The A-10 is an effective support aircraft, mainly because of its Avenger GAU-8 cannon. Suppose the enemy has very little armour? Even if the cannon is loaded with HE ammo instead of AP the high velocity of the rounds fired from a high angle will bury them in the ground, making the weapon less effective for attacking infantry.
The Avenger gun has a training round that consists of a stack of washers in an aerodynamic casing. This breaks up when it hits the ground, minimizing the danger of ricochets. Suppose we expand on this concept. Instead of a stack of washers the casing contains several donut shaped explosive charges threaded on a pencil shaped detonator. As the round hits the ground it breaks up, and the deformation of the detonator triggers the explosive charges. This idea can be expanded further-a small charge in the nose of the shell ejects the explosive submunitions from its base, allowing them to scatter and explode several inches about the ground.
Armour Expert Ralph Zumbro adds:-
Something you may not know about the Avenger 30mm round. The TRAINING ammo gives a remarkably good imitation of a solenoid jackhammer when applied to cinder block construction.
The Training rounds breaking up as they hit the ground may have a fragmention effect if fired into the middle of an infantry formation.
William Clarke has another idea for improving the Avenger GAU-8 and GAU-13
Here's a little tidbit I just learned myself a month ago. The 30mm HV API(DU) round of the A-10 is NOT APDS. It is a standard full-bore round. So I did a little math, and determined that a 30mm APDSDU would have MORE kinetic energy @ 1000M as the current round has at the muzzle. The US just adopted a 20mm APDSDU recently, so a 30mm should be no problem. A 1,000M the current round will penetrate almost 200mm of RHA(steel) plate. At the muzzle it carries 40% more KE, so would penetrate 280mm of RHA. The APDSDU would penetrate greater than 280mm @ 1000M.
Just in case you'd like to check my math here's how. The current API fires a .66lb projectile @ 3,500fps. It loses about 75-90fps per 100M(As per an A-10 pilot I know). This yields an average velocity of 2,675fps @ 1,000M. Your typical APDS round will carry 25% more initial velocity than an equivalent weight full bore, and generally has a BC 20% superior(due to the vastly superior aspect ratio of an APDS projectile) to that of the full bore. This would yield an initial velocity of 4,375fps. The average velocity loss per 100M would be approx. 66fps. This yields a velocity of 3,715fps @ 1000M. As you can see, the APDS would seriously outperform the current round. To calculate KE just use the following formula- MxV2x 0.5 This will yield KE in a vacuum. Next / the result of the first formula by 32.16, which is atmo pressure @ sea level. Finally, the original formula is for objects weighing one pound. For a projectile which weighs .66lb, as the 30mm does, just multiply by .66 This will yield Kinetic energy in Ft-lb.
Here are my estimations of the performance of the 30mm HV cannon round with a 15mm APDS penetrator vs. a FB projectile @ the muzzle, 500m and 1000m
| ||PGU-14 30mm HV-APDU|| ||30mm HV-APDSDU|| |
|Range||Velocity||Energy foot lb(fpe)||Velocity||Energy foot lb(fpe)|
These calculations are based on a 0.66 lb penetrator(the weight of the DU penetrator of the current round), and an aspect ratio of 3.5:1 for the full bore, vs. 7:1 for the APDS. Note also that the 15mm APDS, assuming 50% less frontal area than the full-bore will exert it's energy on an area half the size of the FB 30mm, greatly increasing penetration performance at like velocities. As is plainly evident, a 15mm APDS penetrator will possess MORE energy at 1,000M than the full-bore currently produces at the muzzle.
Such a round, given equal sectional density, will penetrate approximately 30-40% more armor at a given range, as well as bestowing the beneficial side-effects of drastically reduced flight time, as well as a far greater resistance to wind effect. Obviously, this would allow for easier and more accurate targeting, especially at longer ranges.
Conversely, a full-blown APFSDSDU round would add even more performance, with velocities in the region of 5000fps!
However, such a projectile would require the use of a smooth-bore muzzle to gain full potential. This would be a VERY expensive re-fit considering each A-10 has 7 barrels.
It would also preclude the effective use of current full-bore HVAPDU and HE ammunition, which requires rifling for stabilization. Therefore, the APDS is the most effective way to go.
The above figures clearly demonstrate the superiority of the APDS design. I think a one second burst of 35x 30mm APDSDU rds from a GAU-13, each penetrating 280-290mm of armor at 1000M would REALLY ruin a tanker's day.
"A-10 ammo. The GAU-8/A as used in the A-10 doesn't use APFSDS for the same reason that no other plane does - too much risk of the discarded sabots being sucked into the engines."
Author "Rapid Fire: the Development of Automatic Cannon, Heavy Machine Guns and their Ammunition for Armies, Navies and Air Forces"
Details on Military Gun and Ammunition website
It has also been suggested to me that 30mm HE rounds using some form of proximity fuse would be an effective anti-infantry load.
Ralph Zumbro comments:
The Germans have a muzzle set projo fuze for a 35mm AA gun that can be set by an on-board computer for any distance including muzzle action. If that were scaled down to 30mm, the A-10 would be able to duplicate the effect of tank gun cannister from CAS altitude. It'd be like tripeling the ammo capacity.
This is an excellent idea. Such fuses are already in developement for 30mm weapons -I've been advocating them for ASP cannon for several years.
LTC Walter Bjorneby (USAF) comments
All you need for antipersonnel 30mm is a frag load with a superquick fuze: - neither of which require any new inventions.
There are twin-50 gun pods. Also in-your-face CBU24 is a good CAS weapon if the friendlies aren't real close. We used it releasing at about 2400 foot slant range with the radar-fuzed canister opening up at 800 AGL. 665 mini-frags in an area about 50m wide and 100m long.
Also - I hate to say this but DOD's charge is to defend the USA - any special aircraft to fight third-world wars will have to be very badly needed and very heavily fought for. (PW: Which is will be and therefore must be) After having thought this over for some time now I'd go for a STOL OV10 with more wing and bigger engines and tires. The engines it had were a shame, just as are the engines on the A10. Nice engines, but too small for the mission. Gotta be big enough to load the bird wall-to-wall and still maneuver for CAS.
FWIW the superquick fuze is detailed in my pre-WW2 'Elements of Ordnance'. I'm sure a lot simpler one could be made nowadays. Also there was a plan in the late 60's to use rocket motors from the old MB1 Genie to propel CBU24s for standoff flak suppression, sort of like the USN's Skipper standoff bomb. Don't know what happened to the idea - too much competition and not enough money I suppose.
2.75" FFARs with the M255 flechette warhead would probably work quite well too, particularly if fitted with a Laser guided head