In this paper the subject is considered from an aerodynamic point of view and no discussion of the possibilities of structural integration of the engine and airframe in the sense of using parts of the engine to contribute to the structural strength or stiffness of the airframe is included, beyond the statement that the simplest consideration and roughest calculations suggest that the sort of deflections obtained on typical aircraft structures at full load do not seem compatible with the integration into such a structure of engines having rotating parts and fine clearances, although in the case of units such as ram-jets such structural integration may well be practicable and desirable. Another structural problem which leads naturally to the consideration of engine and airframe as a single unit is the problem of improving flutter characteristics by placing the concentrated masses of the engines in suitable positions relative to the wing.

The general requirements for the complete air conditioning of aircraft are discussed in the light of the complete system concept. The author takes into consideration safety, differential pressure, weight saving, power and air supply, passenger comfort, cooling and humidity. Particular systems are then described and there is a section on the test equipment required for the laboratory testing of air conditioning equipment. Cooling systems are taken first and divided into the air cycle system embodying bootstrap, turbine fan, and regenerative applications of cold air units–the vapour cycle system employing a boiling tank and that using proprietary refrigerants; properties of liquid refrigerants are discussed. Regulation of cabin temperature, air flow, humidity, pressure and oxygen is done by control systems and the equipment used is described. Four appendices give (1) suggested detailed requirements for air conditioning equipment and user requirements, (2) sample data and calculations for air conditioning a 100-seater civil transport, (3) some notes on the definition of refrigeration terms and (4) data on pressure losses in aircraft ducts.

High temperatures affect buckling because the properties of the materials change and because thermal stresses and creep develop. A survey is given of the known solutions of problems arising in consequence of these phenomena and new theories of the creep buckling of columns and of thin circular cylindrical shells are presented.

A problem which occurs frequently is that of choosing a suitable shape for a duct, such as a wind tunnel contraction or an air intake. Basically similar problems, involving potential flow fields, occur in other branches of engineering, particularly in electrical engineering, and the electrolytic tank is now established as a tool which may usefully be employed in their investigation. The use of the simple shallow tank is limited to those fields which can be treated as two-dimensional or axisymmetric, but many problems fall within these categories.

In forming a duct model for the electrolytic tank the walls of the duct are represented by insulating surfaces, and electrodes are positioned to represent two suitable velocity potential surfaces up- and down-stream of the duct. To represent a sector of an axi-symmetric duct the base of the tank must be inclined at 3°-5° to the horizontal and the water line on the tank base then represents the axis of symmetry.

Flight tests were made to verify a method of predicting pressure cabin leakage rates at altitude from ground test results proposed in a Technical Note published in The Journal in August 1954 The results showed very good agreement with the theoretical treatment of the problem.

It is therefore recommended that the method of the Technical Note be used to estimate the change of leakage rates with altitude and also to estimate the time for the excess pressure to fall during a descent with no pressure supply.

The free and forced vibrations of a multi-rotor system where one section of the shaft has a nonlinear elastic characteristic are considered in this paper. For any frequency of steady vibration the system is reduced to an equivalent rotor at either end of the nonlinear section. The vibrations at all points are assumed to be one-term approximate solutions and the amplitudes of steady forced vibration are determined by a method outlined by the author in an earlier paper.