RAF P-39 Caribou

Whatever went on, it smacks of meeting the letter of the contract but not delivering a quality product that could actually perform as advertised under operational conditions.

buffnut453 said:

Whatever went on, it smacks of meeting the letter of the contract but not delivering a quality product that could actually perform as advertised under operational conditions.

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More like fraud

MIflyer said:

On 13 April 1940 the British ordered 675 of the Bell Model 14, the export version of the P-39, which they named the Caribou. They specified two .50 cal nose guns, a 20MM Hispano instead of the 37MM cannon of the P-39, four .303 wing guns, and a maximum speed of of 394 mph at rated altitude, plus or minus 4%.

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Zipper730 said:

378.2 - 409.8 mph

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I'm so glad you are here to do the maths for us.

MIflyer said:

But the drag reduction mods were not applied to the rest of the production run. Testing in England of a standard production Caribou, renamed Airacobra I in 1941, showed a top speed of only 359 mph.

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Zipper730 said:

Why?

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$$$$$$$

Zipper730 said:

More like fraud

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How do you figure?

P-39 Expert said:

How do you figure?

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As a general rule promising something and then not delivering something with money being involved usually fits the definition.

The British knew about the weight increases, they were probably their idea.

You keep blaming the British, any real source for this?
There seems to have been a problem with the drag calculations, seeing as most (all?) Of the modifications were drag reduction ones.
Granted expectations changed but most countries wanted combat capable aircraft and in 1940/41 that included guns and protection. Things the prototype XP-39 lacked and Bell seemed to take no account of.
They promised a service aircraft with the same performance as the unequipped prototypes and in fact, their prototype never flew at speeds they claimed.

P-39 Expert said:

The British knew about the weight increases, they were probably their idea.

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The drag reductions reduced weight by 200 pounds, considering they were expecting the a/c to meet this capability in production models -- it's ridiculous that they didn't incorporate this into the line.

Shortround6 said:

You keep blaming the British, any real source for this?
There seems to have been a problem with the drag calculations, seeing as most (all?) Of the modifications were drag reduction ones.
Granted expectations changed but most countries wanted combat capable aircraft and in 1940/41 that included guns and protection. Things the prototype XP-39 lacked and Bell seemed to take no account of.
They promised a service aircraft with the same performance as the unequipped prototypes and in fact, their prototype never flew at speeds they claimed.

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The British were the purchasers on the contract. Acting like they didn't know what they were doing, or that Bell somehow cheated them is crazy.
The Brits (thought they) needed the planes so they ordered them. The situation changed, no invasion by Hitler, they didn't need them. The planes got heavier during the process because they needed self sealing tanks and pilot armor. The Brits knew how much the planes weighed during the entire process. They even increased the order from 170 to 675 planes after the P-400 had been tested at the (new) contract weight.
The British weren't hoodwinked and Bell didn't cheat them. After Pearl Harbor the AAF needed the planes so they took over the order.

This flight of the P-400 prototype before the British increased the order to 675 (or by 675) was accomplished with the aid of a time machine?

The order was in June/July of 1940. At which time the ONLY P-39s that had flown were the XP-39 (with turbo) and the XP-39B (which was the XP-39 airframe rebuilt). The first YP-39 didn't fly until Sept 13, 1940 and the first few YP-39s (out of 13) were completed without guns. Performance of the YP-39s with guns fell to a maximum speed of 368 mph at 15,000 feet. These aircraft had engines that were good for 1090hp.
They were followed by 80 P-39Cs with 1150hp engines. This order was changed to 20 P-39Cs without armor and self-sealing tanks and 60 aircraft with armor and self-sealing tanks to be called P-39Ds. The First P-39C was delivered in Jan of 1941. Performance of the P-39C included maximum speed was 379 mph at 13,000 feet. The First D was delivered to the AAF in Feb 1941 and had the four machine guns in the wing, armor and self sealing tanks. Speed was down to 360mph at 15,000ft and 368mph at 12,000ft.

Bell was quite aware of the performance shortfall of the P-39 series during the fall/winter of 1940 and into the spring. One Question is how much did the British know? another is why wasn't the contract amended/modified to reflect the lower performance? The Speed tests on the modified aircraft (2nd P-400 built) were done at the end of April 1941 which was a good ten months after the the change to 675 aircraft on the British order.

Bell must have known there was a problem because of the extensive modifications (much more than just the special paint job) that were done to test airplane. Bell was on shaky financial ground in 1939 and early 1940 and without the French and British orders it's future as a viable company may have been in doubt. The P-39C and D orders were later than the British order but delivered earlier, at least to start.

buffnut453 said:

Whatever went on, it smacks of meeting the letter of the contract but not delivering a quality product that could actually perform as advertised under operational conditions.

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Our RAF didn't want their Cobras, they lacked the altitude performance needed over Western Europe, and there was a long list of defects to fix, so we gave 212 to the Russians who tested them out for 6 months, fixed the defects and evolved group area fighting tactics for them. They couldn't get enough of them. Half of all the Russian aces flew Cobras. The top scoring allied fighter aces, flew Cobras.