RESEARCH FOR AERONAUTICS—FARREN 255 
But the practical problems of achieving the full result are still only 
partially solved. Few power plants will stand up to critical examina- 
tion on such points as low-loss ducting or airtight cowlings. It is a 
difficult engineering problem to design and make such features at the 
same time light and easily removable and replaceable without damage. 
Throughout the whole history of this development there has been 
intimate association between the three parties chiefly concerned. But 
in my view we can now see that a better planning of the enterprise as 
a whole would have saved much time and waste of work. In particu- 
lar, an earlier realization by the designer of the outstanding advance 
that was within his grasp would have brought him to a closer coopera- 
tion, on strictly practical lines, with his only source of specific infor- 
mation—the research establishments. They in turn were backward in 
that they did not provide themselves with the right material by which 
alone convincing information, directly applicable to practical prob- 
lems, could be obtained. This is a case in which I believe the enlight- 
ened user, if correctly advised, could have forced the pace. 
A SURVEY OF 25 YEARS’ ACHIEVEMENT 
The final criterion of our success in using the knowledge with which 
we have been supplied is the extent to which the product of our efforts 
has improved as time has passed. The curve of advance is not a 
smooth one. Over longish periods we often see little beyond a slow 
rise in achievement, and we tend to believe that there is little more to 
be expected. Then there comes something in the nature of a trans- 
formation. It is often ascribed to a single cause and, generally, one 
can say that there is an outstanding stimulus. But if we compare the 
final product—in this case, the airplane itself—before and after the 
event, allowing a long enough time for the situation to reach a fairly 
stable state, we can make a fair assessment of the relative weight of all 
the influences which have contributed to the change. I believe such 
an examination of the advance of the airplane between say 1917 and 
1942 is useful in providing us not only with a means of examining how 
far we have been successful in using the results of research but also a 
guide to the part played by sheer engineering skill and initiative. 
Finally, it may serve as a base from which we may survey some of the 
potential advances that are now opening out to us and judge what 
resources we shall need in order to achieve them. 
I shall take two typical aircraft that were in general and successful 
use in 1917 and compare them with two modern aircraft of similar 
duties. Naturally there are striking differences, and we shall find no 
difficulty in tracing them to their sources. But perhaps equally strik- 
ing are the characteristics that have apparently undergone little 
