In this photo of the C-140 JetStar on the Dryden Ramp, a subscale propeller has been fitted to the upper fuselage of the aircraft. NASA's Dryden Flight Research Facility, in co-operation with the Lewis Research Center, investigated the acoustic characteristics of a series of subscale advanced design propellors in the early eighties. These propellors were designed to rotate at a tip speed faster than the speed of sound. They are, in effect, a "swept back wing" version of a propellor. The tests were conducted on Dryden's C-140 Jetstar, seen here on the ramp at Dryden in Edwards, California. The JetStar was modified with the installation of an air turbine drive system. The drive motor, with a 24 inch test propellor, was mounted in a pylon atop the JetStar. The JetStar was equipped with an array of 28 microphones flush-mounted in the fuselage of the aircraft beneath the propellor. Microphones mounted on the wings and on accompanying chase aircraft provided far-field acoustic data. In the 1960s, the same JetStar was equipped with an electronic variable stability flight control system. Called then a General Purpose Airborne Simulator (GPAS), the aircraft could duplicate the flight characteristics of a wide variety of advanced aircraft and was used for supersonic transport and general aviation research and as a training and support system for Space Shuttle Approach and Landing Tests at Dryden in 1977. In 1985, the JetStar's wings were modified with suction and spray devices in a laminar (smooth) air flow program to study ways of improving the flow of air over the wings of airliners. The program also studied ways of reducing the collection of ice and insects on airliner wings.
