The Chairman said the subject was of paramount importance to all helicopter designers, manufacturers and operators The Association had not previously had a lecture which dealt specifically with the problem and the importance of the subject meant that such a lecture was long overdue They knew that, in spite of the claims made from time to time by sundry manufacturers, helicopters did vibrate, some to a very great extent Indeed, one eminent fixed wing designer thought that by virtue of this vibration helicopters were rather more grandiose fatigue testing machines than the conventional test equipment for the purpose

The Chairman said that this was a very important occasion for the Association since it was the opening lecture of the Session It had become the custom of the Association to invite eminent persons from abroad to deliver the inaugural lecture, which frequently took the form of a broad survey by operators or manufacturers This year the Council had decided to focus attention on an engineering aspect of the helicopter, and what more important aspect was there than that of the rotor blade?

The Paper to be given was prepared jointly by Mr Price and Mr Stulen, of the Parsons Corporation, Michigan, USA, who had had extensive experience in this work Mr Price was Assistant Manager of the Aircraft Division engaged in the development and the manufacture of rotor blades and Mr Stulen was Director of Research

The CHAIRMAN, in introducing the Author, said that Dr MORLEY, who was Forward Projects Fngineer, D Napier & Son Ltd, had been sixteen years on the scientific staff of the Engine Department of the Royal Aircraft Establishment, and at the end of the war was deputy head of the Gas Dynamics Division, which ultimately became the Supersonics Division For three years thereafter, he had lectured on aircraft propulsion at the College of Aeronautics, Cranfield In his present position as Forward Projects Engineer with D Napier & Son Ltd, he was engaged principally on technical investigations into developments in aeronautics

The CHAIRMAN extended a welcome to non-members of the Association and introduced the speaker He said that Mr WILLANS had a long association with aircraft which extended back to 1935 Apart from a period during the war, when he was engaged on engine and propeller overhaul with B O A C, he had been continuously associated with aircraft maintenance in one form or another After the war he joined British European Airways as Chief Inspector, later he played an important part in BEA’s “sealed servicing” experiments, in 1950 he began his association with helicopters and since 1951 he had been engaged full time on helicopter operational and development problems (including maintenance) as Works Manager of the Helicopter Unit Against that background the Chairman felt that Mr Willans’ paper would be of interest and value to everyone

The Chairman said the Association were transferring their thoughts for the evening from the pure technicalities of the vehicle to the equally important problem of what facilities it required for operation, particularly for the inter-city transport role which had caught the imagination in the last two years, not only in this country but in the United States and elsewhere abroad

They had been very fortunate in that Mr Hough, the City Engineer and Surveyor of the City of Liverpool, would address them on the subject Liverpool was one of the cities in this country which had given a great deal of thought to the matter

The CHAIRMAN, in introducing the Author, said that Mr HARPER was educated at Latymer School, London, and at the London School of Economics in Sociology He spent seven years with I C I Ltd, in the Leather Cloth Division and Plastics Division in personnel management He became involved in work study problems and their application towards the end of the war and spent his last two years m I C I practising and teaching work study to management and other grades

The Chairman said that a short biographical note would illustrate the Lecturer's very wide experience Professor RICHARDS was engaged in research at the Royal Aircraft Establishment, Farnborough, and then went to the Bristol Aeroplane Co Ltd, from 1937 to 1939 He was a scientific officer at the National Physical Laboratory from 1939 to 1945 and then went to Vickers-Armstrong Ltd, where he was Assistant Chief Designer and Chief Aerodynamicist between 1945 and 1950 He became Professor of Aeronautical Engineering, University of Southampton, in 1950

During the past few years, it has become recognised that one of the major objections to the introduction of helicopters fitted with pressure jets at the blade tips is the high level of noise set up by the jets The source of this noise lies m the jet stream itself When air travelling at high speed mixes with the surrounding air, turbulence is formed in the region of high velocity shear and noise is emitted into the stationary or near stationary medium surrounding the jet The large velocity gradient or shear actually amplifies the sound (Ref 1) which increases as a very high power of the jet velocity, normally about the eighth power Needless to say, if turbulence exists initially in the jet stream, either from poor internal shaping of the engine or from incomplete burning of the fuel, the noise will be aggravated and a different noise law achieved With well designed jet umts, however, the eighth power law is obeyed surprisingly well