Endurance

Endurance tells you how long an aircraft can remain in the air if it keeps burning fuel at a steady rate. It works because time is found by dividing the total amount of fuel available by how fast that fuel is being used: if you have more fuel, endurance increases; if the engine uses fuel faster, endurance decreases. The units must match, so if fuel flow is in litres per hour, the answer will be in hours.

Use this when estimating flight duration from fuel onboard and engine fuel consumption, especially in basic planning or exam problems. It is also useful for comparing how changes in throttle setting or power affect how long an aircraft can stay airborne.

• Using fuel flow in the wrong units, such as litres per minute without converting to litres per hour
• Reversing the fraction and dividing fuel flow by fuel, which gives the wrong meaning and units
• Treating endurance as distance travelled instead of time in the air