Dalton E-6B Dead Reckoning Computer by Jeppesen

In this instrument a white rectangular plastic sheet slides between two white discs that are held together with black plastic bars and metal grommets. The sheet is marked in green on both sides, with a polar grid and rectangular grid on one side and a polar grid on the other side. The front disc has scales for altitude computations at the top and for air speed computations at the bottom. The back disc has a scale to correct direction readings for wind and a scale for converting temperature readings from degrees Centigrade to Fahrenheit. The center of the back disc is clear for viewing the grid. A salmon plastic sheath stores the instrument.
The device is marked on the front: DALTON DEAD RECKONING COMPUTER (/) TYPE E-6B. It also is marked: WEEMS SYSTEM OF NAVIGATION (/) (A DIVISION OF JEPPESEN & CO.) (/) DENVER, COLORADO; PAT. NO. 2,097,118. The grid is marked in pencil: FL[IGH]T OFF COURSE (/) 2 MILES/SQUARE. The back of the disc is also marked in pencil. The three lines in the clear part of the disc are illegible, but below the temperature conversion scale, the marks read: 3.5° F/1000'. A ring at the top of one black plastic bar is marked: U.S. PAT. 3,112,875.
Naval Reserve pilot Philip Dalton, in consultation with navigation instructor Philip Van Horn Weems, developed the Dalton dead reckoning computer for the U.S. Army Air Corps and received a patent in 1937. The device was widely used during World War II.
After the war, many manufacturers in the United States and Europe made the E-6B. Elrey Borge Jeppesen, a pilot for what became United Airlines, founded his company in 1934 and moved it to Denver in 1941. Jeppesen & Co. made aeronautical charts and navigational tools and guides. It became a subsidiary of Boeing in 2000. The patent number on the back of this object refers to the design of the computer with the gridded rectangular sheet and two discs. The patentees were employed by Felsenthal Instruments Co., which frequently supplied companies with the plastic for manufacturing Dalton computers in the 1950s and 1960s.
The donor purchased this object around 1965 and used it for about two years in airplane navigation.
Paul McConnell, "Some Early Computers for Aviators," Annals of the History of Computing 13, no. 2 (1991): 155–177, on 156. Philip Dalton, "Plotting and Computing Device" (U.S. Patent 2,097,116 issued October 26, 1937).
Ben Van Caro and Burton L. Fredriksen, "Computer Slide Construction" (U.S. Patent 3,112,875 issued December 3, 1963). "E6B," http://en.wikipedia.org/wiki/E6B.
"Jeppesen," http://en.wikipedia.org/wiki/Jeppesen.
"On the Beam," advertisement for Dalton Dead Reckoning Computer, Felsenthal Plastics, Flying 35, no. 2 (August 1944): 10.
Paul Sanik, "U.S. Army Air Corps Aerial Dead Reckoning type E-6B," Journal of the Oughtred Society 6, no. 2 (1997): 32–34 .
Currently not on view
Object Name
plotting board
date made
Jeppesen & Co.
Physical Description
metal (part material)
plastic (overall material)
overall: 1 cm x 12.5 cm x 24.3 cm; 13/32 in x 4 29/32 in x 9 9/16 in
place made
United States: Colorado, Denver
ID Number
accession number
catalog number
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Plotting Boards
Slide Rules
Data Source
National Museum of American History, Kenneth E. Behring Center


My sisters and I just found our dad's E6-B Dalton Dead Reckoning Computer ( Weems system of navigation) in my oldest sister's basement. She had stored a lot of stuff for our parents years ago . This item is very special! When we were little our dad flew small private aircraft in New Mexico. & later in Georgia. He worked for Holloman Airforce base at one time and for Land Air. Our dad died September 10, 2016. He is flying in heaven now and shouldn't need his old navigation tool. It will stay in our special daddy museum. :)

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