A STUDY ON THE EFFICIENCIES OF CARGO AIRPLANE DESIGNS. 440135
An extensive study on the efficiencies of cargo airplane designs, especially with respect to increasing speeds resulting from different combinations of wing and power loadings, is presented.
As it is always possible to achieve great speeds for a given price with sacrifice in economy (this, however, not being the best solution to the problem), a study was therefore prepared on the air cargo transportation economics with respect to obtainable cruising speeds.
Several designs are presented for three different engine sizes and four different wing loadings. As a primary takeoff requirement, the Hon. E. P. Warner's formula, which specifies that the product of wing and power loadings should equal 300, is used. This is assumed for normal gross weights, while for the alternate overload weight condition, a 20 per cent overload effectsis analyzed. This brings the product of wing and power loadings to 432, which would still give a fair takeoff performance on existing A class airports.
The different designs are projected around the basic high wing, twin boom, twin engine monoplane satisfying the requirements for cargo hold size, accessibility, loading facilities, and C.G. variations.
For such designs, complete estimated weight breakdowns are presented and useful loads are established. Their respective performances, as far as cruising speeds and ranges are concerned, are determined for normal gross weight and alternate overload conditions.
The comparative efficiency factors, based on cargo load carried per airplane empty weight, range, cruising plus handling time, landing speed and fuel cost per cargo load, are determined for different ranges at normal gross and overload weights. The effect of 30 MPH head wind on such comparative efficiency factors is also analyzed.
Most of the figures are presented in tables and charts, from which the detrimental effect of high wing loadings and resulting higher cruising speeds, not only on the amount of cargo load carried, but also on the economy of cargo transportation, can be visualized.
It is determined that from the standpoint of economic efficiency for medium sized cargo airplanes, both for short or long range operations, the most efficient wing loading will be only between 20 to 26 pounds per square foot with respective takeoff power loading of 15 to 11.5 pounds per takeoff horsepower.