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Wayne Hadath

Active Member
It has been my practice to enter the airport pattern on the right tank due to left hand circuits and in my experience mostly left hand crosswinds. This practice has served me well until recently.
I was coming back to Kitchener Ontario from Portsmouth NH just after hurricane Earl had moved up the US East coast and the winds were strong and gusting from the north west. The trip which usually takes 2.5 hrs took 3 hours and 40 minutes. Most of the trip I was grounding 120 to 125 kts but at times I was down to 107 kts.
As I approached my home airport I was cleared to a 4 mile final on runway 26 with reported winds 300 at 23 gusting 37 knots.
This gave me a 40 degree cross wind. I had 9 gals in the left and 7 gals in the right tank and had chosen the right tank for approach and landing. I was indicating 110 kts on approach but grounding 75. Runway 26 is 7500 feet and I had decided not to land at the threshold due to past experience with turbulence at the threshold of 26 due to some trees. I was planning to attempt touch down about ? way down the runway. The turbulence on approach was considerable and I need almost all of the left rudder to keep the right wing low and the aircraft lined up with the runway. As I came over the threshold the engine began to surge adding to the difficulty to keep the aircraft stable. I generally land power off so I decided rather than switch tanks I just pulled power to idle and continued with the landing. My major concern at the time was that this had now become a landing and not an attempt to land as I had no power to go around. As fortune would have it the turbulence subsided as I went into the flair and the landing was uneventful. I switched to left tank and taxied back to the hangar. My family was onboard and we talked about what had just happen and I said I would trouble shoot the problem as this was not a situation that I would like repeated.
I decided to drain the fuel tanks to confirm the gauges were accurate and yes they were and I had 9 gals in the left and 7 gals in the right. I pulled the gascolator and it was free of debris. I did a fuel flow test on each side and confirmed that the flows were good.
The weather was clear today so I decided to see if I could duplicate the surging but at 4000 feet.
The aircraft did not surge on either tank while taxiing or in cruise and in coordinated turns.
I turned on the boost pump put the selector on the right tank and was burning 13 gal/hr at 120 knots. I set the timer, dropped the right wing and put in full left rudder to hold a steady heading. 31 seconds later the engine began to surge. I switched to the left tank and seconds later the engine recovered and ran smoothly. I repeated this experiment 3 times on the right tank and the interval was 31 to 35 seconds. I switched to the left tank and did the same tests and the results were the same.
I believe the fuel pick up which is located at the lowest corner of the fuel tank is being unported when the fuel moves to the wing extremities in these uncoordinated maneuvers.
I intend to do this experiment with more fuel in the tank to see at what fuel levels the pick up can be unported. I will also test this on my F1 Rocket.
It looks like my pattern approach has to be rethought and cross winds considered when I select which tank to land on.
There does not seem to be an end to the stuff to learn in this endeavor.
Wayne Hadath
RV 10, 82 hrs
F1 Rocket, 435 hrs
 
Does your airplane have a "Both" position for the fuel tank selector?

That might make a positive difference.

Right now you've got an operational restriction: you must use the fuel on the wing that's high during slips.
 
Fuel selector

David
As far as I am aware we cannot use a both selector switch on low winged aircraft. We are restricted to left or right. Until I can test at what fuel level the pick up unports I will select the high tank on landings.
Thanks
Wayne
 
Fuel Pressure

Norman
I have run the fuel tanks dry on previous flights and just before the engine begins to really shake there is fluctuations in the fuel pressure with the boost pump on. I have never ran a tank dry without the boost pump running. If I can make the switch before the fuel pressure enters the red zone there is very little time before the engine runs smooth again. On this particular occasion I did not look at fuel pressure but did notice that the right tank read 0 and the left read 14. First thought was that I was pumping fuel across to the other tank but soon realise that was not possible.
Wayne
 
David Paule said:
Does your airplane have a "Both" position for the fuel tank selector?

That might make a positive difference.

Right now you've got an operational restriction: you must use the fuel on the wing that's high during slips.
Click to expand...

A search will show many threads on "both" settings on our fuel selectors. The short story is that on low wingers, a both setting is a recipe for a fuel management related engine failure.

If the original poster's RV-10 was my plane, I'd check for obstructed fuel vents and/or induction leaks.
 
Wayne Hadath said:
Kyle
I will check the vent lines. What do you mean by induction leaks?
Thanks
Wayne
Click to expand...

On a carbureted engine, you could have a leaking induction tube (cracked tube or loose clamp on the rubber hoses that connect the air intake and the induction tubes on the cylinder) or someone could have left a plug out of a port on a cylinder (maybe a primer port or manifold pressure port), leading to odd engine behavior.

A fuel injected engine could have the same plug/port issue, as could a throttle body type injector. I'm not sure what kind of induction leaks an engine with injectors on individual cylinders might have.

Good luck tracking this down.
 
Doesn't the checklist...

Wayne Hadath said:
It has been my practice to enter the airport pattern on the right tank due to left hand circuits and in my experience mostly left hand crosswinds. This practice has served me well until recently.
....
Click to expand...

...in most low wing certified aircraft specify "Switch to Fullest Tank" as part of the Landing Checklist?

Perhaps you need to modify your practice?
 
Do you have an MT prop governor? I remember reading about an rpm surging issue with certain revisions of MT governors.
 
Wayne, let's not overthink this...

If you had almost full left rudder and the right wing low, you more than likely unported the pickup since you were low on gas and the -10 doesn't have much dihedral. The turbulence probably sloshed the gas left and right and occasionally unported the pickup.

Try it again but with the left tank selected, right wing low, left rudder...it will have an abundance of gas piled up in the root area.

FWIW, our Air Tractors ONLY have Off and On fuel selection because we have a tubular header tank in the belly that gets fed from both tanks and stays full. The belly is 6" lower than the tanks...not so on the RV's, so you can't have a header tank that will work.

Best,
 
Hold your crab on final a bit longer

Just my .02

You may be using cross control way too early in your approach if this in fact was your problem. I maintain a crab until I'm almost ready to flair. Then I nudge the nose over to align with the runway while lowering the upwind wing to compensate for drift. The winds can be very different at the runway enviroment and 300' AGL. It's also a very uncomfortable feeling flying a slip for any length of time during final. By maintaining a crab during final you remain in balanced flight, making a go around a lot smoother transition.
 
Just what I was thinking too Rocky...

Check to ensure you have enough rudder after turning final then switch back to crab until short final. Glad you made it down safely.
 
Wayne,

Sounds like it was a pretty sporting arrival home. Nice job staying cool and bringing it in! Barb, Amelia and Eddy were surely proud of you!

I'll "third" the motion for a longer crab and a "kickout" at the end (kickout is just another name for the technique Rocky and Wayne described...crab to the flare...or wherever you feel comfortable...then rudder to align and wing down to stop/prevent drift, like they said). An added benefit is that the visual glidepath is easier to maintain down a windy final without the cross control inputs in (IMHO).

Next time we race, if you want to swap rides, we can work it in your Rocket and in my 6, so you see it in a side-by-side as well. Not that you need me to show ya, but it's a good excuse to fly (and I'm workin' ya for a ride in Lil' Bit!)

Concur with Pierre on selecting the "Up" wing tank as well. Gil is right about fullest tank, but a viable reason to alter that is the situation you were in, as needed based on fuel state and winds. If you can manage the tanks to allow the Up wing to be the fuller wing, all the better...of course the wind rarely cooperates, does it. I'll try to keep the tanks about even as I get light, but its never right on.

I think I'll be running the same test as well, just to see. Quick question: how long after taking out the slip did the engine stop surging? Will let ya know what I see. Good info brudda...thanks for posting it!

Cheers,
Bob
 
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another thought

I have experienced the induction problem listed earlier, and it could certainly do what you are saying. Check where the induction tubes go into the sump; if they wiggle you may have a leak there. Also, the gaskets where the induction tubes attach to the cylinders dry out and leak. Someone posted that they change gaskets every other year or something like that.

It also occurs to me that if it was actually that gusty, the wind may have been speeding up and slowing down your engine. I know it does that to mine on the ground sometimes during runup. I haven't experienced it in the air.
 
I took the rocket up tonight and duplicated what happened to Wayne. I did not exactly count the time but it had to be around 30 seconds. I did not have the boost pump on so that I would have a worse case scenario but if the fuel is not there the pump will not make any difference. The fuel pressure dropped to 13 psi for a few seconds before the engine coughed. When it hesitated I turned on the boost pump and got about two seconds worth of power, then nothing. Rather then switch tanks I leveled the wings and it took quite a while before the engine actually ran smoothly.
To get the tank to draw air I banked so that the right wing was high and then applied left rudder to keep the plane going straight. This was done at 85 to 90 knots with partial power. The fuel followed the ball and fell down the wing un-porting the fuel pickup. Clearly it would be best in these situations to keep the fuel in the high wing. In fifteen years of RV and rocket flight I have never had this happen in the normal course of events but armed with this information there is no reason why it should in the future.
 
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I use to fly a Cessna 210 and POH said that when you are low in fuel (like 20% of your tanks) you should fly coordinated;)

Just my two cents!
 
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