 g per bullet, 3000 ft/s.

 

The total weight of the bullets fired is 160 pounds, and takes 20.25 seconds. The resulting thrust is 740 lbf.

 

Assuming the aircraft is floating in space with no drag, friction, engine thrust or anything, and ignoring the expanding gases from the powder, the aircraft will recoil 530.6 ft by the end of the 20.25 seconds, and end up moving backwards at 35.7 mph.

Edited December 1, 2012 by Rotareneg
I botched my numbers badly

[billeinstein]

I get the number about it, the recoil force should about 3000N if keeping fire.

 

Compared to this, if a p-51d is cruising with max cruise power of 790 HP at 280 mph, the thrust is about 4,706 N.

Edited December 1, 2012 by billeinstein

[Weta43]

Ok, ran some numbers:

 

Assuming an aircraft weight of 9200 pounds,

270 rounds per gun (so they all run empty at the same time,) 800 rpm per gun,

45 g per bullet, 3000 ft/s.

 

The total weight of the bullets fired is 160 pounds, and takes 20.25 seconds. The resulting thrust is 740 lbf.

 

Assuming the aircraft is floating in space (no drag, friction, engine thrust or anything)... the aircraft will recoil a whole whopping 6.6 feet during the 20.25 seconds of firing and end up moving backwards at a blazing 4 mph.

 

I think that would be true at the receivng end, at the firing end there's a substantial component of the recoil that comes from the high pressure gasses leaving the barrel, not the actual imparting energy to the bullet (propellant is ~ 1/4 the weight of the projectile, but leaves the barrel going many times faster) .

That's what muzzle brakes are about...

[billeinstein]

Ok, ran some numbers:

 

Assuming an aircraft weight of 9200 pounds,

270 rounds per gun (so they all run empty at the same time,) 800 rpm per gun,

45 g per bullet, 3000 ft/s.

 

The total weight of the bullets fired is 160 pounds, and takes 20.25 seconds. The resulting thrust is 740 lbf.

 

Assuming the aircraft is floating in space (no drag, friction, engine thrust or anything)... the aircraft will recoil a whole whopping 6.6 feet during the 20.25 seconds of firing and end up moving backwards at a blazing 4 mph.

wrong number:(

740 ibf @ 9200lb for 20.25s, the dv should be...15.96 m/s=35.71 mph. And 530.2ft, not 6.6ft.

Have you forgot the 9.8?

Edited December 1, 2012 by billeinstein

[Rotareneg]

That's not possible, I don't make mistakes... oh, wait. You're right. :D

[Yo-Yo]

I get the number about it, the recoil force should about 3000N if keeping fire.

 

Compared to this, if a p-51d is cruising with max cruise power of 790 HP at 280 mph, the thrust is about 4,706 N.

 

This table does not count gases. DCS does.

[Griffin]

Here's a modern video of P-51D static test firing.

 

http://www.eaavideo.org/video.aspx?v=1826158611001

 

I think the gun cam shakes so much because it's mounted in the wing rather close to the guns and the further out from the fuselage you are, the more it shakes. That's how I figure it anyway.

[joey45]

Plus the cameras used didn't have the anti-shake high tech stuff used today..

[billeinstein]

Plus the cameras used didn't have the anti-shake high tech stuff used today..

 

Neither should the cams in dcs I think:D

[billeinstein]

Finally I got the aircraft moving on the ground by the recoil.

Release the brake, lock the tail, remove all of the fuel, set unlimited ammo and firing.

If ammo is limited, the dv is not enough and the aircraft can only move less than one foot.

 

The recoil is also useful in swimming.:D

fire1.trk

[Chill31]

Here's a modern video of P-51D static test firing.

 

http://www.eaavideo.org/video.aspx?v=1826158611001

 

I think the gun cam shakes so much because it's mounted in the wing rather close to the guns and the further out from the fuselage you are, the more it shakes. That's how I figure it anyway.

 

It looks like this video shows clearly that the P-51 should move backwards when the guns are fired. If you watch the main tires, they rotate. It is not just "shaking."

 

While that first post of how much V change it should have is quite inaccurate, the undeniable effect from firing the 6 guns is that the plane should move if configured the same as that P-51.