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

z42 said:

Considering how long it took for the Hispano to get into a usable shape, why are we assuming some other new guns would have such an amazingly short and trouble free gestation? Seems, uh, optimistic?

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The problems with the Hispano were varied and somewhat installation dependent.
The gun was designed to be bolted to an over 1000lb engine. Bolting it inside a wing was a problem.
The gun was designed to mounted upright with the drum on top feeding down. Flopping it over 90 degrees and feeding from the side caused problems.
The gun was designed for the fired cases to be ejected downwards. When flopped on it's side and fitted with a chute with a 90 degree bend in it to direct the fired cases downwards some cases didn't get around the bend in the chute and clear the way for the following cases.
The gun may have required oiled/greased ammo which gave trouble at higher altitudes in cold air. Not as bad in warmer air. Later solved by making the chamber shorter (which the Americans ignored and built their guns to French chamber dimensions).
Not saying upright guns would have been trouble free but would not be the headache that Spitfire guns were.

Which does not invalidated your point about other guns.
Or the advantages of AA guns having several men who can assist in moving the Breechblock back and forth in cold/wet conditions vs trying to pull on handle (one handed) with several meters of cable between the gun and the pilot. Or needing powered cocking system/s?

Was the Hispano a problem in France?

Howard Gibson said:

Was the Hispano a problem in France?

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????
The MS 406 and D 520s used the engine mount and the upright positioning. Some of the twin aircraft with fuselage mounted guns may have been OK.
The Bloch 151-152s guns may have given trouble but not reported well?
The 1939-40 winter was cold but not a lot of combat? Most of the May-June air fighting was at lower attitudes that were warmer??

Just had a thought, the Engine mounted guns were in the engine V and behind the engine block. They probably got enough heat from the engine not have a cold temperature problem.
Germans had problems in 1937-39 with the through the prop guns overheating and jamming.
One reason for the Spitfires with belt feed cannon to rarely be fitted with 4 20mms. They could not get enough hot air past the inner 20mm to adequately heat the outer gun.
The Spits with 2 20mm and 2 .50s reversed the gun positions. The .50s were in the inside bay, more room for the duct to get around the gun.

Westland Whirlwind. Four 20MM cannon and it could carry bombs, too.

Alternate/Supplement: Hawk 75. Already a fighter bomber right out of the box. Bombs worked very well, before cannon and rockets.

MIflyer said:

Alternate/Supplement: Hawk 75. Already a fighter bomber right out of the box. Bombs worked very well, before cannon and rockets.

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The Madson cannon's gondola imposed a serious performance penalty and was not introduced into service.

GrauGeist said:

The Madson cannon's gondola imposed a serious performance penalty and was not introduced into service.

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Okay, but I was not counting on that cannon. I assumed bombs would do the job. I guess that the specified timeframe offers more gun options for the aircraft due to the lighter armor. And the 37MM of the P-39 could not penetrate German tank armor, so it is out.

z42 said:

Considering how long it took for the Hispano to get into a usable shape, why are we assuming some other new guns would have such an amazingly short and trouble free gestation? Seems, uh, optimistic?

Also, a gun that works well enough for a ground or ship installation where weight doesn't matter that much, and you have crew available for changing ammo boxes and clearing jams, no G-forces to worry about, etc. etc., might not work well when mounted on a plane?

My take would be to just focus on getting the Hispano into shape. When/if that is too weak to punch through tank armor, use it to strafe armored cars, half-tracks, trucks etc., and use bombs (rockets might not be ready in 39-40?) against heavier armor.

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At Falaise in 1944, most of the German tanks weren't destroyed at all. They were abandoned as they were trapped within the trail of destroyed trucks, wagons, and unarmored artillery pieces that had been destroyed. A gun sufficient to strip tanks of supporting arms and elements such as fuel bowsers and ammo trucks renders those tanks just as useless, though it might take longer.

MIflyer said:

Alternate/Supplement: Hawk 75. Already a fighter bomber right out of the box. Bombs worked very well, before cannon and rockets.

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MIflyer said:

Okay, but I was not counting on that cannon. I assumed bombs would do the job. I guess that the specified timeframe offers more gun options for the aircraft due to the lighter armor. And the 37MM of the P-39 could not penetrate German tank armor, so it is out.

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I have actually thought about the H75 as well. In fact, go with something similar to the H75N with fixed undercarriage as an Army Cooperation aircraft operating off rougher fields and not trying to be a fighter. Arm it with cannon and bombs to also operate in the CAS role - much like the Ju-87 TBH.



Re the Madsen 20 mm cannon, supposedly there was a variant, the Madsen F5, that was designed as an anti-tank gun. It supposedly was a fully automatic weapon, with a 15-round magazine. At 100 m, it was able to pierce 42 mm of armour, and 32 mm at 500 m.

While perhaps not spectacular against later war tanks, for 1939/40 against Panzers I/II/III/IV it would have been effective, especially if not only going against frontal armour. And consider:

• Panzer I armour thickness: 7–13 mm
• Panzer II armour thickness: 5–15 mm
• Panzer III (only available in small numbers in the timeframe we are looking at) armour thickness: 15–30 mm
• Panzer IV (again, only available in small numbers in the timeframe we are looking at) armour thickness: 15–30 mm
• Panzer 35(t) armour thickness: 8–25 mm
• Panzer 38(t) armour thickness: 8–30 mm

Dimlee said:

About the accuracy of the "anti-tank" aircraft cannons.
...
2. Soviet NS-37 (LaGG-3, Il-2).
Google translated:
"During the war, a test firing of stationary tanks with the NS-37 cannon was conducted at the NIIBT testing grounds. In a calm environment at a range of 300-400 meters, three out of 35 shots fired from a LaGG-3 aircraft hit, and three out of 55 shots fired from an Il-2 aircraft also hit. It should be noted that not every small-calibre shell that penetrated the tank's armour disabled it." The source - Alexander Shirokorad's History of Aircraft Armament

Авиационное вооружение СССР - НС-37

So, the accuracy was 5% to 9% on the test site, against the stationary target.
From the same article:
"Overall, during the war, combat losses of Soviet medium and heavy tanks by type of weapon were: 88-91% from artillery; 8-4% from mines and high-explosive shells; 4-5% from bombs and air force artillery fire. Although in some operations, losses from air force fire reached 10-15%."
. Soviet VYa-23 (Il-2)
I can't quote the original document; it was probably one of the books by Oleg Rastrenin and Vladimir Perov. Years ago, I made a summary, and it contained this quote (translated) about tests of VYa-23:
"...the firing accuracy of the best test pilot against a single tank was 7.4%, and against a tank column — 9.5%.".
Probably, the figures were from the tests conducted by NII VVS (Scientific Test Institute of the Air Force) or NIIBT (Armored Vehicle Proving Ground) in 1942-1943.
...

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Neither the LaGG nor the Il-2 were well suited to mounting large guns - both were unstable or/and underpowered artillery platforms. According to the recollections of Mikhail Nyukhtikov, who was one of the most famous Soviet test pilots (for example, he tested the Tu-2), Polikarpov's VIT-1/-2 (I posted the photo above) were potentially the most effective Soviet (and perhaps not only Soviet!) "panzerknackers" - both with the Sh-37 and the 11P (NS-37) cannons. The VIT was well controlled and stable in flight, the pilot had good view. But VIT was unlucky - it needed M-105 engines, which were at that time absolutely unfinished and caused huge problems. Actually, these engines were finalized on VIT and SPB.
Armor-piercing shells of the VYa could consistently penetrate armor up to 20 mm thick - even against medium German tanks it was of little use. Just as 37-mm cannons were of little use against "Tiger" armor. Interestingly, the VYa and the 11P had almost the same recoil, but the VYa's mounting design was more rational, which greatly affected the accuracy of fire.
Il-2s with 37-mm guns could be effectively used only by the most experienced pilots (they could achieve a hit probability of several percent, for less experienced pilots this probability was practically zero), so such planes were produced in a relatively small series. Target shooting could be done only in short bursts (no more than 4 shots), which required repeated passes on the target and greatly increased the probability of being shot down.
The Il-2's best weapon against tanks was small shaped charge bombs.

Thumpalumpacus said:

At Falaise in 1944, most of the German tanks weren't destroyed at all. They were abandoned as they were trapped within the trail of destroyed trucks, wagons, and unarmored artillery pieces that had been destroyed. A gun sufficient to strip tanks of supporting arms and elements such as fuel bowsers and ammo trucks renders those tanks just as useless, though it might take longer.

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That is what happened. Mortain was the same. German tank crews soon new about the results of a tank being hit by rockets.
That resulted in a lot of bail outs from tanks and other vehicles when aircraft appeared. Typhoons and Thunderbolts were very effective
at causing this response. As a result the rockets didn't necessarily hit a lot but these two larger aircraft could also carry a big whack
of MG / cannon ammo. Strafing then decimated not only the support vehicles but also the troops of all types taking cover outside their vehicles.

Howard Gibson said:

For '39/40, how about the French Hispano cannon? This was already mounted on Morane-Saulnier M.S.406s, which were available in significant numbers. This would quickly become obsolete as a tank busting weapon, but you are talking about '39/40. This is simply a matter of switching from air superiority to ground attack. The French would quickly add armour if they somehow stayed in the war.

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Both Hispano and the Oerlikon S (that French made under licence and used on the pre-war fighters) will do bad things to most of the German tanks and other vehicles of 1939/40. And contrary to the British situation, they have these actual 20mm cannons in service in good numbers before the German onslaught in May. So outfitting them with AP ammo would've made the life ... interesting to the German soldiers.

FWIW and IIRC, Dowding was of opinion that, in case of invasion, Whrilwind's cannons will find a lot of work in the flying anti-tank business.

Shortround6 said:

lenhiem I had wing loading of 27lbs/sq/ft. The Blenhiem IV was 30.7lbs/sq/ft and a clean Whirlwind was over 40lbs/sq/ft. The Ki-45 both late and sort of squishy.

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I was referring to the size of the Ki-45, not about the actual aircraft being the next best thing after the sliced bread.

Shortround6 said:

Can we please, please, PLEASE stop trying to drag the Gloster F.5/34 and MB.2 in many of these hypothetical "What ifs" about 1930s British aviation. They had few, if any, redeeming qualities as actual aircraft. Actual performance levels may not be what is often quoted. Certain construction features may have had merit but they not in the front ranks of aerodynamics.

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Note that this is about the possible tank-busters, not about 'let's introduce yet another fighter'. So the (very) high performance at 15000 ft is not a requirement. Either of the two - Gloster with the low-level Mercury, MB.2 with the Dagger VIII - will be far cry vs. the up-gunned Blenheim, let alone Battle. The less we talk about the merits in aerodynamics of the two of the later aircraft, the better.

Shortround6 said:

You want a cheap ground attack plane? Well the fixed pitch prop is certainly cheap but a 24 cylinder H engine is not. You just have to change so much you might as well start over.

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Same with high performance at high altitude - cheapness is not a requirement here.

Shortround6 said:

Unlike the British and French the Germans had hundreds of these in 1940

Also mounted in small trucks. A few were horse drawn wagons.
And the few thousand 20mm AA guns the Germany army had.
Granted the Allies may have been ignorant of how many the Germans had before they tried bombing the French bridges.

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Having the fixed U/C might be an advantage, since there is less stuff that can be damaged by the enemy AAA. The wheels sticking halfway out on the Gloster also don't look like an disadvantage here.

Greg Boeser said:

406s are front line aircraft. How 'bout repurposing those obsolete D 510s?

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Some cleaning up might've helped here. Like making a normal, enclosed cockpit. Less draggy undercarriage, even if still fixed? The two combined can add perhaps 15-20 km/h on the top speed? Replace the gearing of the S/C with the one for the low-level altitudes, gains 100-150 HP down low. Neither of the changes is taxing on either the military budget or time, but should make it spiritedly on the lower altitudes. Useful in any kind of hostile airspace, while also being a threat to the German aircraft. Mix 2 AP + 1 HE in the ammo drums for the cannon?
Small size and good maneuverability are still a major plus, too.

Shortround6 said:

The problems with the Hispano were varied and somewhat installation dependent.
The gun was designed to be bolted to an over 1000lb engine. Bolting it inside a wing was a problem.

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Do the French confirm the bolted statement?

Hi
Attached is the RAF 'history' of the 20mm Hispano Gun from AIR 41/82 SD737 Armament Vol. II, Guns, Gunsights, Turrets, Ammunition and Pyrotechnics, 1954 (Whole document available online from the British Air Historical Branch [AHB]). There is a separate chapter (Ch.6) on the feed mechanisms for the 20mm. Included is the US production 'failure':










I hope that is of interest.

Mike

tomo pauk said:

Do the French confirm the bolted statement?

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Germans could pull the engine out of a 109 and leave the gun behind.
The Hispano needed a support/mount out on the barrel and attempts to mount Hispano guns in ground mounts can show this

P-38s used a cradle to help mount the gun. Much heavier than the /50 cal mounts.
and the famous Lysander mount

Forward mount is where the bomb racks went and is attached to the main landing gear leg. Rear struts met the stut (tube?) going back under the gun from the forward mount tying everything together. The Hispano barrel moved and had a recoil spring on it. The Hispano had a lot more recoil than the short Oerlikon.

Hi
Details reference the feed mechanisms on the 20mm Hispano:






Mike

10 May 1940, 1st to 10th Panzer divisions,
554 I
920 II
118 35t
207 38t
349 III
280 IV
154 Command
2,582 Totals
About 25% Panzer III and IV

22 June 1941, Barbarossa, 1st, 3rd, 4th, 6th to 14th, 16th to 20th Panzer Divisions, plus 2 flampanzer units
84 Flam
152 I
794 II
155 35t
625 38t
269 III 37mm
707 III 50mm
439 IV
188 Command
3,413 Totals
About 41% Panzer III and IV

2nd and 5th Panzer arrived in September 1941, with 118 II, 210 III, 40 IV and 12 command vehicles.

Many thanks to Mike Meech for his posts.
They also show the problems with details. Good magazines give little trouble. But good magazines are expensive. Rushed subcontractors have trouble and some solutions work good at first but aren't durable.
Trying to condense over 4 pages from a gun book to 2-3 sentences in a aircraft book means most of the details are lost and many books/articles about airplanes give wrong ideas about the guns used or why there were problems.

These excepts also so the dangers in a "what if" of come up with ideals like "use gun XXX and just change the 6 round hopper feed to a 40 round drum. Gun YYY used a drum and it worked fine".
The 20mm Hispano worked but it was balanced on a fine line. And often peace time didn't put the strain on things that war time did. production of spare magazines. Number of rounds fired in training per year/month. Practice training did not use full ammunition loads so springs were not stretched as much. Here the US was guilty, they often flew training exercises with 100 rounds or less of .50 cal ammo and early .50 cal guns would not pull the 200 round and large belts in the cowl mounts. And doing training in non-winter months doesn't show what happens when the oil/grease is at 20 degrees below zero.

The French were onto something with their Breguet Bre.693 but the timing of the German invasion and their lack of experience with this type of warfare saw the 693's career cut short.

It's also interesting to note that the French had been exploring dedicated ground attack aircraft armed with cannon since the early 1930's.

Geoffrey Sinclair said:

10 May 1940, 1st to 10th Panzer divisions,
554 I
920 II
118 35t
207 38t
349 III
280 IV
154 Command
2,582 Totals
About 25% Panzer III and IV

22 June 1941, Barbarossa, 1st, 3rd, 4th, 6th to 14th, 16th to 20th Panzer Divisions, plus 2 flampanzer units
84 Flam
152 I
794 II
155 35t
625 38t
269 III 37mm
707 III 50mm
439 IV
188 Command
3,413 Totals
About 41% Panzer III and IV

2nd and 5th Panzer arrived in September 1941, with 118 II, 210 III, 40 IV and 12 command vehicles.

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Thank you.
This breakdown doesn't quite show the difference that 13 months made.
In 1940 about 70% of the Pz IIs had an additional 20mm added to the frontal armor, both hull and turret. By June of 1941 all operational Pz Iis were upgraded and the Pz IIF used 30-35mm armor to start. It kept the 14-15mm armor on the sides and rear.
The Pz 35s were not upgraded and had 15/16mm armor on the sides and rear.
The Pz 38s showed some upgrading, the first 475 may not have been but the 5 & 6th batches were, starting in Nov 1940 they doubled the frontal armor (using two 25mm plates) and increased the side turret and superstructure (above the tracks) to 30mm from 15mm. Rear of the turret went from 15mm to 22mm, rear of hull was unchanged. Turret top went from 10mm to 15mm.
The Pz III and Pz IV are even more complicated as far as armor goes.
Pz IIIE 96 produced, 30mm armor all around except 21mm on the rear of the hull/superstructure, all earlier versions had been withdrawn from service before France. Turret top 12mm hull top 17mm
Pz IIIF 435 produced, as built the armor was the same as the E, when many were upgraded from the 37mm gun to the 50mm they got extra 30mm plated add to the hull front and rear and to the superstructure (driver's plate).
Pz IIIG 600 produced. armor was repeat of the F with similar upgrades at later dates.
Pz IIIH 308 produced. got the extra 30mm on the hull/superstructure as built. Turret and hull top stayed the same.
Since there were 5 to 7 factories producing Pz III tanks from the F to the H models exact dates of change over in each factory takes more resources than I have.

The Pz IV is interesting as the early versions were protected by flatten soup cans in comparison to the Pz IIIs.
Pz IV A 35 built, withdrawn after France. 15mm armor all around except top, 10/12mm
Pz IV B 42 built. stayed in service, 30mm front, 15mm side and rear 10/12mm top
Pz IV C 134 built. Stayed in service (or rebuilt) with 30 mm front, 15mm sides/rear and 10/12 mm top.
Pz IV D 229 built. Stayed in service (or rebuilt) with 30 mm front, 20mm sides/rear and 10/12 mm top.
Pz IV E 223 built. turret was 30mm front, 20mm side/rear and 30+30 on the hull/driver front and 20+20 on the sides and 20mm on the rear.
Pz IV F 462 built (?) from April 1941 on, number at the front in June (???)in any case, first with 50mm armor on the front in one piece, both hull and turret. First with 30mm armor Piece on hull/superstructure and turret sides. First with 30mm on the turret rear. Still with 20mm rear hull, superstructure, still with 10mm turret top and 10/12mm superstructure and hull top.

Adjust your aircraft AT guns as you see fit.
I will note that the armor layout of the early Pz IVs rather shows they were not intended to be used as breakthrough or infantry support tanks as is sometimes claimed. The Pz IV does not have equal protection at the sides and rear compared to the Pz III until the E model that appeared in the Fall of 1940.
Designed to sit back a few hundred meters and fire 75mm rounds into the combat area, yes. Also note that the B and C versions did not have bow machine guns and the basic machine gun ammo load out for the Pz IV was almost 2000 round less than the Pz IIIs with 37mm guns (and two co-ax machine guns)