private makers.

A fourth factory machine, produced just before the war, and no less
famous than the other three, was called the R.E., or Reconnaissance
Experimental. It was the first almost completely stable machine.
Stability is not of the first importance to a fighting scout, whose
attention is concentrated on his own manoeuvres, but where a machine is
used for observation, and the pilot must needs pay heed to all that is
visible on the earth beneath, stability is essential. A perfectly stable
machine maintains an even keel in varying gusts of wind. If it is
tilted, it rights itself. If it is nose-dived, the pilot has only to let
go of the control, and after a descent of some hundreds of feet it comes
out of the dive and resumes its horizontal flight. The perfecting of
this type of machine was achieved at the factory, and was the work of
many minds. On the mathematical side the theory of stability was
investigated by Mr. F. W. Lanchester, an authority on the theory of
flight, and by Professor G. H. Bryan, a great pioneer, who in 1911
produced his book on _Stability in Aviation_. He had long been
interested in the subject; his work, which is recognized as
epoch-making, laid a sound mathematical basis for the theory of flight,
and directed the work of others along the lines of fruitful experiment.
The theoretical conclusions of Professor Bryan were reduced to a
practical form by Mr. Leonard Bairstow and the members of the staff of
the National Physical Laboratory, who put the doctrine to the proof of
experiment, at first with models, and then with full-scale machines. The
dangerous work of trying conclusions with the air fell to the young men
of the factory. A brilliant young Cambridge man, Mr. E. T. Busk, of
King's College, who had been trained in the laboratory of Professor
Bertram Hopkinson, joined the staff of the factory in the summer of
1912, having previously spent a month at the National Physical
Laboratory, to acquaint himself with the work there. He understood the
theoretical basis of aeroplane design, and he was a daring and skilful
pilot. The R.E. machine was designed by the staff of the factory; Mr.
Busk, in collaboration with Mr. Bairstow, worked at the problem of
giving it stability. He cheerfully took all risks in trying the
full-sized machines in the air. When the R.E. 1 had been theoretically
warranted, by experiments with models, to right herself after a
nose-dive, he tested the theory by flying the