On a low wing A/C with fuel tanks in the wings, when you run a tank dry with the valve on both, the fuel pump will suck air and no fuel will be pulled from the other tank. The motor will quit. A left and right valve will solve that problem.
good idea? I don't know. I just think it makes sense to eliminate having to remember to switch tanks. Are there special concerns with something like this?
E.
I have pondered this quite a bit and I was pushed to make a decision at the Andair booth to take advantage of their valve/filter/pump combo "special". Building the Cozy we wanted simplicity and went with only an ON/OFF valve. So far we are happy with that decision. On the RV-10 I wanted the option to set the valve to "Both" for T/O and Landings and having the Left/Right/Both option for normal flight. With this valve I can do everything the L/R/O valve can do plus have a Both position,,,and it was the same price. There are pros and cons for both types of valves but Cessna, Piper, Beech, Diamond, ect., have been using this type of valve for a long time and it seems to work OK for them,,, so right or wrong, thats what I ordered.
There are pros and cons for both types of valves but Cessna, Piper, Beech, Diamond, ect., have been using this type of valve for a long time and it seems to work OK for them,,, so right or wrong, thats what I ordered.
Good question... I've flown two RV's now and never could figure out the attraction of playing with the fuel valve every few minutes. Seems to me, the L/R/Both/Off is the way to go.
No one is ever familiar with the Beech Skipper, the Rodney Dangerfield of General AviationThe only low wing certificated airplane that I am familiar with, that had both tanks plumbed together through an On/Off valve is the Varga Katchina.
The Skipper actually has a very low # of accidents, including fuel starvation, even lower rates than a Cessna 150/152. But of course statistics can mislead, since Beech only built 311 Skippers.This airplane has had a very high # of accidents classified as engine stoppages for undetermined reason. Many of them have all appearances of being a fuel starvation type of failure.
In 50 hours of flying my -8A, I discovered very quickly that I feel a ~2 gallon difference in the tanks in the aileron trim. I generally trim it out, but it acts as a good reminder to switch tanks. Now I just have to come up with a good routine for long cross countries with the autopilot on. I really don't understand what the big deal is switching between tanks. I think running in both is asking for trouble in a low wing aircraft. Takeoff and landing should be on the fullest tank - a both selection doesn't provide more safety, it provides less because either tank running dry or sucking air due to a slip will cause the fan up front to stop.
When anything but nearly empty, the Both position should work fine as long as you have check valves.
No it won't. There is still going to be cross-feed. Unlike a high wing gravity system to a header tank, both check valves cannot be closed to prevent draining one tank to the other while banking or slipping. Fuel has to be drawing up hill from an open check valve. A "both" position can't prevent crossflow. It will only promote it.
Now the problem comes from that empty tank..... due to cross flow. As previously stated, once one of the fuel lines is drawing air.............. the other will immediately cease from drawing fuel.
Do NOT install a selector valve with a "both" position in a standard RV fuel system. PERIOD.
You will just create a lot of extra paperwork for your inspector (short term) and the NTSB (not so short term).
There will be no cross-flow. The check valves prevent exactly that. Fuel can flow from the main tanks to the header tank (so long as the correct pressure differential is maintained), but can never flow from the header tank back to a main tank under any circumstances. That would require flowing "the wrong way" through the check valve.
I've heard heard of the "Do it my way, or you're stupid" aspect of this forum from other members... Now having seen it in person, I'm still not impressed.
I've heard heard of the "Do it my way, or you're stupid" aspect of this forum from other members... Now having seen it in person, I'm still not impressed.
I've heard heard of the "Do it my way, or you're stupid" aspect of this forum from other members... Now having seen it in person, I'm still not impressed.
(which should read 'simultaneously'!)The FS20x4 Fuel Selector is designed for high wing aircraft where it is possible to feed from both tanks symultaniously...
OK,,,,I think I understand it now. If I go with the L/B/R/O valve,,,I stand a good chance of sucking air. If that happens, by the time I switch to a tank with fuel in it, I should just about get enough fuel to carry me to the scene of the crash! I'll call Andair Monday and have them change my order to the recommended valve. Thanks everyone.
You will not crash if you "suck air" and then switch tanks. I have ran my left tank dry, and as soon as it sputtered I turned on the fuel pump and switched tanks. The windmilling prop allowed the engine to instantly re-start. Total time, was maybe 5 sec with no loss of altitude or airspeed. My heart may have skipped a beat but I was never in any danger (I expected it to happen, it was intentional).
You will not crash if you "suck air" and then switch tanks.
Do NOT install a selector valve with a "both" position in a standard RV fuel system. PERIOD.
You will just create a lot of extra paperwork for your inspector (short term) and the NTSB (not so short term).
Your decision is yours and yours alone.
Your decision is yours and yours alone.
Stan...
I am not familiar with the US system of 'Experimental' flying, but you are given more latitude to apply for the Darwin Award than we are in the UK
Andy