Pilot Assistance for Helicopter Slung Loads

Abstract

Slung load operation offers wide spectrum of scenarios, ranging from simple transport of bulky goods to rescue of people in mountains or from ships in distress. Some of the external loads are simple bluff bodies, others have an aerodynamically sensitive shape. The transport of external load requires intensive training and exercising of the pilots. The problem is the lack of appropriate cues and situation awareness if the load starts oscillating. Swinging helicopter external slung loads often lead to dangerous situations which not only can result in a total loss of the load itself but also can endanger the helicopter and its crew. Therefore, DLR and its partner iMAR have developed a Flight Director to assist the pilot during slung load transport. The flight director aims at providing the pilot with a convenient aid he intuitively can use to effectively damp the load pendulum motion and to allow manoeuvring without exciting oscillatory load modes. The development of a demonstrator system for the DLR BO105 helicopter is outlined. Flight test results using a stable as well as a marginally stable load are shown. Based on the good experience gathered with the demonstrator system, a 2nd generation flight director has been developed for the large cargo helicopter CH53G. The design and development of this improved flight director system is described in detail. In addition, corresponding flight test results are presented. The paper clearly shows the capability of the flight director to assist the pilot in damping swinging loads very quickly. In addition, it is shown, that the flight director is also capable in expanding the flight envelope for slung load transport. Pilots rated the flight director not only to reduce workload, but also to improve situation awareness.