E6B
Encyclopedia
The E6B Flight Computer, or simply the "whiz wheel", is a form of circular slide rule
used in aviation
. They are mostly used in flight training
, but many professional and even airline
pilots still carry and use these flight computers. These flight computers are used during flight planning (on the ground before takeoff) to aid in calculating fuel burn, wind correction, time en route, and other items. In the air, the flight computer can be used to calculate ground speed as well. The back is designed for wind correction calculations, i.e., determining how much the wind is affecting one's speed and course. See Wind triangle
.
Electronic versions are also produced, resembling calculator
s, rather than manual slide rule
s. Aviation remains one of the few places that the slide rule still is in widespread use. Manual E6Bs/CRP-1s remain far more popular than the electronic ones because they are lighter, smaller, less prone to break, easy to use one-handed, quicker, and do not require electrical power.
Many ASI (airspeed indicator
) instruments have a movable ring built into the face of the instrument that is essentially a subset of the flight computer. Just like on the flight computer, the ring is aligned with the air temperature and the pressure altitude, allowing the TAS (true airspeed
) to be read at the needle.
In addition, computer programs to emulate the flight computer functions are also available, both for desktop computers and PDAs (Personal Digital Assistants
).
The front side of the flight computer is a logarithmic slide rule that performs multiplication and division. Throughout the wheel, unit names are marked (such as gallons, miles, kilometers, pounds, minutes, seconds, etc.) at locations that correspond to the constants that are used when going from one unit to another in various calculations. Once the wheel is positioned to represent a certain fixed ratio (for example, pounds of fuel per hour), the rest of the wheel can be consulted to utilize that same ratio in a problem (for example, how many pounds of fuel for a 2.5-hour cruise?) This is one area where the E6B and CRP-1 are different. Since the CRP-1s are made for the UK market, they can be used to perform the added conversions of Imperial to Metric units.
The wheel on the back of the calculator is used for calculating the effects of wind
on cruise flight. A typical calculation done by this wheel answers the question: "If I want to fly on course A at a speed of B, but I encounter wind coming from direction C at a speed of D, then how many degrees must I adjust my heading, and what will my ground speed be?" This part of the calculator consists of a rotatable semi-transparent wheel with a hole in the middle, and a slide on which a grid is printed, that moves up and down underneath the wheel. The grid is visible through the transparent part of the wheel.
To solve this problem with a flight computer, first the wheel is turned so the wind direction (C) is at the top of the wheel. Then a pencil mark is made just above the hole, at a distance representing the wind speed (D) away from the hole. After the mark is made, the wheel is turned so that the course (A) is now selected at the top of the wheel. The ruler then is slid so that the pencil mark is aligned with the true airspeed (B) seen through the transparent part of the wheel. The wind correction angle is determined by matching how far right or left the pencil mark is from the hole, to the wind correction angle portion of the slide's grid. The true ground speed is determined by matching the center hole to the speed portion of the grid.
The mathematical formulas that equate to the results of the flight computer wind calculator are as follows:
(desired course is d, ground speed is Vg, heading is a, true airspeed is Va, wind direction is w, wind speed is Vw. d, a and w are angles. Vg, Va and Vw are consistent units of speed.
is 3.14159...)
Wind Correction Angle:
True ground speed:
Wind Correction Angle, in degrees, as it might be programmed into a computer (which includes conversion of degrees to radians and back):
True ground speed is calculated as:
The E-6B was developed in the United States
by Naval Lt. Philip Dalton in the late 1930s. The name comes from its original part number for the U.S Army Air Corps
in World War II
.
Philip Dalton (1903–1941) was a Cornell University
graduate who joined the United States Army
as an artillery officer, but soon resigned and became a Naval Reserve pilot from 1931 until he died in a plane crash with a student practicing spins. He, with P. V. H. Weems
, invented, patented and marketed a series of flight computers.
Dalton's first popular computer was his 1933 Model B, the circular slide rule with True Airspeed (TAS) and Altitude corrections pilots know so well. In 1936 he put a double-drift diagram on its reverse to create what the US Army Air Corps (USAAC) designated as the E-1, E-1A and E-1B.
A couple of years later he invented the Mark VII, again using his Model B slide rule as a focal point. It was hugely popular with both the military and the airlines. Even Amelia Earhart
's navigator Fred Noonan
used one on their last flight. Dalton felt that it was a quickie design, and wanted to create something more accurate, easier to use, and able to handle higher flight speeds.
So he came up with his now famous wind arc slide, but 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, the U.S. Navy
, and even copied by the Japanese and Germans. These are commonly available on collectible auction web sites.
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 Air Corps (by then the Army Air Forces) 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 only officially used on the device itself 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 http://www.weemsplath.com 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.
Slide rule
The slide rule, also known colloquially as a slipstick, is a mechanical analog computer. The slide rule is used primarily for multiplication and division, and also for functions such as roots, logarithms and trigonometry, but is not normally used for addition or subtraction.Slide rules come in a...
used in aviation
Aviation
Aviation is the design, development, production, operation, and use of aircraft, especially heavier-than-air aircraft. Aviation is derived from avis, the Latin word for bird.-History:...
. They are mostly used in flight training
Flight training
Flight training is a course of study used when learning to pilot an aircraft. The overall purpose of primary and intermediate flight training is the acquisition and honing of basic airmanship skills....
, but many professional and even airline
Airline
An airline provides air transport services for traveling passengers and freight. Airlines lease or own their aircraft with which to supply these services and may form partnerships or alliances with other airlines for mutual benefit...
pilots still carry and use these flight computers. These flight computers are used during flight planning (on the ground before takeoff) to aid in calculating fuel burn, wind correction, time en route, and other items. In the air, the flight computer can be used to calculate ground speed as well. The back is designed for wind correction calculations, i.e., determining how much the wind is affecting one's speed and course. See Wind triangle
Wind triangle
The wind triangle is a graphical representation of the relationship between aircraft motion and wind. It is used extensively in dead reckoning navigation.The wind triangle is a vector diagram, with three vectors....
.
Construction
They are usually made out of cardboard and plastic, or aluminum and plastic, with printed lettering and markings, or engraved into the metal. Though many think the more expensive metal models are more durable, pivots of metal models (metal with plastic grommet) will wear out the plastic grommet prematurely, causing the wheels to spin freely. This is not beneficial when you are flying while computing. The cardboard models (except when becoming wet) will outlast the metal versions for most people, and will not develop the "free wheel" even after years of use.Electronic versions are also produced, resembling calculator
Calculator
An electronic calculator is a small, portable, usually inexpensive electronic device used to perform the basic operations of arithmetic. Modern calculators are more portable than most computers, though most PDAs are comparable in size to handheld calculators.The first solid-state electronic...
s, rather than manual slide rule
Slide rule
The slide rule, also known colloquially as a slipstick, is a mechanical analog computer. The slide rule is used primarily for multiplication and division, and also for functions such as roots, logarithms and trigonometry, but is not normally used for addition or subtraction.Slide rules come in a...
s. Aviation remains one of the few places that the slide rule still is in widespread use. Manual E6Bs/CRP-1s remain far more popular than the electronic ones because they are lighter, smaller, less prone to break, easy to use one-handed, quicker, and do not require electrical power.
Many ASI (airspeed indicator
Airspeed indicator
The airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the craft's airspeed, typically in knots, to the pilot.- Use :...
) instruments have a movable ring built into the face of the instrument that is essentially a subset of the flight computer. Just like on the flight computer, the ring is aligned with the air temperature and the pressure altitude, allowing the TAS (true airspeed
True airspeed
True airspeed of an aircraft is the speed of the aircraft relative to the airmass in which it is flying. True airspeed is important information for accurate navigation of an aircraft.-Performance:...
) to be read at the needle.
In addition, computer programs to emulate the flight computer functions are also available, both for desktop computers and PDAs (Personal Digital Assistants
Personal digital assistant
A personal digital assistant , also known as a palmtop computer, or personal data assistant, is a mobile device that functions as a personal information manager. Current PDAs often have the ability to connect to the Internet...
).
Calculations
Instructions for ratio calculations and wind problems are printed on either side of the computer for reference and are also found in a booklet sold with the computer. Also, many computers have Fahrenheit to Celsius conversion charts and various reference tables.The front side of the flight computer is a logarithmic slide rule that performs multiplication and division. Throughout the wheel, unit names are marked (such as gallons, miles, kilometers, pounds, minutes, seconds, etc.) at locations that correspond to the constants that are used when going from one unit to another in various calculations. Once the wheel is positioned to represent a certain fixed ratio (for example, pounds of fuel per hour), the rest of the wheel can be consulted to utilize that same ratio in a problem (for example, how many pounds of fuel for a 2.5-hour cruise?) This is one area where the E6B and CRP-1 are different. Since the CRP-1s are made for the UK market, they can be used to perform the added conversions of Imperial to Metric units.
The wheel on the back of the calculator is used for calculating the effects of wind
Wind triangle
The wind triangle is a graphical representation of the relationship between aircraft motion and wind. It is used extensively in dead reckoning navigation.The wind triangle is a vector diagram, with three vectors....
on cruise flight. A typical calculation done by this wheel answers the question: "If I want to fly on course A at a speed of B, but I encounter wind coming from direction C at a speed of D, then how many degrees must I adjust my heading, and what will my ground speed be?" This part of the calculator consists of a rotatable semi-transparent wheel with a hole in the middle, and a slide on which a grid is printed, that moves up and down underneath the wheel. The grid is visible through the transparent part of the wheel.
To solve this problem with a flight computer, first the wheel is turned so the wind direction (C) is at the top of the wheel. Then a pencil mark is made just above the hole, at a distance representing the wind speed (D) away from the hole. After the mark is made, the wheel is turned so that the course (A) is now selected at the top of the wheel. The ruler then is slid so that the pencil mark is aligned with the true airspeed (B) seen through the transparent part of the wheel. The wind correction angle is determined by matching how far right or left the pencil mark is from the hole, to the wind correction angle portion of the slide's grid. The true ground speed is determined by matching the center hole to the speed portion of the grid.
The mathematical formulas that equate to the results of the flight computer wind calculator are as follows:
(desired course is d, ground speed is Vg, heading is a, true airspeed is Va, wind direction is w, wind speed is Vw. d, a and w are angles. Vg, Va and Vw are consistent units of speed.
is 3.14159...)Wind Correction Angle:
True ground speed:
Wind Correction Angle, in degrees, as it might be programmed into a computer (which includes conversion of degrees to radians and back):
True ground speed is calculated as:
History of the E-6B
The device's original name is E-6B, but is often abbreviated as E6B, or hyphenated in other variations for commercial purposes.The E-6B was developed in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
by Naval Lt. Philip Dalton in the late 1930s. The name comes from its original part number for the U.S Army Air Corps
United States Army Air Corps
The United States Army Air Corps was a forerunner of the United States Air Force. Renamed from the Air Service on 2 July 1926, it was part of the United States Army and the predecessor of the United States Army Air Forces , established in 1941...
in World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
.
Philip Dalton (1903–1941) was a Cornell University
Cornell University
Cornell University is an Ivy League university located in Ithaca, New York, United States. It is a private land-grant university, receiving annual funding from the State of New York for certain educational missions...
graduate who joined the United States Army
United States Army
The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...
as an artillery officer, but soon resigned and became a Naval Reserve pilot from 1931 until he died in a plane crash with a student practicing spins. He, with P. V. H. Weems
P. V. H. Weems
Philip Van Horn Weems was a United States Navy officer, inventor of navigational instruments and methods, including the Weems Plotter and the Second Setting Watch, and author of navigational textbooks.-Biography:...
, invented, patented and marketed a series of flight computers.
Dalton's first popular computer was his 1933 Model B, the circular slide rule with True Airspeed (TAS) and Altitude corrections pilots know so well. In 1936 he put a double-drift diagram on its reverse to create what the US Army Air Corps (USAAC) designated as the E-1, E-1A and E-1B.
A couple of years later he invented the Mark VII, again using his Model B slide rule as a focal point. It was hugely popular with both the military and the airlines. Even Amelia Earhart
Amelia Earhart
Amelia Mary Earhart was a noted American aviation pioneer and author. Earhart was the first woman to receive the U.S. Distinguished Flying Cross, awarded for becoming the first aviatrix to fly solo across the Atlantic Ocean...
's navigator Fred Noonan
Fred Noonan
Frederick Joseph "Fred" Noonan was an American flight navigator, sea captain and aviation pioneer who first charted many commercial airline routes across the Pacific Ocean during the 1930s...
used one on their last flight. Dalton felt that it was a quickie design, and wanted to create something more accurate, easier to use, and able to handle higher flight speeds.
So he came up with his now famous wind arc slide, but 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, the U.S. Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...
, and even copied by the Japanese and Germans. These are commonly available on collectible auction web sites.
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
Pearl Harbor
Pearl Harbor, known to Hawaiians as Puuloa, is a lagoon harbor on the island of Oahu, Hawaii, west of Honolulu. Much of the harbor and surrounding lands is a United States Navy deep-water naval base. It is also the headquarters of the U.S. Pacific Fleet...
for the Air Corps (by then the Army Air Forces) 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
Black light
A black light, also referred to as a UV light, ultraviolet light, or Wood's lamp, is a lamp that emits ultraviolet radiation in the long-wave range, and little visible 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 only officially used on the device itself 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
United States Air Force
The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...
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 http://www.weemsplath.com 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.
External links
- Online E6B simulator This simulator shows W/V, TH/TAS, TT/GS and WCA values. Requires Java plugin.
- Online E6B Java applet
- A Tale of Two Whiz Wheels: E6-B versus CR Wind Solutions