The employment of aircraft for surveying has become so usual, and so much has been written about it from one aspect or another, that perhaps the time is appropriate to define exactly what is meant by Air Survey; what the surveyor is trying to achieve, and how he is dependent upon the airman to obtain his objectives. To achieve good results from an air survey, closely integrated team work is required. The airman, photographer, instrument specialist, meteorologist and the surveyor each depend upon the other, any weakness in the chain making results more expensive and less effective. The author, as a surveyor, has worked in harmony for a good many years with the “air” side, and it is proposed in this paper to summarise the surveyor's approach and his requirements, and to explain why he seems never to be satisfied with the accuracy achieved. The greater the accuracy of photography, the simpler, quicker and cheaper become methods of using the results to fulfil the desired specification.

That synthetic glues for wood were used extensively for making Mosquito and Hornet aircraft during the 1939-45 War, and are now used for making Vampires in many European countries, is well known to aeronautical engineers, but not so well known is the fact that, since 1944, synthetic glues for metals have been used in the production of many hundreds of military and civil aircraft. A glue for metals, which gives joints stronger than can be obtained by riveting and which is also resistant to the severe conditions to which aircraft are exposed in service, offers the possibilities of savings in structure weight and of aerodynamically cleaner wing and fuselage surfaces. Such a glue may also be expected to be of value in the manufacture of pressurised fuselages, because it will avoid the large number of small leaks occurring at the rivet heads and may also help to solve the difficult problem of making integral fuel tanks in aircraft wings.

It was desired to confirm quantitatively pilots’ impressions that on turbine-jet aircraft in the region of 40,000 ft. the level speed stabilised very slowly.

The time required to make a conventional level speed measurement has been examined, for a representative turbine-jet aircraft, over a wide range of air speed and height. The results are compared with those for a typical piston-engined aircraft and their implications discussed.

It is concluded that the time required to make a conventional level speed measurement increases rapidly with height, in the absence of compressibility effects on drag, and is about five times as great at 40,000 ft. as at sea level. It is inconveniently large at high altitude and level speed measurements there will require very long runs, unless it is arranged that each run is started at an air speed near the steady level speed.

This increase will be present in most level speed tests, especially those in the region of the best speed for range. In maximum level speed measurements, however, compressibility effects may be present and the air speed may then be expected to settle down quickly.

The need for long runs at high altitude is not peculiar to jet aircraft, but has come into prominence concurrently with them.