Test and Evaluation of Altimeter AN/APN-57

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Report Number: WADC TR 52-193
Author(s): Georgi, J. Paul, Goldman, Albert
Corporate Author(s): Wright Air Development Center
Date of Publication: 1952-04
Pages: 129
DoD Task:
Identifier: AD0013162
AD Number: 13162

The altimeter is designed to indicate the absolute altitude (terrain clearance) between heights of 10,000 and 35,000 ft. A servo-operated 3-pointer dial (calibrated from 0 to 100,000 ft) registers the altitude, and a CRT indicator shows the instantaneous error up to + or - 500 ft. The transmitter- receiver is a modified RT-69/APS-10 with a 0.25-microsec output pulse, 4-kw peak power, and a carrier frequency in the 9345- to 9405-mc range. A 60-in.-diam parabolic antenna reflector provides a beamwidth of 1.6 deg at the half-power points. Flight tests of 16 units showed that the design meets the accuracy requirements, provided that a compensating error of -42 ft is inserted during calibration. An apparent increase is indicated altitude caused by banking the test aircraft as little as 3 deg showed the need for antenna stabilization. The present system of recording altitude indications photographically was considered unsatisfactory.

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