It would have improved it's performance at higher altitudes, and would have allowed it to be used in northwest Europe, so why was a two-stage supercharger omitted? Regards, Strike Eagle
I've always wondered that as well. It had the Allison single-stage supercharger in the beginning, and even though it was modified with better engines and dual superchargers later on, with the urgency of the situation you'd think they would have fixed it to suit England's needs. It was one of the best low altitude fighters, was tough as nails, great dive speed, and had good armaments, so the dual supercharger for high altitude performance could have made it a front line fighter of choice. I do recall reading that even after they put the better engines in it still was a little lacking vs. other mainline fighters in regards to top speed.
I absolutely agree! Hopefully one of the more knowledgeable members of this site will come along and explain the reasons for the early model P-40s lacking a better supercharger.
Perhaps the same reason the P-38 as supplied to the RAF, and the Airacobra when it arrived on British shores lacked one...
That could be the reason indeed, but didn't even P-40s operated by the USAAF also lack two-staged superchargers as well? I mean, while it's true that the lack of a genuine threat of bombers striking the US mainland made high altitude interceptors(As the P-39 was originally intended to be) unnecessary, for over seas deployment, however, wouldn't you think that we would supply our air forces with Supercharged P-40s, as it would make it a more effective fighter at higher altitudes.
IIRC, it also had something to do with the different models of the Allison V-1710; decent power only really arrived with the V-1710-39 in the P40D...which also required a redesigned front fuselage and radiator... But there are two magical words at work here too... ...Lead Time The bugbear of aircraft and tank design right through WWII. The improved-power 87A-2/P40D was only ordered by the British in May 1940....when did deliveries actually start? Ordered in May 1940 - the first flying example only took to the air on the 22nd of May 1941! As far as I can see from checking Green&Swanborough, the main change to the actual Allison installation to create the V-1710-39 was an external spur reduction gear for the dual-stage supercharger. So there's a jump from the P40/40C aircraft which were rated at 1,040 hp for take-off...to 1,150 hp at take-off for the 87A (for the British)/P40D...and on to the 1,350 hp at take off of the visually-identical P40K and E with the V-1710-73 installation.
So the lack of sufficient power in the early model Allison engines, the delays in the delivery of the improved engines, as well as the requirement to redesign the fuselage and radiator, are what prevented the British(and perhaps the USAAF as well?) from acquiring P-40s with better superchargers then? Well thank you for the responses sir, your posts were informative and helpful.
It's worth remembering at times that the design of aero engines was just as young as the aeroplane itself Less than forty years at this point...war does tend to "telescope" design time - as much as lead time permits on the other side of the equation... The need for progressively more powerful versions of the Allison had to be identified...AND to an extent paid for by orders Something as "small" as an external spur gear for driving a dual-stage blower may not sound a huge change - but the engine THEN has to be thoroughly tested and any changes made to ensure it can handle the extra power That's a FULL testing regime taking many months... And in this case you've Curtiss having to redesign the aircraft itself to accomodate the changes - and THEN the resulting aircraft has to be tested fully when the new engine is ready.... Meanwhile work on the NEXT version of the V-1710 is on hands, and probably the version after that one as well! But there WAS the issue of the U.S. government banning the export of the turbosupercharger as fitted to the P38's V-1710-C15s in 1940 So it's very possible that deliveries of the 87A-2 to the RAF with its two-stage blower didn't happen UNTIL after Pearl Harbour and/or this ban was removed. Had the ban NOT been removed....the RAF would probably have been saddled with a V-1710-39 equiped, redesigned P40...but STILL, for "export" with a single-stage blower!!!! That's how the performance of the Airacobra as supplied to the UK was stifled over the original prototype the British Purchasing Commission saw being tested - the turbosupercharger was replaced with a single-stage item
Allison tried to develop two stage superchargers but they had trouble pulling it off. It was pretty complex technology and shows just how good the Rolls Royce super charger was. I can't find the name of the RR engineer who led that effort at the moment. It was described in a Spitfire book I had http://www.enginehistory.org/Convention/2009/Presentations/SuperchargingAllison.pdf I believe the Lightnings the British got were ordered by France without turbos so that their engines would be more common with the P-40s they also ordered. This is also the reason these French/British Lightning engines were not 'handed'. EDIT: Just found this in Wiki: ( I never heard of 'Anglo-French Purchasing Committe before. Have to read that after work ) In March 1940, the French and the British, through the Anglo-French Purchasing Committee, ordered a total of 667 P-38s for US$100M,[43] designated Model 322F for the French and Model 322B for the British. The aircraft would be a variant of the P-38E. The overseas Allies wished for complete commonality of Allison engines with the large numbers of Curtiss P-40 Tomahawks both nations had on order, and thus ordered the Model 322 twin right-handed engines instead of counter-rotating ones, and without turbo-superchargers. http://en.wikipedia.org/wiki/Lockheed_P-38_Lightning