There are several reasons why a Santech E-6B (also called a FDF-57B/60B) dead reckoning computer should find its way onto these pages.

It is a circular slide rule, it’s old technology, it’s a form of computer (in the same way an abacus is a computer...), I happen to own one courtesy of the auction process, and my ex-brother-in-law Keith Hasler used to have one when I was much younger - he was learning to fly at that point in my existence. That would have been around 1966.

I quote the first page of the manual:

“Originally designed by the late Lt. Philip Dalton, USNR, the E6-B computer was adopted by the Army Air Corps in 1942 and has appeared on the civilian market under different labels and variations. It has since been adopted for standard use by the U.S. Navy and now by the U.S. Army for helicopter pilots”.

and further:

“A dead reckoning computer is combination of two devices, one a specially designed instrument for solving wind triangles and the other a circular slide rule for solving arithmetical problems.

Many different types of dead reckoning navigation computers exist, but the construction and design features of the major types are very similar. For illustrative purposes, the Sporty Type E-6B Dead Reckoning Computer is used throughout this manual”.

The device is 12.5cm (5 inches) wide and 24cm (9.5 inches) high. It comes in a suitably-shaped black plastic pouch and mine is complete with manual. I haven’t worked out why the pouch has “asa” embossed on the front in large letters.