US Army Air Force
Operating Instructions for AN/APN-1/A Aircraft Radio Altimeter 1943
This 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, PBM-5 Mariner, and PB4Y Privateer. It was also common in aircraft of the US Army Air Force such as the C-47 Skytrain transport, as well as Korean War-era aircraft such as the A-1 Skyraider.
This 16-page, 8.5 by 11 inch manual covers installation, operation, and maintenance of the system including fold-out diagrams of key components and system layout.
The manual is clearly experienced but in reasonable condition given its age.