Refer to figure.
ATC endurance is the maximum time that the aircraft can remain airborne taking into account the Final Reserve Fuel consumption as well, i.e. ATC edurance is up to dry tanks or ATC endurance is the elapsed time from take-off at which point you run out of all usable fuel, excluding the start-up and taxi fuel in your calculations.

• The Contingency fuel for a helicopter flying VFR in a non-hostile environment is: 5% x Trip fuel = 5% x 4 034 kg = 202 kg, which corresponds to a flight time of: 5% x 103 min = 5 min.
• The Minimum Take-off Fuel is: 6 469 kg (= 4 034 + 202 + 1 058 + 1 175).
• Thus, the Extra Fuel is: 776 kg (7 245 kg - 6 469 kg).
• The fuel flow for the Extra fuel is given as 2 500 kg/hr. So, the Extra fuel of 776 kg will permit to fly for: 776 kg / 2 500 kg/hr = 18 min.

Thus, the ATC endurance is the sum of the following flight times:

• 103 min + 5 min + 27 min + 30 min + 18 min = 183 min.