THIS paper outlines the experience gained on flight trials of the Bristol Proteus turboprop engine in the Britannia Civil Transport. The shortcomings of the conventional turboprop engine as regards take-off power at high-altitude airports and in the tropics are analyzed.
The simplest way of improving the specific fuel consumption of the turboprop engine is, says the author, to increase the compression ratio. To this end, a low- and high-pressure compressor arrangement is desirable, and the concept of the former supercharging the latter is obvious. Furthermore, there is the advantage in throttling the engine at take-off, as with a supercharged piston engine, thus having power to spare to cope with tropical or high-altitude conditions.
The consequences of this approach are examined in relation to the design of the Bristol B.E. 25 supercharged turboprop engine.