Page:Aerial Flight - Volume 1 - Aerodynamics - Frederick Lanchester - 1906.djvu/353

Rh that the aerodrome or flying machine carries 10 per cent, of its mean weight as fuel, i.e., petroleum spirit. The mean weight is, under these conditions, 5 per cent, less than the initial and 5 per cent, more than the final weight, the loss of weight being due to the fuel consumption.

As a maximum estimate of the range of flight conceivably possible without some fundamental discovery in fuel and prime movers we may take the following supposititious case. Using liquid hydrogen as fuel, and carrying 25 per cent, of the total mean weight, and assuming a yet-unheard-of thermal efficiency of 50 per cent., a total mechanical efficiency of 90 per cent., and a propeller efficiency of 70 per cent., with the minimum angle of $$\gamma$$ given in the Table (= 6°), the exhaustion of fuel will be complete after a flight of 6,800 miles distance.

The above estimate is based on an assumed development of the heat engine and other mechanical refinements not yet within sight, and indeed such as may never be realised. If we confine ourselves to existing appliances and existing methods it is doubtful whether the maximum range of flight can (without devoting the whole resources of the machine to the carrying of fuel), ever exceed 1,000 miles, and for the present this may be regarded as the probable extreme outside limit.