Comparison of the specific energy demand of aeroplanes and other vehicle systems

A method will be described which allows for a uniform approach to determine the specific energy demand of aeroplanes and other vehicle systems. By the introduction of a dimensionless figure, it can be used for comparison irrespective of the very dissimilar definitions. The entity ε, well known from the physics of flight, the glide number—i.e. the inverse of the L/D-ratio in Anglo-American literature—proves to be a convenient starting point.

In order to utilise the primary energy demand as a basis for comparison, further factors have to be taken into consideration and expressed as efficiency levels, as is usual in energy sciences. By doing this, a deep insight will be gained into the different physical and technical elements of transportation processes. Some unexpected results are derived. In particular, the role of the aeroplane has to be adjusted substantially with respect to public opinion.