Flight time is defined by ICAO as the total time from the moment an aeroplane first moves for the purpose of taking off until the moment it finally comes to rest at the end of the flight. Total Time (TT) is a fundamental measure in aviation, vital for maintenance scheduling, aircraft management, and pilot records, as it captures every second the aircraft is moving under its own power for the purpose of flight until it stops after landing.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is the definition of total time in aviation?
Total flight time is defined as 1.1: the total of PIC, SIC and flight training time, excluding simulator training. Total time (TT) is the sum of all pilot flight time across categories and is commonly used as the primary measure of a pilot's experience. The International Civil Aviation Organization defines flight time - the core unit of total time - as the total time from the moment an aeroplane first moves for the purpose of taking off until the moment it finally comes to rest at the end of the flight. This definition has been adopted by the European Union Aviation Safety Agency and is echoed in FCL.010 for aeroplanes, touring motor gliders, and powered-lift aircraft. For helicopters, FCL.010 extends the measurement from the moment the rotor blades start turning until they are finally stopped at the end of the flight. Sailplanes are treated differently: SFCL Part-DEF 16.b measures total time from the moment the sailplane commences the ground run for take-off until it finally comes to rest, while for balloons BFCL Part-DEF 11.a counts from the moment the basket leaves the ground until it finally comes to rest at the end of the flight. Although the U.S. Federal Aviation Regulations do not formally define ‘total time’, they define ‘pilot time’, and industry practice equates total time with the aggregate of all logged pilot time, including PIC, SIC, and dual instruction (excluding simulator training). Higher total time on an aircraft log indicates longer overall operation, directly affecting engine and unit longevity.
Where can one find the aircraft’s total time?
To find the aircraft’s total time, one must start with the aircraft's records. Tachometers record time for maintenance purposes; the reading is linked to engine RPM and is written in the engine log. Industry uses the generic term ‘Hobbs’ meter to describe the time recorder; its value is entered in the airframe log. FAA requires that these time records be passed on with the aircraft when it is sold, so the seller must hand over the complete set of logbooks.
If the logs are missing or incomplete, many pilots do catch-up flights to carry-forward time from earlier paper or other logbooks, then enter the revised total in a fresh logbook. For a quick check, open the cockpit and read the Hobbs meter or the recording tachometer; whichever is installed shows the current total time since the last reset.
How to calculate aircraft total time?
To calculate total time, distance is divided by speed. Divide your planned flying distance - typically expressed in nautical miles - by the Ground Speed, expressed in knots, to obtain the flight time in hours: Time (hours) = Distance (nautical miles) / Speed (knots). For example, overcoming an 834 NM leg at 417 knots demands 834 NM / 417 knots = 2.0 h.
Where this calculation refers to speed it must be Ground Speed, never indicated speed. First convert IAS into True Airspeed, then apply the head-wind or tail-wind unit to the latter. These steps turn raw instrument data into a speed you can plug straight into the distance-division formula. For endurance calculations the same principle applies, but you swap distance for fuel volume. Maximum time aloft time equals the amount of fuel divided by the rate at which the fuel is being burned. Regardless of whether you are tracing a plotted course or measuring the absolute clock time the engine runs, two arithmetic operations solve the problem: divide distance by ground speed or divide onboard fuel by fuel flow. Add or subtract wind and convert the indicated airspeed once, and you hold the complete answer to aircraft total time.
