Best dogfight gun?

In article ,
"Hog Driver" wrote:

If you actually ever get into the dreaded knife-fight in a phone booth, the
other guy is going to have second thoughts about screwing with an A-10 when
the nose erupts in a huge cloud of smoke well beyond the range he can employ
his gun.

Didn't some Warthogs chew up some F-15s in an exercise that way, once?
Sit in the weeds, wait for the Eagles to get in "close," and gun kill
them from a couple of miles off...

--
cirby at cfl.rr.com

Remember: Objects in rearview mirror may be hallucinations.
Slam on brakes accordingly.

What I have read here is a lot of hot air coming from people who have
never fired either of these weapons, and probably have never fired on
either an aerial or ground target with any weapon. Spool-up time on a
M61? Have you ever heard one shoot? You sure as hell can't hear it
spool up. I've fired them in the air and on the ground in the firing
butts - all you hear on the ground is a very loud BRRRRR with the
individual shots indistinguishable from the first one. Watching the
gun itself you see it go from 'stop' to 'blur' instantly. The only
difference I ever noted was that the SUU23 pod gun had a slight
'tail-off' as it fired itself dry when you released the trigger. Note
that the 100 rps in the hydraulic driven M61 (25HP motor) in the
F4/14/15/16/ give these aircraft a real high-deflection (actually,
all-aspect) capability - and if a fraction of a second spin-up makes a
difference between a hit or a miss all I can say is the shooter
didn't see the opportunity in time. Even in the electric drive (15HP,
67 rps) gun in the 104A I've seen gun camera film which showed that if
the M61 gun had been firing the other aircraft would have take two
dozen rounds, from nose to tail, crossing at 70+ degrees with the
shooter pulling max G attainable in the situation, just not enough to
track him but enough to get a good shot in at close range - about 100
yards. How do you do this? You start shooting early and hose him as he
sails past. BTW that 104A installation had a 3-mil dispersion - I've
seen that proven in the firing-in butts, too.
Walt BJ -

"Tony Williams" wrote in message
m...
The ideal gun for aerial combat will of course combine the best of all
worlds: a high rate of fire, instantly achieved; a high muzzle
velocity to minimise flight time; and projectiles large enough to
inflict serious damage with each hit (requiring a calibre in the 25 -
30 mm range). The optimum weapon among those currently developed may
well be the new GIAT 30M791 revolver, although its weight means that
two GSh 301s (or a GSh-30) could be carried instead, with a higher
rate of fire. If the Russian guns' 30 x 165 ammunition were loaded
with lighter projectiles for a higher muzzle velocity, its aerial
combat capabilities would be improved, at the cost of some loss of
ground attack effectiveness."

Is there more behind the "requiring a calibre in the 25-30 mm range"
than hand-waving to dismiss 20mm guns? Granted, bigger is better,
but why isn't 40mm required or 20mm enough?

Paul F Austin wrote:
"Tony Williams" wrote

The merits of the 27 mm BK 27 revolver as opposed to the M61A1 can be
clearly demonstrated. In the first 0.5 seconds of firing, the M61
fires 18 rounds massing 1.8 kg in total weight of projectiles, the BK
27 fires 14 rounds weighing 3.7 kg. In the first full second, the M61
fires 68 rounds weighing 6.9 kg, the BK 27 fires 28 rounds weighing
7.4 kg. In weight of fire, as well as the destructiveness of the
individual projectiles, the Mauser clearly has an advantage, albeit
one that the faster-accelerating M61A2 reduces somewhat. This is
significant in that dogfights frequently permit only the briefest of
firing opportunities, and although a skilled pilot anticipating a
firing opportunity can 'spin up' a rotary in advance, such notice
cannot always be guaranteed.

Tony, why have none of the Gatling guns been designed to be "armed"
and spun up with the ammunition feed disengaged and "fired" at full
rate by engaging the ammunition feed? It seems obvious enough. There
are some obvious issues in inertial loads in the ammunition train but
a "burst's worth" of rounds could be decoupled from the main ammo
tank.

One thing I've not thought of before and that's the gyroscopic effects
of a fast rotating drum on the directional abilities of an aircraft ?
It can't be that much of course or it would not have been used at all. I
assume that the drum is relatively low mass ?


Richard.

"John Keeney" wrote in message
...

"Tony Williams" wrote in message
m...
The ideal gun for aerial combat will of course combine the best of all
worlds: a high rate of fire, instantly achieved; a high muzzle
velocity to minimise flight time; and projectiles large enough to
inflict serious damage with each hit (requiring a calibre in the 25 -
30 mm range). The optimum weapon among those currently developed may
well be the new GIAT 30M791 revolver, although its weight means that
two GSh 301s (or a GSh-30) could be carried instead, with a higher
rate of fire. If the Russian guns' 30 x 165 ammunition were loaded
with lighter projectiles for a higher muzzle velocity, its aerial
combat capabilities would be improved, at the cost of some loss of
ground attack effectiveness."

Is there more behind the "requiring a calibre in the 25-30 mm range"
than hand-waving to dismiss 20mm guns? Granted, bigger is better,
but why isn't 40mm required or 20mm enough?

One reason is range but that's a mug's game, trying to compete with SRAAMs.
The other reason, lethality, is driven by the fact that fighters are a lot
tougher targets now than they were fifty years ago. In a progression of
lethality, during WWII, .50cal machine guns were adequately lethal against
fighter sized targets but not against bombers. With the advent of jet
propulsion, increased air speed required stronger structure and fighters got
physically tougher, so 20mm was optimum against fighters in the late forties
and early fifties. Supersonic fighters are tougher still, mostly because of
increase design dynamic pressure but also because they are stressed for
larger loads and higher g-loads, so the thought is that 20mm rounds have
inadequate Pk (given a hit).

Of course, gun installations are questionable now because the SRAAMs have
gotten so good and because guns in general pose a significant cost in
reliability (the firing forces become the design environment for all the
electronics in the vicinity) and a significant maintenance burden.

On Sat, 6 Dec 2003 11:23:25 -0000, "Richard Brooks"
wrote:

Paul F Austin wrote:
"Tony Williams" wrote

The merits of the 27 mm BK 27 revolver as opposed to the M61A1 can be
clearly demonstrated. In the first 0.5 seconds of firing, the M61
fires 18 rounds massing 1.8 kg in total weight of projectiles, the BK
27 fires 14 rounds weighing 3.7 kg. In the first full second, the M61
fires 68 rounds weighing 6.9 kg, the BK 27 fires 28 rounds weighing
7.4 kg. In weight of fire, as well as the destructiveness of the
individual projectiles, the Mauser clearly has an advantage, albeit
one that the faster-accelerating M61A2 reduces somewhat. This is
significant in that dogfights frequently permit only the briefest of
firing opportunities, and although a skilled pilot anticipating a
firing opportunity can 'spin up' a rotary in advance, such notice
cannot always be guaranteed.

Tony, why have none of the Gatling guns been designed to be "armed"
and spun up with the ammunition feed disengaged and "fired" at full
rate by engaging the ammunition feed? It seems obvious enough. There
are some obvious issues in inertial loads in the ammunition train but
a "burst's worth" of rounds could be decoupled from the main ammo
tank.

One thing I've not thought of before and that's the gyroscopic effects
of a fast rotating drum on the directional abilities of an aircraft ?


Which brings up something I've always wondered. Why doesn't the
compressor and turbines of a jet engine have that effect but on a much
larger scale? I imagine the gyroscopic effects of the rotor in an
F110 on an F-16 would be nothing to sneeze at.




It can't be that much of course or it would not have been used at all. I
assume that the drum is relatively low mass ?

"Scott Ferrin" wrote in message
...
On Sat, 6 Dec 2003 11:23:25 -0000, "Richard Brooks"
wrote:



Which brings up something I've always wondered. Why doesn't the
compressor and turbines of a jet engine have that effect but on a much
larger scale? I imagine the gyroscopic effects of the rotor in an
F110 on an F-16 would be nothing to sneeze at.


For one thing the modern aircraft have a greater ratio of mass
of aircfraft as a whole to the engine. The PW-200 series
engine weighs in at around 3400lb or rather less that 10%
of the F-16's all up weight and only a fraction of that is rotating.

In contrast the engine of a Sopwith Camel weighed around
300 lbs and was ALL rotating when the aircraft all up weight
was less than 1000lbs.

Then again the control authority of modern aorcraft is higher
and the fly by wire control system can compensate for
gyroscopic forces rather better than a human being.

Keith

Keith Willshaw wrote:

"Scott Ferrin" wrote in message
...
On Sat, 6 Dec 2003 11:23:25 -0000, "Richard Brooks"
wrote:



Which brings up something I've always wondered. Why doesn't the
compressor and turbines of a jet engine have that effect but on a much
larger scale? I imagine the gyroscopic effects of the rotor in an
F110 on an F-16 would be nothing to sneeze at.

It can be a problem at very slow speeds, which is why the Pegasus engine in
the Harrier has its two spools (low and high pressure) counter-rotate.
Offhand, I can't remember if the F100 or F110 do as well, but then a/c like
the F-15 and F-16 are unlikely to spend much time slow enough for it to
matter (thrust-vectoring nozzles can help there). OTOH, the engines for the
F-35 probably have to counter-rotate.

Guy

Which brings up something I've always wondered. Why doesn't the
compressor and turbines of a jet engine have that effect but on a much
larger scale? I imagine the gyroscopic effects of the rotor in an
F110 on an F-16 would be nothing to sneeze at.

It can be a problem at very slow speeds, which is why the Pegasus engine in
the Harrier has its two spools (low and high pressure) counter-rotate.
Offhand, I can't remember if the F100 or F110 do as well, but then a/c like
the F-15 and F-16 are unlikely to spend much time slow enough for it to
matter (thrust-vectoring nozzles can help there). OTOH, the engines for the
F-35 probably have to counter-rotate.

Guy


In general, engined have counterrotating spools for efficiency not gyroscopic
effect. Most Brit engines use thhis approach but it is hell on bearings because
of the higher rotaional speeds. The three spool RB211 is kind of the ultimate
in that regard.

I'd guess that gyro effect isn't really an issue with the airframe guys since
with most engines since the mass is concentrated more in the center of the
rotors instead of in the periphery whless gyroscopic and centrifugal forces are
generated.

From what I recall from my involvement in the F100-220 and F110-100 engines,
the engine bearing and structural guys are the most concerned because of loads
and load paths during throttle transients. Didn't come up during the
airframe-engine integration meetings. Don't recall it as an issue in my J79
flying days either.

My memory is hazy on this but I think the F119 in both the F-22 and F-35
versions does not employ counter-rotating spools either. Now what forces the
lift fan generates to the airframe is a different story I an sure.

Steve

Chad Irby wrote in message om...
In article ,
"Hog Driver" wrote:

If you actually ever get into the dreaded knife-fight in a phone booth, the
other guy is going to have second thoughts about screwing with an A-10 when
the nose erupts in a huge cloud of smoke well beyond the range he can employ
his gun.

Didn't some Warthogs chew up some F-15s in an exercise that way, once?
Sit in the weeds, wait for the Eagles to get in "close," and gun kill
them from a couple of miles off...

The problem with a GAU-8/A as a fighter gun is that the weapon and its
ammunition tank are so enormous that the plane has to be designed
around them, and they would use up a substantial part of the internal
volume of a fighter aircraft. Better to go with the Oerlikon KCA,
which fires equally powerful ammo in a much more compact package.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk
Discussion forum at: http://forums.delphiforums.com/autogun/messages/