FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1939
1939-1- - 1270.PDF
404 ®» ©DOT? NOVEMBER 16, I939 ONE SOLUTION: The "power egg" standardised unit for the Bristol Hercules engine. INTERCHANGEABILITY Some of the Problems Encountered When Planning a Standardisation of Aero Engine Units Examined By J. A. T. FOR some considerable time past there has been a great deal of talk concerning a scheme which, if it could be satisfactorily developed, would not only greatly simplify the installation of aero engines, but would also permit of an easy change from one engine to another. This scheme is intended chiefly for multi-engined aircraft. It aims at producing a complete installation which can be assembled as a unit and fitted to any particular class of aircraft, without it being necessary to modify the structure. The idea of the scheme is good. In times of emergency one engine could be substituted for another in only a fraction of the time it takes at present. Further, it would make the engine manufacturer completely responsible for the power unit as a whole. The aircraft constructor would only have to connect this unit to his airframe. The result would be a reduction in drawing office expenses, simplified production and a speed-up of output. So far as the opera tor or the Royal Air Force are concerned, maintenance should be cheaper, and there would be fewer machines grounded for repairs to the engine. There are many difficulties which must be overcome before the scheme can be made practicable. However, these snags have apparently been overcome in Germany and in the U.S.A., where similar schemes have been evolved, although there is very little information available regarding them. There is no reason why the scheme should not be a success in this country also. A great deal of time and money has been spent on the idea here, but so far very little seems to have been achieved. It is to be hoped that engine and aircraft manu facturers will get down to the job in a spirit of co-operation, so that the industry may benefit from any improvements resulting from the scheme and from the collaboration of aircraft and engine designers. The difficulties encountered in developing this scheme are of two kinds: aerodynamic and structural. When it is necessary to replace an engine by another of a differ ent type, but of similar horse-power, questions arise regard ing the effect on the flying qualities of the machine. There will invariably be a difference in the position of the thrust line ; this will, of course, affect airscrew ground clearance, as well as having its effect on flight in engine-on and engine- off conditions, or on rudder .control, possibly both. Posi tions of the centre of gravity will also vary and may be serious, enough to throw out the trim of the machine and necessitate structural alterations. Further, frontal area. must be considered. The engine with the largest frontal area will decide the minimum size of the bulkhead. This means that with only one particular engine is a given machine most efficient. Other engines might be working in front of a bulkhead which is possibly a square foot larger than it need be. The advantage of an engine with a small frontal area would, therefore, be lost. The scheme could, of course, be divided into two groups, which we might call A and B. Group A would apply t0' say, four or five different engines of similar horse-power, but it would be immaterial whether they were radial or in line engines. In this group the aerodynamic points nje > tioned would be most apparent. Group B would < solely with engines of a similar type, e.g. with in-line
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
