Can gun recoil really slow a fighter?

[GregP]

I hope they DO keep the A-10's in service. With today's avionics, an avionics upgrade for teh A-10's might not be a bad idea, either.

I believe the experiences of pilots in a type are sufficiently factual for me, but I don't wish to continue to argue about it. Though we disagree, it isn't exacly a cosmic argument, is it? Cheers to you.

I'd purely LOVE to fly an A-10 and find out for sure, but I stand a better chance of marrying Sandra Bullock than I do of flying an A-10. One can hope ... and maybe pigs CAN fly.

 

[tyrodtom]

When a OH-6 (Loach) was armed with a minigun, it was stuck out on a pylon on the left side.
If it was fired from a hover, the helicopter would yaw left, but the pilot could easily compensate with right pedal.

If fired in flight, it had the same effect, but less so.
The minigun had two rates of fire, 2000 rpm, and 4000 rpm. The yaw effect was greater at the high rate.

I wouldn't even have noticed it myself, until it was remarked on by the pilot.

 

[CobberKane]

Noticed a dumb mistake I made in my calcualtions on page one - somehow I attributed the P-51 a weight of nine metric tons (!!). Actually its about half that, so firing the guns should slow the aircraft by about eleven miles per hour, per second. If a five second burst slowed the fighter by 44mph, that really is getting quite significant, even at high speeds.

 

[Francis marliere]

I have a pic somewhere of the Missouri firing a broadside. You can see a wave at the bow, where the recoil is driving the ship sideways at a noticeable speed. And that's a 60K ton ship! Somewhat bigger guns, too, but still....

I am afraid that is an urban myth : battleships don't move sideway when they fire (anyway, they should rather capsize). What you see on the picture is the effect of blast on the water.

Best,

Francis Marliere

 

[vikingBerserker]

I don't think it's a myth. It was said the HMS Rodney did the same thing when firing broadsides.

 

[Shortround6]

I can believe the battleship moves sideways, but part of the question is at what speed. I have moved a 30 ft Ketch that weighed over 4 tons without much trouble using one leg as have many people who have pushed a boat of that size away from a dock.

Sure doesn't mean I can stand in the road and slow a 2 ton car moving at 40mph very much by kicking it as it hits me

 

[drgondog]

nine 16 inch guns firing a 2000 pound projectile at 2800 ft (?) per second would cause both a lateral displacement and a rolling moment. How much? 60,000 tons is a lotta weight being buoyed in much more viscous fluid...

 

[drgondog]

When a OH-6 (Loach) was armed with a minigun, it was stuck out on a pylon on the left side.
If it was fired from a hover, the helicopter would yaw left, but the pilot could easily compensate with right pedal.

If fired in flight, it had the same effect, but less so.
The minigun had two rates of fire, 2000 rpm, and 4000 rpm. The yaw effect was greater at the high rate.

I wouldn't even have noticed it myself, until it was remarked on by the pilot.

A simple comparison between the OH-6 and the Mustang is to assume MV ~ same, 150gr 7.62, 700gr .50 Cal :

At 2000 rpm for mini gun and 600 x 6 (3600) rpm for 50
2000/60=33.3 per second
150gr x 33.33 = 5000 grains per second = .7 pounds/sec at 4000rpm = 1.4 pounds/sec
3600/60= 60 per second
700gr x 60 = 42000 grains per second = 6 pounds/sec

50 caliber battery ~ 8 times the mini gun at 2000 rpm

T

 

[drgondog]

I hope they DO keep the A-10's in service. With today's avionics, an avionics upgrade for teh A-10's might not be a bad idea, either.

The A-10C has a major upgrade in avionics. The cockpit layout is not so different but the image panel on right center for both guidance purposes and 'seeing' is larger. Also DM has a complete IRAN facility which is also rebuilding and installing new wings for the A-10A which is reaching end of life on fatigue cycles. There is also an engine shop that brings all the A-10 fans to spec.

I believe the experiences of pilots in a type are sufficiently factual for me, but I don't wish to continue to argue about it. Though we disagree, it isn't exacly a cosmic argument, is it? Cheers to you.

I'd purely LOVE to fly an A-10 and find out for sure, but I stand a better chance of marrying Sandra Bullock than I do of flying an A-10. One can hope ... and maybe pigs CAN fly.

I have flown the A-10A and A-10C simulators as well as the F-15E and A-7D (long time ago). My daughter has never flown before, but I was able to teach her (A-10 simulator) to take off, pull high G level turns, roll, Cuban 8 and chandelle - then land with only one prang.. the A-10 instructor put me in my place by simulating an ILS approach below minimums - then cut the hydraulic system at low speed on final. I did not survive it.

BTW - the A-10 has a noticeable reduction in airspeed from my perspective as an observer on the range when the 30mm is zipping away.

 

[tyrodtom]

+Those guns on battleships aren't mounted solid, they recoil thru many feet, the recoil soaked up by different systems, you'll still have some left over recoil, but only a fraction of what the gun produces.

Hasn't anyone ever seen a real Civil war era cannon fire a solid shot ? They're driven back several feet. Don't go by what you see in the movies, they're firing blanks, usually through a subcaliber adapter.
One of the great advances in artillery was the invention of the recoil absorbers in the French 75mm in the late 19 century, or early 20th century.
It meant artillerymen didn't have to move the cannon back to position after every shot to aim it.

Most aircraft automatic armaments are recoil operated, the main body of the weapon has to be mounted fairly solid or the weapon won't function.
Even a M1911A1 ( 45 auto ) won't fire the second shot if the firer doesn't hold it firmly, it's called "limp wristing"

 

[Shortround6]

The recoil impulse didn't go away. It is just spread out over time, the total energy is the same. A long shove instead of quick punch.

The French 75 used a recoil spade and locked wheels to prevent rolling while the barrel recoiled. The lower peak load meant the carriage could be lighter without breaking or flipping. Put a castor under the recoil spade and unlock the wheels and you might be surprised at how far the the gun would actually move.

 

[silence]

On Battleships moving sideways, please read this paper, complete with calcs and addendums:

Do Battleships move sideways when they fire?

Landgraff - if his is still alive - was a Naval Architect Technician at the Long Beach Naval Yard for almost 40 years. You can read a short bio here: Richard A.Landgraff Biography.

 

[silence]

I have flown the A-10A and A-10C simulators as well as the F-15E and A-7D (long time ago). My daughter has never flown before, but I was able to teach her (A-10 simulator) to take off, pull high G level turns, roll, Cuban 8 and chandelle - then land with only one prang.. the A-10 instructor put me in my place by simulating an ILS approach below minimums - then cut the hydraulic system at low speed on final. I did not survive it.

BTW - the A-10 has a noticeable reduction in airspeed from my perspective as an observer on the range when the 30mm is zipping away.

I got on the SR-71 simulator once. What a rush!

 

[bobbysocks]

i read that comment by the p47 pilot and iirc he was approximating a 25-40mph loss of airspeed......which i find damn near impossible. IF you had a plane on the tarmac and idling with the brakes off and fired the machine guns...it would probably roll the plane back a little....but so could a man pushing it. IF you were flying right at stall speed...you would probably lose a few mile an hour and break into the stall. but a 10 to 15,000 lb ac moving at 300+ mph isnt going to feel hardly a loss of speed. you will get vibration and probably plenty of it.. as witnessed in gun camera footage. here is the recoil of a semi auto 50 cal. the guy in the first video is shooting one handed with the bipod resting on the table then with arms extended. the guy in the second is shooting semi from the hip. yes i understand that there were 6 MGs on the mustang ( and 8 on the 47...but the 47 was also a couple thousand lbs heavier too ) and firing at ~ 600 rpm. the reverse thrust from those guns is going to be minimal at best....



View: https://www.youtube.com/watch?v=RzUAQoyvrOw

 

[bobbysocks]

View: https://www.youtube.com/watch?v=DoJAA5JIa1I

 

[tyrodtom]

The Barrett has a very effective muzzle brake, and other modern recoil reducing features, it can't hardly be compared with recoil of a M2 .50 cal. designed and refined in the early 20th century.

 

[CobberKane]

There seem to be a few misconceptions floating around. Firstly, whatever effect the recoil of the guns has on the forward speed of the fighter will remain constant, irrespective of the speed of the fighter prior to firing. Ergo, if a five second burst slows my Mustang by 30mph, it will do so whether the Mustang is travelling at 400mph or 150 mph. Of course, the degree to which the Mustang slows expressed as a percentage of it's inital speed will change, but the the actual speed it looses will be the same.
Secondly, recoil damping devices will do nothing to reduce the negative acceleration imparted by firing the guns on a fighter, battleship or anytying else (including a rifle). The force of the recoil will be spread over a longer time period, but it wil be the same. The only way to completely isolate a fighter from the effects of recoil is to have the projectile carry its propellant with it as it leaves, as with a rocket.
Regarding the P-47, as Bobbysocks mentioned it has more guns than the P-51 but also more weight. 25mph loss of speed for a five second burst seems in the ballpark, maybe 40mph for a few long bursts fired in close succession.

 

[tyrodtom]

Actually a muzzle brake doesn't spread the recoil over a longer period, it pushes the rifle forward against the recoil, reducing felt recoil.

 

[bobbysocks]

25mph loss of speed for a five second burst seems in the ballpark, maybe 40mph for a few long bursts fired in close succession.

i dont think its going to be anywhere near 25mph....maybe closer to 5 tops if that much.

and yes the Barrett has an very efficient muzzle break and dampening system....but it doesnt reduce recoil by more than 50% over a ma duce....its going to take a heck of a lot more than 6 ot 8 of them to slow down a 5+ ton ac with inertia.

 

[GregP]

Hi Bobbysocks,

We operate a P-47. A man pushing for all he is worth won't move a P-47 unless he is strong and pushing against a wall. We've seen a small tow tractor simly spin the tires when trying to move it on smooth concrete.

If the engine is idling, the man might get dragged forward or run over, but he won't move it at all.