Question 72, Aircraft General Knowledge - PPL(A) English - Private Pilot License

At least one fuel quantity indicator must be available to indicate the total amount of fuel abord an aircraft. This Indicator must be calibrated adequately to indicate the correct amount of fuel during all phases of flight.
If the fuel indicator fails, the pilot must land at the next available airport.
If no fuel quantity indicator is available to the pilot in flight, the pilot must check the fuel quantity before commencing the flight and recalculate the remaining fuel on board in regular intervals during the flight.
A fuel quantity indicator must be available for each tank and the indicator must be calibrated to read "zero" during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply.