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Early ww2 airborne tank-busters what-if
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Shortround6
Major General
Perhaps 
obviously a direct hit works but they are going to be very rare.
Near misses depend on bomb size and size of the tank. Small tanks might be able to be flipped, large bomb just a few feet or meters away can rip off external fittings and
suspension/tracks. However since most tanks with over 30mm armor were considered "shell proof" (could withstand a hit from a 75mm HE artillery shell) actually destroying the tank vs immobilizing them or killing/incapacitating crew by concussion is going to be difficult.
In the early part of the war AA fire was truly pathetic in some armies giving some advantage to attacking aircraft.
I would note that in the summer of 1940 the US (not in combat) listed the .50 cal guns in an infantry battalion as anti-tank machine guns and the TOE listed Browning Automatic Rifles as the AA weapons mounted on the transport trucks. By 1943 quite a number of transport trucks had a machine gun ring mounted over the drivers cab/compartment even if the gun was not always fitted. US mounted some sort of AA gun (even .30 cal Browning) on just about all tanks/armoured vehicles.
Air Forces may have overestimated their capabilities?
obviously a direct hit works but they are going to be very rare.
Near misses depend on bomb size and size of the tank. Small tanks might be able to be flipped, large bomb just a few feet or meters away can rip off external fittings and
suspension/tracks. However since most tanks with over 30mm armor were considered "shell proof" (could withstand a hit from a 75mm HE artillery shell) actually destroying the tank vs immobilizing them or killing/incapacitating crew by concussion is going to be difficult.
In the early part of the war AA fire was truly pathetic in some armies giving some advantage to attacking aircraft.
I would note that in the summer of 1940 the US (not in combat) listed the .50 cal guns in an infantry battalion as anti-tank machine guns and the TOE listed Browning Automatic Rifles as the AA weapons mounted on the transport trucks. By 1943 quite a number of transport trucks had a machine gun ring mounted over the drivers cab/compartment even if the gun was not always fitted. US mounted some sort of AA gun (even .30 cal Browning) on just about all tanks/armoured vehicles.
Air Forces may have overestimated their capabilities?
P-39 Expert
Non-Expert
Was the target area for the joules number just the area of the shell diameter in sqcm?Basically APCR/HVAP doesn't exist until 1941/42. Yes it was around in prototype form a bit earlier. But the British didn't get into making APCR shot for the 2pdr and 6pdr AT guns until 1943. Germans had little, (if any?) during the first months of Barbarossa.
APCR/HVAP increase the armor penetration by roughly (very roughly) 30%. this varies enormously by range. Better at very close range (thrown rock distance) and less at longer ranges until, with the smaller caliber guns the standard AP shot had better penetration somewhere between 500 and 1000 meters depending on exact gun/ammo. The Squeeze bore guns maintained the better penetration considerably longer.
for a quick method of comparing guns try calculating the Joules of energy per sq cm of target area. As in American 37mm aircraft gun 116,000 joules with a target area of 10.75 sq cm gives 10,790 joules per sq cm.
Hispano gun with a 130gram projectile has 50,000 joules of energy and just 3.14 sq cm of target area and has 15,900 joules per sq cm of target area.
Want to "bust" tanks with a P-39? yank the 37mm and fit a Hispano
For the US 37mm aircraft gun a 30% improvement on crap is still crap.
German 37mm guns on the Stuka had 208,00 joules (APT) so obviously much more energy per unit of target area.
The energy figures are at the muzzle (and gun stationary) so there will be some difference at range.
The Russian 23mm gun in the IL-2 had 77,400 joules for 18.650 joules per sq cm.
The British 2pdr tank and anti-tank had 392,000 joules of energy in one loading and had (at the muzzle) 31,210 joules per sq cm.
The Little John rounds had slightly less total energy but were concentrating it on a much smaller area, diameter of the projectile as it left the barrel was 30mm but the AP core was even smaller.
Shortround6
Major General
Yes.
It is an old formula that goes back to Ironclad warships. Iron cannonballs vrs iron plate and the slow evolution of both projectiles and armor.
So adopt whatever measurement units were in use in the country at the time. I used Joules as it is a quick cheat Because Anthony Williams lists Joules in his books and I don't have to convert anything. Foot pounds per sq in works, it is just a relative number for comparison.
It is a theoretical comparison and assumes a 90 degree impact and at the muzzle or darn close.
It also assumes all armor is the same and that all projectiles are the same hardness and shape.
However if we do this 'quicky' comparison and see that gun A is applying 50% more force to the target area than gun B then we can assume, without some sort of extraordinary circumstances that gun A will out penetrate gun B. Different quality steel or shape or heat treatment of the projectile is unlikely to make up a large difference even though there is some effect.
Formula can be made more complicated to reflect actual results by adding in factors like constants for actual type/quality of armor and so on.
I can see a 10-20% difference disappearing due to different factors in real life but large differences take an awful lot to discount.
Some guns used different projectiles during their history. Just because they start with a simple (cheap) projectile doesn't mean they have to stay with it and if the "potential" is there (good energy per unit of target area) then changing the ammo may be a better bet than introducing a new gun (and ammo).
As impact velocity changes somethings really change. At over 2000fps (610m/s) plain heat treated steel shot starts to break up on impact, depending on the hardness of the shot and the hardness of the armor. So the 2000fps limit is a soft one, just sort of an indicator at when problems may start to occur. However putting a penetrating cap (softer steel) on the nose can delay breakup up to about 2600fps impact velocity so the lower 2000fps limit for plain shot cannot be stretched by a whole lot. Above that 2600fps velocity is when they needed special alloy/material penetrators.
At some point, if the projectile can "over match" the armor by a significant amount it can punch through regardless of the projectile breaking up and/or shattering.
At high impact velocities/energies they start to use equations derived from hydraulic equations.
again this goes back to the age of iron and steel and Commandant Jacob de Marre.
see: Tank Archives: Penetration Equations
It is an old formula that goes back to Ironclad warships. Iron cannonballs vrs iron plate and the slow evolution of both projectiles and armor.
So adopt whatever measurement units were in use in the country at the time. I used Joules as it is a quick cheat Because Anthony Williams lists Joules in his books and I don't have to convert anything. Foot pounds per sq in works, it is just a relative number for comparison.
It is a theoretical comparison and assumes a 90 degree impact and at the muzzle or darn close.
It also assumes all armor is the same and that all projectiles are the same hardness and shape.
However if we do this 'quicky' comparison and see that gun A is applying 50% more force to the target area than gun B then we can assume, without some sort of extraordinary circumstances that gun A will out penetrate gun B. Different quality steel or shape or heat treatment of the projectile is unlikely to make up a large difference even though there is some effect.
Formula can be made more complicated to reflect actual results by adding in factors like constants for actual type/quality of armor and so on.
I can see a 10-20% difference disappearing due to different factors in real life but large differences take an awful lot to discount.
Some guns used different projectiles during their history. Just because they start with a simple (cheap) projectile doesn't mean they have to stay with it and if the "potential" is there (good energy per unit of target area) then changing the ammo may be a better bet than introducing a new gun (and ammo).
As impact velocity changes somethings really change. At over 2000fps (610m/s) plain heat treated steel shot starts to break up on impact, depending on the hardness of the shot and the hardness of the armor. So the 2000fps limit is a soft one, just sort of an indicator at when problems may start to occur. However putting a penetrating cap (softer steel) on the nose can delay breakup up to about 2600fps impact velocity so the lower 2000fps limit for plain shot cannot be stretched by a whole lot. Above that 2600fps velocity is when they needed special alloy/material penetrators.
At some point, if the projectile can "over match" the armor by a significant amount it can punch through regardless of the projectile breaking up and/or shattering.
At high impact velocities/energies they start to use equations derived from hydraulic equations.
again this goes back to the age of iron and steel and Commandant Jacob de Marre.
see: Tank Archives: Penetration Equations
Il-2 with NS-37 cannons. Tests on the firing range. Targets were hit in 43% of flights. Hits/ammunition spent = 2.98%.
Ильюшин Ил-2 НС-37
Il-2 with ShFK-37 cannons. The estimated probability to hit (not to destroy) the target in one attack:
Pz.IIIG 0.04-0.02
Sd Kfz 250 0.09-0.06
In other words, we need the whole squadron just to hit one target in one attack.
Ильюшин Ил-2 ШФК-37
This is a slow-flying Il-2. I don't think any fighter could be more accurate with one cannon and less time to aim and shoot.
Now, this is interesting... Trials of ShFK-37 cannon with BZT-37 shell against Pz.III, Pz.II, Pz.38(t).
Effective firing distance 500 m, not more.
In 33 hits there were 24 penetrations. 17 in 30 mm armor and others in 15-16 mm armor.
Ильюшин Ил-2 ШФК-37
Probably NS-37 and ShFK-37 were not the best weapons and Il-2 was not the best gun platform. Were other cannons and aircraft much better so they could be called "tank busters"? Not in the memoirs (as of Hans-Ulrich Rudel or of Soviet Il-2 pilots), but in real life.
Gee, I seem to recall a plane with a 37mm firing through the hub and an Alison engine optimized for lower altitudes... IIRC that 37 was able to defeat 20mm of armor at 500 meters which would have been more useful against tanks than bombers all things considered.
Shortround6
Major General
The question is a what impact angle?
If the top of the tank is dead level (not sloped forward or back or side to side) and the plane is diving at 30 degrees and the top is 8mm thick your projectile rated at 20mm at perpendicular impact won't go through. Simple geometry says that the projectile has to go through 16mm of armor (double the thickness) but since at high angles of attack they projectile has a much greater tendency to skid/ricochet the armor usually acts about 3 times thicker.
If the sides/rear of the tank and or turret is less than 20mm thick then the 37mm gun may prove effective.
If you are diving at over 30 degrees you better be pulling out of the dive before you get to 500 meters distance from the target.
P-39 Expert
Non-Expert
Soviet pilots were instructed to attach tanks from the rear where armor was thinnest.
Shortround6
Major General
Great, even a 1940 MK III had 30mm of armor on the sides and rear. Later versions got 50mm of armor on the hull rear and kept teh 30mm on the turret sides and rear. MK IVs by the end of the Battle for France had 30mm of armor on the sides and rear.
I don't think anybody tried to take out a tank from the front with a cannon mounted on an airplane as a general tactic. Might have worked for the Hurricane against Japanese tanks.
I don't think anybody tried to take out a tank from the front with a cannon mounted on an airplane as a general tactic. Might have worked for the Hurricane against Japanese tanks.
That sums up all the issues with hitting a tank from an aircraft. All the aids that a trained gunner has on the gun he trained with, on a stationary stable stationary platform , like fine control of elevation and traverse, knowledge of range and ballistic drop and advantage of firing horizontally are missing. The pilot has to make all the fine adjustments on the whole plane and adjust them constantly as everything is changing by the second.
It is interesting that Il-2 with 37 mm cannons were recommended to attack at angles not higher than 30 degrees. Probably due to Il-2 general problems with high-angle diving. So the best angles were simply not achievable in certain aircraft.
Exactly... And there are just 3-5 seconds for everything. Under AAA fire in many circumstances.
P-39 Expert
Non-Expert
Remember that the tank does not need to be penetrated and completely engulfed in flame with the crew killed instantly. A disabled, even just immobile tank is virtually useless in battle.
Shortround6
Major General
True but trying to disable or immobilize a tank is not that easy. Yes the tracks can come off or a bogie wheel get detached but both take a fair amount of effort and.or hits in exactly the right spot.
The P-39 might have been effective on MK I and MK II tanks but they were fading from the scene in 1942 let alone 1943.
The Germans did have a fair number of open topped vehicles, like most of their SP guns and Panzerjagers and halftracks. But then if they vehicles are open topped you don't need an armor piercing cannon. A number of machine gun bullets bouncing around the interior like steel balls in a pinball machine will do the trick.
If the AP shot doesn't penetrate the armor and hit crew or ammo or propulsion system there isn't much besides the suspension and tracks to stop the vehicle. Blow off the tool box? Bend the shovel? remove the radio antenna?
Three whiskeys in, I'm going the full Monty on this one
Take an otherwise obsolete Fairey Battle. Ditch the merlin and fit a Bristol Taurus.
No more power than the Merlin, but much lighter - and air-cooled, so no rad or associated plumbing and coolant - yet more weight saving - should be well over 500lbs.
Chop back the bloody great big greenhouse canopy to save a load more weight, ditch the third crew member and save even more - and bring the gunner up back-to-back with the pilot. Ditch the bomb aiming position site and all extraneous kit. That should even up the C of G a bit and give scope to give the crew some decent armour too in a compact space. Give the gunner a pair of Vickers K on a dual mount as per the Hampden, or dual brownings as per Douglas Havoc. Check with the boffins and look at chopping off as much off on the wingspan for purely sub 5000ft operation and to improve roll and maybe add a couple of mph. Pay attention to self sealing tanks. Maybe reduce the tankage too - this is a tactical bird - not need to have the 1000mile range of the Battle
Take a pair of hotchkiss 25mm anti tank guns. Nice and compact - and should be more than enough oompf for top attacks on early panzers. Strip them right down - lose the shield, carriage wheels etc (dunno what weight that should leave us with - but should give a reasonable reserve. Maybe use the 25 SA-L mle 1935 variant) Develop a simple cassette or magazine feed as per Vickers S or Molins.
Install said cannons in the inboard bomb nacelles in the wings - and ammo in the outers. Hopefully that massively reduces major structural issues or mods- and no draggy external pods.
There you go - a British IL-2 using clobber available in 1939 - and more than enough to knacker any tank in 1940 (I make no claims as to the toll taken by AA or fighters though!)
Image from The lost Battle! (test bed with Taurus engine installation in 1938....)
Picture from British Aviation Resource Center - A Warbirds Resource Group Site showing bomb nacelles:
Take an otherwise obsolete Fairey Battle. Ditch the merlin and fit a Bristol Taurus.
No more power than the Merlin, but much lighter - and air-cooled, so no rad or associated plumbing and coolant - yet more weight saving - should be well over 500lbs.
Chop back the bloody great big greenhouse canopy to save a load more weight, ditch the third crew member and save even more - and bring the gunner up back-to-back with the pilot. Ditch the bomb aiming position site and all extraneous kit. That should even up the C of G a bit and give scope to give the crew some decent armour too in a compact space. Give the gunner a pair of Vickers K on a dual mount as per the Hampden, or dual brownings as per Douglas Havoc. Check with the boffins and look at chopping off as much off on the wingspan for purely sub 5000ft operation and to improve roll and maybe add a couple of mph. Pay attention to self sealing tanks. Maybe reduce the tankage too - this is a tactical bird - not need to have the 1000mile range of the Battle
Take a pair of hotchkiss 25mm anti tank guns. Nice and compact - and should be more than enough oompf for top attacks on early panzers. Strip them right down - lose the shield, carriage wheels etc (dunno what weight that should leave us with - but should give a reasonable reserve. Maybe use the 25 SA-L mle 1935 variant) Develop a simple cassette or magazine feed as per Vickers S or Molins.
Install said cannons in the inboard bomb nacelles in the wings - and ammo in the outers. Hopefully that massively reduces major structural issues or mods- and no draggy external pods.
There you go - a British IL-2 using clobber available in 1939 - and more than enough to knacker any tank in 1940 (I make no claims as to the toll taken by AA or fighters though!)
Image from The lost Battle! (test bed with Taurus engine installation in 1938....)
Picture from British Aviation Resource Center - A Warbirds Resource Group Site showing bomb nacelles:
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Have you been playing with the Time Telephone again?? Someone at Westlands must have been listening out for your call!
Westland Whirlwind Variants and Projects
From what I have read Typhoon rocket attacks caused many tanks to be abandoned even though they weren't actually hit. Hard to say what was a "tank" at the time. Easy to understand why some tank chassis converted to carry field guns or other would be left, but I have also seen a good few pics of tanks that dropped into holes from rocket attacks and couldn't get out. Most of a mechanised division wasn't "tanks" and the tanks went all Tigers or King Tigers anyway. In the early days of the war, like France there wasn't any air force dedicated to the task of attacking tanks and ground forces and they didn't know where they were anyway.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
The Whirlwind prototype pictured, has a 20mm cannon.
There are some sources that claim it was a 37mm, but in fact, was a Hispano 20mm by itself and later, with a couple .303MGs (one to either side, above).
There was a proposal to install and trial either a 37mm or 40mm, but I haven't seen evidence that it ever happened.
Shortround6
Major General
Three whiskeys in, I'm going the full Monty on this one
Take an otherwise obsolete Fairey Battle. Ditch the merlin and fit a Bristol Taurus.
No more power than the Merlin, but much lighter - and air-cooled, so no rad or associated plumbing and coolant - yet more weight saving - should be well over 500lbs.
Chop back the bloody great big greenhouse canopy to save a load more weight, ditch the third crew member and save even more - and bring the gunner up back-to-back with the pilot. Ditch the bomb aiming position site and all extraneous kit. That should even up the C of G a bit and give scope to give the crew some decent armour too in a compact space. Give the gunner a pair of Vickers K on a dual mount as per the Hampden, or dual brownings as per Douglas Havoc. Check with the boffins and look at chopping off as much off on the wingspan for purely sub 5000ft operation and to improve roll and maybe add a couple of mph. Pay attention to self sealing tanks. Maybe reduce the tankage too - this is a tactical bird - not need to have the 1000mile range of the Battle
Take a pair of hotchkiss 25mm anti tank guns. Nice and compact - and should be more than enough oompf for top attacks on early panzers. Strip them right down - lose the shield, carriage wheels etc (dunno what weight that should leave us with - but should give a reasonable reserve. Maybe use the 25 SA-L mle 1935 variant) Develop a simple cassette or magazine feed as per Vickers S or Molins.
Install said cannons in the inboard bomb nacelles in the wings - and ammo in the outers. Hopefully that massively reduces major structural issues or mods- and no draggy external pods.
There you go - a British IL-2 using clobber available in 1939 - and more than enough to knacker any tank in 1940 (I make no claims as to the toll taken by AA or fighters though!)
The simple cassette or magazine feed is not so simple.
If you want a ground attack Battle in 1940 forget the Taurus engine. More Beauforts were lost due to engine failure than the Germans shot down in the early days.
Make more Merlin VIII engines as used in the Fulmar, or RAF equivalent (no Coffman starter), ust change the gear ratio on the supercharger. 1080hp for take off on 87 octane fuel. The British thought so much of the Taurus engine that they bought 200 P&W R-1830s to use instead but the ship carrying the engines was sunk on the trip over and the British figured that bad engines were better than no engines.
It isn't the "kit" that slows the Battle down so much as the fact the fuselage was deep enough for the bomb aimer to lay down under the pilots seat.
A semi automatic cannon (AT, AA or field gun) uses the recoil of the gun to open the breech block and eject the fired round. Springs are compressed for run out, to move the breech block back into position (blocks moved either vertically or horizontal but movement was perpendicular to the axis of the bore), and to cock the ejector spring. When the loader tossed (rammed) the new shell in with his hand/arm the rim hit the ejector and pushed it forward, tripping the release for the spring that slammed the breech block into position. Now please note that the gun barrel had returned to firing position with the breech block open and will sit there waiting to be loaded until it rusts. Yes you can use the energy of the recoiling gun to cock springs in a feed system.
just about all automatic guns (Madisons and a perhaps few others excepted?) have the breech block traveling to and fro in line with the barrel. Barrel may or may not recoil depending on design but the Breech block travels reward, extractor pulls the case from the chamber, ejector simply knocks the casing clear of the bolt/breech block face and out of the gun on the reward part of the trip. Bolt/breech block spring is compressed and at the end of the travel throws the bolt/Breech block forward and the bolt/breechblock picks up a new cartridge from the feed system (box.drum, belt system and pushes it into the chamber.
If you take an existing AT semi auto AT gun and try to turn it into an automatic gun (or just fit a loading system) you need to design a ramming system that will take rounds from the magazine or feed and push them at the proper angle the proper distance with enough force to trip the extractor/ejector catch and release the breech block. You don't have the weight of the bolt/breech block pushing the cartridge with a strong spring behind it. Yes you can install springs and arms and pushrods but it seems a bit complicated.
The Molins company specialized in cigarette making machinery. Their MK I machine was tweaked to make 1000 cigarettes a minute by the end of the 1920s and they were building the MK VI machine in the mid 30s. SO the Molins company was used to making things move at high speed using levers and arms.
In the end what have you got?
Vickers had a 25.4mm gun and cartridge that was functionally identical to the 25mm Hotchkiss AA gun. That is to say with in a few percent of gun weight, rate of fire, shell weight and velocity. Granted the French 25mm AT gun was somewhat more powerful but then you are going to need a heavier gun and with loading system add on it is unlikely to fire as fast.
Shortround6
Major General
The plane in question may have been used for development of the pneumatic feed system that was proposed for the Whirlwind. Instead of the drums pneumatic powered magazines with 110-120 rounds were to fitted but during trials the system consumed way more air than they planned on.
