From time to time w.e hear of mysterious engine failures, sometimes resulting in forced landings, in which the engine is reported to have gradually lost power until it was ticking over or had cut out completely. This may have been accompanied by sticking of the throttle, so that the pilot was unable to control his engine, and by rough running. Full power is usually recovered at lower altitudes or after landing, and when the engine is run up no defects can be discovered. At certain times of the year similar symptoms have been observed in the case of engines running on the test bed.

Seaplane tank testing is an offshoot of ship tank testing, the technique of which was founded by William Froude nearly 70 years ago and is now highly developed. Apart from the fact that a scale model is towed through still water, however, there is little in common between the two systems of test, though one link remains in spite of dissentient voices; Froude's laws are used as the basis of correlation between model and full scale. In other respects, the conditions of operation of a ship and a seaplane on the water are so different that when the R.A.E. tank was built, the whole existing technique was reviewed.