Operating Instructions for AN/APN-1/A Aircraft Radio Altimeter 1943 A-6 type B-9C (formerly AN5772-2) and

type B-9C (formerly AN5772-2) and made by US Gauge

for a dual engine aircraft

A rare item indeed

Torque Pressure

Here is a student workbook that helped cadets understand the functions of aircraft

Operating Instructions for AN/APN-1/A Aircraft Radio Altimeter 1943 A-6 type B-9C (formerly AN5772-2) andThis is an original WWII era manual, Handbook of Operating Instructions for AN APN 1 and AN APN 1A Aircraft Radio Altimeter system, dated June 1943. The Radio Altimeter was used in a number of aircraft of the US Army Air Force and US Navy where close monitoring of height over terrain was critical, such as torpedo bomber TBM Avenger (see image from TBM Flight Manual), dive bomber SB2C Helldiver, patrol aircraft PV 1 Ventura, PV 2 Harpoon, PBY Catalina,