The original title put down for this paper was “The Design and Operation of Commercial Aircraft.” I hope it will be observed that I have actually taken a very much more modest title than that. A paper with so broad a title as the original one might well have been read five or six years ago, but at the present stage of development of commercial aviation, he would be a bold man indeed who would attempt to deal with two such subjects in a single one–hour paper.

It happens that the Society has had two very valuable papers dealing with commercial air transport comparatively recently. I refer in the first place to Sir Sefton Brancker's paper of October, 1925, which gave a very comprehensive review of the progress of civil aviation during its first six years, including a general survey of the development of commercial aircraft design. A little later on we had a most interesting paper by Mr. Cowley dealing with the more theoretical aspects of aircraft transport economy.

What may be termed broadly the medical aspects of flying are far more wide–reaching than is generally supposed, especially since such a term embraces both the physiological and psychological aspects of the subject. All the while, therefore, that man acts as the controlling and co–ordinating mechanism of the machine, the study of man in relation to his machine must occupy an important place in the progress of aviation. It is because this aspect of the subject has tended to be somewhat overlooked that I venture to address this Society again to–night.

In the first place I wish to consider what happens when a man learns to fly. As the result of information gleaned by his various senses he is taught, according to his aptitude, to perform or to try to perform certain arm and leg movements which will control the machine safely while it is in the air. To do this, however, in addition to perceiving, he must in certain circumstances display judgment before he acts, although, as he becomes more experienced in flying, he will automatically perform certain movements in response to certain sensations.

Valuable lives and thousands of pounds worth of equipment are lost in collisions each year.

The graphs of civil aviation traffic show that an accident in May of 1922 was followed in June by a drop in the average monthly passenger traffic of 325 passengers. A more serious accident in May, 1923, was followed by a drop in traffic during May and June of 750 passengers.

There is thus every incentive to minimise the risk of collision as far as possible, if only from an economical standpoint, as apart from the humanitarian.

Under the existing regulations there is danger of collision not only from all points of the compass in a horizontal plane—and, even at sea, with rules based on a thousand years’ experience, collisions are all too frequent—but from every conceivable direction of which the pilot is the unfortunate centre.

Rule of the Air No. 29 is perhaps the best exposition of the present state of affairs in air navigation.

Since the vaiious nations definitely set out upon the course of aeronautical armaments, the problem of the organisation of this new service has arisen, and appears to present serious difficulties if it should be necessary to effect periodical changes and modifications or at least substitutions in personnel.

This uncertainty is due partly to the fact that quite new questions are being dealt with; partly to the erroneous process of enforcing upon the new fighting service the rules of the older ones—the army and navy; and in a larger measure to the practical difficulties which have to be faced at every turn in passing from the theoretical field to the actual.

In the following pages an attempt is made to present the chief problems which arise in the aeronautical field, so as to form an idea for their solution, adducing opinions frequently diverse and antagonistic which the experts maintain in their respective arguments.

Physical–chemical study of light fuels and of lubricants in Aeronautics. (M. Moutte, La Technique Aeronautique, Sept.–Oct., 1926, pp. 279-281 and 305-319) (8.51/5096 France)

Systematic tests of fuels in an engine on the test bench were commenced in 1917, in conjunction with a systematic determination of physical properties, and as far as possible of chemical composition. It was found that homogeneity, volatility and high latent heat of evaporisation were the most desirable qualities. In agreement with Ricardo, the aromatic compounds of hydrogen are found to be the least amenable to propagation of explosion, then the saturated cyclic compounds, and lastly the saturated acyclic compounds. In identifying fuels use is made of characteristic curves of distillation:—

Temperature—Volume Distilled, Density;—Volume Distilled.

Temperature—Density, Temperature—Solubility.

Temperature of distillation plotted against critical temperature of solubility in aniline gives highly characteristic differences, and is considered a fundamental method. Optical methods are also used for approximate quantitative determination. The formation of clouds of condensed drops affords another method of determination. The mechanical conditions were also examined:—Variation of inlet pressure, condensation, centrifugal separation.