V/STOL APPROACH SYSTEM FLIGHT TESTS.

The report describes results obtained during helicopter flight tests 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 MHz 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. The specified maximum fluctuation limits of plus or minus 0.5 degrees for the localizer and plus or minus 0.2 degrees for the glide slope were met. A CH-34C helicopter was operated approximately 80 hours on the VAPS. Fifteen hours of S-61N helicopter 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. The VAPS transmitters accumulated about 700 hours total operating time. Total receiver operating hours are comparable. The failure rate was low. Author