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).
The general progress of Pratt & Whitney single and double row radial engines.
| Identifier | ExFiles\Box 173\1\ img170 | |
| Date | 2nd February 1934 | |
| COPY OF REPORT RECEIVED FROM Rs.{Sir Henry Royce's Secretary} IN U.S.A. DATED 22.1.34. To Sg.{Arthur F. Sidgreaves - MD} c. to Her. c. to R.{Sir Henry Royce} c. to E.{Mr Elliott - Chief Engineer} c. to Ev.{Ivan Evernden - coachwork} c. to Lt. c. to Lb. c. to F.{Mr Friese} Pratt & Whitneys. General Progress. Pratt and Whitneys are keeping about parallel with Wrights with their single and double row radials. They all seem to be about 1.35 lbs/h.p., and have not quite reached 7 B.H.P. per cu.inch. They are not in trouble with exhaust valves at the moment. They can get 160 B.H.P. with 3 c.c. T.E.L/gal. without breaking down on the 150 hr. type test previously commented on. I asked them, what they had actually achieved by the double row radials which have now got to the state of the first production order of twenty five. The reply was that, compared with a single row radial of the same h.p. they had picked up 6-8 m.p.h. in top speed, they were very slightly worse off on power weight ratio, but 12% worse off on consumption per b.h.p. The fact that the double row runs faster, and requires therefore a lower gear reduction, penalises it slightly for weight, as a simple epicyclic cannot be used. I have no figures for the top speed of interceptors fitted with double row radials, but hope to get them in Washington. It may be difficult to compare them with our speeds as the retractable under carriage seems to be almost universal here. Frank Hawks usually has the last word in high speed machines, and I understand his latest does 275 M.P.H. which, if true, does not seem very flattering for the air cooled, as he flies an essentially peak engine. They talk a lot about 'flaps' here reducing the landing speeds of these fast machines; apparently these are a type of air brake, similar in action to that of the Fure Moth, but fitted between the ailerons. | ||