P-40 vs. ME-109

[renrich]

This is beside the point but I know that adding all the cannon, some of them in gondolas, degraded the performance a little of what were essentially small, light fighters in the BF109 and the FW190, but I wonder how the recoil of those weapons affected the fighters, especially of a cannon on one side only jammed. Seems as if there would be a pretty severe yaw component.

 

[Clay_Allison]

To me the following is a pretty good analogy of the cannon-50 BMG topic. A hunter who hunts doves will probably choose size seven and a half shot shell. The reason he does that is that he knows that a few solid hits with 7.5 shot will bring down a dove. A hunter who hunts geese will probably choose size two shot shell because a few solid hits with a size 2 will bring down a goose. Those size twos will bring down a dove also but the pattern is not very dense and a dove can fly though a pattern of twos at thirty yards and only lose a few feathers. Conversely size 7.5 shot will bring down a goose but the range has to either be very close, before the pattern opens up, so that a bunch of solid hits are made or else a lucky pellet hits a vital place. The pattern of a seven and a half is dense enough at thirty yards or even a little further that a dove cannot fly through the pattern without taking some hits.

Now the 20 mm cannon has a ROF of about ten rounds a second, so if a four cannon armed fighter fires a two second burst. he has sent 80 rounds down range at the target. A lucky hit with any of those rounds can bring down a fighter but more probably it will take several hits to be lethal. The 50 BMG has a ROF of about 15 rounds per second and a six gun fighter in a two second burst will then send 180 rounds down range at the target. The 50 BMG round is not as lethal as the 20 mm but still one lucky hit can bring down a fighter and he is far more likely to get hits with 180 rounds in the target vicinity than with only 80 rounds. The fighter is like the dove, which does not take a lot of lead to bring down. On the other hand a bomber is much more rugged, like a goose, and also a much bigger slower target, like a goose. It takes more killing but the pattern does not have to be as dense because the target is slow and big. Another factor is that the P51A with four 20 mm cannon carried 125 rounds per gun which gave it a firing time of 12.5 seconds or slightly more than six two second bursts. The P51D with six 50 BMGs carried 313 rounds per gun which gave it a firing time of 20.9 seconds or slightly more than ten two second bursts. The argument favoring the 50 BMG for fighter versus fighter combat seems clear to me.

If I'm going dove hunting with 7.5 shot, I'd rather not take a 25 pound shotgun to shoot it with.

 

[billswagger]

so better the lighter gun and not hit anything?

You might run out of ammo before you actually hit a dove.


any 109 roll charts?

mentions this is the best the pilots could achieve and dependent on pilot strength.

This report is based on 30lbs of stick force.
http://www.raafwarbirds.org.au/targetvraaf/p40_archive/pdfs/Allied AC rollrate.pdf

Bill

 

[renrich]

So you use a full choked 10 gauge punt gun because it weighs a little less than your inproved cylinder 12 gauge?

 

[Clay_Allison]

So you use a full choked 10 gauge punt gun because it weighs a little less than your inproved cylinder 12 gauge?

I think the analogy broke down somewhere. I'd use a Berezin UB or MG-131 (or similar lighter gun) rather than an M2.

 

[Demetrious]

I think the analogy broke down somewhere. I'd use a Berezin UB or MG-131 (or similar lighter gun) rather than an M2.

You go to war with the guns you've got. Which is, in fact, why the P-40 was used in the Second World War at all after the first months of 1941- the Curtiss-Wright factory was available NOW, and they needed fighters NOW, not in three months after the factory was re-tooled to produce Spitfires.

The reason the Americans got away with using the M2 is because they were in the habit of cramming hideously powerful engines into their airframes anyways, so the extra weight didn't hold down their more successful designs. The planes that would have benefited the most from the weight reduction- early-war underpowered birds like the Warhawk or the Wildcat- never would have gotten them, since the pressure on American forces was the most dire then, and co-operation between America and the Soviet Union was still gearing up- and given who was bearing the brunt of the enemy's attention, the aid was flowing one way.

As for the P-40 in North Africa, I find it odd that so many people doubt it's effectiveness. I'd expect a 1:1 kill ratio against the 109. Most of the combat was at low level, where the P-40s naturally aspirated Allison was in it's element, and the P-40 had a marked advantage over the Bf-109 in turn and roll rates. The 109, for it's part, had superior climb/vertical performance and acceleration. These performance disparities generally counter each other. Firepower was a wash; the 109 was a fragile aircraft so the Warhawk's .50s were more then sufficient, and the 109s cannons were less effective against the incredibly durable P-40.

This analysis, of course, pertains to early war- the Emil versus the Kittyhawk, for example. Both aircraft received substantial upgrades as the war progressed; the Warhawk usually doesn't get enough credit for it's horsepower upgrades since those numbers are usually given for power at 10,000 feet, and as intelligent minds on this forum have told me, the power drop-off is dramatic even at that modest altitude. So later P-40s generating 1,325 HP at sea level would be right back to 1,000 HP by the time they were at 10K.

I don't know if the Gustav was ever deployed to North Africa, or if the campaign there was over by the time it was developed, but if memory served the Gustav was a dramatic improvement over earlier 109s- the turn performance was greatly effected by the improved engine power and other modifications, IIRC. If anybody knows more about that, I'd love to hear it.

 

[renrich]

If the foreign weapons are so desirable, it is a wonder we have not been copying and producing them here in the US instead of still producing the M2, (since the 1920s) The F86 was still armed with a version of the M2 in the 50s and did fairly well. As Demetrious said, we went to war with what we had. I would have like to have seen the Garand chambered for something on the order of a very slightly downsized 270 Win but understand why Mac Arthur insisted we stay with the 3006.

 

[Vincenzo]

As for the P-40 in North Africa, I find it odd that so many people doubt it's effectiveness. I'd expect a 1:1 kill ratio against the 109. Most of the combat was at low level, where the P-40s naturally aspirated Allison was in it's element, and the P-40 had a marked advantage over the Bf-109 in turn and roll rates. The 109, for it's part, had superior climb/vertical performance and acceleration. These performance disparities generally counter each other. Firepower was a wash; the 109 was a fragile aircraft so the Warhawk's .50s were more then sufficient, and the 109s cannons were less effective against the incredibly durable P-40.

This analysis, of course, pertains to early war- the Emil versus the Kittyhawk, for example. Both aircraft received substantial upgrades as the war progressed; the Warhawk usually doesn't get enough credit for it's horsepower upgrades since those numbers are usually given for power at 10,000 feet, and as intelligent minds on this forum have told me, the power drop-off is dramatic even at that modest altitude. So later P-40s generating 1,325 HP at sea level would be right back to 1,000 HP by the time they were at 10K.

I don't know if the Gustav was ever deployed to North Africa, or if the campaign there was over by the time it was developed, but if memory served the Gustav was a dramatic improvement over earlier 109s- the turn performance was greatly effected by the improved engine power and other modifications, IIRC. If anybody knows more about that, I'd love to hear it.

Unlucky for P-40 pilots the rate was over 2:1, the data were posted some day ago in this forum.
Emil versus Kittyhawk maybe a possible engagement, but at time of Kittyhawk came, early 42, the Friederich was already avaialble.
Yes Gustav was deployed, one also captured and tested from british

 

[billswagger]

So later P-40s generating 1,325 HP at sea level would be right back to 1,000 HP by the time they were at 10K.

The P-40F still produced 1050hp at 20,000ft. Later variants of the P-40 like the K and M also used better powered Allisons which allowed for better outputs up into the mid 20k ft region.
The fact remained that up in the thinner air above 20k climb rates sank for all birds but considerably more for the heavier planes. Any power loss at altitude would hinder the P-40 much more than the Spitfire or 109.


Bill

 

[Clay_Allison]

You go to war with the guns you've got. Which is, in fact, why the P-40 was used in the Second World War at all after the first months of 1941- the Curtiss-Wright factory was available NOW, and they needed fighters NOW, not in three months after the factory was re-tooled to produce Spitfires.

The reason the Americans got away with using the M2 is because they were in the habit of cramming hideously powerful engines into their airframes anyways, so the extra weight didn't hold down their more successful designs. The planes that would have benefited the most from the weight reduction- early-war underpowered birds like the Warhawk or the Wildcat- never would have gotten them, since the pressure on American forces was the most dire then, and co-operation between America and the Soviet Union was still gearing up- and given who was bearing the brunt of the enemy's attention, the aid was flowing one way.

As for the P-40 in North Africa, I find it odd that so many people doubt it's effectiveness. I'd expect a 1:1 kill ratio against the 109. Most of the combat was at low level, where the P-40s naturally aspirated Allison was in it's element, and the P-40 had a marked advantage over the Bf-109 in turn and roll rates. The 109, for it's part, had superior climb/vertical performance and acceleration. These performance disparities generally counter each other. Firepower was a wash; the 109 was a fragile aircraft so the Warhawk's .50s were more then sufficient, and the 109s cannons were less effective against the incredibly durable P-40.

This analysis, of course, pertains to early war- the Emil versus the Kittyhawk, for example. Both aircraft received substantial upgrades as the war progressed; the Warhawk usually doesn't get enough credit for it's horsepower upgrades since those numbers are usually given for power at 10,000 feet, and as intelligent minds on this forum have told me, the power drop-off is dramatic even at that modest altitude. So later P-40s generating 1,325 HP at sea level would be right back to 1,000 HP by the time they were at 10K.

I don't know if the Gustav was ever deployed to North Africa, or if the campaign there was over by the time it was developed, but if memory served the Gustav was a dramatic improvement over earlier 109s- the turn performance was greatly effected by the improved engine power and other modifications, IIRC. If anybody knows more about that, I'd love to hear it.

We had 20 years to develop a purpose built aircraft gun and didn't pay any attention to it except for the M4 37mm cannon, which doesn't compare well to other contemporary heavy AC cannon.

"Going to war with what you have" only applies to us and not Germany, who developed AND mass produced the Mk 108 during the war?

The US military just didn't consider the guns on an aircraft to be important, they stuck something from the ground forces on it and upped the rate of fire a little.

Designing a gun is not that hard, maybe 1/500th the complexity of an engine and 1/1000th the complexity of an aircraft. That's the reason that individual men design guns and huge teams design planes. That's also the reason that once a good gun is designed, it continues to be an effective weapon for 100 years. The M1911 is still a very good gun nearly 100 years since its development by J.M. Browning. Nobody is flying even an F-86 into combat tomorrow or any time soon.

Tell any good gun company with a good designer on staff to design a longer, lighter, more linear HMG for aircraft and promise the winner first dibs on putting as many as they can produce into every plane in the inventory. I can guarantee you that Winchester, Remington, Colt, or somebody would come up with something.

 

[renrich]

The M2 weighed around 70 pounds, was 54 inches long and had a ROF of 800 to 900 RPM. The 20 mm cannon weighed 129 pounds, was 78 inches long and had a ROF of 600 RPM. 70 pounds does not seem excessive for a weapon of that power and reliability. How much weight could be saved by a redesign. If 10 pounds per gun were saved times six guns that would only be 60 pounds. There could be that much difference in pilot weight. Methinks there is hair splitting going on.

 

[Clay_Allison]

The M2 weighed around 70 pounds, was 54 inches long and had a ROF of 800 to 900 RPM. The 20 mm cannon weighed 129 pounds, was 78 inches long and had a ROF of 600 RPM. 70 pounds does not seem excessive for a weapon of that power and reliability. How much weight could be saved by a redesign. If 10 pounds per gun were saved times six guns that would only be 60 pounds. There could be that much difference in pilot weight. Methinks there is hair splitting going on.

The MG 131 weighed 36 pounds. The US had, what, six times as many gun manufacturing companies as Germany? We couldn't possibly come up with a weapon half as efficient? That's 234 pounds difference over a six gun battery. That's a whole pilot (larger than average).

 

[billswagger]

The AN/M2, the aircraft version of the gun, was both lighter and more efficient in rate of fire than whats been quoted so far.
It weighed closer to 64lbs as an aircraft gun.
I'm not sure why they couldn't have built it as light as the German 131, but it seems there might have been some ballistic advantages for such guns mounted in the wings.
http://www.warboats.org/stonerordnotes/ANM2HB R4.html


I doubt 30lbs dif was enough to justify weight changes when the gun was proving itself to be effective in the air, at high altitudes and on the ground,
Not just in the capacity to fire at longer ranges but also reliable.
" Nevertheless, the aircraft gun is still around today because no other cannon-sized gun [.60 (15mm) and larger] can compete with it for simplicity, reliability, and cost-effectiveness. "
when your aircraft weighs close to 10,000lbs loaded, there is little difference 100lbs would make especially if it meant having a less accurate or less reliable weapon.

EDIT: not implying the German weapon is less reliable, but if I'm not mistaken it fired a smaller casing.

The 109 already being a light aircraft with moderate horsepower probably got much of its performance by remaining a light aircraft.
Its really a crappy comparison because they weren't loading 6 or 8 Mg131s in the wings of the 109 with the complexities of harmonization and convergence. The 109 was armed with a pair of MGs and a nose cannon. I wonder how reliable and efficient the MG 131 would be as a six gun installation.

I think less than 30lbs difference is splitting hairs when you look at the bigger picture not just caliber and firing time.

Cannons, as the US were concerned, were not an effective air to air weapon until they matched velocity and firing time of the M2.
They didn't get the late war Hispano going until 1945, and even then it could not be used at higher altitudes with out jamming.

I also think the US had the capability to load their planes with 20mm, but the truth is the US never really had to deal with a heavy bomber threat where the HE round would've been more useful.
50 caliber did its job in the air and on the ground.

Bill

 

[tomo pauk]

In a context of major war, a cannon that can substitute 3, or 2 HMGs for a cannon is a great thing. USA produced some 100 000 fighter planes for ww2. Assuming they had 5 HMGs per plane, that's 500 000 all together. Not just producing them, it takes more time/effort/money to mount harmonise those 500K, then 200K of cannons that could do their job.
If the US necked-up their .50 M2 to 18-19mm (as shown by Germans, Russians and Japanese), their 'new' weapon would be a fraction more expensive then original M2. Plus, the plane would have to haul some 100-300 kg less guns ammo, a great thing for any WW2 fighter - F4-F and P-40 would benefited mostly in this example.

As for 'not wanting the cannon until it has the MV as HMG', I don't think it's valid.
If anything, US pilots were well trained, and their planes had great sights, so the cannon with 10-15% less MV would be equally as usefull. Again, as shown by German, Russian and Japanese pilots (majority was less trained and their planes had less sophistical sights).

 

[tomo pauk]

DP

 

[renrich]

I agree that the average pilot weighed a lot less than 234 pounds. After all, the P39 was designed for a five foot eight inch pilot. TP, no matter how well trained the average pilot was in all the US air forces, the fact remains that the vast majority were no better than average gunners. The Navy and Marine pilots were well trained in deflection shooting but the really good gunners were the exception. The 50 BMG gave them all a better opportunity to get some hits because it could put more rounds into the pattern and because of longer firing times. Being only an average gunner was not confined to the US airmen. I believe that Bubi Hartmann has been quoted as saying that he tried to get so close that he could see nothing through the windscreen but the enemy plane before pulling the trigger.
The weights I have quoted for the guns are from Dean's "America's Hundred Thousand" and I assume they are accurate. I have read that the 50 BMGs in the wings of WW2 fighters were anchored at the rear of the gun but were more free floating near the muzzle. I don't really understand that but I wonder if the mechanism used to mount the guns in the wings was not very important also and if the weight of the mounting apparatus varied according to the type of gun. Could it be that a light but heavy recoiling weapon required a more robust but heavier mounting?

 

[tomo pauk]

Sure enough, more bullets mean more hits, so 4 HMGs have advantage vs. 2 cannons.
But there are some issues about that: Me-109*, most of Japanese* Russian planes were equipped with 1-2 cannons (add a pair of LMGs, but that's a minor addition to firepower), yet they served admirably. Another is that, even if enemy plane receives 5-10 hits from HMG, those need to hit where it hurts to make a kill. Much less is needed with cannon hits. One more thing: if the target receives a bullet, it knows it's been hit and can react accordingly. But if it receives a shell, target is dead. This is important since I've read many times that 3/4 of planes were killed without knowing they're target.

As for recoil, guess that a gun mount that could handle the recoil of 2-4 HMGs could handle the recoil of 1-2 cannons. RAF experience with wing-mounted cannons is also positive from 1941 on.



*MG-FF and early Japanes cannons had low eneregy and low ammo supply, and even so they were major players

 

[DerAdlerIstGelandet]

Sorry, but it still comes down to arming your aircraft for the threat it is going to encounter. The .50 was enough to counter the 109 and 190 and other LW or Japenese aircraft. Had the US been up against bombers, they would have surely armed them with heavier weapons.

 

[Clay_Allison]

Sorry, but it still comes down to arming your aircraft for the threat it is going to encounter. The .50 was enough to counter the 109 and 190 and other LW or Japenese aircraft. Had the US been up against bombers, they would have surely armed them with heavier weapons.

You still don't get that I'm talking about the gun and not the caliber (ammunition)? (although I think the .50 should have had HE ammo like every other .50 in the war). The M2 was not an aircraft gun.

 

[DerAdlerIstGelandet]

You still don't get that I'm talking about the gun and not the caliber (ammunition)? (although I think the .50 should have had HE ammo like every other .50 in the war). The M2 was not an aircraft gun.

I get exactly what you are saying. I do however not agree with you. I think the .50 was just fine for taking on the German fighters. I think that maybe a better weapon could have been designed, but the .50 was already built and ready to use. For an army that is trying to win a war of attrittion and needs to build a large army quickly, it was the way to go. Why waste time with R&D, when you can use something you already have?