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Uneven Fuel Flow In Wings while sitting in hangar for a month.

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My plane sat in the hangar for a month due to bad weather.  Recently I checked the fuel and noticed that there was only 1-2 gal. in left wing and 8 gal.  in the right wing.  When I checked fuel after the last flight they were mostly even.  So somehow fuel drained to right tank  while just sitting in the hangar.  The wings looked level but I didn't use a carpentry level to measure. I would appreciate any suggestions as how to avoid this and what would cause this to occur.  thanks....

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I use a digital level to check wing level.  It can be hard to see a couple of degrees difference in the hangar, but it can result in considerable transfer of fuel from one wing to the other.  

That's the long way of agreeing with Ed's short, but accurate, reply.  

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There are only 2 ways for fuel to move from one side to the other while the airplane is sitting on the ground. The first is unlikely, but it is having pressure applied to one tank pushing the fuel. The other is gravity as said above. 2 things if the airplane is not level is the fuel measurement will be off significantly, and fuel will transfer to the other tank. You likely have a combination of both going on.

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I remember reading that FlyingMonkey’s CTSW was somewhat leaning to one side permanently ... he may have some advice on what to look for in the long run and if it makes much difference.

but I am wondering what’s the underlying cause... a hard landing or just some more benign reason..

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If you want the fuel to stay where you put it, just build a little ramp lift for the low side.  Should not take much.

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1 hour ago, Warmi said:

I remember reading that FlyingMonkey’s CTSW was somewhat leaning to one side permanently ... he may have some advice on what to look for in the long run and if it makes much difference.

but I am wondering what’s the underlying cause... a hard landing or just some more benign reason..

there are other things that can lead to this besides a bent airplane. A tire a little low on pressure on one side for example.

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My left wing tip is about 1/2" lower than the right, with even tire pressures, and there is always a few gallon difference between the wings after sitting even a couple hours.  As Tom said, uneven pressures definitely makes a difference as well.  I learned this early in my ownership when I filled the tanks one evening in preparation for a long flight the next day, and had fuel stains all over the left wing in the morning.

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12 hours ago, Warmi said:

I remember reading that FlyingMonkey’s CTSW was somewhat leaning to one side permanently ... he may have some advice on what to look for in the long run and if it makes much difference.

but I am wondering what’s the underlying cause... a hard landing or just some more benign reason..

I have a triangular cushion that raises up the right wheel an inch or so and makes my airplane more or less level.  If I park the airplane with full tanks, I put the cushion under the wheel.  Mainly though I got in the habit of only adding fuel more than about 12 gallons per side right before a flight.  I also quit flying with full tanks when I didn't need to, so that I don't get fuel sloshing out when I'm at a fly-in parked on uneven grass.  

My airplane is probably one of the more uneven ones out there, the corner of the right droop tip is almost 2" lower than the left.  It's been that way since I got it, and there are permanent fuel stains on the underside of the right wing (also since I got it) so it's probably been that way a long time.    I kind of suspect a "firm" landing by the previous owner, but I have inspected the gear legs carefully and found no warps, bends, cracks, or other indications of such I could find.  It may just have been that way from the factory.  I'm used to it, it has not gotten any worse, and I just work around it.  It's not a big deal.

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Andy, with just a 2" difference you will likely not be able to see a bend in the gear leg while it is installed in the airplane. Most I've seen just had a slight bow to the leg. Out of all that I have replaced only one had an obvious visible bend in the leg.

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1 hour ago, Tom Baker said:

Andy, with just a 2" difference you will likely not be able to see a bend in the gear leg while it is installed in the airplane. Most I've seen just had a slight bow to the leg. Out of all that I have replaced only one had an obvious visible bend in the leg.

Thanks Tom, I do understand that I could have a bend not visible to the naked eye.  

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1 hour ago, Tom Baker said:

Out of all that I have replaced only one had an obvious visible bend in the leg.

Tom,

It is my understanding, that the gear legs come undrilled, is that correct? If so, how do you go about match drilling from the old leg?

How much labor do you estimate in replacing one main gear leg?

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10 minutes ago, WmInce said:

Tom,

It is my understanding, that the gear legs come undrilled, is that correct? If so, how do you go about match drilling from the old leg?

How much labor do you estimate in replacing one main gear leg?

The center hole is drilled. I remove the old gear leg and install the new temporarily to mark the top holes through the bracket. I then drill the top holes on the drill press undersized and from both sides meeting half way through. I then reinstall and finish drill through the bracket and install the top bolt. Next you put on the bottom gear knuckle with wheel and tire. It has a slit and clamp screw, so you can set it in place. I set the alignment then tighten the clamp screw. I then recheck the alignment and drill the bottom hole using the bracket as a guide. I also drill half way through from both sides. After drilling the bottom you have to take it back off, then put everything back together and bleed the brakes. If all goes well it is a 2-3 hour job, however I did have one that took all day. It included a trip to a welding shop to get a slide hammer made. The top end was stuck in the socket, but this airplane had also been in a flood.

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4 minutes ago, Tom Baker said:

The center hole is drilled. I remove the old gear leg and install the new temporarily to mark the top holes through the bracket. I then drill the top holes on the drill press undersized and from both sides meeting half way through. I then reinstall and finish drill through the bracket and install the top bolt. Next you put on the bottom gear knuckle with wheel and tire. It has a slit and clamp screw, so you can set it in place. I set the alignment then tighten the clamp screw. I then recheck the alignment and drill the bottom hole using the bracket as a guide. I also drill half way through from both sides. After drilling the bottom you have to take it back off, then put everything back together and bleed the brakes. If all goes well it is a 2-3 hour job, however I did have one that took all day. It included a trip to a welding shop to get a slide hammer made. The top end was stuck in the socket, but this airplane had also been in a flood.

That was excellent Tom.

Thank you.

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I am curious Tom how do you detect potentially slight bend gear leg that is not visible to the naked eye ? And also if the leg is made of carbon fiber ( as opposed to metal ) is it possible for it to bend or is it more that in this cAse  the actual attachment assembly gets dislocated , say during a hard landing , and the net effects is the same even though carbon fiber is not supposed to bend ..

I am asking cause my Sting is leaning about 2 inches to one side and I can’t find anything suspitious with the gear ( nor I had any seriously hard landings ) but again, I bought it slightly ( 150 hours ) used so it is hard to say

 

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The CTSW has an aluminum gear leg, the CTLS has composite. The composite leg will break instead of deforming from a hard landing. I did replace a composite leg once and the airplane did sit crooked after. I think the composite legs might take a set over a period of time causing an airplane with a new leg matched to an old leg to sit crooked. I have also seen a bent axle on a composite gear. It allowed the tire and wheel to be canted in at the top, also dropping the wingtip slightly.

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1 hour ago, Tom Baker said:

The CTSW has an aluminum gear leg, the CTLS has composite. The composite leg will break instead of deforming from a hard landing.

If I didn't know better, I'd say you prefer the aluminum over the composite leg. Any truth in that?

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Metal has a "yield strength", where the material will deform but not break.  Composites are typically stronger than metals for the same weight, but have no yield strength.  When they reach their ultimate limits, they fail suddenly, sometimes spectacularly.  Bother are appropriate for gear legs, but that difference leads to different characteristics when failures do occur. 

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When I first saw the CTLS gear legs I was pretty jealous but truth is I have no need for them.  The CTSW legs are comfortable for all my landings.

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Make good landings either type work just fine. Out of the 1800 CT's world wide most have aluminum. Drop it in from too high and you'll break either set. Even if you have over engineered leg struts you'll break the next weak point. The SW will usually just bend, the LS may not only break the strut, but the fuselage to.

Why worry you all make good landings right? :)

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Unless you have flown both airplanes a fair amount the difference is something you may not realize. If you make good landings in both airplanes it doesn't really matter. If you make bad landings both can be broken. The difference come in the not so good landings that are not bad enough to break anything. If you drop the CTSW in just a little bit the spring rebound from the gear will bounce you back into the air. The CTLS gear will absorb the drop without much rebound giving a solid feel when you touch, and the airplane tends to stay on the ground. Because of this it is harder to make a nice feeling landing in the CTLS compared to the CTSW. The landings have to be perfect to be completely smooth. The CTSW gear is a little softer you don't have to be as perfect, it allows for a little more margin of error.

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11 minutes ago, Tom Baker said:

"The CTSW gear is a little softer you don't have to be as perfect, it allows for a little more margin of error."

Are you sure you didn't mean CTLS there?:)

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4 minutes ago, WmInce said:

Are you sure you didn't mean CTLS there?:)

I have it correct. The CTSW has an area between just rolling the wheels on for a perfect landing and being dropped in enough to bounce you back into the air that you can have a relatively smooth landing, where the CTLS has more of a thump when you touch. It is when you get just beyond that point that the CTLS shines, because it stays on the ground instead of being bounced back into the air.

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An other thing on the gear difference between the two airplanes. They moved the main gear back slightly on the CTLS compared to the CTSW to make it more stable on the ground.

 

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