All of us know the history of the helicopter, but certain facets of this history need to be repeated in the framework of the development of the rigid rotor helicopter. It was in 1919, I believe, that Juan de la Cierva, shocked from the death of his brother in a spin accident, reasoned that the best way to build an aeroplane was to build one that made use of the spin as a fundamental. He put a bearing between the spinning wings and the fuselage so that the wings could spin without spinning the fuselage. This was a great advance in the state of the art and created an aeroplane with some rather good low-speed characteristics.

It is well known that the performance of the practical gas turbine cycle, in which compression and expansion are non-isentropic, is critically dependent upon the maximum temperature of the working fluid. In engines in which shaft-power is produced the thermal efficiency and the specific power output rise steadily as the turbine inlet temperature is increased. In jet engines, in which the gas turbine has so far found its greatest success, similar advantages of high temperature operation accrue, more particularly as aircraft speeds increase to utilise the higher resultant jet velocities. Even in high by-pass ratio engines, designed specifically to reduce jet efflux velocities for application to lower speed aircraft, overall engine performance responds very favourably to increased turbine inlet temperatures, in which, moreover, these more severe operating conditions apply continuously during flight, and not only at maximum power as with more conventional cycles.

Lifting surface computer programs now exist for calculating the air forces on oscillating wings of general planform. These have made it practicable to evaluate the transient forces on wings entering step gusts by using a long-established relation between oscillatory and indicial forces. As examples, the indicial forces on a low aspect ratio wing in incompressible flow and the indicial pressures on a delta wing at a low subsonic Mach number are calculated. In the latter case the calculated results, which are based on attached flow, are compared with measurements on the same wing in conditions of separated flow. Despite the differences in flow, surprisingly similar development histories are found.

One of the difficulties in giving a talk on flight instrument displays is that everyone in aviation seems to be an expert on this particular subject—or at least everyone has such fairly violently held prejudices that new ideas tend to be automatically opposed and are certainly viewed with suspicion. I am no exception although, of course, I consider my prejudices to be calmly reasoned opinions. Accordingly, being nominated by my Commanding Officer to address this test pilots’ group I swam into the literature on the subject— and there are fathoms of it—to find that most of my “new” ideas have been put forward before and, not only that, have often been rejected on pretty good grounds.

In fact, insofar as instrument displays are concerned, history is anything but bunk and, quoting C. G. Grey of Aeroplane fame, “history is the greatest plagiarist and repeats itself to such an extent that if you knew all history one would never make a mistake in life because one would know all the mistakes that had been made”. And as you know, the difference between plagiarism and research is that if one steals ideas from more than one person, it is research.

I hope to show that many of the latest ideas on displays have been previously tried but not pursued until later technological developments made their use necessary and possible. I also hope to put forward some of my ideas on this subject.

The problems associated with the design of a stopped rotor aircraft are summarised. The decision to attempt to overcome the aerodynamic difficulties by the choice of a rotor blade section which is basically insensitive to atmospheric gusts dictates a largely circular cross section. During the rotor lifting phases of the flight the circular section is constrained to lift by a technique called circulation control by blowing — this technique is described and some results presented. A scale model hingeless rotor has been tested at the National Gas Turbine Establishment. Typical performance figures are presented and their implications discussed. In particular, it is shown that operating rotors at high values of thrust coefficient per blade leads to high induced power factors. Cyclic control of rotor lift is achieved by hub throttling the air to the circulation control slots —a simple mechanism to achieve this result is described. Two possible schemes for a VTOL circulation control stopped rotor transport are discussed and compared.

The crudest way of taking account of the airframe superstructure in calculating undercarriage performance is to represent it by a single concentrated mass. Crude as this method is, it is often used by aircraft firms because the only alternative known to them, apparently, is something they hesitate to face. And no wonder, because it means having to represent the wing-fuselage system by a large number of lumped masses and springs, each of which means an extra degree of freedom. This complicated dynamic system has then to be integrated with the undercarriage system, itself complicated by its non-linear characteristics.

The natural approach that suggests itself is not to consider the w/f (wing-fuselage) structure ab initio but to make use of its (usually known) normal modes and frequencies. But this is just what cannot be done by existing techniques—hence the present impasse.

Much of what I am going to say is opinion and many will find it controversial. It is therefore essential to start off from a firm and incontrovertible basis of fact. By this means it should be possible to narrow down the controversy considerably.

Table I represents the state of aviation in this country in comparison with the USA. These facts are confined to civil aviation since it is the growth of civil aviation that I am talking about.

This paper describes seven city heliports in the US, considering first their physical features and associated operating factors and, second, the possible application of the operational experience gained with these heliports to future heliport design.

Three of the seven heliports are in New York City—the Pan American Building rooftop, Wall Street Pier near the confluence of the Hudson and East Rivers, and the World's Fair Heliport. One is in Chicago, at Midway Airport. The remaining three are in California; Los Angeles International Airport, Anaheim / Disneyland, and Oakland.

Taken collectively, the seven heliports are representative of city heliport operation in the US today. Taken individually, they represent considerable variation in the significant factors affecting their operation, such as noise, height above ground level, traffic control towers, interface with other modes of transportation, both air and surface, lighting, instrument operation, obstacle clearance, turbulence, and related factors.

The authors were requested to present short papers giving opposing views on the subject of Guided Weapon Simulators. Much of this subject is now a matter of fact and the authors found themselves in agreement on far too many points regarding the present situation to follow the requested approach, and instead have adopted the method of writing a joint paper briefly reviewing the past history of simulation and setting out the present state of the art as they see it, leaving the discussion of probable future trends to encourage controversy. It has still been difficult to be controversial, but if some of the statements made stimulate discussion then a useful purpose will have been served. It may turn out that what the authors have found difficult to produce between themselves has been created only too readily between themselves and their audience.

It is not possible to discuss simulators without bringing in the concept of modelling, indeed an apt title for this paper could have been “From Simulation to Modelling”. The model technique has been defined as “a procedure in which a representation of a system is developed in some more convenient medium and checked to show that its behaviour agrees with that of the original system for a wide variety of conditions”.

A forecast of future development for a period of 10 years postulates a complete change in civil air transport. Future city centre heliport developments are considered from an airport operator's point of view.

Full consideration has been given to helicopter sites in London by the Morris Report of 1961 and a VTOL Working Party of the Aeronautical Research Committee is now considering a report on the siting of Terminals for an Intraurban VTOL transport system.

Generally, the main considerations of committees on heliports consider the problems under the headings: —

1. Characteristics of the aircraft.

2. Noise limitations.

3. Safety, including aerodynamic effect of neighbouring buildings.

4. Air traffic control and operating procedures.

5. Traffic growth considerations.

6. Design layout and location of terminals.

7. Access to the city centre must be good and possibly not more than 15 minutes journey time.