Fuel usage

[Jerry]

I've had my 2007 CTSW for a little more than a year and something has always puzzled me about the fuel usage.   Why does my left wing tank empty twice as fast as my right wing tank?   For instance, with full tanks of 17 gals each, a flight to Nashville from Cincinnati will use roughly 20 gals of fuel round trip.   When i land back in Cincy and check the tanks, I'll have 4 gals in the left tank and 10 gals in the right tank.   Anyone's thoughts on this?

[Tom Baker]

Some will say it is just the way it is, but in my experience you are either flying crooked or slightly wing low. Also if you have a D-100 the ball may not be set right.

[paul m]

Why do so many of us fly crooked?  I have the same issue.  

[Ed Cesnalis]

Why do so many of us fly crooked?  I have the same issue.  

 

Because you can't see the nose

[Ed Cesnalis]

Because our planes fly in the relative wind, while in flight we are not effected by the wind with some exceptions.

• Our track is effected and this is why we crab to match our bearing and track
• Wind shear does effect the plane, think turbulence

Pilots of America has a thread currently where the argument is that weathervanning is the force that turns the plane and that argument is persuasive. http://www.pilotsofamerica.com/forum/showthread.php?t=74929

 

CTLSi, the crosswind indication on your dynon is quite helpful in visualizing a crosswind landing.  When cruising that crosswind does not represent wind impacting your plane from the side it instead describes how the entire air mass is drifting and your CT drifts with the airmass.  I used to have a yaw string on the wind screen of my CT and if my ball was centered the yarn went strait up the wind screen even with a big crosswind component.  The yarn showed me the relative wind not the actual wind. 

[FastEddieB]

1) No matter what the velocity of a steady crosswind, the airplane in cruise is still just straight and level - if not out of rig/trim.

 

2) For some reason, this seems to be more of a problem with CT's. Other high wing planes may occasionally feed unevenly, but throughout a career of flying LOTS of high wing planes with just a fuel shutoff, most of them have fed pretty evenly most of the time. Minor rigging issues did not seem to have the same effect on them as in the CT.

[FastEddieB]

When you go up in a CT one day you will learn about it.

 

Please bear in mind that there are pilots here with thousands of hours, much logged before GPS and wind vectors were even a gleam in some engineer's eye.

 

And most of us managed to gain a deep understanding for what the wind does and does not do to a plane in flight. 

 

I've had the fancy wind vectors presented to me on the Avidyne in my Cirrus, and if I do some inputting of data, I can tease the same information out of even my lowly 496. And the technology is truly amazing - and useful.

 

But ultimately not necessary, and I think we may have a case here of all the technology actually getting in the way of the deep understanding most of us had to work towards.

 

To tell us that showing us a fancy panel showing derived information will finally allow us "to learn about it" is condescending at best and insulting at worst.

 

In my humble opinion, of course! 

[Doug G.]

I have seen the low wing phenomena largely corrected by a remounting of the Dynon display with the plane verified level. I have seen it done by correcting a tilt in the mushroom also.

[josjonkers]

Here is a thought.

Most of us fly from the left seat and are experiencing left preferential drainage. Wonder if flying from the right seat would result in right preferential drainage of fuel? Assuming the other seat empty of course.

[DocRon]

Gentlemen,

 

I've had this problem and (with help) solved it.  My plane as well flew with one wing low and fuel always was used from one tank faster than the other.  The problem was that the entire instrument panel was not bolted into the plane on the level.  It was angled in one direction.  You can check this pretty easily by placing your aircraft on as perfectly level a surface as you can find.  Then take a six-foot bubble level and place it equally on both wings to insure that your wings are as level as humanly possible.

 

Then turn on your battery switch and see where your ball is setting in your EFIS.  It is probably off or out of center. If so, by flying with the ball centered in your EFIS you are actually flying slightly sideways and probably is the cause of the "one wing low" and usage of fuel difference between tanks.  In this situation, take a small digital level and measure the amount the EFIS is out-of-center by placing the level under the EFIS screen.  Mine was tilted about 2.5 degrees from level.

 

There are two solutions (that I'm aware of).  First you can have the entire instrument panel leveled in the aircraft.  Second, you can have the EFIS screen alone leveled.  My mechanic chose to level the EFIS alone within the instrument panel.  After that: problem solved.  It flies wings level and fuel drains equally from both tanks.

 

It might work for you.

[Jerry]

Thanks to all for your recommendations and advice, very much appreciated.

 

One more dumb question.   The fact is that the fuel drains faster from the left wing than the right for a myriad of reasons and should the left wing drain completely of fuel while the right wing still has 5-6 gallons remaining, the engine shouldn't experiance any less performance...correct?

[Jim Meade]

Both wings are feeding. Fuel is heavier than and will displace air so you should have fuel as long as one tank has the fuel port covered.

[FlyingMonkey]

I like Charlie Tango's explanation:  "If you can see fuel in either of the sight tubes, the engine sees fuel too."

 

If one tank is empty and the other is low and you are significantly uncoordinated, then yes you can unport the tank with fuel in it and starve the engine.  But if fuel is making it to the sight tube, it's covering the fuel port (which is basically right below the sight tube and slightly outboard) and the engine is getting juice.

 

You can also put the slip/skid ball to the side you want to feed from, and you will preferentially feed from that side...you can do that to balance your tanks if you feel the need.

 

I basically don't worry about the fact that my left drains faster, as long as I can see fuel in the right side tube. 

[Ed Cesnalis]

You can also put the slip/skid ball to the side you want to feed from, and you will preferentially feed from that side...

 

Other way around, fuel will follow the ball, ball on the right will transfer some fuel to the right making the left the preferential feed.

[FlyingMonkey]

Other way around, fuel will follow the ball, ball on the right will transfer some fuel to the right making the left the preferential feed.

 

 

Ah, when you explained this before I understood it as the fuel *feed* follows the ball.  I didn't really consider it logically since I haven't actually used it in flight yet.  Thanks for the clarification.

[Ed Cesnalis]

Managing fuel in flight has a counter intuitive aspect.  Gravity provides a  vector towards the motor when wings are level.  Yaw or low wing provides a 2nd vector towards a wing tip.

 

If I see my right wing is low on fuel and fly with the ball off to the right the right sight tube will show a lower level yet as I transfer. When you go back to wings level / ball centered you will then see your new fuel level which should then be closer to the level in the left wing.  Its hard to increase the level but not hard to keep the level where it is while you feed primarily from the other wing.

[Jerry]

Thanks everyone, my questions have been answered to my saticfaction...Happy Flying!