WOW - Shots fired at skydiving plane in NY...

"G.R. Patterson III" wrote in message
...
Ok, I admit to not paying attention, but didn't some thread state that
thrust
and horsepower are equivalent? Or a 2/1 ratio? Something like that.

Nope. Or rather, if some thread did say that, it wasn't correct.

There's no single ratio to convert thrust to horsepower. You need to take
into account the aircraft's speed as well.

I have a 160 hp engine. I'd be moving backwards shortly after hitting the
trigger.

Well, regardless of the conversion, a 850 pound recoil thrust would
certainly hurt your airspeed. Hard to say exactly how much, since it would
depend on how long that 850 pounds of thrust was acting on the airframe.

Seems to me that there's a pretty good chance the force would just tear the
gun from the airframe, or break the airframe. Assuming a structure strong
enough to withstand it, you might find you can't take off with your 160hp
engine.

However you slice it, there's problems afoot with the plan.

Pete

I came up with the 850 lb from (probably defective) memory. I worked it out
once based on muzzle velocity, firing rate (6,000 rpm) and bullet mass, to
see if Arnold or Jesse could actually hold and fire a minigun hand held. I
think I ignored propellant mass. IIRC the number was 850 lb. The number
that's more interesting (and accurate because it's quoted in a book I have)
is for the 30 mm Avenger gun in the A-10. That one produces 9,000 lb of
thrust at its maximum rate of 4,200 rpm, which effectively cancels out one
engine! I was thinking about a movie plot once where someone would mount an
Avenger gun in a full sized van (rigidly, firing forward) to use for some
nefarious purpose. Unfortunately, if the van plus gun weighed 9,000 lb, the
acceleration would be - 1 g backwards. Might be a problem...

--
Bob (Chief Pilot, White Knuckle Airways)


"Peter Duniho" wrote in message
...
"G.R. Patterson III" wrote in message
...
Ok, I admit to not paying attention, but didn't some thread state that
thrust
and horsepower are equivalent? Or a 2/1 ratio? Something like that.

Nope. Or rather, if some thread did say that, it wasn't correct.

There's no single ratio to convert thrust to horsepower. You need to take
into account the aircraft's speed as well.

I have a 160 hp engine. I'd be moving backwards shortly after hitting
the
trigger.

Well, regardless of the conversion, a 850 pound recoil thrust would
certainly hurt your airspeed. Hard to say exactly how much, since it
would
depend on how long that 850 pounds of thrust was acting on the airframe.

Seems to me that there's a pretty good chance the force would just tear
the
gun from the airframe, or break the airframe. Assuming a structure strong
enough to withstand it, you might find you can't take off with your 160hp
engine.

However you slice it, there's problems afoot with the plan.

Pete

In article , Peter Duniho
writes

Well, regardless of the conversion, a 850 pound recoil thrust would
certainly hurt your airspeed. Hard to say exactly how much, since it would
depend on how long that 850 pounds of thrust was acting on the airframe.

Seems to me that there's a pretty good chance the force would just tear the
gun from the airframe, or break the airframe. Assuming a structure strong
enough to withstand it, you might find you can't take off with your 160hp
engine.

What is needed to assess that effect better is
1. The mass of each shell
2. The muzzle velocity
3. Rate of fire
4. Time for shell to accelerate down the barrel and/or effective
muzzle length.

Rapid but short applications of force might shake the airframe violently
rather than stop it in mid air. 3000 ft/sec in 5 ft might only take less
than .007 secs.

As long as the weapon is rigidly fixed to the airframe it is the
momentum change that the airframe feels in terms of velocity.
--
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