NATIONAL RESEARCH COUNCIL 
741 
(e) Develop equations and laws of comparison by which the behavior of 
large aircraft may be more accurately foretold from tests of models. Apply 
further the principle of dynamical similarity. 
(/) Investigate more direct and effective methods of securing a lift or thrust 
in the air from the consumption of fuel. 
(g) Complete theory of the air-screw. 
2. Engine problems requiring research. — (a) Fuel. Possibly the most far- 
reaching problem is fuel. A fuel that will carry more power into an engine 
per unit volume will be a direct gain. 
Attempts have been made to combine alcohol, gasoline, acetylene, picric 
acid, ether and other hydrocarbons with the above object in view. Ques- 
tionable results have followed. There has been an increase of power, but 
nothing so far commercially or practically useful. 
This question must be studied with the greatest of care and from a truly 
research standpoint. 
(b) Solid fuel. Solid fuels that can be converted into hquid in small quan- 
tities just prior to use, are desirable for military aviation. In case of acci- 
dent from shot or shock, leakage of liquid fuel is a danger. SoUd fuel could 
be carried in quantity with less danger. 
(c) Engine cooling. The problem of radiation is important. If some 
substance could be found that would circulate through the cooling system, 
at higher temperatures than water, it is probable that greater engine efficiencies 
would result. Oils, salt waters, and other materials have been tried with 
indifferent success. 
(d) Liquid fuel pipes. Tubing that will resist vibration (causing rupture) 
is desired. An oil and gasoline proof rubber tubing is reported as used in 
Europe. This development is highly important, not only for tubing, but for 
containers in which to carry Hquid fuel. Some sort of fabric and rubber tank 
that would really resist the action of gasoline, would be of the highest benefit. 
A difficulty hes in the fact that the tanks are large (say 20 to 100 gallon 
capacity). The structural problems would be serious. The tanks now used 
are large and of metal. Vibration causes much difficulty and leakage. 
(e) Metal coating. The protecting of the metal parts of an airplane, es- 
pecially the fittings and cables, is a serious problem. A material is desired 
that would really prevent dangerous corrosion. Nickel plating over copper 
is very good, but will not suffice. Rust strikes through very rapidly. Baked 
enamel is the best coating. It is impossible to apply in many cases. 
(/) Sound. The question of eliminating the noises involved in the opera- 
tion of aircraft is one of importance. The pecuhar note of the propeller of 
a Zeppelin can be heard for several miles, and is usually the first warning of 
its approach at night. 
3. Miscellaneous. — (a) Physiological. Study the physiological and psycho- 
logical effects of low density air at high altitudes on the performance of pilots. 
(b) Transparent wing covering for airplanes. A wing covering which 
