This project aims at developing a highly accurate and economical aircraft altimeter. The motion of an evacuated bellows will be monitored by an optical position sensor which will give an electrical analog signal linearly related to the atmospheric pressure. While the sensor is very small, rugged and inexpensive, it has a large dynamic range (lOO,OOO), high linearity (0.01%) and high sensitivity (maximum bellows wall displacement needed: 0.0014 inches). Important advantages are foreseen in this new altimeter concept: the errors and the limited resolution inherent in the complex mechanical system of a mechanical altimeter are avoided; nothing disturbs the bellows except for a light beam; zero setting. barometric pressure correction and calibration can all be done electronically; its electrical signal is directly compatible with digital display, computer interface and automatic altitude transmission, and finally, its simplicity of design should lead to high reliability. Phase I will determine the feasibility of building optical altimeters having an overall accuracy equal to or better than + 20 feet over the range of altitude O to 60,000 ft. In Phase II actual units that meet stringent accuracy and performance specifications will be built, with aims at producing a commercial instrument. Other commercial applications in the area of air pressure measurement are also anticipated, such as air speed, rate of climb, mach number and true air speed indicators, very sensitive barometers for land surveying, for weather monitoring and for air turbulence studies.
