Artifact of the Month: April 2018

Aerial Dead Reckoning Computer

Pilots utilize a variety of tools to aid in navigation, and one of the most basic methods to navigate is by dead reckoning-a manual form of navigation based on mathematical calculations of time, speed, distance, and direction. In the late 1930s, Naval Lieutenant Philip Dalton developed the E-6B, otherwise known as the aerial dead reckoning computer. The device, also nicknamed the "whiz wheel," is a round mechanical analog computer. Its name comes from the original part number from the U.S. Army Air Corps, the predecessor of the Air Force.

The E-6B is a slide rule that consists of an aluminum disk attached to aluminum housing with a slot for a sliding plastic grid. This month's featured artifact is stored in its own brown leather case bearing the original owner's name, "R.E. Ellis." While mostly used in flight training, E-6Bs also have applications during flight planning and once the aircraft is in the air. Pilots can use them to calculate estimated fuel burn, wind correction, time en route, and ground speed. The back side is designed to help determine how much the wind affects the speed and the course. While modern pilots have radios, satellite, GPS, and smartphone apps, the E-6B is still useful in the event of mechanical malfunction.

Alaska aviation pioneer and legendary bush pilot, Robert (Bob) E. Ellis, used this aerial dead reckoning computer while serving in the Aleutian Theater during World War II. Ellis is well-known in Ketchikan for starting his own air business in 1936. During the war years, he was recalled to service and was stationed in various Alaskan locales, including Sitka, Kodiak, and Attu. Following the war, Ellis returned to Ketchikan and resumed management of Ellis Air. In 1947, Ellis gave this E-6B to Eugene Heath, who used it to study for his Commercial Pilots License. Heath, born and raised in Ketchikan, began working for Ellis Airlines in 1941. He became an Ellis pilot in 1948, and later flew for Alaska Airlines until he retired in 1985.

Ketchikan Museums, KM 98.2.43.1 A-C