From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Performance of engines in aircraft, focusing on power, weight, and propeller compatibility.
| Identifier | ExFiles\Box 182\M21\ img014 | |
| Date | 30th July 1917 | |
| To EH. from R.{Sir Henry Royce} c/c to BJ. ORIGINAL RECEIVED 30 JUIL 1917 X.2959 Re Performances of our Engines in Planes. With reference to the letter from Mr. Walker of the Aircraft Company on the performance of aeroplanes fitted with our engines, we think you will notice that in all cases our engines are more powerful and probably heavier (though light for their power) than other engines fitted to the planes with which they are compared. This results in a certain amount of inefficiency over which we have no control, and I think the less favourable behaviour of our engines will be found due to the two following points:- X3022 When an engine is more powerful and of increased weight, the lifting planes have a tendency to be over-loaded, and so are reduced in efficiency. We have the impression that the D.H.4 machine fitted with our 360 HP engine is approaching the limit where the efficiency of the plane falls off rapidly owing to the increased load. X.2118 In addition to this, it will be remembered that we have always thought 360 HP demanded a propeller considerably larger than has ever been fitted to the D.H.4. X2533 There is no doubt that better results can always be obtained from a lower powered engine with a big propeller, and unless the propeller diameter can be made adequate for the 360 HP, it would have been better to have fitted the smaller and lighter engine; that is to say, our Falcon engine, which would have reduced the load on the planes, and if fitted with a 10 ft. propeller would have been nearer the correct size, in our humble opinion, for the (Contd.) | ||