Johnston, R., "Flight and Range Characteristics for a Subsonic Advanced Propeller-Driven Blended Wing Body Composite Air Frame Capable of Transporting a 150-Ton Military Cargo," SAE Technical Paper 2016-01-2019, 2016, doi:10.4271/2016-01-2019.
An advanced composite Blended Wing Body (BWB) air frame previously used as a study aircraft to transport a 75-ton military cargo halfway around the world and back unrefueled has been modified and evaluated as a 150-ton heavy lifter. The modifications include enlarging the forward trim canard, reducing fuel load by 151,850 lbs, increasing the high-mach NASA-type counter-rotating propellers from 12 feet to 13 feet diameter, extending the propeller support pylons' height by 6 inches and modifying cruise flight and prop control strategies. Due to structural and propulsion system changes, the air frame Operational Empty Weight (OEW) was increased by 1,850 lbs. but the maximum Take Off Gross Weight (TOGW) was held to 800,000 lbs. Brief descriptions of the major propulsion system components are provided. In addition, a comparison of three different counter-rotating propeller systems is presented. The first is a Standard configuration. The second Modified (Mod.) configuration uses a proposed variable hub radius ratio device to keep the front prop wash (PW) matched to the aft prop tip while the third system employs a “Clipped” aft prop to reduce take-off noise. Eight 14,000 Shaft Horsepower (SHP) Advanced Variable Cycle Diesel (AVCD) aircraft engines individually driving 8 counter-rotating propellers are used as highly efficient prime movers. A complete flight profile is calculated and the larger trim control lift requirements are shown to have a significant effect on overall air frame drag levels. The flight profile is also selected and modified to preserve optimum Lift over Drag (L/D) values for the majority of the flight. FAA instrument flight rule fuel reserves along with an added 2-hour flight fuel reserve requirement are included in the range calculations. This results in a maximum 7946 Nautical mile (Nm) mission capability for this military heavy lifter cargo plane using the Mod. propeller installation.