Flight-planning arithmetic for general aviation: wind, altitude, airspeed, descent, turns and balance.
The E6B in pieces: crosswind and the wind triangle, pressure and density altitude, true airspeed and Mach, the standard atmosphere, top of descent, climb gradient, turn performance, glide and weight and balance. Every page states its formula and takes the aircraft figures from you — nothing is looked up from a handbook. These are planning aids, not a substitute for the pilot’s operating handbook, the aircraft’s limitations or the rules that apply to the flight.
Climb gradient in percent, ft per nm and ft per minute at your ground speed, and the gradient an obstacle needs with the clearance you choose.
You get: One gradient in all three forms (and metres per kilometre and per minute), the rate of climb it needs at a ground speed, and whether it clears an obstacle of a given height and distance by your margin.
Open Climb Gradient ConverterCrosswind and headwind or tailwind on a runway from the reported wind and gusts, true-to-magnetic done for you, and your own crosswind limit compared.
You get: How much of the wind is across the runway and how much along it, in the steady wind and in the gust, which side it comes from, whether it exceeds the limit you enter, and the rule-of-thumb table beside it.
Open Crosswind & Headwind ComponentWhere to start down and how fast: descent distance from an angle, rate or gradient at your ground speed, the rate a 3° path needs, and the point before a fix.
You get: The distance the descent takes, the vertical speed the path needs at your ground speed, the time, how far before a fix to begin, the altitude you would cross the fix at, and the 3-to-1 and 5-times-ground-speed rules beside them.
Open Top of Descent & Descent RateThe wind triangle solved exactly: wind correction angle, heading and ground speed from course, TAS and wind, plus leg time and fuel at your burn rate.
You get: The heading that holds your course, the ground speed you will make, the headwind and crosswind components, and for a leg of a given distance its time and the fuel at the burn rate you enter.
Open Wind Correction Angle & Ground SpeedEstimated cumulus base from surface temperature and dew point at the convergence rate you enter, above ground and sea level, with the base temperature.
You get: The height at which a rising parcel reaches saturation — the cumulus base — from the dew-point spread, in feet or metres AGL and MSL, the temperature there, and the freezing level at a lapse rate you choose.
Open Cloud Base from Dew Point SpreadDensity altitude from pressure altitude (or elevation and QNH) and the OAT, exact through the ISA density law, with the 120 ft per °C rule beside it.
You get: The density altitude and how far above the field it is, the pressure altitude and ISA deviation it rests on, the density ratio and air density, and the rule-of-thumb figure with its difference from the exact one.
Open Density AltitudePressure altitude from field elevation and altimeter setting, exact through the ICAO atmosphere with the 30 ft per hPa rule beside it; inHg ↔ hPa and QFE.
You get: The pressure altitude for a field and QNH, the correction that was added to the elevation, the rule-of-thumb figure and how far it drifts, the station pressure in both units, and the ISA temperature at that altitude.
Open Pressure Altitude & Altimeter SettingICAO standard atmosphere to 20 km: temperature, pressure, density, θ δ σ and the speed of sound, a table around the altitude, and the ISA deviation of an OAT.
You get: The standard temperature, pressure, density and speed of sound at an altitude in feet or metres, the ratios performance charts use, a seven-row table either side, and how far an outside air temperature is from ISA.
Open Standard Atmosphere (ISA)True airspeed, Mach and EAS from calibrated airspeed, pressure altitude and temperature by the exact subsonic relations, with the 2 % per 1,000 ft rule beside.
You get: TAS in knots, mph and km/h, the Mach number and the speed of sound at your temperature, EAS and CAS, the density ratio and ISA deviation, and how far the rule of thumb is from the exact figure.
Open True Airspeed & MachTotal weight, moment and centre of gravity from a list of stations, the landing figures after fuel burn, and a check against the handbook limits you enter.
You get: Take-off weight and CG from your stations, the landing weight and CG after fuel burn at the fuel arm, a station-by-station moment table, and whether each is within the limits you entered — with the margins.
Open Aircraft Weight & BalanceHow far a glide reaches from a height at the glide ratio (or sink rate and speed), with head- or tailwind, its time, and the height needed to reach a point.
You get: The glide distance in still air and over the ground with the wind, the glide ratio and angle, the time in the glide, and for a point at a given distance the height needed with your margin and whether it is reachable.
Open Glide Ratio & Glide DistanceLoad factor, turn radius and rate of turn at a bank and airspeed, how much the stall speed you enter rises in the bank, and the bank a standard-rate turn needs.
You get: The g the wings carry at that bank, the radius and rate of the turn, the time round 360°, the stall speed in the bank from your level figure and the margin to it, and the bank angle for a rate you choose.
Open Turn Performance & Stall Speed in a Bank