Revisiting 8KCAB Fuel Stick Calibration

[mamontb]

Using a dipstick to measure the fuel in one SuperD tank, how much fuel is in the tank when the dipstick is wet to a height of 0.25" (or so)? How much of that is useable fuel? I assume that while the dipstick goes vertically to the bottom of the tank there might be a stand-pipe to prevent debris from entering the fuel line, such that the dipstick is including unuseable fuel.

We need to fuel our SuperD to the minimum level that we can reliably measure for acro flights with two pilots and chutes such that by the time we get to the practice area, the MGW is NGT 1800#.

We've calibrated the dipstick by filling the tank and then pumping out two gallons at a time, measuring with a dipstick at two gallon intervals. We assumed we started with 20 gal in the tank. However, we don't trust the calibration and think we need to do it again. We're hoping to avoid completely emptying one tank through its fuel drain, then adding measured amounts of fuel until we have a dipstick reading, then calibrating as we add more fuel.

We also thought of modeling the tank to estimate how much fuel is in the tank when it's at a 10 degree angle, but we can't get tank dimensions to create a 3D model. We'd appreciate it if someone could provide those dimensions (2005 8KCAB).

Anyone have a better idea?

 

[wpbarnar]

I know it is a pain but the only way to obtain something I could trust was use the method you are trying to avoid. Started with empty tanks and added a gallon per side. Once I had the tanks about 1/2 full, went to 2 gallon per side until full.

I emptied both tanks to eliminate any possibility of false readings from the tanks trying to equalize.

I was more interested in flying with minimum fuel hence wanting more resolution toward the empty side.

I did buy a small hand pump that had a short hose on the suction. I was able to place the suction at the back of tank. The pump will siphon once started. Able to mostly empty the tank with little effort.

Difficult to answer your question how much useable fuel is 1/4 “, Lot of variables, the aircraft and how it is setting, how you hold the fuel stick, etc... You also have the volume in the header tank. The total is more than you probably think, but it is best that you determine that number for your aircraft and technique.

Bill

 

[mamontb]

Thanks. I bought a squeeze-bulb siphon and extension hose that I plan to use to empty one tank (relying on a locking sump drain to get it as empty as possible after using the siphon). I'll add a gallon at a time using an external fuel tank and measuring as I go until I get an observable dip stick indication.

I'm planning on adapting a Bosch fuel sender to manually indicate fuel level below what I think will be about the 9 gal level. I'd like to be able to measure 6-10 gal in each tank at one gallon increments.