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
Science & Mathematics
Slide Rules
Plotting Boards
See more items in
Medicine and Science: Mathematics
Plotting Boards
Slide Rules
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of William E. Gilbert
Additional Media

Visitor Comments

Add a comment about this object

**Please read before submitting the form**

Have a comment or question about this object to share with the community? Please use the form below. Selected comments will appear on this page and may receive a museum response (but we can't promise). Please note that we generally cannot answer questions about the history, rarity, or value of your personal artifacts.

Have a question about anything else, or would you prefer a personal response? Please visit our FAQ or contact page.

Personal information will not be shared or result in unsolicited e-mail. See our privacy policy.

Enter the characters shown in the image.