Learn what a flight computer is, what E6B and onboard computers calculate, and how pilots use them for planning, navigation and fuel checks.
A flight computer is a tool that calculates information pilots need for planning and flying, such as groundspeed, wind correction, fuel use, time and altitude. In aviation, the term can mean a pilot’s E6B calculator or an onboard computer, such as an air data computer or flight management computer.
In aviation and real-world flying, context determines which meaning applies. A flying instructor asking for a “flight computer” usually means an E6B or electronic equivalent; an aircraft manual normally identifies a particular avionics computer.
Which type of flight computer do pilots mean?
A flight computer may be a manual planning instrument, a handheld electronic calculator or part of an aircraft’s avionics.
| Type | Primary job | Typical use |
|---|---|---|
| Manual E6B | Solves wind, speed, time, fuel and altitude calculations | Training, pre-flight planning and in-flight checks |
| Electronic flight computer | Performs E6B-style calculations digitally | Faster planning with entered values |
| Air data computer | Processes pitot, static and temperature data | Airspeed, altitude, Mach and vertical-speed information |
| Flight management computer | Calculates routes, guidance and performance predictions | Airliners and advanced business aircraft |
| Flight control computer | Processes control laws or autopilot commands | Autopilot and fly-by-wire systems |
A tablet or electronic flight bag is not automatically a flight computer. It may contain flight-calculation software, but it can also be used only for charts, documents or weather information.
What does an E6B flight computer calculate?
An E6B combines a circular slide rule with a wind-vector plotting surface to solve common planning problems without requiring electrical power.
- Wind correction angle and groundspeed from true airspeed, course, wind direction and wind speed.
- Time, speed and distance, using relationships such as
time = distance ÷ groundspeed. - Fuel required from flight time and a known fuel-flow rate.
- True airspeed and density altitude from airspeed, pressure altitude and temperature inputs.
- Unit conversions involving nautical and statute miles, kilometres, gallons, litres, pounds and kilograms.
The computer does not obtain weather, fuel flow or aircraft performance by itself. Its answer is only as accurate as the values entered. It also does not replace the aircraft flight manual, operating limitations or required fuel reserves.
How do you use a flight computer for planning?
For a basic visual flight rules calculation, the flight computer turns chart and weather information into headings, times and fuel estimates.
- Measure the course and distance. Establish the true course and leg length from the chart. Our explanation of planning a VFR route with a plotter and ruler covers this stage.
- Collect the inputs. Obtain forecast wind, expected true airspeed and planned fuel flow. Check whether directions are referenced to true or magnetic north and keep all units consistent.
- Solve the wind triangle. Use the wind side of the E6B, or the corresponding electronic function, to find wind correction angle and groundspeed.
- Calculate the heading. Apply wind correction to the course, then account for magnetic variation and compass deviation as required. Do not treat course, heading and track as interchangeable terms.
- Calculate time and fuel. Use groundspeed rather than true airspeed for the estimated time en route, then apply the aircraft’s expected fuel flow and the required reserve.
- Recheck in flight. Actual groundspeed, wind and fuel consumption can differ from the plan, so update the calculation using observed values.
A mistake we see constantly is mixing knots with miles per hour, or nautical miles with statute miles. Pilots also enter wind as though it were blowing towards the reported direction; aviation winds are normally described by the direction from which they blow.
Is an FMC the same as a flight computer?
An FMC is a type of flight computer, but “flight computer” is a broader term that also covers E6Bs, air data computers and flight control computers.
The flight management computer is the calculating element within a flight management system. Depending on the aircraft architecture, pilots interact with it through a control display unit or multifunction control and display unit. It uses route, navigation and aircraft-performance data to calculate a desired path, speeds, fuel predictions and guidance.
The autopilot is a separate system. It moves or commands the flight controls according to selected modes and may follow guidance produced by the FMC. Our guide to the practical difference between an FMC and an autopilot explains where one system’s job ends and the other begins.
Other onboard computers perform narrower tasks. An air data computer derives flight information from sensors, while navigation equipment combines satellite, inertial and radio sources. See our overview of how aircraft navigation systems combine those inputs for the wider avionics context.
What does flight computer mean in a simulator?
In a flight simulator, “flight computer” normally refers either to an E6B-style planning tool or to the simulated FMC, GPS or avionics computer fitted to the chosen aircraft.
- Basic general aviation aircraft: use an E6B or planning calculator to determine headings, groundspeed, time and fuel before departure.
- GPS-equipped aircraft: the receiver calculates tracks, distances and route sequencing from its navigation database. Our guide to GPS calculations and route guidance in flight simulators explains what the unit is doing behind the display.
- Airliners: enter the route, aircraft weights, fuel, cruise level and performance data through the CDU or MCDU, then verify the resulting lateral and vertical guidance.
Why can a simulated flight computer give the wrong answer?
Unexpected results usually come from incorrect inputs, an incomplete route or limitations in the simulated avionics rather than a calculation fault.
- A route discontinuity prevents normal waypoint sequencing.
- Incorrect weight, fuel, cruise altitude or cost settings distort performance predictions.
- True and magnetic headings, or metric and imperial units, have been mixed.
- The simulator’s weather differs from the wind used during planning.
- The aircraft and planner use different navigation data, so waypoints or procedures do not match.
- The add-on models basic route entry but not full vertical navigation or performance calculation.
- The FMC has generated guidance, but the required flight-director or autopilot mode has not been selected.
Treat every result as a calculation based on supplied data. Cross-check headings, distances, fuel and active guidance rather than assuming that a computer-generated value must be correct.