Bonanza Fuel Starvation/ Fuel Unporting: Is it a Thing?

The controversy is that lots of folks think you can’t unport the fuel pickup line in a coordinated turn. For them it’s not a Thing.


I on the other hand think it is a Thing. My theory is that it happens a lot more than folks think it does. I think several of the accidents in 2019 were a result of fuel unporting. The trouble with this theory is that the FAA/NTSB don’t really track data that would corroborate the theory. So, we have no real idea how big a problem it is. Granted as a percentage of overall accidents there aren’t really that many that could fit into this category. But if it is indeed a Thing, the fix, once we know the dimensions of the problem, is easy.


I set off with a simple concept of a test for this idea. Just run the tank down to a low fuel state and try some turns. I did 30 degree turns and 45 degree turns in smooth air. And.... nothing happened. So, at first I thought that I had disproved my theory. I did realize that if I had a baffle it would make a difference and turbulence would also affect the outcome. Scott Philiben, at CiES Inc, clued me in to the fact that their testing had revealed that fuel in parting is indeed a problem and their fuel level gages record data that could reveal what was happening in the tank.


So, I promptly sent my JPI 900 data files to him to reduce the data and see what was happening in my tanks (Full disclosure, I had CiES sensors in the airplane). The accuracy of the CiES sensors is tremendous! The result showed that during the turns there was not much in the way of sloshing. But in the descent and landing phase the fuel level sloshed from 5 gallons to zero and stayed there for a significant period of time. So, indeed Fuel UnPorting is a thing and the implication is a serious problem could confront you if you fly at very low levels in the fuel tank.


To find out the extent of the problem I’m going to redo this flight test with a more rigorous profile and plan on using the data collection capabilities of the JPI 900. Frankly, this is a safer idea than actually trying to flirt with unporting the fuel for real, especially close to the ground. When the weather clears I[m going to try this again.


I’ve been asked whether I would do a video on the CiES sensors in particular. If you’d like to see that, leave me a note!


Thanks,

gunny

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