A 'proper' tank-buster A/C for 1939-40?

[tomo pauk]

Looking for a possible & plausible what-if aircraft types for the different air forces/services. The aircraft, developed from 1936-37, needs to have sufficient weaponry to badly harm a tank that is expected to appear on the battlefield of 1939-40 (so a 20mm autocannon might and might not be enough), some sort of protection at least for the pilot since one can expect a lot of automatic weapons to be trained against the A/C. If the A/C can also do good against other land targets, like the infantry or the non-armored vehicles in the open, the better.
Engine choice - whatever the respective country makes, even the 2nd rate engines should do. A plausible mod of an existing engine is okay. If an easily available foreign engine can be used as an alternative, that's a plus. Use two engines if needed. A rear gunner is nice to have, but not mandatory. Design needs to be adopted for series production in the country of origin.
Weapons - a good gun is a must. If the off-the-shelf gun can fit, even with some modifications - great. Otherwise, whip up a plausible alternative. Ammo can use some love, there is no need to remain on the plain AP shot.
Sprinkle with MGs and bomb racks to the taste, but not in such quantity/weight that other features take a back seat, like a good main gun(s), handling and protection.
Speed is not of a concern.
The A/C must be of a modern layout (a monoplane with enclosed cockpit, basically).

 

[muskeg13]

Hold my beer...

Not just one, but TWO 37mm cannon!

 

[Howard Gibson]

Hold my beer...View attachment 847464 Not just one, but TWO 37mm cannon!

What a fun thing to bail out of at low altitude, especially if are in a nacelle reloading those 37mms.

 

[Howard Gibson]

Looking for a possible & plausible what-if aircraft types for the different air forces/services. The aircraft, developed from 1936-37, needs to have sufficient weaponry to badly harm a tank that is expected to appear on the battlefield of 1939-40 (so a 20mm autocannon might and might not be enough), some sort of protection at least for the pilot since one can expect a lot of automatic weapons to be trained against the A/C. If the A/C can also do good against other land targets, like the infantry or the non-armored vehicles in the open, the better.
Engine choice - whatever the respective country makes, even the 2nd rate engines should do. A plausible mod of an existing engine is okay. If an easily available foreign engine can be used as an alternative, that's a plus. Use two engines if needed. A rear gunner is nice to have, but not mandatory. Design needs to be adopted for series production in the country of origin.
Weapons - a good gun is a must. If the off-the-shelf gun can fit, even with some modifications - great. Otherwise, whip up a plausible alternative. Ammo can use some love, there is no need to remain on the plain AP shot.
Sprinkle with MGs and bomb racks to the taste, but not in such quantity/weight that other features take a back seat, like a good main gun(s), handling and protection.
Speed is not of a concern.
The A/C must be of a modern layout (a monoplane with enclosed cockpit, basically).

Did anybody other than the French have a good, high velocity 20mm cannon?

 

[swampyankee]

Hold my beer...View attachment 847464 Not just one, but TWO 37mm cannon!

Arguably, one of the worst aircraft ever bought by the US.

In 1939-40, a 0.5 inch with a good AP round would probably work. A 20 mm with a good muzzle velocity definitely would.

 

[Greg Boeser]

Hold my beer...View attachment 847464 Not just one, but TWO 37mm cannon!

My first choice!
It would need a bit of work. Armor for the pilot and gunners, put a generator on both engines for starters. I read about Eric Schilling's experience.

 

[Greg Boeser]

What a fun thing to bail out of at low altitude, especially if are in a nacelle reloading those 37mms.

They didn't just reload, they aimed them!

 

[Greg Boeser]

They didn't just reload, they aimed them!

Ok this appears to be an error. Sorry.

 

[GrauGeist]

The B-18 was tested with a 75mm cannon in 1939.

 

[Thumpalumpacus]

Me-110?

 

[yulzari]

Hurricane + 2x40mm S Guns.

 

[GrauGeist]

Me-110?

The Bf110G-2 was outfitted with BK3.7 cannon, so it *technically* could have been used for ground attack, but the cannon arrangement was intended for attacking bombers.

 

[bf109xxl]

 

[Thumpalumpacus]

The Bf110G-2 was outfitted with BK3.7 cannon, so it *technically* could have been used for ground attack, but the cannon arrangement was intended for attacking bombers.

I was thinking the earlier variants could be modded.

 

[Shortround6]

Germans could have used the MG C/30L, same ammo as the Flak 30 or Flak 38.
Close enough to the Hispano for all practical purposes. As is the Japanese Ho-1/Ho03 cannon.
Once side and rear armor hits 30mm this class of cannon is just about done for dealing with medium tanks.
Still useful for shooting up light tanks or armored cars but then the crappy 37mm AT guns of just about any army could deal with those so going to the expense of building dedicated special flying anti-tank guns seems to not be cost effective?
Trying to use 20mm cannon on many of the French tanks of 1940 was not going to work well (damaged yes, burned out hulks no) so each air force has to really figure out what their opponents are going to using for tanks.

Larger cannon (more powerful) usually means heavier and with the pretty much under 1100hp engines of 1939/40 that starts presenting problems.
Trading larger shells for lower velocity (aka Madison 23mm) doesn't get much better AP penetration unless you start using trick ammo.
Trick ammo can get real expensive real quick. Also turns the plane into a one trick pony. Hispano guns (and cousins) can alternate AP and HE rounds for GP load out. Similar point of impact and while not ideal for either it is effective on different types of targets. Using carbide cores gets more expensive, not just in gold but in rare material, shooting up the cored ammo on marching troops or even trucks is costly for the effect on targets. Unlike tanks or towed guns, the plane cannot take out the expensive ammo and put in the cheap or HE rounds in just a few seconds if that is the target presented to them.

Gemans were alone with their 30mm MK 101 gun.
The American 37mm M4 gun sucked at anti-tank. 550/560ms velocity doesn't do much different than a 20mm Hispano.

 

[tomo pauk]

Germans could have used the MG C/30L, same ammo as the Flak 30 or Flak 38.
Close enough to the Hispano for all practical purposes. As is the Japanese Ho-1/Ho03 cannon.
Once side and rear armor hits 30mm this class of cannon is just about done for dealing with medium tanks.
Still useful for shooting up light tanks or armored cars but then the crappy 37mm AT guns of just about any army could deal with those so going to the expense of building dedicated special flying anti-tank guns seems to not be cost effective?
Trying to use 20mm cannon on many of the French tanks of 1940 was not going to work well (damaged yes, burned out hulks no) so each air force has to really figure out what their opponents are going to using for tanks.

Germans might've used the derivative of the 3.7cm Flak to deal with anything that is not a Matilda or the Char B. A bit more ambitious take on an armored attacker, talk 'Hs 129+', with two 9 cyl radial engines should've been more than capable to have both a good protection and good firepower.

Gemans were alone with their 30mm MK 101 gun.
The American 37mm M4 gun sucked at anti-tank. 550/560ms velocity doesn't do much different than a 20mm Hispano.

The MK 101 hits the stride once the cored shot is available - perhaps by some time of 1942? A tad late for this thread.
Americans are better in modifying the 37mm AA gun into a tank-buster, than to hope for the M4 to kill the tanks.

 

[Shortround6]

Germans might've used the derivative of the 3.7cm Flak to deal with anything that is not a Matilda or the Char B. A bit more ambitious take on an armored attacker, talk 'Hs 129+', with two 9 cyl radial engines should've been more than capable to have both a good protection and good firepower.


The MK 101 hits the stride once the cored shot is available - perhaps by some time of 1942? A tad late for this thread.
Americans are better in modifying the 37mm AA gun into a tank-buster, than to hope for the M4 to kill the tanks.

Both guns have potential. The problem is the 1939 aircraft.
For our 1939/40 aircraft with 1939/40 engines we run into the problem of getting the guns off the ground and not being total sitting ducks while carrying them.
As a guide the Ju-87G used a a 1400hp Jumo 211J and is not known for spritely performance

For tank busting you need to be able to fire a certain amount of shots during the attack run (leaving room to pull out) and most of the Big guns fired so slow that the Germans and British wanted two guns to maximize chances of a hit. But the 37-40mm guns were heavy.

Gun.......................................................................Weight................................Rate of fire..................................joules of energy(?).............................Feed
French HS 404....................................................50............................................700rpm...............................................49-50,000..................................drums
French 25mm Hotchkiss................................115..........................................220........................................................115,000.......................................box 15 rounds

German C30/L....................................................64........................................300-350....................................................48,000(?)....................................100 round drum
German KwK 38(AA gun) ...........................57-71..........................................450..........................................................48,000(?)...................................20 round box
German MK 101...............................................180............................................230......................................................130-140,000...............................30 drum
German BK 3.7..................................................295............................................160..........................................................218,000......................................6-12 round strip

British HS 404..................................................50...............................................600..........................................................49-50,000.................................60 round drum
British 40mm S gun (too late)...................134............................................100...........................................................214,000.....................................15 round drum

Madsen 23mm................................................53.............................................400(?)........................................................46,000(?).....................................belt
US 37mm M4...................................................96.........................................140-150.......................................................116,000....................................15 round belt?
US 37mm M9 (too late)...............................181...........................................140.............................................................317,000....................................belt
US 37mm AA gun..........................................161............................................120.............................................................317,000..................................10 round clip

Area of a circle
20mm = 3.14cm
23mm = 4.15cm
25mm = 4.9cm
30mm = 7.07cm
37mm = 10.75cm
40mm = 12.56cm

So we have to juggle the weight of the guns and the number of shots fired in an attack and the number of attacks per sortie (although successful repeated attacks on the same target depends on poor AA).

Not including Japanese or Soviet guns. Italian 20mm AA guns use the same ammo as the Germans. Guns fire slower.

Using two normal sized 9 cylinder engines gives the AA gunners a large target. (about 1.5 sq meters each instead of 0.71 sq meters of the GR 14M engines on the Hs 129).

 

[GrauGeist]

The Germans had a few potential aircraft for the job (aside from the Bf110 and Fw187) that existed in this timeline:
Bf161
Bf162
Do17
Fw57

 

[Dimlee]

Taking the low efficiency (accuracy, short time on target) of aircraft guns against small moving ground targets into account, should not the "tank buster" aircraft concept be considered as a dead-end in the 1930s-1940s?
Otherwise, I'd vote for anything that:
- can deliver bombs of 250kg or heavier with the lowest CEP possible for the existing technology
- will survive after the bombs are dropped
- is easily serviced and repaired in the field
- can be produced in large quantities

 

[tomo pauk]

Taking the low efficiency (accuracy, short time on target) of aircraft guns against small moving ground targets into account, should not the "tank buster" aircraft concept be considered as a dead-end in the 1930s-1940s?

Efficiency of the better tank-busting aircraft of the ww2, armed with cannons of 30mm and bigger, was good/very good.

Otherwise, I'd vote for anything that:
- can deliver bombs of 250kg or heavier with the lowest CEP possible for the existing technology
- will survive after the bombs are dropped
- is easily serviced and repaired in the field
- can be produced in large quantities

Good bullet points.