Helicopters have several advantages over conventional fixed-wing aircraft, but so far as future operation on a wide scale is concerned, one of the most important may well be that they can be operated successfully in or near to city centres. Their acceptability to the general population depends principally on the effects of noise produced by them but no national or international standards exist at present which specify the maximum noise levels and /or the number of movements permissible for city-centre operation. There are many regulations pertaining to aircraft noise near to airports and to various noise sources in cities but none of these can be directly applied to helicopters.

The problem has been considered by the Committee on the Planning of Helicopter Stations in the London Area, which was set up by the Minister of Aviation in 1959, and whose report was published in 1961, the Wilson Committee on the Problem of Noise who reported in 1963 (Cmnd 2056), in the United States, particularly by Messrs Bolt, Beranek and Newman and also many others. It is not possible to review the literature in this short paper which gives some account of the practical work and considerations concerning the use of helicopters in London with which the author has been associated.

When I agreed to give this paper I did not appreciate the problems I would have in trying to quantify what I had as a pilot been putting into practice for some years, I have always been conscious of helicopter noise when operating into heliports or landing areas within a community and tried, by practical means, to reduce the amount of noise annoyance.

Subject to the economics being satisfactory, the more widespread use of helicopters in passenger transport might easily be seriously inhibited by restrictive noise limitations. Pilots can help to avoid this if they operate the present generation of noisy helicopters with due regard to this problem.

The experience of the New York/New Jersey metropolitan area in the setting up of the “downtown” heliport will give some notion of the obstacles one encounters, and how the interested agency may surmount those obstacles—which it is possible to do when all goes well.

If someone were to introduce a certain gracious lady as ”… that well-known Queen of England, Elizabeth II …” he would expect to meet with a slightly incredulous stare. We agree that it is a bit superfluous to say that the lady is well-known. Some propositions are so inherently true that it is better to say less rather than more, to make a point. I hope I have not gone excessively round-about to express my diffidence in setting out to prove the obvious, that the helicopter has a place in the modern, urban transport system. Equally obvious should be the fact that the down-town heliport is a natural and essential link in such a system. The proposition may require demonstration. It hardly needs proof.

This paper is intended to show what would be necessary for a heliport suitable for scheduled helicopter services should a vehicle become available which proves economically viable for inter-city services. BEA is considering the possibilty of scheduled services from Central London to near-European capitals and in this respect, some preliminary investigation of sites has been carried out. However, the views expressed in this paper are personal and do not necessarily reflect BEA policy.

In this context we are therefore concerned with a heliport which will meet the required standards of safety and regularity, and will provide passenger handling facilities, car parking and support services at least comparable with equivalent fixed wing operations. Other types of landing place for helicopters, such as helipads, helistops, and conventional airports are outside the scope of the paper although similar design criteria may apply to these facilities.

It WOULD be foolish to pretend that helicopters do not have their competitors but some may be surprised to know that in recent years one of the main competitors to the executive passenger carrying helicopter in this country has not been another aircraft but the excellent inter-city service operated by British Rail.

It would equally be misleading to pretend that there are not occasions when enquiries are received to charter a helicopter but because of the particular circumstances, including perhaps the stage length of the journey, they have to be frankly and honestly advised that it would be better to travel by scheduled air service.

This, however, has applied to the past. We are now at a stage when a whole new breed of helicopter is becoming increasingly available with improved performance, they are faster, are equipped for day and night and all weather operation and hopefully as the result of this very symposium, will be provided with the facilities to enable them to land in or close to the centre of cities and towns throughout the UK.

This paper concentrates on helicopter operations in the London area. There are of course, other fields of helicopter operations—most topically those to and from oil rigs in the North Sea—but times does not permit consideration of them on this occasion. I shall first then, attempt to set the scene by describing the layout of the controlled airspace which contains the helicopter route system for the London area.

This consists of the London Control Zone (Fig. 1), centered on London (Heathrow) Airport and it measures approximately 26 nm east to west and 16nm north to south. Its vertical extent is from ground level to FL 110 (11 000 ft approximately). This Zone is surrounded by the London Terminal Control Area, the base of which varies between 1500 ft and 2500 ft with a top limit of FL 250 (25 000 ft).

This lecture is devoted to small gas turbines defined as those in the power range up to around 3000 shp and 4000 lb thrust, ie engines for general aviation, corporate and executive aircraft and limited trainer applications and helicopters. I do not propose to deal with APUs as these were the subject of the excellent paper given by C. H. Paul in a recent Halford Lecture.

I intend, as you may have gathered from the title, to treat this subject more in a total business context rather than as a strictly technical lecture. Recognising both the strong technical traditions of the Society and the man, Major Halford, whose memory we honour, I shall, however, take some time to deal with selected technical aspects of the subject.

From tests on tunnel cascades one of the sources of loss in axial compressors could be corner stall, i.e. local separation of the flow in and near the corners between the annulus walls and the convex surfaces of the blades.

Tests on a tunnel cascade at entry Mach numbers of 0·5 and 0·6 show that, at least in a tunnel, the stalling may be cured by boundary layer control. The present tests obtain control by suction through a corner slot. The tests show that removal through the slot of 1·3% of the flow decreases the total losses of the cascade by about 25%.

A more detailed examination of the losses in the tunnel cascade without suction suggests that about three-quarters of the end losses are due to the separation and reverse flow. Much of the remaining end loss appears to result from the fact that the low energy stream tubes in the entry boundary layer would experience a disproportionately large increase in cross-sectional area during diffusion, even in attached two-dimensional flow. The suction corner control can eliminate the greater part of the end losses, by eliminating the separation.

I have chosen to speak on what I would term the military customer's point of view. You may rightly fee] that a more appropriate audience for such a talk would be the SBAC, but the country, and indeed the world, only benefits from the original and imaginative ideas and the ingenuity of aeronautical scientists and engineers by the production of aircraft and the equipment associated with their operation. It occurred to me, therefore, that this lecture presented me with an admirable opportunity for setting out some personal—and I emphasise that word—views as a representative of the largest customer of the British Aerospace Industry.