Non-turboed P-61: Jack Northrop's idea or the Air Corps' demand?

[Stephan Wilkinson]

Zero answers after 250-odd views at WIX, so maybe you folks can help...

I have read that the idea of putting supercharged but non-turbocharged engines on the P-61 was Jack Northrop's idea (presumably to save the weight and space of the turbos and their big intercoolers), and I have read that Northrop very much wanted turbos but the Army insisted on the lighter non-turbo engines. Does anybody know of any references that might show which is correct?

 

[davparlr]

I don't have much data but I suspect that it met the original 1940 spec requirements, but later improvements in enemy aircraft resulted in more power needed. It was panned pretty well in the 1944 fighter conference for inadequate speed and climb. I don't think turbos were considered as I don't think the threat was at high altitude. I could be wrong here.

 

[Shortround6]

Something to consider is that the engines used in the P-61C (the one that did get turbos) were the R-2800 "C" series which didn't exist in 1941-42. It was the same engine used in the P47M N. 2100hp at 30,000ft compared to the earlier "B" series engines which gave 2000hp at 25,000ft. Performance difference between the earlier turbo engines and the mechanical two stage engines was a bit closer.
WEP didn't exist either during the initial design stages.

 

[rinkol]

There are several possible concerns that may have influenced the original requirement

- concerns that turbosuperchargers available at the time were tempermental and provided poor throttle response
- a desire to avoid production demands that would impact production of other aircraft that clearly needed them, such as the B-17 and P-38

Aside from this, altitude performance was probably a relatively low priority as it would have seemed a reasonable expectation that night operations would be conducted at moderate altitudes to maximize payloads. In any case the altitude performance of the standard Luftwaffe bombers was limited by their single stage supercharged engines.