Right, the engine was pulling from the fuel lines and it took that long for those lines to run dry.
I would do that only as a demo. I've never done it before. This showed me how long it takes after you turn the tank selector switch OFF for the engine to finally die. It was a much longer time than I thought.
Testing 'em: Usually the checklists for my type of aircraft (low wing, two separate fuel tanks, one in each wing) say: "Set the switch to one tank, talk to ground control and taxi over to the runway, now you know that tank works and has fuel in it, switch to the OTHER one, run the engine up to 2000 rpm and do some checks, now take off." This is done in an attempt to make sure fuel is feeding properly from both tanks before you get into the air.
The demo showed me that with this procedure if your *second* tank was bone-dry (or had something wedged in the fuel line where it meets the tank) you'll have an engine failure shortly after takeoff... not, as most pilots suspect, while you're still on the ground. Shortly after takeoff is the worst time ever. This safety procedure is therefore potentially harmful instead of helpful! So the idea is: if you're going to switch, switch before you taxi, leaving yourself as much time as possible for the engine to tell you something's wrong. (O'course that means less time for the engine to tell you something's wrong with the *first* tank. I'm going to ask Benjamin about this next time.)
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I would do that only as a demo. I've never done it before. This showed me how long it takes after you turn the tank selector switch OFF for the engine to finally die. It was a much longer time than I thought.
Testing 'em: Usually the checklists for my type of aircraft (low wing, two separate fuel tanks, one in each wing) say: "Set the switch to one tank, talk to ground control and taxi over to the runway, now you know that tank works and has fuel in it, switch to the OTHER one, run the engine up to 2000 rpm and do some checks, now take off." This is done in an attempt to make sure fuel is feeding properly from both tanks before you get into the air.
The demo showed me that with this procedure if your *second* tank was bone-dry (or had something wedged in the fuel line where it meets the tank) you'll have an engine failure shortly after takeoff... not, as most pilots suspect, while you're still on the ground. Shortly after takeoff is the worst time ever. This safety procedure is therefore potentially harmful instead of helpful! So the idea is: if you're going to switch, switch before you taxi, leaving yourself as much time as possible for the engine to tell you something's wrong. (O'course that means less time for the engine to tell you something's wrong with the *first* tank. I'm going to ask Benjamin about this next time.)