Spit IIa is now so much more inferior to the 109

[camber]

Originally Posted by lane

You've got that all scrambled. N3171 hadn't even flown yet on 9-6-39. The power figures on the engine Inspection and Test Certificate come from "test bed conditions", either at RR, RAE or the dynamometer at AAEE, i.e. the engine wasn't even mounted in an airframe and the engine surely wasn't running at 12,500 feet without an airframe.

Didn't you see the pic of the RAE Anson with the Merlin mounting on the top

I got a bit confused by the height reference...but of course these are test bed figures.

I would be interested in the test bed setup. For the Merlin hooked to a dynamometer setup, there would be a variable load (allowing rpm setting for any throttle etc. setting) with bhp measurement. To simulate altitude, the supercharger intake could be connected to a chamber of correct maintained underpressure. Then height and rpm could be set and boost/bhp measured.

But to know the real setup would require the actual protocol and equipment used here, which is not in these reports. I would be interested in whether a test run Merlin III could handle +10.5psi boost on the bench (even briefly)with 87 octane without predetonation reducing power, but couldn't these be calculated values in the reports anyway? (actual tests at SL, but corrected for particular FTH etc)