Minimum fuel paths for a subsonic aircraft

Abstract

to the afterbody by three supporting beams, one at each wing root and one below the fin. The slot between the afterbody and the leading edge of the ejector, divided into three parts by the beams, is the combined inlet for ambient air and nozzle for reverse exhaust gas. Instead of blow-in-doors, the slot has a translating sleeve which in the open position is retracted into the afterbody structure by hydraulic power. In the ejector shroud there are three blocker doors flush with the surface in the retracted position. When the reverser control is engaged, the doors are turned to their closed position by hydraulic actuators and the exhaust gas is deflected forward through the slot, forming one ground jet and two jets above the wing on either side of the fuselage. (See Fig. 1.) Thrust reversal can be preselected by the pilot in the air, and is then automatically initiated at touchdown of the main landing gear. The development work on the reverser system included a number of activities. Besides model testing in wind tunnels and rigs and full-scale testing on the engine test bed, a large number of test runs (including landings) were carried out in prototype aircraft for evaluation of the complete reverser system and for demonstration of roll distance and aircraft stability at thrust reversal. During thousands of reverser operations in the flight test program, invaluable but also hard-earned experience was gained. The problems encountered were mainly due to influences on aircraft pitch and yaw stability. Owing to the aerodynamic ground interference from the lower jet of the deflected flow, a strong variation in pitching moment with forward speed and degree of reverse thrust occurred. The yaw stability problem was also caused by aerodynamic interference. With the upper jets close to the fin, small asymmetric disturbances in the jet boundaries could result in side forces and yawing moments too great to be controlled by the