20/20 Hindsight - different armament?

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F6F Hellcat

Length - 33'7"
Wings - 42'10"

Empty weight - 9,042lbs.

F4U-1 Corsair

Length - 33'4"
Wings - 41'

Empty weight - 8,980lbs.

P-47D Thunderbolt

Length - 36'2"
Wings - 40'9"

Empty weight - 10,700lbs.
 
Thanks Jank.
I originally had a weight distribution table in mind, like this example (He-162A1, excerpt from my database)

airframe: 839 Kg (1847.5lbs)
engine and related equipment: 673 Kg (1482lbs)
all time equipment: 11 Kg (24lbs)
--------------------------------
empty weight: 1523 Kg (3353lbs)
--------------------------------
+ additonal equipment(including guns, optics, ejection seat): 339 Kg (746.5lbs)
+ crew: 100 Kg (202 lbs)
--------------------------------
"Rüstgewicht": 1862 Kg (4100 lbs)
--------------------------------
Fuel: 780 Kg (1718 lbs)
ammo: 58 Kg (128 lbs)
--------------------------------
loadings: 838 Kg (1845 lbs)
--------------------------------
usual take off weight: 2800 Kg (6166 lbs)
--------------------------------
additional weight (not included): jettisonable rocket assitence take off booster
--------------------------------
-guns are fuselage mounted, guns do not share recoil with the engine.
relative loading factor: 100%
off centre recoil: little
gun recoil factor (2 MG 151/20): 0.0593
composite structural recoil-weight: 0.198
relative structural recoil strength (1.0=average, higher=better): 1.685
--------------------------------

Sal, I do see Your points. But I cannot shift from Hurricane to F4U that easily (lag of database), thats a lot of computing for me. So please tell me F4U or Hurricane?
No, I didn´t know that the P47 wings were designed for 1600 lbs bombs, thanks for Your clarification.
The ammo You had in mind would weight more thanks to non projectile weight related equipment (cases, boxes, "Gurte"(don´t know the correct engl. translation), but this isn´t my concern as You recognized.
Bombloads and recoil are physicly different loadings with different vectors, loads and different loading types (recoil=impulse). You cannot draw experience from one to the other.

 
delcyros said, "I do have one factor for my argumentation left: A six 20 mm gunned version (either P-47, F4U or P-80) was never executed. So I ask why, if the relative loads would be the same in comparison with 0.5´s? The answer only can be because of the issues of recoil and / or recoil related structural reinforcements."

First, I never said the relative loads would be the same with six 20's as eight .50's. I pointed out that the weight load could be the same or less depending on the ammunition load carried. I also indicated that given the overengineered strength of the P-47's structure (By way of example, it was designed to handle a far greater bomb load for instance than it actually carried into combat and thus may have been able to handle far greater gun recoil forces as well.) it was possible that little if any additional weight would be required to reinforce the wing. Keep in mind that the little Hurricane, designed to handle a compliment of .303 machine guns, only required 129lbs of reinforcement (your claim) in each wing to handle 20mm cannons.

As for your calling into question why 20mm guns weren't used if they were possible, I think you know better than to pose such a specious point. You know very well that there are a whole host of considerations that go into the choice of armament for an aircraft that have nothing to do with whether it is possible or better.

The .50 was performing just fine and to quote one P-47 pilot, ""When eight fifty caliber machine guns converge at 200 yards, things happen." A switch to 20mm cannons would have only had a benefit for ground attack as eight .50's often caused enemy fighters to just desintegrate or explode. Targets succeptible to 20mm fire were usually succeptible to damage from .50 rounds as well. The USAAF also liked uniformity in production and application for reasons of efficiency.

We all know that the .50 was obsolete in the Korean conflict as an air to air weapon. Quite often, Mig-15's made it back with many hits from .50 cal guns. The USAAF knew the same thing the USN knew in WWII and that was that the 20mm was 2-1/2 to 3 times more effective than the .50. So why did the F-86 utilize six .50's instead of four 20mm's? The answer to that question tracks the answer to your question about why the USAAF outfitted its late war WWII fighters with 20mm guns.
 

To the earlier part of Your post I want to underline that the P-47 may carry these loads (6 HS MKV, wingmounted) with a structural reinforcement of the wing. I am not familar with the P-47 wingstructure, only knowing she is thick skinned and has a rugged fuselage. Nethertheless it makes a difference to handle bombs or recoils. Whether or not the original wing structure was overdesigned enough to handle the recoil of three times a 0.5 cal. without reinforcement is very much of speculation. I do hear it for the first time. Would be interesting to know if and to what degree structural redundance played a role in her design.
At least, there are tradeoffs for such an overgunned P-47:
heavy off-centre recoil (always makes problems at prolonged aiming&shooting and may cause loss of controll once assymetric recoil [due to one jammed or damaged gun] ocurred), recoil-weight on the upper edge of what is usual, at least for fighterplanes (this may have low impact at low alts but grave impacts at hi alts), a lower ammo-load with a reduced total firing time (reducing the tactical flexibility of the A/C), higher vulnarability (due to unprotected ammoboxes in the wing), possible performance reduction (due to increased weights of the wings).

Does any of You have the weight of the P-47D-airframe? (exclude all equipment, fueltanks and engine related equipment. Only weight for load distributing structural parts of the airframe and the fuselage)

I cannot agree more on the latter part, Jank. The 0.50 was a decent gun and more than adaequate for USAAF needs, at least against the Luftwaffe fighter force. My estimation is that the use of 0.50 was excellent for hi alt fighter, such as the P-47.
 
red admiral said:
120round drum. The 20mm was often removed in service.
Click to expand...

Where did you find this I've never heard of either. 20mm is often mentioned as the pilots favorite gun, and 150 is the standard ammo capacity though some references cite slightly reduced count (120) for added reliability but not as the capacity.

wmaxt
 
If it helps one P80 was tried with 4 x 20 instead of the 6 x .50 but it wasn't taken up. If anyone knows why it might be a valuble input into this debate.
 
I would bet that the 20 mm P-80 was tried after a whole bunch of .50 cal. planes were already flying and standardization was what the USAF was thinking. Just a guess but the military brass thinks in those strange ways.

Here's some more random thoughts on guns and pilots. We assume and make excuses for the "average" pilot's ability to hit targets with ordnance. As we know the Imperial Japanese Navy, Air Force and the Luftwaffe had towering requirements for pilots which exceeded more than just gunnery. The men accepted were few and they were the elite of the elite in all around perfection in aerial combat.

These men were shooters and could hit with any weapon given them. They made no excuse that their ordnance was too slow or too weak. They knew how to shoot and hit the target even alternating between weapons of different projectile velocities.

They weren't equal to newly graduated American pilots by 1944 who went on to fly 149 missions and score 2 kills. While the mass training of men that came out as "pretty good" pilots was enough by that time in the war, it was not comparable to IJN or Luftwaffe meistros that were trained in 1939 and were "excellent." The "average" pilots from those ranks were far above the American "average" of 1944.

Of course we know the loss of the elite cadre was devastating to the Germans and Japanese. They couldn't be easily or quickly replaced. Neither country envisioned a conflict where vast hordes of airmen would be required in a protracted struggle. The American system produced quantities that simply overwhelmed its foes.

Fifty calibers could kill at a mile and there were cases of that happening. There were gunnery virtuosos in the USAF. Being that I have long associated with aces I never heard "average" guys whining about real or perceived advantages the enemy had. Fifties were adequate weapons. 20 mms had more punch but magazines held fewer rounds. So were fifties better for the "average" pilot who could squander ammo to some extent? Perhaps. But not hitting with 400 rounds of .50 ammo is the same as not hitting with 150 rounds of 20 mm. If you can't hit with 50s, 20s aren't going to do you any good!

The truly great American aces had the "force" like Japanese and German aces did. They killed with fifties at up to 1/2 a mile away on a regular basis. Their planes had enough ordnance to make multiple kills. What else do you need if you have skill?

This was hammered home to me by 10 victory Korean War ace Hal Fischer. Remember the F-86's fifties had a faster firing rate than the WW 2 weapons. They carried 297 RPG. I was thinking that was not much ammo like most people here asked him about it.

Fischer grinned in amusement to my lame question. "More than enough. A one second burst was all that was needed," he nearly whispered. "And it doesn't take much to damage a turbine, he added.

When I asked if the 6 guns was sufficient his soft voice continued," Four would have been enough. It takes less rounds to kill a jet due to its fewer engine parts."

Another 10 kill ace Ralph Parr answered my question of the adequacy of fifties with, "sure 20 mms would have been great." Yet in the next sentence explained how he used the F-86F's A-4 lead computing gun sight to take out his seventh victim at a phenomenal 4,800 feet!!

Gunther Rall smiled when he explained how it was "quite easy really if you have the experience to alternate bewteen the MG FF and the MG 17 or 131," when I asked about velocity differentials.

It was an even sixty rounds per plane times six. That's all it took for Hans-Joachim Marseille to down six Tomahawks of the British Desert Air Force (DAF). What's more amazing is that the 20-millimeter nose cannon had jammed after only ten rounds were fired. The Star of Africa finished them all off with the pair of 7.9 mm MG 17s above the cowl!

So if .50s were so "average" why the heck did the military continue to arm planes with them? I can see that in WW 2 the industial-military complex was geared for the Brownings' production. This is like the many other weapons, vehicles or equipment produced- even if something demostrably better was found the alteration to production facilities might have been more than was deemed acceptable at the time. IE., don't rock the boat.

I think that goes back to the 20 mm vs the .50 calibered P-80. There was probably a USAF comment like "yeah we already produced 1,000 with fifty calibers and maintence and is set up for that on form # AP-34590 for ordnance procurement, bla, bla, bla."
 
Excellent post, Twitch. But I do not think anyone has stated the .50 cal to be average. The feeling of most people on this site is that the .50 cal was enough to bring down any fighter. But the 20mm was, obviously, more destructive and probably more flexiable because of it's ability to take on both fighters and bombers.

I have to ask, did any of the Korean pilots you spoke to mention anything about MiGs escaping with the battle damage they'd inflicted on them?
 
Twitch said, "It takes less rounds to kill a jet due to its fewer engine parts."

Perhaps but in Korea, the planes had far sturdier construction as the speeds and g-forces they were subjected to were greater. I understand that the non-explosive .50 was obsolete due to the greater resistance the thicker skin and structural pieces posed to the non-explosive .50.

I have read a number of accounts of .50's not getting the job done. That's not to say that there weren't plenty of instances where it obviously did but a lot of Migs made it back peppered pretty good with .50 hits. F-86's, on the other hand, didn't fare so well against non-critical hits from the Mig's 23mm (.92 cal.) explosive rounds.

The USAF was stubbornly wedded to the .50 in an era where literally everyone elso had figured out the advantages of the 20mm. The USN was ahead of the curve and outfitted even its propeller driven Corsairs and Skyraiders with 20mm's. In WWII though, against enemy fighters, it did just fine.
 
Korea was different in many ways.
Funny thing is I just read the opposite opinion from a veteran, describing how much it took to knock it out with 0.50 cal. because the engine had fewer parts and could take more punishment. Sounds logical if we factor the vulnarability of piston engines due to cooling equipment properly.
I think the P80 was tried with four 20mm, am I correct?
 
Re the damage I suspect it would depend on where you hit. If a .50 hit the blades then its almost certain to almost disintigrate as the early engines didn't contain damage very well. The blades would fly in all directions and totally take out the engine and anything else around it.
If the .50 hit any other part of the aircraft then it wouldn't cause as much damage due to the additional strength required.

If a Mig 15 hit the F86 then it was almost certain to go down. Few survived a hit from the 37mm and one hit from the 23mm had a high probability of destroying the F86. It should be remembered that her engine was equally liable to self destruct and the 23mm chucks out a lot of shrapnel any piece of which would take out the engine if it hit the blades.

The ability to contain damage is still a major part of the engine design and is a difficult test to pass.
 
Thicker skin mentioned by Jank is exactly why you'd want armor-piercing power such as the API belts had. Explosive shells exploding outside the fuselage do far less damage than ones going boom inside.

The NS-23 cannon had a low cyclic speed of just 550 RPM and a slower muzzle velocity of 690 meter per second. Forget the NS- 37 unless sheer luck was at work with a 250 RPM but with a quicker 900 MPS.

Actual muzzle power scales show the MiG 15 lower at 2,070 vs the Sabre's 2,200 but wins in weight of fire per second at 8.69 kg to the F-86A's 5.82 with the .50 M3 weapons firing at 1,200 RPM.

The FJ-2 Fury with 4- Mk. 12 20 mm cannon had a muzzle power of 3,740 and a weight of fire of 7.32 kg. The 4X20 mm Panthers and Banshees with Hispanos had a 2,600 muzzle power with 7.37 kg weight of fire.

When the F-86H arrived in combat with 4 M39 20 mms it boasted a muzzle power of 6,070 with 11.44 kg weight of fire.

The MiG 15's NS 23s had just 80 rounds per gun! Early on the inadaquacy of these weapons was a concern so the Nudelmann 37 mm was installed but carried just 40 rounds. This gave 8.7 seconds of 23 mm fire and 10 seconds of 37 mm. The 267 RPG of the F-86A-F gave 13.3 seconds of fire.

While we all know if the MiG 15's performance abilities it still comes down to putting ordnance downrange and on target. Since MiG drivers didn't have G suits the F-86 guys had it all over them in that respect all the time. You can't shoot strait when you're being slammed by Gs. The radar controlled, lead computing Mk. 18, A-1CM and later A-4 gunsights had no Soviet counterpart. THAT alone compensated for any perceived advantage of armament.

The MiG 17 carried over the same 23/37 mm mix but the newer NR 23 mms fired at 1,100 RPM now. The 37 was finally dumped and replaced by a 3rd 23 mm weapon.

In fact the only saving grace was the intrusion of experienced Russian pilots in the mix. There were only 2 North Korean aces with 6 and 8 kills respectively. The Chinese produced 6 aces with a combined total of 48 kills. So if it was up to indigenous pilots their performance was sadly lacking.

This is the same kind of results as with the Gulf War- decent imported hardware but the inability to successfully engage in the air and scored ZERO kills.
 
Twitch I seem to have different numbers to you. According to my records the NS 23 had a ROF of 690 RPm not 550 and a MV of 740m/s not 690m/s.

These are not fantastic but not bad for the size of the weapon and make it quite a dangerous weapon against other fighters. You are correct re the 37mm which was only useful against bombers.
The observations re the radar gunsight are also spot on once it arrived in theatre. However the early F86 didn't carry it and neither did the other aircraft so the Mig 15 still made a decent showing.
 
Sal, you may have the same or a similar publication as I have. The surprising thing is that not only is the P-47M designed to carry 1,600lb bombs under each wing but also a 1,000lb bomb under the belly. That's 4,200lbs of bombs!

The P-47N has the same bomb capacity under the wings but only a 500lb bomb under the belly for a 3,700lb bomb load.

While the design capacity was high though, I have never heard of P-47's carrying more than 2,500lbs of bombs.
 
Sorry to arrive late for this one, gentlemen - I have a few comments.

The US outfit of six (or eight) .50s was entirely adequate to deal with fighter opposition in WW2. However, good 20mm cannon offered a better power-to-weight ratio because of the explosive/incendiary contents of their shells, so you could achieve equal destructive effect with a lighter armament weight - or faster destruction with the same weight. The RAF found that their normal allocation of 120 rpg for the 20mm was adequate, few pilots expended all of their ammo on a mission.

I have never read of any inherent problems caused by the recoil of 20mm cannon. The British found specific installation problems which had to be solved on every plane with wing-mounted Hispanos, but solving them was a matter of fine-tuning the installation. The Hurricane IIC was not designed as a specialised ground-attack plane (that was the IID, with two 40mm guns and more armour) but as a fighter: the fact that from about 1943 it was used for ground attack was simply because its performance as a fighter was outclassed by then.

Note that in every air force which had a choice of good HMGs or cannon, they went to cannon even when they didn't have heavy bombers to deal with (the Soviets had the excellent 12.7mm Berezin UB series, as powerful as the .50 M2 and lighter and faster-firing, but they still switched to the heavier, slower-firing 20mm ShVAK where they could). Even the USN wanted to move to cannon, being held up by the unreliability of the US-built Hispano. The USAAF was the only organisation to prefer the HMG.

In Korea, it took an average of over 1,000 .50 cal rounds to down each MiG-15. The MiGs sometimes returned to base with up to fifty .50 cal holes in them. The USAF responded to criticism of the .50's ineffectiveness by setting up Project GunVal, equipping some F-86's with 20mm cannon and trying them in combat. After Korea, every new US fighter had 20mm cannon.

If you're interested in aircraft guns, you'll find a lot of articles, data, illustrations etc on my website.

Tony Williams: Military gun and ammunition website and discussion forum
 
Finnish pilots found the .50 inadequate to deal with planes like the Il-2 and the Pe-2 and even the I-153 had pilot armour often sufficient to resist .50 fire.
 
pasoleati said:
Finnish pilots found the .50 inadequate to deal with planes like the Il-2 and the Pe-2 and even the I-153 had pilot armour often sufficient to resist .50 fire.
Click to expand...
True, but IIRC their fighters only had a couple of .50s and they were synchronised, drastically reducing their rate of fire. The .50 was effective in USAAF planes because it was used in quantity.

Tony Williams: Military gun and ammunition website and discussion forum
 


Welcome to our discussion, Tony Williams!
The recoil phenomen is a troublesome one. There are few docs, dealing completely with them and even in cases when the recoil made use impossible (Fw-190 with underwing mounted MK 103), recoil isn´t adressed as the main problem. I may submit an excerpt from my database which clearly shows that recoil/weight ratios are specific ones for fighter A/C, which -beside from a very few exception- generally avoid a ratio over .1. Attack A/C do have a higher ratio, but are often limited to low level (high air density) purposes.

best regards,
 
Recoil is a complex subject with a number of different aspects.

First of all, guns of equal power do not necessarily produce equal recoil effects on the aircraft. There is a difference between the recoil impulse generated by a cartridge - which basically equals (projectile weight x muzzle velocity) + (propellant weight x escape velocity) - and the severity of the recoil kick transmitted to the mounting. Heavy guns recoil more slowly than light ones. Certain types of gun action also soften the recoil kick by spreading it out over a longer period, for example long-recoil designs (the P-39's 37mm M4 and the Hurricane IID's 40mm Vickers) and API blowbacks (Oerlikon FF, MG-FF, MK 108 ).

Then there was the effect of the mountings, some of which could absorb and smooth out the recoil kicks better than others. The US Edgewater mounting was particularly good in this respect and was promptly adopted by the British. This is an extract from 'Flying Guns – World War 2: Development of Aircraft Guns, Ammunition and Installations 1933-45' by Emmanuel Gustin and myself:

"To give some examples, the .50" Browning in the Spitfire IX had a peak recoil load of 2,700 kg (which was reduced to 1,000 kg when the absorbent Edgewater mounting was used); the 20 mm Hispano peak load varied between 1,450 kg (Edgewater) to 4,000 kg depending on the mounting; while the 40 mm Class S peaked at just 2,270 kg and the 57 mm Molins gun at 2,900 kg. Of course, the total recoil of the big guns was far greater than the smaller ones, but it was spread much more evenly through the firing cycle."

It is worth noting that there are different effects on the aircraft where recoil is concerned; the effect on the aircraft's structure and the effect on its flight attitude. The effect on the structure mainly concerns the degree of vibration caused, and this is where the type of mounting matters such a lot. The effect on the flight attitude depends on the total recoil, and the location of the guns. Firing powerful underwing guns tended to make the nose drop, which meant that only two or three shots could be fired before reaiming. This certainly affected the Il-2M3 with its NS-37 cannon, and also the Hurricane IID. It may also have partly explained why the Fw 190 + MK 103 was not a successful combination (another possible reason is that the mounting and/or wing were not rigid enough to maintain accuracy).

And of course, if a powerful wing-mounted gun jammed, the aircraft would slew sideways from the recoil of the gun(s) on the other side, making aiming impossible. As a matter of interest, with modern fighters in which the only gun is mounted to one side of the centre line, the rudder automatically corrects for this when the gun is fired.

Tony Williams: Military gun and ammunition website and discussion forum
 
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