The E-6B Flight Computer
Despite what some might consider to be its outdated appearance and
mode of operation, the E-6B Flight Computer is still an important part of the aviator's
planning kit. The E-6B Flight Computer (professionally referred to as the Dalton
Flight Computer) is one of the few true slide rules still in general manufacture and
active use today. Most every student pilot has been taught to use one during
his or her early training. Although its slide rule features are limited to the
unlabelled C/D scales on the circular front portion, this low-tech device is commonly used
by pilots for flight path calculations, wind correction, fuel consumption, etc. (the back
of the rule has a useful graphical method of doing vector calculations involving
trigonometry).
Today, of course, hand-held electronic versions are available to do all these functions and more, but I suspect a lot of flight enthusiasts don't want to trust their lives to the charge storage capacity of your average alkaline battery -- especially on a long flight and over unknown territory.
Note: My thanks to Kevin Darling for providing updated information.
The Dalton flight "computer" is the sole remaining example still in production of the classic navigation slide-rule. Before the electronic-age, slide rules of various types were the back-bone of aircraft engineering and navigation. Aircraft manufacturers, as an example, had huge buildings with tens of thousands of technicians using slide-rules to compute sums related to aircraft structures. These technicians were called "computers", and the term was transferred to the electronic versions with the advent of the microprocessor.
The origin of this particular ingenious device is centered around Philip Dalton, a Cornell University graduate and U.S. Naval Reserve pilot. Dalton developed a series of slide-rule flight computers in the 1930s. In 1932, he designed the E-6B (originally called the Dalton Dead Reckoning Computer) Aviation historian, Kevin Darling, notes that British navigation tools all carried the prefix "6B" to their part numbers, thereby causing some confusion as to the origins of the Dalton "E-6B." Regardless of the part number confusion, the Dalton Dead Reckoning Computer, or "E-6B", has survived to this day in slightly modified form through the hands of a large number of civilian manufacturers such as Jeppesen and ASA.
History
The origins of this ingenious device (and flight computers in general) is clouded in
mystery and the shadows of history.
But, it seems the standard accepted theory is that a U.S. Navy pilot named Philip Dalton developed a series of flight computers in the 1930s, including the ever-popular E6-B, somewhere around 1932 (originally called the Dalton Dead Reckoning Computer).
Another argument suggests that the design is of British origin dating to the 1920s.
But, whatever the origins there is no arguing that without this useful device piloting and navigating would be much more difficult.
I recently came across photos of several vintage examples of these early computers on auction sites on the internet.
Two examples of a Dalton Aircraft Navigational Computer
FRONT BACK Dalton Aircraft Navigational Computer, Mark VII (c. 1934)
Dalton Aircraft Navigational Computer, Mark VII (c.1935)
The Dalton Aircraft Navigational Computer was a favorite with airline pilots of the day as
well as the few recreational pilots who had aircraft fast enough to need one. It had
a Speed-Time-Distance binary computer and Dead Reckoning slide rule, with a Wind Drift
Index on reverse side. The insturctions for Airspeed and Altimeter Correction
printed in red with a Flight Log on lower portion.
Yet another example...
Flight Computer Offered by Stanavo Oil Company
This computer was a promotional item given to aviation customers of the aviation
division of Standard Oil sometime during the 1930s. The computer is four inches in
diameter and is a binary pilot's time-speed-distance computer. It is printed
on both sides with true airspeed and altitude correction on one side and time-distance on
the other. The Stanavo Red Eagle logo is emblazoned on the front face.
Much of the development of aviation was fostered by corporations who had some stake in its success. Large oil companies were huge supporters of aviation and as such, often promoted themselves with give aways. Stanavo was Standard Oil's aviation arm. The Stanavo Eagle was one of the most well-known logos of the era.
So, how the heck does one of these things work?
Well, the E6B looks complicated but is easy to use. It's also known as a slide graphic computer or CSG. Many of the possible operations resemble common mechanical computers. An E6-B features a wind component grid and comprehensive crosswind correction chart, and on the other side the slide computes time, speed, distance (in nautical and standard scales), altitude, true airspeed, and density altitude problems. With the computer a pilot can also make standard conversions of temperature, miles, and compute altitude corrections.
The function discussed here is are relevant to navigation.
There are two sides to the computer. The face is referred to as the
calculator side and has two circular discs attached at the center. The top disc has
cut outs or windows. There is an index pointer on the inside disc.
Fortunately, there are directions printed on the E6B for the pilots that forget how to use
it. If you look at the discs, they are circular scales, and moving from the outside
circle to the center, these are named by letter, from the outside to the center.
There are five scales and six functions:
A scale Speed, Distance, Fuel This scale is fixed B scale Time in Distance This scale rotates to complete the computation. It is sometimes referred to as the "inner circle." C scale Time in Hours D scale Air Temperature and Pressure Altitude E scale Temperature and Statute to Nautical Conversions: 1. time, speed, distance
2. fuel consumption
3. density altitude
4. airspeed calculations
5. wind correction
6. conversions
The back is known as the wind side. Wind problems have six variables; course, true
airspeed, wind direction, velocity, magnetic heading, and groundspeed. By following
step by step procedure that is detailed on the E6B in case there is a memory lapse, a
pilot can establish a wind correction calculation quickly while enroute, and maintain the
best course and time for the conditions.
By knowing the current ground speed, corrections can be made for fuel stops to eliminate
the element of emergency glider practice. They call a propeller a fan, because when
it quits, you ought to see the pilot sweat! When a prop stops, it is usually from
fuel starvation and fuel mismanagement. The pilot has plenty of quiet, except for
wind noise to refigure fuel consumption rate, and practice with the E6B while looking for
a place to land. These quiet approaches are called dead stick landings.
You can still purchase a Dalton Flight Computer (now called the
E6B) at most any pilot supply shop. E6-B models come in a variety of sizes and
materials (including aluminum, plexiglass, and the cheap fiberboard model shown above),
and are easily obtainable at any of the online pilot-gear stores. You can certainly
find one at Sporty's Pilot Shop.
It's where I got mine. Not only do I use it in the "real" world, but it's
great for virtual flying as well.
ASA E-6B Flight Computer
