In July, 1935, I had the honour of reading a paper before a joint conference of the Royal Aeronautical Society and the Society of British Aircraft Constructors, entitled, “ Future Research on Air-Cooled Aero Engines.” Much water has flowed under the bridges since that date, and we have entered on a period of intensive activity and development in aeronautical matters not fully envisaged 18 months ago.

A number of the suggestions put forward in my previous paper, as being suitable subject matter for research or investigation, have been, or are in course of being, investigated by various Government departments, or interested firms in this country, so that, when I received an invitation from the Royal Aeronautical Society to read another paper during the present Session, I thought it might prove useful to endeavour to write an addendum to the original paper, and try to outline the trend of a future air-cooled power plant for aircraft which would be built during the next five years, it being presumed that these engines would be designed as a result of the experimental work which had already been completed, or is being carried out at the present time, and with the object of meeting the more searching requirements demanded by this increased activity.