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).
Letter from the Air Ministry discussing the safety and necessity of a master switch for forced landing relay circuits.
| Identifier | ExFiles\Box 168a\2\ img240 | |
| Date | 1st October 1936 | |
| Tel. No. HOLBORN 3434. Any communications on the subject of this letter should be addressed to:- THE SECRETARY, AIR MINISTRY, ADASTRAL HOUSE, KINGSWAY, LONDON, W.C.2. and the following number quoted :- 544116/36/A.D./R.D.E. Hs{Lord Ernest Hives - Chair}/Wst.1/JH. [Handwritten top right]: r 6139. AIR MINISTRY, LONDON, W.C.2. 1st October, 1936. [Handwritten left margin]: DOR{Mr Dorey} Please note and return WTY/S Gentlemen, Forced Landing Relay Switches. Reverting to your letter of above reference of June 22nd, I am to state that, in the Department's view, the master switch in the circuit between the accumulator and the generator, will be dangerous, and the question could only be considered in connection with the cables to the starter motors; the fire risk due to short circuit is extremely remote, especially as both poles are insulated from "earth". As each starter motor circuit is already controlled by the starter relay, a large proportion of the system is normally "dead", and the installation of a further main switch would not be justified. It might, however, be desirable to provide means for preventing an accidental operation of a push switch, either by protecting the push button, or by fitting a switch in the push switch circuit. To sum up it is understood that you advocate the use of a master switch (a) to reduce fire risk due to short circuits, (b) to prevent an accidental kick on the airscrew, and (c) to avoid the necessary of removing the accumulator. /It [Handwritten bottom left]: Seen [Signature] 10/10/36 Rolls Royce Ltd., Nightingale Road, Derby. | ||