ericlb

Well-known Member
ok wwll guys i started a heated discussion on another site, the subject is the p - 39, it was a great ground attack aircraft below 12000 ft, but above that its performance was, well, disappointing. now if i read correctly the first mustangs had the same problem, until a Packard Merlin engine was fitted to it, then it was one of the fastest propeller airplanes built. so since the p-39 was a heavy hitter in the ground attack role, why wasnt that power plant put in it, making it better too, ???
 
My understanding was that the airframe, like the P-40, was already outdated at the beginning of the war compared to the P-51's laminar flow wing. One of the things people also forget is that Allison had relatively few engineers working on superchargers for their V-12. Rolls Royce had a a much bigger incentive, namely Nazis knocking at their front door.
 
Rolls no doubt the better engine but the British ones were basically hand made. Took American engineering to produce them in the quantities needed for the war effort.
 
Well, there are a number of reasons, the main one being that Merlins were needed for Mustangs. Since the P-39s were almost all going to the Soviets, there wasn't a lot of motivation to divert Merlins for Airacobras destined for the USSR.

Bell did build a prototype P-63 Kingcobra with a Merlin, but the P-63 ended up going into production with the Allison V-1710 instead.

Understand that the poor high-altitude performance of the P-39 wasn't so much that it was powered by the Allison V-1710 but because the turbocharger was left off due to packaging considerations. If the Bell engineers had figured out how to squeeze the Allison's turbo into the tight Airacobra fuselage without any drag-inducing protrusions, they would have done so and the P-39's altitude performance would have been far better.
 
ARMY AIR CORPS DELETED TNE BLOWER IT NEEDED...BUT, RUSSIANS KILLED TANKS & ARMOR, LIKE NO TOMORROW, W/EM...THEY LOVED THEM...P-63 KING COBRA, HAD LAMINAR WING, BIGGER ALLISON...DID U KNOW, P-39 HAD PILOT DOOR, ON BOTH SIDES?? WHY?? CONTROLS ON L, NO EXIT...BUT LARRY BELL WAS BRILLIANT INVENTOR/SALESMAN...MANY X-PLANES & VICTORIES...BE BLESSED, GRATEFUL, PREPARED...CAF P-39, HAD GARDEN HOSE FEMALE, TO KEEPTOPPING UP COOLING, AFTER LONG TAXIIS...READ 'RAGGED, RUGGED WARRIORS""
 
Merlin production

Total about 168000

Packard 55873

Rolls Royce Derby about 31090

Rolls Royce Crewe 26065

Rolls Royce Hillington 23647

Ford (UK) 30428

Continental 897

From Haynes Rolls Royce Merlin 1933-50 (all engine models) Owners' Workshop Manual

The Rolls expert on superchargers was Stanley Hooker. More in his book "Not much of an engineer"
 
I'll add that the P-38 Lightning was also powered by the Allison V-1710, and there weren't many complaints about its performance at altitude. The difference being that the P-38's engines were turbosupercharged and intercooled.
 

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