19 February 2019
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Viscount history


Discover the history of the Viscount with film, video, contemporary reports from the pages of Flight Magazine, our newsletters, and aircraft operational records and photos from our database.


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Established 2005
Vickers Viscount Network
A Virtual Museum dedicated to the Vickers-Armstrongs VC2 Viscount

Viscount Technical Details

Introduction

Photo of the prototype Viscount G-AHRF The Rolls-Royce Spirit of Ecstasy


The magic of a name: Rolls-Royce. It is still a byword in automobile engineering, and their aero engines have been equally famous since the first half of the Twentieth century. The Dart is the name of a smooth-flowing, fast-running English river, and Rolls-Royce named their first and at the time their most unique engine after it - unique for two reasons, firstly because it was the first turbine in the world to drive a civil aircraft, and secondly on account of its striking simplicity.

The operating cycle of the propeller turbine (turbo-prop) follows that of the well-known jet engine. A large volume of air is sucked in at the front of the engine, compressed and blown out behind the compressor into combustion chambers where fuel is continuously sprayed in and burnt. This releases enormous heat energy, with the result that incandescent columns of gas roar out of the chambers, past the turbine blades which drive the compressor, and escape through the tail pipe into the atmosphere as a high energy jet-stream.

This is the noise you hear when a jet flies over, the roar coming from its turbines. Its power is in the form of thrust, derived from the 1,000 mile-per-hour acceleration it has imparted to the air between entering and leaving the engine, like the recoil of a gun as it fires a shell. In just the same way, the thrust of a propeller derives from the acceleration of the air it pumps through it, only of course there's much less acceleration, less noise but correspondingly more air. The noise you hear from a Dart engine is the high pitched whine of the low pressure compressor rotating assembly. The reason for the noise is that the tips of the rotating parts are virtually travelling at supersonic speed.

Turbo Prop Diagram

The efficiency of either of these 'propulsive pumps' is highest when the speed of the air leaving it is the same as that of the aircraft itself, or in other words, when the slipstream is not moving relative to the atmosphere and there's no wasted energy. It can never quite happen, but that is the theory, and when you have grasped it you can see why a jet is inefficient at the slow-to-medium flight speed suited to the propeller, and why jet automobiles will never be built.

On the other hand, there are practical limits to the velocity which a propeller can impart to its slipstream - the blade tips soon reach the speed of sound and then areodynamics are apt to go haywire - and so it in turn is unsuitable for very high-speed aircraft.

Photo of the prototype Viscount G-AHRF Propellers were the logical choice when it came to deciding how to power the Viscount

But since speed costs money, commercial jets engines are mostly confined to long-range airliners, and so propellers were the logical choice when it came to deciding how to power the Viscount, which was designed for economic cruising speeds over medium ranges. It was known that a propeller's economy might be combined with the smooth-running and compact simplicity of a turbojet, if the latter's turbine were made big enough not only to turn the compressor, but to harness the remaining jet energy for driving a propeller.

Photo of BEA - British European Airways Viscount G-AOJC

The Vickers Viscount Network is always interested to hear from anyone who has information or photographs to help complete the story of the Viscount. If you can help please contact us at
Information@VickersViscount.net.


Click here for more details about the Vickers Viscount Network

This website has been designed, built and is maintained by Geoff Blampied, Norwich, Norfolk, England.