Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules
THE REASON WAS WEIGHT. WEIGHT per your photo says the P-400 gross weight was 7845#. The P-39C weighed 7075#, that extra 770# is the difference in the 355mph vs the 379mph. Everything about the P-39C and the P-400 was exactly the same (engine, propeller, aerodynamics) except the additional 770#. To put this in perspective, you know the performance benefits of dropping your external tank for combat, it is quite substantial or the pilots would not have dropped them. A 75 gallon external tank only weighed 500# FULL OF FUEL. We're talking about 770# here. This is the same reason that the Russian P-39s outperformed the Luftwaffe, they discarded the useless 30 caliber wing guns and one of the radios (didn't use their frequency) and got much better performance.
I think drgondog has answered this more expertly than I could, my short answer would be "any marque of either v any marque P-39".Okay, pick one. FW190 or Me109. Either one. Which version of each so we know we are comparing the correct version of the P-39.
Glad you are sourcing wwiiaircraftperformance, that is the source of most of my radical theories on the P-39. Please indulge me, print the P-39K performance chart. Then take a pencil and chart the performance figures of the A6M2, SpitV, Me109G1 and maybe the Wildcat over the P-39K lines. Then chart the P-39C figures in your report above. This will clearly show the performance of the P-39C as compared to the other planes. Couple of observations, the 6689# figure is with "mean fuel" which is roughly half the tank capacity. Add back half the fuel 360# and you get approximately your 7075# gross weight. Virtually all the American fighter tests used this "half fuel" figure for gross weight, since you couldn't fight your enemy full of fuel since you would still be on the runway and you couldn't fight with no fuel for obvious reasons so for calculations they used mean fuel.The P-39C did have armor, at least some and had BP glass, it didn't have self sealing tanks.
I would not use the Ray Wagner figures as gospel however. I used the photo to show the British aircraft only had 2 more RCMGs than the P-39C.
SOme of the disparity in figures come from different test conditions.
http://www.wwiiaircraftperformance.org/P-39/P-39C_40-2988.pdf
A P-39C that did do 379mph, however it was at 6689lbs, roughly 400lbs lighter than the figure Ray Wagner used. One wonders what was left out, ammo or fuel? A bit of both?
Please note the comments where under no circumstance was the oil cooling satisfactory to USAAF standards and in both high speed level flight and in climb both oil and prestone cooling did not meet USAAF standards.
Please note that Larry Bell & company were promising a LOT more than they could deliver.
Company performance chart.
http://www.wwiiaircraftperformance.org/P-39/P-39C_Chart-Bell_Aircraft-1400.jpg
Dated feb of 1940 which is well before the YP-39s flew.
I would note that the British had 675 Aircobras on order about 4 months before the first YP-39 flew let alone any P-39Cs
British test
http://www.wwiiaircraftperformance.org/P-39/AH573.pdf
I would note that while the US tested climb at 3000rpm for the first 5 minutes the British used 2600rpm for the entire climb but this was British procedure. ALL british climb figures are done at max continuous or a 30 minute rating and not at a 5 minute rating.
The Army changed the 5 minute maximum to 15 minutes maximum RETROACTIVE during mid year 1942 for virtually all their fighter combat engines (V-1710, R-2800, etc.). Now all these planes could climb at full power (3000rpm for the V-1710) for the full 15 minutes which greatly increased their climb rates. Give the P-39C the same benefit of 3000rpm for 15 minutes.
Got a better idea for you. Compare 'Period P-39 vs Period 'whatever' at the rated Hp and Boost and combat weight for each?Glad you are sourcing wwiiaircraftperformance, that is the source of most of my radical theories on the P-39. Please indulge me, print the P-39K performance chart. Then take a pencil and chart the performance figures of the A6M2, SpitV, Me109G1 and maybe the Wildcat over the P-39K lines. Then chart the P-39C figures in your report above. This will clearly show the performance of the P-39C as compared to the other planes. Couple of observations, the 6689# figure is with "mean fuel" which is roughly half the tank capacity. Add back half the fuel 360# and you get approximately your 7075# gross weight. Virtually all the American fighter tests used this "half fuel" figure for gross weight, since you couldn't fight your enemy full of fuel since you would still be on the runway and you couldn't fight with no fuel for obvious reasons so for calculations they used mean fuel.
Now when you graph the P-39C climb take one thing into account: see that little curved line starting at 12500' lowering the climb figure? The engine was at that time limited to 5 minutes at maximum power. So these tests had the pilot climb at full power (3000rpm) for the 5 minutes and then reduce rpm to 2600 (maximum continuous or max cruise) for the remainder of the climb. Check the P-38, P-40 and P-47 tests before August 1942 and they all reduced power from max power to their respective maximum cruise power in climb at the 5 minute mark per regs. The Army changed the 5 minute maximum to 15 minutes maximum RETROACTIVE during mid year 1942 for virtually all their fighter combat engines (V-1710, R-2800, etc.). Now all these planes could climb at full power (3000rpm for the V-1710) for the full 15 minutes which greatly increased their climb rates. Give the P-39C the same benefit of 3000rpm for 15 minutes. Take the rate of climb at 5 minutes (3700fpm) and from that point draw your climb rate line up diagonally to a ceiling of about 37000' and you have the climb rate for the P-39C at 15 minute full power. Full power (3000) for 15 minutes in climb makes a huge difference over full power for 5 minutes then reducing power to max continuous/max cruise (2600rpm). Once you graph all these lines on the same graph it is easy to see the performance of each plane at every altitude.
I'm with the school of thought that endorses all MG's- whether wing, cowl or through the prop hub be the Browning M-2 in .50 cal. Much more reliable than the 37 mm cannon, and as General Patton once remarked: "In combat, a gun that won't fire reliably is as useful as a pecker on a Pope" I like the prop hub mounting, when feasible, as then, where the nose is pointed, the rounds go--HansieThree comments. First the mixed armament thing, trying to deal with two different trajectories when deflection shooting. That is why I suggested an all 50 cal armament package. Second, history tells us the most US versions of the 20mm Hispano cannon had almost as much trouble with jams/un-reliability early in the war as the 37mm. Another point for staying with just Browning 50 cal guns. Finally, as far as I know, during WW2 'wet wings' implied unprotected fuel tanks. I am suggesting adding self-sealing rubber bag tanks as per other American fighters.
Is this a wind up? Are you saying that if the RAF and US air forces had been given the correct graph and data then the P-39 would have been a winner in service? 601 squadron changed from Hurricane Mk IIs to P39s flew one mission with it then changed to Spitfire Mk Vb and went to Malta. The P 39 would have been no use at all in Malta. In the UK the FW 190 was superior to the Spitfire MkV forcing the Typhoon into service early. When the P51A arrived it was used because at low / medium altitudes it was a top performer, liked by all who flew it. As soon as the P 51 arrived people started figuring out how to put a Merlin in it because its only problem was altitude performance. Merlins were also put in P-40s for the same reason. Did anyone ever suggest putting a Merlin in a P-39?Here you go boys, the vaunted FW190A6 vs. P-39N is attached. Looks like the little Cobra is faster below 5km, and the same combat speed at 8km (26000'). A little slower than the FW190's emergency maximum good for one minute with liquid injectant. US war emergency was good for 5 minutes and the engine had to be torn down and inspected after every use. Bet that German emergency maximum was an engine destroyer. Second page is rate of climb. The P-39N climbs significantly faster at all altitudes, period. A whole hell of a lot faster below 6km (20000') and about 65% faster at 8km (26000'). Personally, give me the best climb rate.
I'm with the school of thought that endorses all MG's- whether wing, cowl or through the prop hub be the Browning M-2 in .50 cal. Much more reliable than the 37 mm cannon, and as General Patton once remarked: "In combat, a gun that won't fire reliably is as useful as a pecker on a Pope" I like the prop hub mounting, when feasible, as then, where the nose is pointed, the rounds go--Hansie
Depends on the timeframe you're talking about. The 50cal only became an effective weapon in wing installations in 1942 which wouldn't be much use to the RAF in the Battle of Britain.
I'm with the school of thought that endorses all MG's- whether wing, cowl or through the prop hub be the Browning M-2 in .50 cal. Much more reliable than the 37 mm cannon, and as General Patton once remarked: "In combat, a gun that won't fire reliably is as useful as a pecker on a Pope" I like the prop hub mounting, when feasible, as then, where the nose is pointed, the rounds go--Hansie
The P39 arrived in Aug 1941 roughly when the Fw 190 entered service with the Luftwaffe and the Me109F was the standard fighter both of which had clear advantages over the P39.Just which Luftwaffe plane(s) were so superior to the P-39?
The RAF didn't need the P39 because it was so far behind the performance of contemporary fighters and your right, production was more than sufficient. The point behind the comment on lend lease was if and I repeat if, the RAF had needed them then they could have been supplied via lend lease.Regarding lend lease, how could the British take the P-39 under lend lease when they had so publicly derided them as inferior under the hard money contract? "Oh these P-39s suck, but we'll take them for free"? They no longer needed them after winning the BoB and their internal fighter production was then adequate. They didn't need them and couldn't pay for them. Bell had the last laugh though. They got a $2million cash advance from the British in the original order. Bell was a relatively new company struggling under depression era economics and although $2mil doesn't sound like much today, in 1940 dollars it was a fortune and put them in the black for the rest of the war. And the Army took over the British order and had P-39s available from 1941 on.
I am sorry but this is total rubbish. The P39's were ordered by the UK in September 1940 when it was already clear that the BOB had been won and of course France had fallen some time before. As a result it wasn't a case of cutting losses, or weaseling out of a contract (not a fan of the UK are you) it was because the P39 wasn't a match for the latest fighters and wasn't combat ready for Ground attack, a role it could have been very useful in. We did what we did with later Hurricanes, send them to Russia or somewhere else anywhere apart from Europe.Cost was the big issue, especially for the British. They had stood alone against Germany since the fall of France and they were dead broke. They had to order those planes before France fell not knowing how long the war would run. After they were safely past the Battle of Britain and a German invasion was no longer possible, they moved to cut their losses and weasel out of not only the P-39 contract but a similar contract for P-38s that were ordered without turbochargers. Those were hard money contracts and payment was demanded. The British knew that if the Battle of Britain had not gone their way and they needed the P-39s that they could have quickly stripped the excess weight (.30 cal MGs, heater, unnecessary radio equipment) from those planes to make them competitive.
Yes, and didn't Browning chamber the .30 cal. 1919 MG for the British .303 cal. round?? Not sure, but seems likely to me. ThanksDepends on the timeframe you're talking about. The 50cal only became an effective weapon in wing installations in 1942 which wouldn't be much use to the RAF in the Battle of Britain.
Agree, the weight of 4 .50 Brownings in the wings, fully loaded and mounted properly would most assuredly have increased the drag..Buy the heavy machine guns in Belgium or Italy in the second half of 1930s if the US types were not up the task with 600 rpm.
Having 3 synchroised .50s under the cowl of the P-39 and 4th firing through the prop, with wing guns deleted, would've made the P-39 lighter and would've also shaved some drag. I'd also remove one of radio sets, and replace the rear-most armor with duraluminium deflection plate.
Not only did the British order 675 P39s named as "Caribou" in 1940, there were also another 150 ordered under lend lease in 1941. When they arrived they were tested and tried out, found to be not good enough so all were sent or diverted to Russia.Apologies to one and all as I hadn't seen this posting when I replied to the other response.
I am sorry but this is total rubbish. The P39's were ordered by the UK in September 1940 when it was already clear that the BOB had been won and of course France had fallen some time before. As a result it wasn't a case of cutting losses, or weaseling out of a contract (not a fan of the UK are you) it was because the P39 wasn't a match for the latest fighters and wasn't combat ready for Ground attack, a role it could have been very useful in. We did what we did with later Hurricanes, send them to Russia or somewhere else anywhere apart from Europe.
Just a thought did the UK pay for the P400's used by the USAAF?
Buy the heavy machine guns in Belgium or Italy in the second half of 1930s if the US types were not up the task with 600 rpm.
Buy the heavy machine guns in Belgium or Italy in the second half of 1930s if the US types were not up the task with 600 rpm.
Having 3 synchroised .50s under the cowl of the P-39 and 4th firing through the prop, with wing guns deleted, would've made the P-39 lighter and would've also shaved some drag. I'd also remove one of radio sets, and replace the rear-most armor with duraluminium deflection plate.