E6B Calculator
The E6B calculator solves the same wind triangle as the manual flight computer, returning wind correction angle and groundspeed alongside crosswind and headwind.
WCA = asin(25 × sin(50°) ÷ 110) = 10.0° RGS = 92 kts
Hold 100° to track 090°, a 10.0° correction into wind from the right.
Where the E6B Came From
The E6B was designed by Philip Dalton, a US Navy reserve officer and Cornell-trained engineer, in the 1930s, and reached its familiar form as standard equipment for Second World War aircrew.
Dalton's insight was that the two hard problems of dead-reckoning navigation have different shapes and need different instruments. Time, speed, distance, and fuel are proportions, and a circular slide rule handles proportions elegantly. Wind, course, and groundspeed form a vector triangle, which a slide rule cannot touch. He built a device with a slide rule on one face and a sliding-grid vector plotter on the other, and the combination has outlived every technology that was supposed to replace it.
The designation itself is a catalogue number, not a product name. The US Army Air Corps listed Dalton's dead reckoning computer as the E-6B, and the label attached itself to the whole class of instrument. Wartime production ran into the hundreds of thousands, which is why originals still turn up in flying club lockers. The modern aluminium version differs from a 1943 example in materials and printing rather than in method: the same grid, the same grommet, the same procedure.
Mechanically, the wind side is a graphical vector solver. The transparent plotting disc rotates to set a direction against the true index, and a card slides underneath carrying concentric speed arcs and radial drift lines. Marking the wind as a dot up from the grommet and then sliding the card until that dot rests on the airspeed arc physically constructs the triangle, and the answers are read off where the dot and grommet land. Nothing is computed; the geometry does the work.
The Wind Triangle It Solves
Every wind-side problem is the same triangle of three vectors, where the aircraft points, what the wind does to it, and where it ends up going.
The air vector runs along the true heading at true airspeed: it is what the aeroplane is doing through the air mass. The wind vector runs from the tip of that vector in the direction the wind is blowing towards. Whatever the two combine to produce is the ground vector, and its direction is the true course while its length is groundspeed. Given any two complete vectors, the third is determined, which is why the same instrument can solve for heading before departure and for actual wind after measuring drift in flight.
Digital Against Manual Accuracy
A digital solution is exact to the trigonometry while a manual E6B is limited to about a degree and two or three knots by how finely a human eye can read a printed grid.
That gap matters less than it first appears. The wind figure fed into either method is a forecast or an observation rounded to ten degrees and five knots, so an answer computed to four decimal places rests on an input good to maybe ten percent. Both methods land comfortably inside the error the input already carries, and a manual E6B has never lost anyone.
The genuine advantages of the digital version are speed and repeatability: recalculating four legs after a forecast update takes seconds rather than minutes, and it cannot be misread under a red cockpit light. The genuine advantage of the aluminium one is that it works with a dead battery, in direct sun, and at any temperature. Plenty of pilots carry both, and the reason is not sentiment. If you want just the navigation answer without the runway components, the drift angle calculator gives a narrower view of the same triangle, the full formula reference shows the equations underneath, the runway crosswind tool handles the landing case, and the observation decoder supplies the wind figures to feed in.
E6B Questions
Is a digital E6B allowed on a checkride?
Yes. The FAA permits electronic flight computers on practical tests, including dedicated E6B units and phone applications, provided the examiner can verify the device holds no prohibited reference material. Some examiners still ask a candidate to demonstrate the manual instrument to prove the underlying understanding, so knowing both is the safe preparation. Check with your examiner before the ride rather than assuming.
What's the difference between the wind side and the calculator side of an E6B?
The wind side is the flat face with the sliding grid and rotating compass rose, and it solves vector problems: wind correction angle, groundspeed, and the crosswind and headwind components. The calculator side is a circular slide rule that solves proportions, time, speed and distance, fuel burn, true airspeed from indicated, and unit conversions. They are two separate instruments sharing one piece of aluminium.
Can an E6B calculate true airspeed from indicated airspeed?
Yes, on the calculator side. A small window on the slide rule face aligns pressure altitude against outside air temperature, and reading indicated airspeed against that alignment gives true airspeed directly. It is the same correction an air data computer performs continuously, done once by hand. The result feeds straight into the wind side as the airspeed input for the triangle.
Do all pilots still learn the manual E6B?
Most primary students still meet it, though the depth of training varies widely. Flight schools teach it because the underlying triangle is easier to understand when you can see it drawn, and because it keeps working with a flat battery. Airline pilots almost never touch one after training, since flight management systems handle the same arithmetic continuously and more accurately.
Is E6B a brand name or a generic term?
E6B started as a US military designation rather than a brand. Philip Dalton developed the underlying computer in the 1930s, and the E-6B model number came from the Army Air Corps stock catalogue during the Second World War. The name stuck as a generic term, so any manufacturer can sell an E6B and every one works the same way.