Perhaps this isn't on-topic, but is the A-10 effective against tanks (tank armour) when using its cannon?

For example, this page claims:

Using the cannon, the A-10 is capable of disabling a main battle tank from a range of over 6,500 m.

Is that true?

If that were so, why does a "main battle tank" (e.g. an M1 Abrams) have a 120 mm gun -- contrast that with the A-10's 30 mm cannon?

I thought that in WW2 you needed something like a 75 mm or 88 mm gun to be effective against the then-heavy tank armour. And the gun on a "main battle tank" has if anything increased in size since then -- or converted to missile instead of projectile -- is a 30 mm cannon effective?

Is the armour-penetration of an A-10 exaggerated (if it is effective against only e.g. softer armour than main battle tanks)? Does the cannon being mounted in a plane make it especially effective (I'd guess not, the muzzle velocity of a GAU-8 is 1000 m/s and and A-10's airspeed only adds 200 m/s to that)? If it is effective then why isn't that the primary armament of a main battle tank?

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    $\begingroup$ This question is as much about, "why aren't tanks equipped with gigantic 30mm gatling guns" as anything - which is way, way off topic. That the A-10 is effective as a tank killer is, imho, sufficiently on-topic, but the explanations for why tanks don't use the guns that aircraft do, and vice versa, really isn't. $\endgroup$ – Ralph J Mar 7 '19 at 1:02
  • $\begingroup$ I think it's more-or-less on-topic, e.g. Why do fighter jets still have guns/cannons? seems purely about armament rather than flying. $\endgroup$ – ChrisW Mar 7 '19 at 1:06
  • $\begingroup$ The last question was an afterthought to express scepticism -- "If a 30 mm cannon were really effective against main battle tanks, then wouldn't they be used by tanks, instead of the 120 mm guns that they actually use?" $\endgroup$ – ChrisW Mar 7 '19 at 1:10
  • $\begingroup$ Your source quoting 6500m for the gun seems wildly optimistic. Killing something at that range with a Maverick, possibly. But the wikipedia page says 4000m effective, 12,000m max range. To address the afterthought question, tanks handle one big recoil well; aircraft handle sustained recoil well. Neither would do well the other way around. $\endgroup$ – Ralph J Mar 7 '19 at 1:14
  • $\begingroup$ @RalphJ Your source quoting 6500m for the gun seems wildly optimistic Yes, I think so. "My source" was simply one of the top Google search results on the subject. And I'm even sceptical whether they're effective at any range against a "main battle tank" -- that's my question -- maybe something quite a bit older, or lightly-armoured personnel carrier -- that I could believe easily. $\endgroup$ – ChrisW Mar 7 '19 at 1:18

Well it depends....

It depends on the tank, where you hit it, what angle you hit it, how far the A-10 was from the tank when it fired, and what kind of ammunition was used.

Wikipedia quotes that a GAU-8/A firing the PGU-14/B depleted uranium API ammunition offers the following armor penetration capability.

Armor penetration of Armor-Piercing Incendiary ammunition, BHN-300 RHA, attack angle 30 degrees from vertical:

  • 76 mm at 300 meters
  • 69 mm at 600 m
  • 64 mm at 800 m
  • 59 mm at 1,000 m
  • 55 mm at 1,220 m

Whether that's a declassified spec with all other known values a secret or a realistic representation is unknown. I'd say it sounds reasonable. Tanks tend to have heavy armor on the front and sides but lighter on the top. Certainly the PGU-14/B could defeat armor on APCs and older generation MBTs. Modern MBTs with advanced composite/reactive armor may be more difficult to crack. While it might not be able to penetrate the chobham hull of an M1A2, it can certainly take out fuel tanks, destroy the engine, etc.

Keep in mind that a GAU-8/A can hammer a 5-mil Circle with 70 such rounds with a 1 second burst, provided the pilot has a steady trigger hand. This also can have a cumulative destructive effect on armor plating.

While the gun can be employed against armor, the preferred method is to attack tanks using standoff weapons like the AGM-65 Maverick missile. Getting close enough to tank columns to use the gun can be hazardous, especially if the group has mobile AAA/SAM escorts.

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  • $\begingroup$ One could also say modern tanks don't do toe-to-toe combat, but engage much farther than a blink-and-you'd-miss-it A-10 would. $\endgroup$ – ymb1 Mar 7 '19 at 6:16
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    $\begingroup$ Thank you -- I hadn't noticed that in Wikipedia. What's a "5-mil" circle? The article you quoted says that the precision is such that "80% of rounds fired at 4,000 feet (1,200 m) range hit within a 40-foot (12 m) diameter circle". That's about 1 round per 2 square metres per second, unlikely to hit the same bit of armour twice. Also I think of main tank armour as being, like, 350 mm; and from videos I thought it would be not nearly as vertical as "30 degrees from vertical". I guess that answers my question though, thanks again. $\endgroup$ – ChrisW Mar 7 '19 at 9:04
  • $\begingroup$ I see -- "5-mil" is presumably a (small) unit of angle, meant to measure the scatter. $\endgroup$ – ChrisW Mar 7 '19 at 9:33
  • $\begingroup$ @ChrisW consider that splitting the armor and blowing up/killing the crew isn't the only method for disabling a tank. Destroying a tread, jamming the turret rotation mechanism or gun elevation mechanism will effectively render the tank useless until repaired. The crew will not want to be outside the tank fixing a tread while there are a pack of A-10s circling, especially if those A-10s are providing cover for nearby ground troops. $\endgroup$ – FreeMan Mar 7 '19 at 15:17
  • $\begingroup$ Yes, Wikipedia's articles say that the A-10 killed 900 tanks during the Gulf War, and that the Maverick was used 5000 times against armoured targets -- that's compatible with the answer's suggesting that the Maverick is the principle anti-tank weapon. The A-10 was designed in the 1970s, I'm guessing the cannon might be effective against any target possibly except a "main battle tank". $\endgroup$ – ChrisW Mar 7 '19 at 16:25

The thinnest armour on most MBTs is the roof of the turret and hull. The A-10, when it attacks with its cannon, is diving from a fairly high aspect and therefore shooting at the most vulnerable parts, the roof and engine compartment.

Also, the rate of fire of the gun is so high and the projectiles are therefore so close together, there is a high probability of multiple hits on the same point. The result is an 30mm depleted uranium AP round, even if it doesn't penetrate the first time, has a good chance of being followed by another right behind it into the divot made by the first one and finishing the job. An old GE video of the GAU8 on a test range shows the effect of follow up rounds hitting the crater made by their predecessors, and basically chewing their way through quite thick armour.

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  • $\begingroup$ I haven't seen that video -- I've only ever seen videos of obsolete hulks of tanks being shot at, with debris and so on flying around, but without details of the damage. But perhaps you're right, various modern anti-armour munitions try to use Top attack. Effective against a "main battle tank" seems to me to be quite a tall claim though. $\endgroup$ – ChrisW Mar 7 '19 at 1:38
  • $\begingroup$ This is the correct answer. Tanks don't have more than 30-40 mm of armor on top. This armor isn't anywhere as sophisticated as frontal protection, and is either just steel or steel backed by a bit of lightweight composite material (fiberglass, aramid). 30mm AP rounds can penetrate MBT top armor. $\endgroup$ – Therac Jul 17 '19 at 14:18
  • $\begingroup$ Given the threat posed by air attack, why don't modern tanks have thick armour on the top as well as the sides? $\endgroup$ – Sean Jul 17 '19 at 20:43
  • $\begingroup$ @Sean Weight - something has to give somewhere. Modern warfare is generally a combined arms affair. Tanks have air support to deal with things like that. $\endgroup$ – T.J.L. Jul 17 '19 at 23:44
  • $\begingroup$ @T.J.L.: So lighten it in some other way, like having it carry less ammo (a higher ammo capacity won't help you if it means you have to skimp on the armour and get blown up as a result), or simply give it a more powerful engine. $\endgroup$ – Sean Jul 17 '19 at 23:46

Define effective

Using the cannon, the A-10 is capable of disabling a main battle tank from a range of over 6,500 m.

While modern battle tanks have quite sophisticated armor protection (for the crew), there are many vital components with less protection. In the image below, we see the tracks and the wheels, which are exposed. We see some optical systems for awareness and fire control.

If an aircraft manages to damage enough of these exposed systems to render the tank incapable of fulfilling its role, then the tank has been effectively knocked out, despite it being not killed.

The quote of the OP talks of disabling, not destroying. Thus, making the tank blind, or unable to move, may be sufficient to disabling it.

A Challenger 2 tank Image source: Wikimedia Commons

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First of all adding "only" 200 m/s aircraft speed to 1000 m/s barrel velocity will give 40% more kinetic energy to those depleted uranium rounds.

Secondly, an aircraft can attack at many more angles than another tank, more easily finding thinner armor points.

Thirdly, even if aircraft could carry an 88mm gun, it has a much higher probability of a miss as it is moving in three dimensions. There for, it fires a guided missile at longer range and closes to point blank with its Gatling, accomplishing its task with multiple hits.

A tank on the ground can aim much better with its gun and goes for one good shot.

But nothing wrong with helicopters carrying missiles to help out, along with the Warthogs. As long as the A-10 is effective, it will still be around.

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