Running a Fuel Tank Dry
CF-NZB has four fuel tanks that allow for 90 gallons total. My father would call those small wimpy US gallons. I had the tip tanks added soon after acquiring the aircraft for the range and to be able to file a decent IFR flight plan. The added range allows a good four hour leg while still having two hours to get to far away alternate if required.
However, there is the problem of leaving fuel behind in the tanks. If you switch while the tanks still show some fuel, then you have a few gallons of useless fuel sitting around. You won't switch back because it might only be a few minutes. If you had to extend the range as much as possible due to some situation (which is why you would even consider it) would you switch to a tank where you don't really know how much is in there? While distracted by an urgent situation?
So I run the tip tanks dry. The procedure is:
- keep careful records in flight and estimate time to empty on the tip tank,
- do a briefing to ensure their will be an airfield nearby,
- ensure you are high enough to reach that airfield should something bad happen,
- ensure you won't be distracted with ATC or what have you at the time,
- when close to empty turn on the electric pump and keep a careful eye on the fuel pressure gauge,
- when the pressure gauge starts to dip switch tanks.
I do have a fuel totalizer installed which, with practice, allows me to estimate within a few minutes when the tank will run dry. It is an excellent bit of kit.
I have drawn the tip tanks down completely empty (15.3 to 15.4 gallons each time) and the engine never misses a beat. The careful records required allowed me to find a fuel leak a few years ago, and it also keeps me very aware of how much fuel is really there, and where I am when switching tanks, and what kind of repeatable reliable performance I get out of those tanks.
I have gotten distracted while doing this and allowed the engine to run rough or quit. My wife really does not like this. Says it causes frowning which causes wrinkles. So now I also ensure that I won't be distracted at a critical time. Say directly over Calgary transiting the zone for example. Or during an IFR approach. Those times are where I switch to a full tank and concentrate on the task at hand and not fiddling with fuel tank selectors.
However, there is the problem of leaving fuel behind in the tanks. If you switch while the tanks still show some fuel, then you have a few gallons of useless fuel sitting around. You won't switch back because it might only be a few minutes. If you had to extend the range as much as possible due to some situation (which is why you would even consider it) would you switch to a tank where you don't really know how much is in there? While distracted by an urgent situation?
So I run the tip tanks dry. The procedure is:
- keep careful records in flight and estimate time to empty on the tip tank,
- do a briefing to ensure their will be an airfield nearby,
- ensure you are high enough to reach that airfield should something bad happen,
- ensure you won't be distracted with ATC or what have you at the time,
- when close to empty turn on the electric pump and keep a careful eye on the fuel pressure gauge,
- when the pressure gauge starts to dip switch tanks.
I do have a fuel totalizer installed which, with practice, allows me to estimate within a few minutes when the tank will run dry. It is an excellent bit of kit.
I have drawn the tip tanks down completely empty (15.3 to 15.4 gallons each time) and the engine never misses a beat. The careful records required allowed me to find a fuel leak a few years ago, and it also keeps me very aware of how much fuel is really there, and where I am when switching tanks, and what kind of repeatable reliable performance I get out of those tanks.
I have gotten distracted while doing this and allowed the engine to run rough or quit. My wife really does not like this. Says it causes frowning which causes wrinkles. So now I also ensure that I won't be distracted at a critical time. Say directly over Calgary transiting the zone for example. Or during an IFR approach. Those times are where I switch to a full tank and concentrate on the task at hand and not fiddling with fuel tank selectors.
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