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RV-7 Fuel Level Senders

SonexGuy

Active Member
I'm about to order my wing kit, and was wondering what people thought about the stock fuel level senders versus any others on the market that people might like better. I plan to do aerobatics and will have inverted fuel and oil systems.
 
I considered the CIS senders, but they are just too expensive for me to justify. I have great luck with the stock ones in my -4, and I use the totalizer to really know exactly what I have onboard. My fuel totalizer is accurate within .2 of a gallon.
I also enjoy aerobatics, but I don’t care for negative G. I loop and roll, but I keep it between 0 and positive G. I think inverted oil is useless without inverted fuel, and think the inverted fuel flop tube tends to be a neglected item.. how often do you think people replace that flexible flop tube in the tank?
 
Thanks. Of course I don't care much about what the fuel quantity reads when inverted :p And I will have a Red Cube or similar for totalizing fuel (I have one in my Sonex). I've been doing positive G's in the Sonex for 8 years, and really want to be able to do inverted maneuvers and some negative G's, so the flop tube will definitely be in my tank.
 
I wouldn’t do the flop tube without doing the inverted oil. I would rather the engine stop producing power while the oil pressure goes to zero. With a flop tube and fuel injection, the engine will remain producing power , and if there’s no inverted oil, the oil pressure goes to zero while the engine continues to run. With a carb, the engine quits momentarily while the oil pressure disappears, kind of nice, as no power, no damage in my mind.

If you want to hang from the seat belts inverted, for extended periods of time, then sure, inverted oil and fuel is required, but in my opinion, these aren’t really the planes for that. Gentleman aerobatics are just fine without the extra weight, complexity and maintenance of inverted systems IMO.

A big fear of mine is flying a plane with a flop tube that hasn’t been changed in several years, and has gone hard, or worse, and having an engine quit. At least on a RV, if you do one flop and one not, you have the option of changing tanks to restore power.. just something to keep in mind!
 
To answer the original question, I've got the standard senders in my tanks and they work beautifully. Quite happy to run a tank down to 1 gallon in the cruise and switch tanks. Works great
 
Early on in the testing phase having calibrated my EFIS properly I took off with 20 gallons in the right and 2 in the left tank. I climbed to 6000 feet above the airfield and switched to the low tank. I watched as the fuel level dropped to zero and at that point the engine ran for a further 10 minutes before losing fuel pressure (ie running dry). I switched tanks and landed. I then drained the low tank to measure unusable fuel then repeated the exercise for the other tank. I think I got something like 100 ml of unusable fuel in each tank.
The exercise gave me great confidence in my fuel management and confidence to know what a low fuel condition looks and feels like. I'll happily fly with 10 gallons total and run it down to VFR/IFR minimums weather and conditions dependant of course. All back up by the red cube.
 
FYI, from the AFP manual:

WARNING
Airflow Performance and Bendix/Precision fuel injection systems are non-returning systems. In the event that a tank is run dry in flight, an air lock will be formed on the out let of the pumps. It is possible that the auxiliary pump will not pick up fuel, as the auxiliary pump cannot create enough air pressure to over come the flow divider opening pressure, thus displacing the air and resume pumping fuel. It is not recommended to run a fuel tank dry in flight without adequate testing and proper documentation of the procedure for this operation.
 
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