Here we have a complicated piece of hardware… real hardware. It’s made of Aluminum, and it must have served the US Air Force well in its time.
This contraption is a Computer, Air navigation, Dead Reckoning, Type CPU-26 A/P (Backwards talk loves to the Military, Yoda the Jedi like). On the front it has a sliding translucent window with a rotating compass dial and many incomprehensible markings. On the back it has a rotating disc that aligns with the scales below, full of equally incomprehensible markings. And there are some instructions: “If ‘D2-D1’ is +, drift is left in northern hemisphere”; “Use calibrated airspeed and press. alt. to obtain F Factor. Multiply F factor by TAS obtained with computer to obtain TAS corrected for compressibility”; and so on.
This computer, built by the Felsenthal Instruments company sometime around 1960 (but based on a pre-WWII design), was aimed at the mobile individual, in any hemisphere. It placed the ability to swiftly implement numerous computations useful to a pilot in a lightweight, handheld unit — all without batteries or blue screens. It is a variant of the iconic E6B, which was ubiquitous in all aircraft back in the day and was still being taught to trainee pilots well into the electronic calculator era.
Here are some more pictures.
Exhibit provenance:
I bought this item in an antique mall in Folsom, California.
More info:
– E6B flight computer on Wikipedia.