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Aviation History
1948
1948 - 2162.PDF
DECEMBER 16TH, 1948 "TO KEEP YOU TECHNICALLY INFORMED •'•.-if it monthly digest of news from the Zfjli^toL aero-engine division j THE BRISTOL THESEUS PROPELLER TURBINE An attractive design feature of all Bristol propeller turbines is the mechanical separation of the com- pressor and its corresponding turbine from that of the turbine driving the propeller, giving important advantages in easy starting, stable running and greater flexibility in flight. EASY STARTING When starting the Bristol propeller turbines, the load on the starting system is very small, since only the compressor system is rotated. It is not necessary, as with direct coupled turbines, to accelerate the propeller during starting, neither is it necessary to put the propeller into zero pitch with its attendant risks of engine overspeeding. STABLE ENGINE CONDITIONS During normal flight, abrupt changes in flight con- ditions do not react on the compressor system, tending, therefore, to avoid conditions leading to unstable engine operation. RAPID ACCELERATION Acceleration of the propeller from idling to maximum speed in about three seconds is possible with Theseus propeller turbines, which again is due to the absence of mechanical coupling between the compressor and propeller turbines. FLEXIBILITY OF CONTROL Wider control over the propeller system is obtained, making it possible to vary the propeller RPM while maintaining a constant compressor speed. This makes possible better take-off performance, while under cruising conditions the ability to reduce propeller speed results in improved efficiency and less noise. LOWER WINDMILLING DRAG Aircraft performance with one engine cut and the propeller windmilling is improved, since under these conditions the propeller is not called upon to drive the compressor. This is a great advantage under the critical conditions which arise before the propeller is feathered. ENGLAND 7 621A
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