The CHAIRMAN, in opening the meeting, said that Mr Zimmerman, a member of the scientific staff of the National Advisory Committee for Aeronautics, at Langley Field, Virginia, had long been concerned with the development of S T O L aircraft, having originated and developed the Chance-Vought circular-wing project during the war at Stratford, Connecticut In the rotary wing field, he was perhaps best known as the originator of the Flying Platform, having designed and built at Nicholls, Connecticut, shortly after the war, his so-called “Aerial Motor-cycle,” which had two side-by-side lifting propellers of disc loading about 20, interconnected by a tiny platform which he strapped to his feet like skis By 1947, he was able to demonstrate to his satisfaction that this device required no controls other than a throttle for the two engines, and that he could hover safely by applying the same reactions to his feet as he used for balancing himself when standing on the ground

The CHAIRMAN, in opening the meeting, said that it was a pleasure to welcome the first lecturer of the 1958/59 season Mr Gerstenberger, who was Chief of Dynamics at the Sikorsky Aircraft Division of the United Aircraft Corporation, Bridgeport and Stratford, Connecticut, would be discussing the equipment necessary for the all-weather operation of helicopters

The Association was grateful to Mr Gerstenberger and to his Company for making available the benefit of their considerable experience in this field, and they were to be congratulated on having successfully evolved very reliable systems equipment, especially in their latest machine, the HSS-1N, of which Mr Gerstenberger would be speaking this evening

The CHAIRMAN, in introducing the Author, said that Mr HOOPER was presenting to the Association its first lecture on the subject of wind tunnel testing of helicopter models Mr Hooper had a long experience of wind tunnel techniques and had also been able to apply some of these techniques recently in investigating the aerodynamic features of one of the latest rotary-wing prototypes—namely, the Rotodyne

Mr Hooper had been engaged on aerodynamic testing for many years, and next year would be his thirtieth year with the Fairey Aviation Company He had investigated a wide range of subjects such as the aerodynamics of sails for application to racing yachts and had also been concerned with the attainment of flight speeds greater than Mach 1 Thus it was not surprising that he had taken the wind tunnel testing of helicopter models in his stride and was tonight able to give an authoritative assessment of the value of this work

A method suitable for dealing with extended longitudinal manoeuvres is outlined, based on a step-by-step integration process It is shown how the necessary calculation is carried out on a digital computer, using a programme consisting of two parts A general part is applicable to any manoeuvre, and a special part idealises the pilot's action in performing the particular manoeuvre under consideration Using two illustrative examples, it is demonstrated how the method can be used to deal with problems which usually come under the heading of performance, but nevertheless involve handling qualities Some numerical results aid in the illustration

The CHAIRMAN, in opening the meeting, said that the Author required no introduction As Technical Director of the Westland Aircraft Company since 1952, MR HOLLIS WILLIAMS had been responsible for a very successful family of helicopters, all based on well-established Sikorsky experience Previously, as Chief Engineer of the Fairey Aviation Company, he had been responsible for the development of naval aircraft, and prior to that, as Chief Engineer of General Aircraft at Hanworth, his developments had included the well-known troop-carrying gliders, the Hotspur and the Hamilcar He was a member of Council of this Association and a Fellow and Silver Medallist of the Royal Aeronautical Society He was also a helicopter pilot, having undertaken a conversion course under BASIL ARKELL in 1946, as a result of which he now held Royal Aero Club helicopter certificate No 13

The problem of installing a V H F communications equipment in a helicopter is the fitting into the aircraft of a transmitting and receiving unit and associated parts The installation should be planned with three considerations in mind, namely, operating efficiency, crew comfort and maintenance I intend to amplify these three considerations but before doing so let us look at two examples of modern V H F equipment on display here tonight

Outwardly they are of similar pattern and in both cases consist of a rack-mounted, quickly detachable, transmitter/receiver unit, which incorporates the frequency selector switch, an aerial and various types of cable connector The Murphy MR 80, MR 100 equipment has a backplate or junction box attached to the rear of the rack into which the main unit slides All control unit, aerial, and battery cable connections terminate in the backplate

The Standard Telephones STR9X is of similar form except that the cable connectors terminate on the front of the main unit

The CHAIRMAN, in introducing the Author, said that Dr Kuchemann had been a member of the scientific staff at the R A E, Farnborough, since 1946, and was now head of the Supersonics Division of the Aerodynamics Department From 1930 to 1936 he studied at the Universities of Munich and Gottingen, where he obtained the degree of Dr rer nat, and from 1936 to 1946 he had worked in the Aerodynamics Research Establishment at Gottingen under Professor Betz He was, perhaps, best known on both sides of the Atlantic for his classic textbook with J Weber “Aerodynamics of Propulsion”

The integration of the aerodynamics of a propulsive system with the aerodynamics of a lifting system as achieved in the helicopter was of fundamental significance in aeronautics and promised to become much more so in the future The Author had undertaken to discuss the generalised subject of an integrated aircraft, and it would be difficult to find anyone better qualified to present a paper of this nature

The stability of the ‘flying platform’ type of helicopter is investigated in order to determine the margin of stability and ease of control to be expected and to show the effects of the system, weights, inertias, dimensions and aerodynamic forces

This paper deals with the theory of stability in hovering and the theory is illustrated by a numerical example of a ‘typical’ pilot and platform

The stabilizing actions of the pilot are assumed to take the form of controlling moments at his ankles in linear response to errors in his attitude, rate of change of attitude, horizontal velocity and horizontal acceleration, the constants of proportionality being termed control constants

Within this framework it is shown that in the absence of delay in the pilots’ response it always is possible to stabilize the platform Further, the size of the control constants required is determined solely by the weight and centre of gravity height of the pilot, the forces involved being of the same order as those used in standing

Without a good aerial system an Aircraft Radio Equipment is about as useful as a helicopter without a rotor and yet it still happens that the proper provision and siting of aerials is neglected The intention of this paper is to outline the basic requirements of aerials for the radio systems in general used on helicopters and to show how the difficulties peculiar to this class of aircraft can be overcome

CLASSIFICATION

For the purposes of this discussion three broad categories of radio equipment can be distinguished These are

1. 1 Low frequency—i e, up to 2 Mc/s or wavelengths greater than 150 meters In this range the major aircraft dimensions are much less than the wavelength

2. 2 High frequency (H F) 2 to 30 Mc/s or wavelengths of 150 to 10 meters in which the aircraft size is becoming comparable with the wavelength

3. 3 Very High frequency (VHF), 100 to 300 Mc/s wavelength to 1 meter where the major aircraft dimensions are appreciably greater than the wavelength but where cross-sectional dimensions may be of the same order

The CHAIRMAN, in opening the meeting, said that the paper, which Mr Stallabrass had come over from Canada to present, dealt with a very important subject in the helicopter field, having as a practical objective the eventual achievement of all-weather helicopter operation The National Research Council of Canada had been studying the problem of aircraft icing long before it was necessary to devote attention to the special problems of helicopter de-icing, no doubt the climate in that part of the world having had something to do with this

Mr Stallabrass had served in the Royal Air Force from 1941 to 1947 and had experience as a pilot with Coastal Command in anti-submarine operations Later, he took an honours degree at London University in electrical engineering and worked for a year on guided missiles with the General Electric Company In 1952 he went over to Canada, where he worked on various aspects of icing research at the low temperature laboratory of the National Research Council

The CHAIRMAN, in introducing the Author, said that Dr Morley had been for 16 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 subsequently became the Supersonics Division Three years after that he was senior lecturer of aircraft propulsion at Cranfield In his present position as Forward Projects Engineer for the Napier Company he was engaged on technical investigations into developments in aeronautics

The recent years have seen a tremendous increase in the importance of the helicopter both as a defence aircraft, for anti mine, anti submarine and assault purposes and as a civil transport between busy centres, and it has been overwhelmingly successful in a multitude of special duties from rescue work to crop spraying, some impossible with fixed wing aircraft The wider application of the helicopter in these many roles has directed increased attention towards the enhanced engine performance possible with the gas turbine, and to the more difficult problems of coupling the greater potential output of this form of engine with the inherent safety features of the aircraft

A method for predicting the flutter boundaries of a helicopter rotor blade is developed which is intended to provide

1. (a) an illustration of the effects of fundamental characteristics of the blade on the flutter boundaries, e g, mass axis location, flexural axis location, stiffness of control circuit, etc

2. (b) a basic approach which may be developed and expanded to provide more detailed representation of any particular blade problem For example, in addition to giving the flutter boundaries for the blade, the equations in the form presented could be used to determine the response of the rotor blade to force distributions which are simple harmonics of the rotor angular velocity Another example is given at the end of this report in which the familiar blade resonance diagram is obtained for the torsion and flapping modes considering dynamic and stiffness properties only, and then again for the blade including the effect of aerodynamic damping