JonJay
Well Known Member
Fuel system maintenance/upgrade prompted me to drain my tanks. I contemplated plugging the vent and doing a quick hose removal and plug of the main line at the tank and keep the fuel in them, but chose to drain the tanks. I don't think it is a bad idea to pull the quick drains and completely drain the tanks once in a while. (I have done it two or three times in 700 hours for various reasons). Follow safety procedures insuring the aircraft and vessel you are draining into are commonly grounded.
As I inspected the fuel tank bung, I noticed that on one side the fuel pick up screen laid very closely to the top of the bung. On the other side, it was quite a bit higher, perhaps 1/4" or so. Really? Had the fuel pick up moved? No, it was tight to the fitting, anti rotation brackets where installed, nope, must have been that way from the beginning. Way too many years ago to remember this.
Now I am a bit concerned. I know I did my unusable fuel tests early on and set my unusable fuel at 1 gallon each tank. I remember that was conservative and purposefully. But, I just had to know, what was the minimal fuel level before the fuel pick up would be uncovered?
I needed to flush my new fuel lines out anyway, so, I lifted the tail to something close to level flight and started with the tank with the fuel pick up that was the lowest. I put in a quart of fuel, hit the boost pump, and in a short few seconds, steady flow was established.
Now onto the tank with the higher pick up. Dump a quart of fuel, hit the boost pump, and much to my surprise, same result.
So, I really don't know how low the tank could get in real flight scenario. However, if the only limiting factor was the fuel pick up, lower than a quart.
I am a fuel chicken. I rarely fly with either tank going lower than 4 gallons. My fuel senders and fuel computer are set at 36 gallons, not 38.
After 9 years and 700 hours since I did any fuel studies on the RV, it feels good to reconfirm.
As I inspected the fuel tank bung, I noticed that on one side the fuel pick up screen laid very closely to the top of the bung. On the other side, it was quite a bit higher, perhaps 1/4" or so. Really? Had the fuel pick up moved? No, it was tight to the fitting, anti rotation brackets where installed, nope, must have been that way from the beginning. Way too many years ago to remember this.
Now I am a bit concerned. I know I did my unusable fuel tests early on and set my unusable fuel at 1 gallon each tank. I remember that was conservative and purposefully. But, I just had to know, what was the minimal fuel level before the fuel pick up would be uncovered?
I needed to flush my new fuel lines out anyway, so, I lifted the tail to something close to level flight and started with the tank with the fuel pick up that was the lowest. I put in a quart of fuel, hit the boost pump, and in a short few seconds, steady flow was established.
Now onto the tank with the higher pick up. Dump a quart of fuel, hit the boost pump, and much to my surprise, same result.
So, I really don't know how low the tank could get in real flight scenario. However, if the only limiting factor was the fuel pick up, lower than a quart.
I am a fuel chicken. I rarely fly with either tank going lower than 4 gallons. My fuel senders and fuel computer are set at 36 gallons, not 38.
After 9 years and 700 hours since I did any fuel studies on the RV, it feels good to reconfirm.