RV-4 Fuel Selector Questions

[Mark Albery]

Originally Posted by rus23

I had an engine quit on me this past August. O-320, rv4. Switched tanks, turned on pump. Looked for field.

Did you try carburetter heat? The boost pump should have enough dry lifting capacity to handle any air in the lines and get you running in a few seconds.

Glad you got to walk away from it!

[Tomcat RV4]

I agree with Sid, I had an instructor show me that in a 150, and it is scary how far (long) engine will run on whats in pipes, carb,etc.

[Whitman]

Originally Posted by Tomcat RV4

I agree with Sid, I had an instructor show me that in a 150, and it is scary how far (long) engine will run on whats in pipes, carb,etc.

Some things are better left verbally teaching. The technique of placing the fuel selector to OFF to prove a point is dangerous and has cost lives in some cases where instructors forgot to change the selector to both before takeoff. However, SID is spot on. Pick the tank before you start engines (or after landing the flight before) and don't touch it until you are airborne.

[Infidel]

Years ago, I had a Titan Tornado II and under the direction of someone whom I placed a lot of trust in his experience because of my ignorance of experimental aircraft at the time, I installed an electric fuel pump he provided and insisted I install. Unbeknownst to me at the time, the fuel pump was from a motor vehicle and was not "free flowing."

Long story short; for my first maiden voyage, I started the Rotax 912, tightened the sea tbelts, (which prevented me from reaching the panel) taxied to the runway, did my run-up, and took off. 200' above the ground the engine stopped. Subsequently, I successfully made an off field landing by threading the plane through a myriad of perk holes in a subdivision under construction.

In hindsight, if I would have turned the electric pump on, the engine wouldn't have starved for fuel for that flight. But that fuel pump could've surely posed a problem in the future.

My ground operations before launching was anywhere between 5-10 minutes so, like stated before, one would be amazed at how long an engine will run with no fuel being supplied from the tank(s).

[skiandtom]

My brother and I have an Andair fuel selector valve in our -4. We have a 160 HP, 8.5 compression ratio engine. We use 93 octane or 100LL in the left tank only and 100LL in the right tank only. Anytime we are in the pattern we are on the right tank, so we are using 100LL on take off or landing. We have the same arrangement on our -7A with 180 HP.

[Thunda Down Under]

Interesting reading.

I have an RV 4 with the standard 120 litre wing tanks with an axillary 55 litre tank on the back seat (not happy with this, see my other post inquiring about seat tank)

I usually fly 1.5 hours over open water then another 3.3 (depends on conditions) and end up with required reserve fuel.

I start off on axillary, time it @ 35 liters per hour then switch to left or right main tank, because I never trust fuel gages l again time it and change tanks and look at ETA.

I usually get there with plenty of reserve fuel, like I said l plan my trip when looking have a good tail wind in front of a high pressure system.

But.....
I have often wondered if l ran the axillary tank out and the engine coughed, would l be quick enough to change the selection valve over to mains, could l restart without going swimming?

I've never tried it, anyone got into this situation and exactly what happened?

Thanks in advance.

[Slice]

I had a 9 gallon aux tank made that I keep behind the rear seat. Yes you can do that. If you keep an eye on fuel pressure you should see a drop before the engine coughs and can switch over. Even if it coughs, the engine will pick back up within a second or two once resupplied with fuel. I turn the electric pump on before switching tanks in all cases and let it go for 30-60 seconds afterwards.

[Thunda Down Under]

Thanks Slice.

That makes good sense, with the fuel pump, mine is a fuel injection system, so if l hit the primer it should do the same thing, unless the fan stopped and l flooded it with an attempted hot start.

Still would like to hear from someone else who has ran it out to find out how they went.
Cheers.

[Michael Henning]

Try it with the safety of a runway underneath you?

[Slice]

Originally Posted by Thunda Down Under

Still would like to hear from someone else who has ran it out to find out how they went.
Cheers.

I have. I usually do when going on a long trip to maximize range. The prop will windmill and engine will surge back to life within a few seconds of switching to a tank with fuel. I recommend caution in doing so though unless you have options to land in case you happen to have a selector or feed issue(blocked vent, etc) after switching. The fuel pressure surging I mentioned above starts to happen about a minute before you run the tank dry unless you're at an unusual pitch angle at the time. So unless I happen to miss it, that's when I try to switch over now.