In giving this paper, my aim is to give an outline of the practical aspects of flight tests performed with a Bo. 105 helicopter, in the speed range of 100 kt to 220 kt, rather than to dwell on theoretical explanations for the results obtained, which have been dealt with in Refs. 1 and 2. In a short paper of this nature it is not possible to deal in detail with all aspects of such a test programme, so I have selected some results which I hope will be of interest. A number of similar investigations have of course been performed with other helicopters during the past, albeit not with this type of main rotor system, and to those who are familiar with these flight programmes I must apologise for not bringing any startling new discoveries.

I am breaking new ground—new ground to me—in addressing the Institution of Engineers and Shipbuilders in Scotland, since I am a dyed-in-the-wool aeronautical engineer and my professional contacts with your part of the world have been largely with Scottish aeroplane and missile activities; I know less than I should about your shipbuilding and general engineering scene apart from occasional excursions to the NEL at East Kilbride.

During the past few years there has been a surprising amount of discussion about the possibility of reviving airships. A number of schemes for new designs of rigid airship have been canvassed, all of them postulating important advances in lighter-than-air technology as compared with the ‘state-of-the-art’ at the time rigid airship development was abandoned just before the Second World War. Consideration of the factors responsible for the airship's failure may throw useful light on the validity of some of the assumptions made in recent proposals.

The aim of this paper is to describe some flight research on the aerodynamics of helicopters recently carried out by the Royal Aircraft Establishment at Bedford. Helicopter flight research has been a continuous part of the RAE programme since a Sikorsky R4 helicopter was delivered to Farnborough in 1945. Various types of single rotor helicopter including such types as the Sycamore, Sikorsky R6 and S51, Bell 47, Westland Wasp and Whirlwind have been used as test vehicles in the intervening period. More recently, two aircraft, a Westland Wessex and Westland Research Scout, have been used on aerodynamic research which includes performance, handling stability and control and some operational problems particularly those associated with operation from ships. Currently a Puma is being instrumented to take over the role of the Wessex. There is of course other flight research activity at RAE, notably in the general area of avionics in which other helicopters are used. All the tests described in this paper were made on a Wessex and are concerned with the aerodynamics of the main rotor. The work on the Research Scout which has a hingeless rotor with characteristics similar to the Lynx is used mainly for stability control and handling research and is not specifically discussed in this present paper.

The flow along the corner formed by two semi-infinite intersecting flat plates is considered in which the corner line is parallel to the streamlines of a uniform incident flow and a uniform suction is applied at the plate surfaces.