This paper deals with the instability of a hovering helicopter with controls fixed The generalized simple stabilization system, which is composed of rods, springs, dampers and masses and uses the rotor shaft to generate gyroscopic forces, has been analysed Special cases of a Second Order System have been considered and show that good stability can be achieved, thus overcoming the limitations of First Order Systems

The CHAIRMAN, in introducing the Author, expressed great pleasure in welcoming Mr MacMahon to this, the first lecture of the eleventh series of Annual Lectures on the helicopter situation He said that Mr MacMahon was educated at Twickenham Technical Institute During the war, he was with the Admiralty Research Laboratory, working on electromc equipment for anti-submarine warfare development After that, he was engaged on electronic developments with one or two firms and subsequently with the De Havilland Propellor Company as a development engineer engaged mainly on research and development of flight test equipment for high speed aircraft

Wing Commander BRIE said that Mr BRISTOW had been connected with many aspects of helicopter development for a number of years He first learned to fly helicopters in 1944 at Floyd Bennett Field, U S A, and in 1946 was a helicopter test pilot with Westland Aircraft Ltd In 1948 he received the Royal Aero Club Silver Medal for the relief of the Wolf Rock Lighthouse, and in 1949 the Croix de Guerre for jungle rescue in Indo China whilst he was Technical Manager and Chief Pilot with Hehcop-Air, Pans In 1950 he formed his own company, Air Whaling Ltd and pioneered the use of the helicopter for whaling m the Antarctic In 1955 he formed Bnstow Helicopters Ltd , and tonight we are to hear an account of the work being done by this Company in the Persian Gulf and the large part the helicopter plays in transporting men and materials from the mainland to the drilling rig fifty miles out in the Gulf

In this essay the projected design for a spring tab rotor system is discussed for a particular size of rotor The size of rotor discussed is one designed to lift a comfortable 2,000 lb all up weight, for a single rotor helicopter

The behaviour of the rotor system collectively and the tab particularly is discussed under various conditions with respect to performance, vibration, weight, etc

Some possible applications are considered, and suggestions for simple helicopter configurations to which the rotor system might apply are put forward

Finally there is a technical appendix, in which the assumptions made and the formulae used to get results are stated In some cases where necessary the formulae have been derived

Graphs are presented to demonstrate the necessary parameters and the behaviour of the system

The CHAIRMAN, in introducing the Author, said that Dr ROBERTS was very well known by everybody in the helicopter field m this country and abroad He had taken his B Sc Engineering Degree at Queen Mary College and his Ph D at Imperial College He had served with General Aircraft Ltd, and had also been a lecturer at Imperial College Subsequent to this appointment he had been with Saunders-Roe as Chief Project Engineer (Helicopters), and was now on the staff of Fairey Aviation where initially he had been Chief Aerodynamicist and was now Chief Project Engineer Dr Roberts was a Founder Member and a member of the Council of the Association

Considerable work has been done on wind tunnel testing of helicopter and autogyro rotors and of specific helicopter fuselages but there is no available information on the wind tunnel development of a complete design prior to construction of a prototype helicopter With interest in the stability and control of helicopters and to assist the development of a specific design the wind tunnel development was undertaken by the Aeronautical Research Laboratories