ON AERONAUTICAL PROBLEMS. 413 
speed required for steady flight. So we need to go further, and to provide 
him with means for checking that tendency to spin which we have seen 
to be characteristic of the ‘ stalled’ condition. 
This is the problem of low-speed control,—a problem which only in 
the last few months has yielded to attack. At Farnborough, now, you 
may see an aeroplane flying steadily and straight, or performing normal 
evolutions, equally as well above as below stalling incidence. The 
credit for this result is due, in the main, to a small panel of the Aeronautical 
Research Committee which has been occupied with the problem, under 
the leadership of Professor Melvill Jones, since 1920; and throughout 
that time the aim of the panel has been, first of all, to understand. 
When we began our work, we had not even a language in which to 
express our difficulties ; not only had we no experimental data,—we did 
not clearly see what data we required, how the necessary data could be 
obtained, or how presented in diagrams when found. So for some years 
we seemed to be making little headway ; but gradually the fundamental 
idea presented itself, that something different from the conventional 
controls is needed, in that we must give the pilot power to ‘roll’ his 
machine (that is, to turn it as my model wing has been turning on this 
spindle) without introducing any tendency to ‘ yaw’ (that is, to turn to 
left or right). Even when this requirement had been formulated, much 
hard work and hard thinking was necessary before it could be satisfied ; 
but at last we achieved success, combining in one control two devices 
which had been discovered previously,—by Messrs. Handley Page and the 
Bristol Company. Though much remains to be done, we have the satis- 
faction not only of having found an effective device, but of understanding 
why it is necessary and how it works. 
Problems of the Future. 
36. Finally, what of the future? Along what paths are we directing 
our inquiries now ? 
Well, much work still remains to be done before these problems of 
stability and of control can be said to be completely understood, and that 
work takes a high position in our programmes. Ultimately the aim is that 
we shall be able to predict, from a knowledge of the characteristics of its 
wing and tail sections, what will be the characteristics of the complete 
aeroplane. Our experiments, that is to say, are aimed at making similar 
experiments unnecessary in the future. 
Why does an Aerofoil Lift ? 
37. This seems a sufficiently ambitious aim. There are those who 
regard it as Utopian, and would have us hitch our wagon to a more 
accessible star. As a matter of fact, it does not content us in these post- 
War years. We want to go back further still,—for we are not content to 
accept the characteristics of aerofoil sections as the ultimate verities, 
beyond which human intelligence cannot probe. We are not satisfied to 
know that a given aerofoil will lift a given weight, and needs a given 
thrust to push it forward. Why does an aerofoil lift at all ? 
Evidently the cause lies, somewhere, in the reactions which arise 
between the aerofoil and the air through which it moves. The aerofoil 
