FLYBOYJ
"THE GREAT GAZOO"
From Joe BNot being an expert on the subject I am a little confused. The list of engine variants for the Allison V-1710 says that the -47 variant was an "E" model, those with the aux supercharger were F variants. Was the plane that crashed after 15 hrs flight testing fitted with the Aux supercharger?
"On April 10, 1941, two P-39Ds were ordered modified and flight tested under contract AC18373 as flying testbeds for the experimental Continental V-1430-1 supercharged inverted-Vee engine that was expected to deliver 2100 hp. These aircraft were assigned the designation XP-39E. The company designation was Model 23. A third machine was later added to the order as a nonflying static test example. Serials were 41-19501, 41-19502, and 41-71464. I am not sure whether these were newly-built aircraft, or modified P-39Ds that were assigned new serials.
However, the Continental engine was not yet ready when the XP-39E airframes were completed, and the 1325 hp Allison V-1710-47 engine was installed in its place. In pursuit of better high-altitude performance, the -47 engine was equipped with a two-stage supercharger and drove an Aeroproducts propeller."