1314. Problems Associated With Cargo Airplanes Having Aft Mounted Engines
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Paper
Abstract
In preliminary design, the weight engineer is expected to perform weight and balance analysis on a wide variety of airplane configurations. One such configuration, which appears fairly frequently, is an aircraft with engines mounted on the aft fuselage instead of the wing. There may be a good, logical reason for an arrangement like this, but sometimes it is nothing more than a whim of the designer or an attempt to apply some innovation.
In most cases this choice of engine location will cause penalties to the airplane, both in fuel and structural weight. In general, both the wing and fuselage weight is increased for fuselage mounted engines. Such a configuration also requires an extremely wide center of gravity envelope to allow for uniform payload loading. Although these problems exist to some extent on passenger aircraft, they become especially significant on cargo configurations.
This paper examines the effects of engine location. A baseline configuration with four wing mounted engines is presented for comparison with several arrangements. In the first section of the analysis some simplifying assumptions are made which allow for some trends to be established. Three airplanes with engines mounted on the aft fuselage are examined, each with a different approach to the solution to the balance problems. In the second section of the study two of the configurations are analyzed in more detail. A third configuration, with two wing mounted engines and one tail mounted engine is added at this point for comparison purposes. The results indicate that if an airplane is designed for use as a cargo aircraft, it should have wing mounted engines.
