Navigation Log & Flight Planner

A navigation log is a structured pre-flight document that records all calculated values for each leg of a cross-country flight: waypoint names and frequencies, leg distances, true course, magnetic variation, wind correction angle, true heading, magnetic heading, compass heading, planned altitude, true airspeed, groundspeed, estimated time en route, estimated time of arrival, and fuel burn per leg. Pilots use the navlog to navigate without GPS and to verify GPS-computed values. It is a legal requirement in many jurisdictions for student pilots on solo cross-country flights. Even for experienced IFR pilots, a completed navlog is the single most important backup if avionics fail en route. It also serves as a legal record of the pre-flight planning performed.

Step 1: Mark all waypoints on the chart and measure the True Course (TC) and distance for each leg using a plotter and the nearest meridian. Step 2: Note the magnetic variation from chart isogonic lines for each leg. Step 3: Obtain the forecast winds aloft at your planned altitude from the weather briefing. Step 4: For each leg, solve the wind triangle to get True Heading (TH), Magnetic Heading (MH), and Groundspeed (GS). Step 5: Calculate ETE for each leg (distance ÷ GS) and cumulative ETA from your planned departure time. Step 6: Calculate fuel burn per leg (ETE × burn rate) and cumulative fuel used. Step 7: Check total fuel against fuel available less regulatory reserve. Step 8: Add ATIS frequencies, radio navigation aids, and emergency divert options to each leg entry.

A navigation log (navlog) is an internal pilot document used for navigation — it contains the detailed calculations for each leg. A flight plan is an official ATC document filed with the relevant aviation authority to activate ATC services and search-and-rescue protection. A flight plan typically contains: aircraft registration, aircraft type, equipment suffix, departure aerodrome and time, cruising altitude, route (waypoints, airways), destination aerodrome, alternate aerodrome, total endurance, and number of persons on board. The navlog feeds the flight plan — the route in the flight plan is typically a simplified version of the detailed navlog waypoints. Both documents are required for IFR flight and strongly recommended for VFR cross-country flights of any significant distance.

A correctly completed navlog using forecast winds aloft is typically accurate to within 5–10 nautical miles for position and 3–5 minutes for timing over a 2–3 hour flight. The primary source of error is wind forecast accuracy — winds aloft forecasts are typically accurate to within 5–10 kt direction and 5 kt speed. Secondary errors come from variation in TAS with altitude and temperature changes, and from the approximation that TC and MH are constant throughout a leg when in reality the aircraft may be slightly off track. GPS is accurate to within 10 metres under normal conditions. The difference matters: for terrain clearance, obstacle avoidance, and airspace avoidance, use GPS. For understanding your situation when GPS fails, the navlog is your lifeline.

At minimum, include departure and destination aerodromes plus any mandatory reporting points for the route. Beyond the minimum, include: prominent visual checkpoints that are unambiguous from the air (coastlines, lakes, motorway junctions, towns, airfields); VOR/NDB stations that can be used for position verification; Class D, C, and B airspace boundaries that require specific entry procedures or communications; high terrain and obstacle areas requiring altitude adjustments; fuel stop aerodromes; and divert aerodromes for each major portion of the route. Spacing between waypoints is typically 20–30 nm for VFR low-level navigation — sufficient to identify each point within 5 minutes of scheduled passage.

Each leg of the navlog can have a different wind. For a short domestic flight below 5,000 ft, one wind from the area forecast may apply to all legs. For a longer cross-country flight at varying altitudes, use the winds aloft forecast for the planned altitude at each waypoint — typically from the UAV (winds aloft) forecast. If the flight climbs through different altitude bands, use the wind at the planned cruising altitude for each leg. When two adjacent legs have significantly different forecast winds (e.g. crossing a front), calculate each leg separately with its own wind entry. The biggest error in navlog planning is applying a single surface wind to all legs of a long flight.

A VFR flight plan is filed with ATC or the relevant authority to activate search-and-rescue coverage. If you do not arrive at your destination within 30 minutes (typically) of your filed ETA and have not closed your flight plan, a search is initiated. Filing requirements vary by country: in Canada, a VFR flight plan is required for flights beyond 25 nm from the departure aerodrome. In Australia, SARWATCH is required for remote area flights. In the UK and most of Europe, VFR flight plans are not mandatory but are strongly recommended for overwater or remote area flights. In the USA, VFR flight plans are not mandatory but provide SAR protection. IFR flight plans are mandatory for IFR flight in controlled airspace everywhere.

Calculate fuel for each leg separately: Fuel per leg = ETE (in hours) × Fuel Burn Rate. Sum all leg fuels for trip fuel. Add regulatory reserve fuel: VFR day 30 minutes, VFR night 45 minutes, IFR 45 minutes plus alternate. Add contingency fuel (typically 5–10% of trip fuel) for unexpected headwinds or routing changes. Add taxi and startup fuel (typically 0.5–1 US gal for piston aircraft). Total all components and verify against usable fuel available. If the calculation exceeds fuel capacity, options are: fuel stop en route, reduce payload, reduce cruise altitude (lower TAS but shorter route may be possible), or change routing to avoid headwinds. Always express fuel requirements in both volume and weight — weight is needed for weight and balance, volume is what you request from the fuel operator.

A PLOG (Pilot Log) is the specific term used by many UK training organisations and the CAA for the standardised navlog format required for the PPL skills test. A PLOG typically includes: waypoint name, track (TC), variation, deviation, heading, altitude, TAS, wind, groundspeed, distance, ETE, ETA, fuel used, fuel remaining, and ATIS/radio frequencies for each leg. The PLOG format is also used in commercial licence training (CPL, ATPL) and is the format examiners assess during flight tests. The term "navlog" is generic; PLOG specifically refers to the UK/EASA standardised format. This calculator produces a PLOG-compatible output with all the fields required for UK licence tests.

The most common navlog errors in order of frequency: (1) Wrong wind direction entry — entering the wind direction TO instead of FROM. Winds are always given FROM in aviation. (2) Failing to convert ATIS/METAR wind from Magnetic to True before using it in the wind triangle. (3) Applying the wrong sign for magnetic variation — subtracting when adding is required (East is Least, West is Best). (4) Using a single wind for all legs of a long flight at varying altitudes. (5) Forgetting to add reserve fuel, or using the wrong reserve requirement for the flight rules in use. (6) Calculating ETE correctly but adding it to local time instead of UTC/Zulu, leading to incorrect ETAs. (7) Using the same TAS for all legs without correcting for altitude and temperature changes. Reviewing the navlog systematically — checking each column for arithmetic consistency — catches most errors before departure.