Groundhog Thread Part Deux - P-39 Fantasy and Fetish - The Never Ending Story (Mods take no responsibility for head against wall injuries sustained) (8 Viewers)

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There were two original XP-39Es plus a static airframe.

The first XP-39E (with a single stage Allison?) crashed about a month after the first flight. The 2nd air frame was intended from the start to use the two stage engine and be used for performance tests while the 1st was to be used in determining handling qualities, armament tests and maneuvers.
According to some accounts the static test airframe was brought up to flight standard. In any case a 3rd airframe was flown. The Performance was better than a standard P-39, but only at higher altitudes.

Bell chief test pilot Bob Stanley in a Bell company report from May of 1942.
" At 393 miles per hour at approximately 24,000ft the XP-39E is definitely faster than the P-39D. Only in speed, however, does it surpass the latter airplane, the XP-39E is inferior to the P-39D in regards to takeoff distance, landing speed, rate of climb, ceiling and general handling qualities."

Since the plane grossed over 9,000lbs with no real change in power until the higher (teens and low 20s ) altitudes were reached this is not surprising.
The engine in the 2nd and 3rd XP-39Es did have an auxiliary supercharger (2nd stage) it just wasn't very good and did not have the hydraulic variable speed drive.
26 flights had been made with the 2nd prototype by May 11th 1942. A connecting rod failed on the 27th flight and it took until June to repair the plane and flying started again in July.
Most of the flying from July to October of 1942 was concerned with propeller tests, in large part to support the P-63 program. The two remaining XP-39Es served as test beds for the two stage Allisons.
While 4000 had been on order at one point the contracts were canceled or rewritten to P-63 contracts because the XP-39E was not living up to expectations/promises (where have we heard that before :-k )

The XP-39E used the some P-39D parts and assemblies like the gun bay, landing gear parts and cabin sub assembly.
 
Definitely, it's been stated here many times that the P-63 was built because that was an issue with the P-39, but someone's not taking note... Again though, if the P-39 was so good, why build the P-63, which was better?
Well if the Bf109 and Spitfire had the engine in the middle (almost) every engine upgrade would need a completely different fuselage and wing arrangement so it would have been a different plane / type number. Much of the argument about the P-39 with an Aux supercharged engine is based on it taking to the air, I cant see that it ever did until it was a P-63. There was a huge advantage at the time to have a fuselage (or whatever) to use for mock ups and make your final drawings from what worked and what fitted, especially when you are shifting various ancillaries about in the air frame, sorting out whether things actually fit and what the effect on CoG are is more easily done on the real thing than a drawing board.
 
These were the only P-39s to really shoehorn a monster engine, but they were racers.

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Engineers at Allison recommended that a modified Allison XV-1710-135 (E31) engine be used for the two racers. The modified engines used an increased-diameter supercharger impeller and undersized pistons to reduce cylinder wall friction. Using 140-octane Mobil aviation gasoline, they produced 2,000 horsepower at 3,200 r.p.m. with 86 inches (291 kilopascals) of manifold pressure. The high power output required that the engine be provided with a continuous injection of a precisely-measured water and ethyl/methyl alcohol solution when operating above 57 inches (193 kilopascals) of manifold pressure. An 85 gallon (322 liter) tank for the injection mixture was placed in the nose.

The increased power of the modified XV-1710-135 required that the P-39's standard three-bladed propeller be replaced by a four-bladed unit from the P-63 Kingcobra. This was an Aeroproducts A624S constant-speed propeller with hollow steel blades. Its diameter was 11 feet, 0 inches (3.531 meters). The propeller gear reduction ratio remained the same, at 2.23:1, as did the remote gear box, at 1.8:1.

The V-1710-E31 was longer and heavier than the -E19 because of an outboard reduction gear box. It was 17 feet, 4.00 inches (5.283 meters) long, 3 feet, 0.75 inches (0.933 meters) high, with the same 2 foot, 5.28 inch (0.744 meters) width. It weighed 1,500 pounds (680 kilograms).



 
Well if the Bf109 and Spitfire had the engine in the middle (almost) every engine upgrade would need a completely different fuselage and wing arrangement so it would have been a different plane / type number. Much of the argument about the P-39 with an Aux supercharged engine is based on it taking to the air, I cant see that it ever did until it was a P-63. There was a huge advantage at the time to have a fuselage (or whatever) to use for mock ups and make your final drawings from what worked and what fitted, especially when you are shifting various ancillaries about in the air frame, sorting out whether things actually fit and what the effect on CoG are is more easily done on the real thing than a drawing board.

The point's the same, a bigger supercharger didn't fit in a P-39 without serious modification, yet our friend is saying it could.
The P-39 airframe was limited in design and was very much a product of its time that couldn't be adapted to keep up with advances in powerplant design. Most of the prominent WW2 fighter designs underwent powerplant variant changes and some were fitted with entirely different engine types to their original ones. Fitting the engine where Bell did gave the P-39 built-in obsolescence. For one manufacturer to have to build an entirely new aeroplane to cater for a new engine modification to keep up with trends is extraordinarily wasteful and time-consuming within that time period.
 
Let us not forget, though, that the 3rd P-63 prototype was originally intended to have a variant of the V-1650/Merlin. I have not been able to find the specific mark of the V-1650 they intended to use, but I have always assumed the V-1650-1. There is, however, more than enough room in terms of length for a Merlin 60 series. I wonder if they intended to lengthen the fuselage for the 3rd prototype? Fit a 4-blade prop? Would they have had to modify the structure of the aft section of the engine compartment in a similar manner to what they did for the production P-63?
 
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You could make a 4-row 5-cylinders per row radial and use that .... or a 6-row, 3 cylinders per row ... but what's the point?

Just put in a big battery and a Tesla motor.
Well they did put an 18 cylinder radial mid-ship in a fighter.
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It actually had good flight characteristics and performance.

Although I have no idea about the nose armor, IFF and CoG.
Pretty sure it wasn't involved in the great Stewart-Warner cockpit heater conspiracy, either...
 
They only made one Piaggio P.119. The armistice ended its development.

Max speed was 398 mph. 1,500 hp, 9,016 lbs normal, 5,373 lbs empty. Was a fighter / dive bomber. Had 4 x 12.7 mm MG + 1 x 20 mm cannon. Ceiling was only 33,000 feet,
 

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