Every flight is a problem in applied geometry: the aircraft points in one direction, the wind pushes it in another, and the goal is to track the intended path over the ground at a known speed and fuel burn. These three tools solve that problem — from a single E6B computation through to a complete multi-leg navlog and a holding pattern entry procedure — using the same mathematics taught in every flight school worldwide.
3 Free Navigation Tools
All tools are free, browser-based, and require no account. Results match the methodology used in FAA and EASA written examinations and practical checkrides.
The complete digital E6B circular slide rule. Solve time, speed, and distance for any two known values; compute true airspeed from IAS, altitude, and temperature; resolve the wind triangle for wind correction angle and ground speed; calculate fuel burn and endurance; and convert between all common aviation units.
E6B Flight ComputerBuild a complete VFR or IFR navigation log across multiple waypoints. Computes true course, magnetic variation correction, wind correction angle, magnetic heading, ground speed, estimated time en route, and cumulative fuel burn for each leg. Outputs a formatted navlog ready for the cockpit.
Navlog & Flight PlannerCalculate the correct holding pattern entry procedure — direct, teardrop, or parallel — from any inbound course and aircraft arrival heading. Includes outbound timing correction for wind and distance adjustment for the target leg length at your groundspeed.
Holding Pattern CalculatorNavigation Mathematics
Converting a line on a chart to the heading the pilot actually flies requires four sequential steps. Every navlog and every E6B computation follows this chain.
| Step | Value | Correction Applied | Direction of Correction |
|---|---|---|---|
| 1 | True Course (TC) | Measured from chart or computed from coordinates. Referenced to true north. | — |
| 2 | Magnetic Course (MC) | Apply magnetic variation from isogonal lines on chart or GPS database. | + Westerly variation / − Easterly variation |
| 3 | Magnetic Heading (MH) | Apply wind correction angle from E6B wind triangle computation. | Into the wind (left for left crosswind, right for right crosswind) |
| 4 | Compass Heading (CH) | Apply compass deviation from the aircraft’s compass correction card. | + Westerly deviation / − Easterly deviation |
Magnetic variation changes with geographic location and with time as the Earth's magnetic field shifts. In the contiguous United States, variation ranges from approximately 20° east in the Pacific Northwest to 20° west in New England. The agonic line — where magnetic and true north coincide and variation is zero — currently runs through the eastern Midwest. In the UK, variation is approximately 1–3° west. In eastern Australia it is approximately 10–13° east.
Isogonal lines on aeronautical charts connect points of equal magnetic variation. For navlog calculations across long routes that cross multiple isogonals, the variation should be updated for each leg or at significant variation change points. GPS navigation databases automatically account for magnetic variation in their magnetic track and bearing computations.
Even after applying magnetic variation, the aircraft's magnetic compass does not read true magnetic direction because the aircraft's own magnetic field — from electrical wiring, engine components, and avionics — distorts the compass indication. This error is called compass deviation and varies with the aircraft's heading. It is measured during compass calibration (swinging the compass) and the results are recorded on a compass deviation card mounted in the cockpit near the compass.
Deviation is typically small (1–5° on most light aircraft) and is often negligible for VFR navigation but should be applied for precise IFR operations. The conversion from magnetic heading to compass heading follows the same rule as variation: add westerly deviation, subtract easterly deviation. The memory aid is East is Least, West is Best.
Operational Workflow
A complete navigation plan follows a structured sequence that transforms a desired route into a set of specific headings, times, and fuel states that can be monitored in flight. The navlog is the output of this process.
Choose the route based on airspace constraints, terrain, weather, and operational requirements. For VFR, identify easily recognisable visual waypoints at 20–40 NM intervals. For IFR, use airways, VORs, NDBs, or GPS waypoints as specified in the ATC system or company route structure. Record each waypoint name, identifier, and coordinates or chart position.
Using a navigation chart or coordinate calculator, measure the true course (referenced to true north) and distance in nautical miles for each leg between consecutive waypoints. For VFR, a plotter and chart provide this. For IFR, the route structure publishes magnetic course and distance between airways fixes, which must be converted back to true course for the wind triangle calculation.
Retrieve the winds aloft forecast (FB in the US, GAMET or gridded forecasts internationally) for the planned cruise altitude. Note the wind direction and speed at each waypoint or along each leg. Where winds vary significantly across long legs, use the midpoint or segment the leg. Record the OAT at altitude for true airspeed computation.
Use the E6B flight computer to convert planned IAS to TAS using pressure altitude and OAT. Then solve the wind triangle for each leg: enter the true course, TAS, and wind vector to compute the wind correction angle and resulting ground speed. Apply magnetic variation to convert true heading to magnetic heading.
Divide each leg distance by the computed ground speed to get the estimated time en route in hours. Multiply by the planned fuel burn rate (from the POH power setting table) to get fuel burn per leg. Sum the leg ETEs and fuel burns to get total flight time and total fuel required. Add required reserves (30 min VFR, 45 min IFR in the US) and any alternate fuel to get the total fuel to upload.
Confirm the planned fuel load, passengers, and baggage are within weight and balance limits using the weight and balance calculator. File a VFR or IFR flight plan with the appropriate ATC unit, including the total estimated time en route, fuel endurance, alternate airport (IFR), and equipment suffixes. Carry the completed navlog in the cockpit for in-flight monitoring.
Common Questions
The wind triangle is the vector relationship between three quantities: the aircraft heading and true airspeed (the direction and speed the aircraft is pointing and moving through the air mass), the wind direction and speed (the movement of the air mass itself over the ground), and the resulting track and ground speed (the actual path and speed of the aircraft over the ground). Because the aircraft moves through a moving air mass, the track across the ground differs from the heading the nose is pointing, and the ground speed differs from the airspeed the aircraft is flying. Solving the wind triangle gives the wind correction angle — how many degrees left or right of track the pilot must point the aircraft to maintain the desired ground track — and the resulting ground speed for time and fuel calculations. Every flight involving any crosswind component requires solving the wind triangle.
The E6B flight computer is a multi-function circular slide rule that has been used in aviation since the 1940s. Its primary functions are: time, speed, and distance calculations (given any two, solve for the third); true airspeed from indicated airspeed, pressure altitude, and outside air temperature; wind correction angle and ground speed from the wind triangle (aircraft heading, TAS, and wind vector); fuel burn rate, required fuel volume, and flight endurance; and unit conversions between nautical miles, statute miles, kilometres, knots, mph, gallons, litres, pounds, and kilograms. It is required knowledge for FAA and EASA PPL, CPL, and ATPL written examinations, and its functions are tested in the practical checkride as a demonstration of preflight planning competency.
Magnetic variation (or magnetic declination) is the angular difference between true north and magnetic north at a specific geographic location. Because the Earth's magnetic pole does not align with the geographic pole, a compass pointing to magnetic north will deviate from true north by an angle that varies with location and changes slowly over time. In eastern North America, variation is currently around 10–15° west, meaning a magnetic heading is 10–15° clockwise from the corresponding true heading. In western Australia, variation may be 2–3° east. To convert a true course (from a chart, computed from waypoint coordinates) to a magnetic heading (what the compass will show), add westerly variation or subtract easterly variation. This step is essential in any navlog — flying a true course as a compass heading will result in a progressively increasing cross-track error.
Wind correction angle (WCA) is the number of degrees the pilot must angle the aircraft into the wind to maintain the desired track over the ground. It is calculated from the wind triangle using the formula: WCA = arcsin((wind speed × sin(wind angle from track)) ÷ true airspeed), where wind angle from track is the angle between the wind direction and the desired track. For example, if tracking 090° with a 30-knot crosswind from 360° (90° from track) at a TAS of 120 knots, WCA = arcsin(30 × sin(90°) ÷ 120) = arcsin(0.25) ≈ 14.5°. The aircraft must be pointed 14.5° into the wind (heading 075°) to track 090° over the ground. A positive WCA means the nose points left of track; a negative WCA means it points right. The E6B computer solves this graphically without requiring trigonometric calculations.
True course (TC) is the direction of the desired track measured in degrees relative to true north, as read directly from a navigation chart or computed from waypoint coordinates. Magnetic course (MC) is the true course corrected for magnetic variation — it represents the same track direction expressed in terms of the magnetic compass reference. Magnetic heading (MH) is the magnetic course further corrected for wind correction angle — it is the actual compass heading the pilot must fly to track the desired course in the prevailing wind. The memory aid for the conversion sequence is TC + Variation (W+/E−) = MC; MC + WCA (into wind) = MH. A fourth value, compass heading (CH), accounts for compass deviation (the error in the specific compass installed in the aircraft), though deviation corrections are typically small and are applied from the aircraft's compass correction card.
The correct holding pattern entry is determined by the angular relationship between the aircraft's inbound heading to the holding fix and the holding pattern's inbound course. The airspace around the holding fix is divided into three sectors. If the aircraft arrives within 70° of the outbound end of the pattern on the holding side, the entry is direct — the pilot immediately turns to the outbound heading on entering the hold. If the aircraft arrives within a 110° sector on the non-holding side, the entry is teardrop — the pilot flies 30° toward the holding side for one minute and then turns back to intercept the inbound course. For the remaining sector, the entry is parallel — the pilot flies outbound parallel to the inbound course on the non-holding side for one minute, then turns back toward the holding side to intercept the inbound course. ICAO and FAA sector boundaries differ slightly for the teardrop and parallel sectors.
True airspeed (TAS) is the speed of the aircraft relative to the surrounding air mass. Ground speed (GS) is the speed of the aircraft relative to the ground. The difference between them is caused by the wind: a headwind reduces ground speed below TAS, a tailwind increases it above TAS, and a crosswind component affects ground speed indirectly through the altered flight path. At cruise, a 120-knot TAS aircraft flying into a 30-knot headwind has a ground speed of 90 knots — it covers 90 nautical miles per hour over the ground despite flying through the air at 120 knots. Ground speed is the correct value for calculating estimated time en route (ETE) and fuel burn for a specific leg distance. TAS is the correct value for solving the wind triangle to find the required magnetic heading.
Standard holding pattern timing requires a one-minute outbound leg (or one and a half minutes above 14,000 feet MSL in FAA airspace). However, wind affects the time spent on the inbound and outbound legs differently — a headwind on the inbound leg means less time is needed on the outbound leg to achieve the correct inbound leg length, and vice versa. The outbound timing correction adjusts the outbound time to compensate: the pilot adds half the inbound leg time error from the previous circuit to or subtracts it from the outbound time. Alternatively, many pilots use the wind component along the holding course to calculate a direct correction. The holding pattern calculator automates this adjustment for the planned wind and ground speed so the correct outbound time is computed before entering the hold.
A VFR navigation log (navlog) is a structured planning document that records all the information needed to fly a specific route. A complete navlog contains: waypoint names and identifiers; true course for each leg; magnetic variation at or between waypoints; wind correction angle and the resulting magnetic heading; true airspeed and wind-corrected ground speed; leg distance in nautical miles; estimated time en route for each leg; cumulative time from departure; fuel burn per leg based on planned power setting; cumulative fuel used; and planned fuel state at each waypoint. Many navlogs also include ATIS frequencies, radio frequencies for relevant ATC facilities, and planned altitudes. A completed navlog allows the pilot to monitor progress and fuel state at each waypoint, cross-checking actual vs. planned to detect navigation errors early.
SELCAL (Selective Calling System) is an alerting system used on HF radio communications during long-range oceanic operations, where continuous HF radio monitoring by the crew is impractical due to interference and noise. Each aircraft is assigned a unique 4-letter SELCAL code, and ATC can activate the aircraft's SELCAL decoder to alert the crew that a call is waiting. While SELCAL is not directly computed in navlog planning, long-range oceanic operations require specific planning elements beyond the standard navlog: ETOPS considerations, oceanic clearances, position reports at ocean entry and waypoints, equal time point (ETP) calculation, point of no return (PNR) calculation, and SELCAL check with the oceanic control area at entry. The navlog is the foundation document for all of these planning elements.