An approximate theory of parachute opening is suggested. A formula is derived for the critical opening speed (the highest speed at which the canopy develops fully) which indicates variation of the critical speed with fabric porosity, rigging line length and so forth, of the order observed in wind tunnel tests. Assuming a simple form for the air flow about the parachute, a formula is obtained also for the rate of opening of a canopy. This enables an analysis to be made of the motion of a store-parachute system during canopy development. The theory confirms the possibility of a large increase with altitude, found experimentally, in the maximum parachute force on the store.

In his article “The Expanding Domain of Aeroelasticity,” Professor Collar explains how, in the course of a few years, the subject of aeroelasticity has grown from a mere collection of problems of common interest to the aerodynamicist and the structural specialist to become a main branch of aeronautical engineering. Aeronautical engineers owe Professor Collar a debt of gratitude for defining in the clearest terms what aeroelasticity purports to be, and for removing the vagueness and uncertainty which so often permeates any new branch of science or engineering, especially when it is derived from long–established subjects, as aeroelasticity is from aerodynamics and theory of structures.

As is to be expected from one so distinguished in the aeroelastic field, Professor Collar writes especially from the standpoint of the aeroelastic specialist. Engineers with a different background, while accepting the broad principles which Professor Collar lays down, may see their applications and development in a different light.

In my little book, An Approach to Winged Flight, published in 1928, I advanced the view that the flight of all human gliders might fairly be regarded as a winged flight with locked wings.

I suppose that if the wings were unlocked they would flap upwards and the aviator would come down; but that if they could be unlocked and yet restrained by springs so strong that, until any other force were applied, they would retain their horizorital position, then it seemed credible that their movement would be under the control of the aviator and that, as soon as he knew how to exercise that control to his own advantage, he would actually be flying.

In this paper the thrust of the turbo-jet engine is rigorously defined, and is divided into the three components front external, internal and rear external. The measurement of thrust in static tests and in flight is discussed. Current methods are critically examined and test methods are proposed. Special attention is given to a method of calculating flight performance from simple static tests with different nozzle areas. A convenient form of engine curves for static tests is shown and a method of flight testing is given.

From time to time attempts have been made to produce a dynamometer capable of measuring the power output of an aero-engine during flight at various atitudes. The type that has proved the most suitable up to date in flight tests is the Bendemann hub acting on the hydraulic principle which was originally designed in Germany. The principle has recently been tested in America with moderately satisfactory results, and experiments with a modified form of the apparatus are at present being conducted at the Royal Aircraft Establishment. The Bendemann hub and its accessories are somewhat complicated and are difficult to instal in a machine and to maintain in a serviceable condition, also the apparatus will not work properly at altitudes above 20,000 feet owing to increased viscosity of the working fluid at low temperatures.

The apparatus described below is simpler in construction, lighter and more robust than the Bendemann hub, and should be capable of giving equally good results irrespective of altitude; moreover, the work of fitting it to a Service machine would not be great and would not necessitate the employment of specially skilled mechanics.

This was a joint meeting of the Royal Aeronautical Society and the Institution of Automobile Engineers, and was held in the Lecture Hall of the Royal Society of Arts, John Street, Adelphi, W.C.2, on Thursday, November 8th, 1928.

The President : He extended a hearty welcome to all present and particularly to the new President of the Institution of Automobile Engineers (Mr. L. H. Hounsfield), whom he hoped would attend many future meetings of the Society as well as the joint meetings which had been arranged. The joint meetings had been very successful indeed in the past and he hoped that, in addition to those which had already been arranged for the present session, there would be many others in future sessions.