This paper presents the twenty or more principal problems encountered in the designing of aeroplanes for passenger service at altitudes of about 20,000 to 30,000 feet, together with a discussion of the recent attempts made in the United States to solve these problems. Particular attention is given to the design features of pressure cabins for maintaining low altitude air pressure at high altitudes.

In certain problems such as the vibration of airscrews or gyroplane rotor blades, account must be taken of the effect of the imposed rotation on the frequencies of vibration. A direct solution of the appropriate equation of motion is usually impracticable and in consequence recourse is had to the application of Rayleigh's Principle. But even this powerful device may involve increasing labour as ascending overtones are considered. In this note an empirical rule is indicated whereby the effect of rotation may be assessed. For a uniform rod the empirical rule is shown to be a very close approximation, particularly with ascending overtones. In other cases such as a tapered rod the rule is shown to apply, but the approximation is not so close.

In many branches of engineering, especially the aircraft industry, numerous geometric problems arise which present considerable difficulty to draughtsmen and designers. The object of this paper is to present methods which the writer has developed which enable any problem of the type under consideration to be rapidly solved. The majority of these problems arise in cases where, although sufficient data is provided to enable ordinary three view drawings of a particular part or assembly of parts to be made, angles and lengths have to be found which cannot be directly obtained from this three view drawing.

Observations on the wing-beats of pigeons, based on cinematograph films taken by the author; with conclusions regarding the characteristics of the wing and its lift in the various phases of the beat.