PROBLEMS AND IMPROVEMENTS OF CANOPY JETTISONING SYSTEMS

Abstract

The paper "Evaluation of Canopy Jettisoning System for Sailplanes", read at the OSTIV Congress in 1989 pointed out the magnitudes of the aerodyramic forces and moments acting on the canopy. This paper now presents details of the motion and flight path of the canopy after its release in an emergency. The tests were performed with an IS 4 fuselage mounted on the roof of a car. During these tests the influence of the speed, angle of attack, side slip angle and the automatic raising of the front and the side were investigated. It becomes apparent that none of the existing mechanical systems installed in a today's glider guarantee a problem-free jettisoning of the canopy. The canopy does not fly away t it blocks the exit and there is a high risk of injury to the pilot by the moving canopy. The main reason for this is a nose-down pitching and the nose inwards yawing moment acting on the canopy. The occupant is urnble to control the motion of the canopy during jettisoning. To overcome this problem the nose down moment can be transformed into a nose-up moment by a simple rear hinge between the top of the canopy and the fuselage. The hinge may take the form of a simple clasp. This clasp ensures that after the release the canopy rotates around this hinge with a nose-up moment, separates from the fuselage and passes high above the rudder. There is no risk of iniury to the occupant. Manual jettisoning can be performed without any trouble using this hinge.