Light aircraft with left & right fuel tanks with on or off fuel selectors.
Never turn your fuel selectors off (unless you have an emergency situation or are operating to the limits of the aircraft endurance). This is particularly true after start and taxing for the take off. Sample the fuel from the same source during the entire taxi – do not change tanks.
An accident occurred approximately in 1970 when a piper Cherokee 140 took off from an airfield at the clarence river mouth with all available fuel through the fuel selectors turned off. The Pilot and his passengers died as a result. At that time all Flying Schools and Aeroclubs had a policy of turning off the fuel selectors at night after the last flight.
After the clarence river month fatal accident it was immediately decided never to turn off the fuel selectors. As a “B” cat flight Instructor since 1970 I taught this to all my students and never had a problem.
Unfortunaly this amended policy did not filter through to the recreational flight Instructors, they still teach to turn off fuel selectors on many occasions. This has resulted in many accidents of fuel starvation after take off.
There are several conflicting, fuel management, methods even in the aircraft flight manual, technical advice some of which is too complex.
The botton line is never turn off your fuel selectors unless you have an emergency. This is of particular importance when parking your aircraft up after the days flying.
If fuel loss occurs through the fuel vents etc, tough – go buy fresh fuel and next time you park up make sure the wings are level.