Fuel starvation?

[Ron B.]

New to the low wing seen. I'm wandering , in a low wing with the selector on say left wing and you make a steep left turn with a low quantity of fuel ( not close to empty) would you not unport the fuel supply? Do you fly a low wing with fuel unporting in mind at all times? And lastly, reading the instructions that came with the ES Airflow pump ( as I understand them )that say not to run a tank dry as the ES pump will probably not allow the fuel from the other tank (once selected) to be picked up. How does one protect themselves from encountering this situation other than necer running a tank below say 1/2 tanks?
Still trying to learn
Ron

[Ron Lee]

G-forces and inter-molecular hygroscopic bonding keeps the fuel in place. As for the fuel pump issue, can't say. I have run tanks in my RV empty multiple times until the engine stumbles and when I change the fuel selector the engine starts right up.

[Rick S.]

Ron, I'm hitting ya hard tonight!!

This was addressed on the matronics list this morning. Here is a great response by Tim Olson...I don't think he will mind if I paste his response here...Thank you Tim for your continuing input!!

"As for the un-porting of fuel, it's a real problem, which is
why many certified planes are placarded or have POH warnings
about minimum takeoff fuel and such. Coordinated approaches
are very important too, and while they teach you in your private
pilots course that you can choose between crabbing on final
and kicking the crab angle out at the last second, or slipping
to keep the nose aligned with the runway, you really have to
be wary of what you do when you're carrying less than 5 or
maybe even 10 gallons in a tank.

So that is why I personally love having just left/right/off,
and not both. I have a totalizer and two float gauges,
and can roughly mentally calculate my fuel levels that I
should have burned. Keeping them isolated helps me
ensure that I know more positively what my tanks hold.
Incidently, even in high-wing planes, I think the "both"
position perhaps promotes sloppy fuel management in some
cases. Myself, I don't have rarely....extremely rarely,
landed with less than 5 gallons of fuel in a tank. Maybe
only 2 or 3 times, and 2 of them where when I purposely
ran the tank dry having a near-full opposite tank. But,
when I am on a long flight, I alternate fuel tanks a couple
times during the flight and then as I get lower in quantity
I keep one tank set to arrive in the terminal area with
at least 10 gallons of fuel, whereas I don't mind at that
point if the other tank has only 5 or 6 gallons left.
But, being conservative, there have actually been very few
times I've landed with under 16-18 gallons, because I set
my high alarm to go off at 7 gallons per side. Fuel and
spark are the 2 most important things to making it safely
to the ground, as far as I can tell."

[Ted Johns]

...you make a steep left turn with a low quantity of fuel ( not close to empty) would you not unport the fuel supply?

You plan on keeping this turn coordinated or not?

If the answer is yes, then the fuel stays right where it was before the turn was started. Google "Bob Hoover" and "Ice Tea" for video proof.

If the answer is no, are you going to slip it or skid it?

[Ron Lee]

Rick, I assumed coordinated turns.

[Geico266]

Originally Posted by Ron Lee

G-forces and inter-molecular hygroscopic bonding keeps the fuel in place.

Whoa! Now there is a phrase I'm gonna Google!

I've landed (allegedly ) with only 3 gallons in one tank and the other was bone dry. I'm just not sure what all the fuss is about.

[rwhittier]

As many have already said, this is not an issue normally unless you fly in a real cavalier manner (not saying you or anyone does - but it is theoretically possible). To have a problem you would have to be very low on fuel (last gallon or two) and be flying in very uncoordinated flight. Its not something realistically pilots are prone to doing. I have deliberately run tanks dry when they needed service and its really uneventful. Switch tanks, hit the pump and the engine will fire up in mere (like 2) seconds, although it may feel like an eternity.

What can be an issue is running a tank dry in flight and not bleeding the air out of it before you need to rely on it. Don't trust a tank that's been run dry until you have run it long enough to bleed that air out. A worst case scenario (just an example) would be to say run the left dry, land on the right. Refuel and taxi out run up on the right and then switch to the left for TO. Your gonna get a momentary blip of air rather than fuel at a inopportune time and it will get your attention If a tank has been run dry, switch to it on the ground and run it for a while or do it at a high enough altitude to be safe.

Originally Posted by Ron B.

New to the low wing seen. I'm wandering , in a low wing with the selector on say left wing and you make a steep left turn with a low quantity of fuel ( not close to empty) would you not unport the fuel supply? Do you fly a low wing with fuel unporting in mind at all times? And lastly, reading the instructions that came with the ES Airflow pump ( as I understand them )that say not to run a tank dry as the ES pump will probably not allow the fuel from the other tank (once selected) to be picked up. How does one protect themselves from encountering this situation other than necer running a tank below say 1/2 tanks?
Still trying to learn
Ron

[RV6_flyer]

In coordinated flight, unporting is not a problem.

How do I know?

To do the service bulletin for safety wiring the fuel pickups, I flew burning fuel out of my tanks. (RV-6, Constant Speed, Carb) I only had one 5-gallon can, one 2-gallong can, and three 1-gallon cans. Once the fuel level got low, I made LEFT turns above the airport above the traffic pattern watching fuel pressure and fuel flow on my monitor. Once I saw the fuel pressure drop and fuel flow start decreasing, I switched tanks. Engine never missed a beat. I landed normally on the other tank and taxied to the hangar. I then removed the drain from the left tank and measure the fuel. I got about 6 ounces out. The other side I removed 9.5 gallons.

During ground testing before first flight, I jacked the tail of the airplane up, disconnected the carb fuel line, then turned the boost pump on till I could pump no more fuel. I could not get 1/2 gallon fuel out of each tank.

Flight testing now tells me that I have less unusable fuel than what my ground test determined.

The key to getting the fuel out it to fly coordinated. I have never run a tank dry in flight. The above example is the 2nd time in 11+ years and more than 2,170 RV-6 flying hours that I have tried to run a tank intentionally dry. The other time I was fighting headwinds greater than forecast. I had enough fuel for the flight with more than legal reserves but did not like the idea of 5 gallons in each tank at my destination. I chose to run one tank dry and have 10 gallons in the other tank. Did the same thing. Watched fuel flow and fuel pressure and when both started down, switched tanks. On the gound, the fuel pump said that the tank had no fuel in it based on the amount that went in.

IMHO, the calibrated fuel totalizer is the best safety item but not necessary instrument in the aircraft.

[Ron Lee]

Gary, I can't say that actually running one dry is without risk but I did it to know what my usable fuel is and to experience the symptoms. The first time the circles I made over an airport became smaller and smaller for some undetermined reason.

I probably should get the fuel down to a gallon or so in one tank and try different normal maneuvers to see what happens. Realistically, I would have to make serious errors to ever land with only a gallon or so in both tanks.

I did make up the intermolecular term.

[Ron Lee]

Originally Posted by rwhittier

What can be an issue is running a tank dry in flight and not bleeding the air out of it before you need to rely on it. Don't trust a tank that's been run dry until you have run it long enough to bleed that air out. A worst case scenario (just an example) would be to say run the left dry, land on the right. Refuel and taxi out run up on the right and then switch to the left for TO.

Good point. I taxi, do the run up and take-off on the same tank just for that class of problems.