Fuel System Design Review

[David-aviator]

Originally Posted by pvans

David,
Remember, the whole point of these filters is to protect the AFP pump, which has very small tolerances.

Steve, the automotive designs are good, but they now mostly all have pumps installed inside the fuel tanks where they are always flooded and thus have no suction problems. Tank shape becomes an issue for this. And if the pump fails the engine won't run. Airplanes try to have redundant/failsafe modes so as to preclude this.

You are absolutely correct about protecting the pump. The auto installs have a fine screen in the tank to keep junk out of the pump and also a filter down stream to keep the nozzles clean. Recommended filter change is at 30,000 miles, that may equate to 5 years for us. I have always had a gascolator or in line filter and quite frankly have never found much stuff in them during the condition inspection. I pour fuel through a Mr. Funnel, that screen is so fine it will separate water from fuel.

We do have good redundancy with a mechanical pump or with 2 electric pumps. (or with my arrangement - 2 electric pumps and the mechanical pump - Don at AFP says that is over kill. He is right. I have them because they were in and wired to start with.)

[RVbySDI]

Originally Posted by pvans

Steve, the automotive designs are good, but they now mostly all have pumps installed inside the fuel tanks where they are always flooded and thus have no suction problems. Tank shape becomes an issue for this. And if the pump fails the engine won't run. Airplanes try to have redundant/failsafe modes so as to preclude this.

I would like to understand the ideas behind why we cannot have the same fuel pumps inside the fuel tanks in our aircraft. What precludes us from using this design if it will eliminate the vapor lock issue.

[rv6ejguy]

Low wing aircraft, uncoordinated banked turns with low fuel level = uncovered pump pickup possibilities. Same thing happens to many EFI cars on the race track with fuel levels below 1/4 tank and high lateral G. One reason why in-tank pumps may not be the best idea with fuel injection.

Header tanks ensure a constant fuel supply and are well proven.

Make sure you test fuel feed at altitude during Phase 1 to ensure it works at high bank angles, low fuel levels and with improper rudder use. You don't want to find out the engine quits under these conditions as you turn final at low altitude. This has hurt more than a few people unfortunately.

[RVbySDI]

Originally Posted by rv6ejguy

Low wing aircraft, uncoordinated banked turns with low fuel level = uncovered pump pickup possibilities. Same thing happens to many EFI cars on the race track with fuel levels below 1/4 tank and high lateral G. One reason why in-tank pumps may not be the best idea with fuel injection.

Header tanks ensure a constant fuel supply and are well proven.

Would it be reasonable to assume then that having a header tank with an in-tank pump could reduce the risk of an uncovered pump? If so, it seems this would be a simple solution to using a submersed fuel pump and therefore eliminating the "suction" pump issues and all the complexities associated with suction type pumps. Am I still off base with this thought?

[Bevan]

Originally Posted by RVbySDI

Would it be reasonable to assume then that having a header tank with an in-tank pump could reduce the risk of an uncovered pump? If so, it seems this would be a simple solution to using a submersed fuel pump and therefore eliminating the "suction" pump issues and all the complexities associated with suction type pumps. Am I still off base with this thought?

Sounds right to me. My qustion is, what difference does it make where the pump is actually located (when using fuel injection)? Isn't air going to be sucked into the intake tube and make it's way to the pump whether the pump is close by or further down downstream having the same effect?

With the Van's fuel injection setup, how does the pump assembly deal with the air?

The newer ECI fuel injection system has a return to the tank. Does this handle any air bubbles better?

Bevan

[frankh]

With my wingroot system I have landed with low fuel and it has never been a problem in uncoordinated flight.

to be honest..in the standard system if you have the wrong tank selected for a cross wind landing ..this would be far worse than having two low wing pumps with both pumps running.

frank
IO360 electric wingroot pumps only, now featuring 10 ETOH

[Zaramella]

Hello,

I have a Dynon Fuel Flow Sensor (Floscan) to install in my new ACS-100 SORA. I am wondering if I can isntall it inside the engine compartment and also if it is necessary to have a by pass.

Thanks,

Zaramella