Originally Posted by
amplitude1000
I remember reading somewhere, more years ago than I care to remember, that the reason the Vickers Viscount had such long engine nacelles - longer than was strictly necessary to accommodate the Dart engines - was that the initial design called for four Alvis Leonides radial engines.
Recently I've been searching the net for some confirmation of this account, but without success. Can anybody out there throw light on this?
Hiya
amplitude1000, FWIW, some thoughts!
The Brabazon Type 11B (the Viscount) was always destined for Turboprops with the Type 11A (the Ambassador) being piston-powered. That was all 1945-time. The first RR turboprop was actually a pair of modified Derwents on a Meteor, again in 1945, and the Dart evolved from that work - and, I suspect, inherited much from the Derwent.
The Dart was first flown on the nose of a Lancaster 1947 and the first "all Dart" plane was a Wellington in 1948 which exhibited the long nacelle as seen on the Viscount, as did all subsequent Dart aircraft (I believe!!). So, I think it's more taking the long (including the jet pipe) Derwents and deriving the Dart from that which has led to the familiar Dart nacelles.
The Dart is quite stretched out - the reduction gearbox on the front is quite long, then you have the 2-stage centrifugal comps. The real length seems to be in the combustion section - probably due to the early technology (such as cooling the cans etc with early metals available and even dropping turbine inlet temps sufficiently, again for the metals available then) a throwback from Derwent days - and then the "Derwenty" jet-pipes.
Now, here we get to your "piston" then "TP" thoughts maybe! The Britannia prototype (the Brabazon Type 111) was designed with the Centaurus in mind before finally moving to the Proteus so it's nacelles could have looked more "chunky" as a result but, they too are quite long. However, being "chunkier" they look "shorter" than the sleeker Dart nacelles. So, while you are correct in that an aircraft did move from piston to TP, it was the Brit that did that and what you are seeing is more an "optical illusion" - I suspect the Brit and Viscount nacelles are probably of similar length, it's just they are chunkier on the Brit so appear "shorter".
Anyway, that's my take on it - sadly most of those who were working on this around that time are probably sadly departed so we are left to educated guesses. Anyway, my thoughts FWTW!!!! Hope of some use! Cheers,
H 'n' H