V/STOL APPROACH SYSTEM STEEP ANGLE FLIGHT TESTS.

The report describes results obtained during flight tests with an S-61N helicopter on the VerticalShort Takeoff-Landing VSTOL Approach System VAPS. The system consists of a solid-state microwave localizer and glide slope operating in the 15,000 Mcs frequency region. All ground equipment is housed within a 5-foot high radome, 4 12 feet in diameter. The localizer bearing and the glide slope angle can be readily changed by hand cranks at the ground station. Fifteen hours of flight time were expended on approaches, with glide slope angle ranging from 3 degrees to 60 degrees. The conclusion is reached that the S-61N helicopter approaches at angles greater than 20 degrees encountered VAPS equipment limitations - deficient guidance signals, and aerodynamic limitations - marginal control, roughness and excessive descent rates. Author