Flight Tests of A Ground Speed Indicator Over Measured Runs,

A series of flight tests have been conducted in order to obtain further information on the problem of ground speed measurement. The equipment used was a continuous wave Doppler radar, operating at X band, having a power output of 15 milliwatts, and a single antenna with a gain of about 30 db. The radar was flight tested in a four engine Navy bomber, the PB4Y-2. Following an initial calibration flight over a measured mile at Chesapeake Bay, numerous flights were made between check points off the Atlantic coast. The true average velocity was determined by accurate measurement of the flight time and compared with the record of the ground speed indicator. In only one case did the error exceed 2 percent. It is concluded, therefore, that with suitable refinement, a ground speed indicator of definite value is entirely practicable over water as well as over land.