E6B

Here is a history of the E6B using Harry’s collection of historic flight computers.

The source of this information is from Wikipedia and a few other resources.

Invented by Naval Lt. Philip Dalton in the late 1930s.  The early E6B computers were made of brass; aluminum and plastic models were made during WWII. Dalton joined the United States Army as an artillery officer, however, he resigned from the Army and became a Navy Reserve pilot.

During WWII and perhaps into the 1950s, The London Name Plate Mfg. Co. made a “Height & True Airspeed Computer Mk. IV (these may have had a model reference of 6B/345).  It calculated true airspeed on one side and time-speed calculations on the other side.  These models were in use throughout the 1960s and 1970s by several European Air Forces (German Air Force was one of them).

The name comes from the original part number for the US Army Air Corps.

Dalton teamed up with Philip Van Horn Weems to develop and market a series of flight computers.

The first popular model was the Model B (made around 1933).  Here are a few Model B computers from Harry’s collection.  In 1936, Dalton included a wind correction side to his computer, the U.S. Army Air Corps (USAAC) designated these as the E-1, E-1A, and the E-1B.

Mid 1930s he had the  Mark VII. The Mark VII used the Model B slide rule.  It is said that Fred Noonan used this model on his flight with Amelia Earhart.  Dalton wasn’t happy with the wind side so he set out to improve on it and came out with the very popular wind arc slide.  Dalton’s wind arc slide was printed on an endless cloth belt moved inside a square box by a knob. He applied for a patent in 1936 (granted in 1937 as 2,097,116). This was for the Model C, D and G computers widely used in World War II by the British Commonwealth (as the “Dalton Dead Reckoning Computer”), the U.S. Navy, copied by the Japanese, and improved on by the Germans, through Siegfried Knemeyer’s invention of the disc-type Dreieckrechner device, somewhat similar to the eventual E6-B’s backside compass rose dial in general appearance, but having the compass rose on the front instead for real-time calculations of the wind triangle at any time while in flight.

The U.S. Army Air Corps decided the endless belt computer cost too much to manufacture, so later in 1937 Dalton morphed it to a simple, rigid, flat wind slide, with his old Model B circular slide rule included on the reverse. He called this prototype his Model H; the Army called it the E-6A.

In 1938 the Army wrote formal specifications, and had him make a few changes, which Weems called the Model J. The changes included moving the “10” mark to the top instead of the original “60”. This “E-6B” was introduced to the Army in 1940, but it took Pearl Harbor for the Army Air Forces (as the former “Army Air Corps” was renamed on June 20, 1941) to place a large order. Over 400,000 E-6Bs were manufactured during World War II, mostly of a plastic that glows under black light (cockpits were illuminated this way at night).

The base name “E-6” was fairly arbitrary, as there were no standards for stock numbering at the time. For example, other USAAC computers of that time were the C-2, D-2, D-4, E-1 and G-1, and flight pants became E-1s as well. Most likely they chose “E” because Dalton’s previously combined time and wind computer had been the E-1. The “B” simply meant it was the production model.

The designation “E-6B” was officially marked on the device only for a couple of years. By 1943 the Army and Navy changed the marking to their joint standard, the AN-C-74 (Army/Navy Computer 74). A year or so later it was changed to AN-5835, and then to AN-5834 (1948). The USAF called later updates the MB-4 (1953) and the CPU-26 (1958), but navigators and most instruction manuals continued using the original E-6B name. Many just called it the “Dalton Dead Reckoning Computer”, one of its original markings.

After Dalton’s death, Weems updated the E-6B and tried calling it the E-6C, E-10, and so forth, but finally fell back on the original name, which was so well known by 50,000 World War II Army Air Force navigator veterans. After the patent ran out, many manufacturers made copies, sometimes using a marketing name of “E6-B” (note the moved hyphen). An aluminium version was made by the London Name Plate Mfg. Co. Ltd. of London and Brighton and was marked “Computer Dead Reckoning Mk. 4A Ref. No. 6B/2645” followed by the arrowhead of UK military stores.

The Model C, D, and G computers were used during WWII.

Kane Mark VI Dead Reckoning Computer from 1957.

Dalton E-6B Mark 1

Here is a Weems Dalton Dead Reckoning Computer.

Warner Model B-1.

E6B9

Felsenthal Dalton E6B  Mark I.

A friend’s American Airlines issue Type C1.

Felsenthal AN-5835-1 (1944).

Here is another military issue altitude correction computer AN-5837-1.

A.C. Type G-1.

Air Force Type MB-2A.

U.S. Army Air Forces Type D-4.

ASA E6B.

APR E6B.

Does anyone know why they have the little eye or loop on one side? It is so that it can be secured to a lanyard around your neck.  Early aircraft did not have a floor as we know it today and if you dropped your E6B, you would have a hard time getting it since it would fall between the spars and/or ribs of the aircraft.  You would have to reach down and try to find it.

The flight computer was very popular during WWII.  Along with the US, the British, Germans, and Japanese had their own version.

Here are some pictures of the German Dreieckrechner Flight Computer, invented by Siegfried Knemeyer.

Here is a rare Sanderson SC-6 Flight Computer.  Here is a little history on the Sanderson name in aviation.  The well know Jeppesen was once Jeppesen Sanderson.  That company actually started as Jeppesen.  It was founded in 1934, by Elrey Borge Jeppesen, a pilot working for an airline.  He is credited with making the first aeronautical charts.  At first he gathered information for his own use. Soon other pilots started giving him information to use on his charts.  It wasn’t long before Jeppesen was too busy making charts, that he had to quit his job as an airline captain.  In 1974 his company merged with Sanderson Films to form Jeppesen Sanderson. Sanderson Films was founded by Paul Sanderson in 1956.  Here is another Sanderson SC-4 Flight Computer from Harry’s collection.

For a while, many fuel suppliers had their own flight computer that they would give out at FBOs.  Here is a rare Esso Aviation Products computer in Harry’s collection.

Here are a few that were developed to assist in traffic pattern entry.

Here are a few that were used to determine aircraft performance.  Note the name on them is the Federal Aviation Agency.

Some were developed to assist in ADF navigation such as these from Harry’s collection.

Many aircraft manufacturers made their own series of slide rule/flight computers that were aircraft specific.

Here are a few from Cessna Aircraft.

Here are a few from Piper Aircraft.

Other industries.

Slide rules are very popular in scuba diving.

Retail Sales.  Here is one that is used for price mark up.