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Fuel exhaustion with 4.5 gallons in one wing


tennesseect

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My co-owner, Chad, and his wife were landing at Panama City Beach this past Wednesday after flying our CTsw down from Tennessee when the engine quit on final just as they passed over the runway threshold.  After a quick attempt at a restart they thankfully made an uneventful landing and rolled to a stop.  The engine would not start to taxi off the runway even though there were about 4.5 gallons of fuel remaining - all in the right wing.  Fuel ran freely out the sump drain when Chad checked, but the engine still would not start until the plane was towed to the ramp and the left wing tank was refueled.  A technician checked the tank vent tubes and the engine's fuel plumbing but found nothing amiss. Chad did an extended run-up followed by a solo trip around the pattern before they headed home today.  Chad encountered no further problems getting home but observed again that 14 gallons were used from the left tank and only 3 from the right.  The winds at altitude were light and variable, requiring no rudder or aileron trim - the ball of the turn indicator stayed pretty much centered.

 

How many others have encountered a similar issue?

 

Ted Carlson

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Most, gravity fed aircraft have one tank that drains faster than the other. From what it sounds, Chad was forward slipping to landing (which can unport the fuel line). He should check fuel quantity in the wing high side if he's going to do that.

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He may not have had 4.5 gallons left in that tank at all. On my CTSW somehow before I owned the plane the sticker that shows the amount of fuel must have come off and been replaced without any calibration as to how high up or low the sticker was placed. 

You might drain the fuel down and see how close to accurate the alignment is on the amounts shown on your sticker. I had to move mine up quite a bit from the place that it was in order to get it to read the correct amount of fuel remaining.  

Larry

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I've had it happen to me as a low-time pilot with 6-7 gallons remaining in my right wing.  I put myself into a right-hand orbit while waiting for clearance to enter the Washington D.C. ADIZ.  If I had utilized a oval pattern, or a figure eight pattern, it wouldn't have happened, but it did.  Now-a-days, I always refuel when my tanks are near the 1/2 way mark (3-4 hours into the flight), and I always take-off full fuel.  

 

I am much more careful with fuel management -- it's not going to happen again.  I am careful, and I use the sight gauges .......... 

 

As the old saw said.... " It ain't what you don't know that kills you, it's what you know for sure, that ain't true, that does you in at the end".

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It seems like CT's are a bit quirky when it comes to getting even fuel flow.

 

As a bit of an aside, neither winds nor turning (as long as the turns are coordinated) should affect the rate the the fuel flow from either wing. Crosswinds themselves do not require trim nor affect the ball, and one could be in a right-hand "orbit" for hours, and as long as the turns were coordinated, fuel flow should not be affected.

 

Just bringing this up so that those things don't get blamed for an issue that must have another proximate cause.

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GUMP  =   GAS,  undercairrage, mixture, prop

 

 

You only have to worrry about 1 of these in when approaching to land in your CT and that is GAS!

 

If you cannot see gas on final neither can your engine, if you continue long enough in this slip the engine will quit.

 

Set a timer and check your fuel every 15 minutes.  Test first with 6 gallons per side.  In level flight adjust rudder trim until both tubes show tubes 1/2 full and note the slip/skid ball's position in (or not quite in) the cage.  If  your CT shows one side near full and one side near empty with the ball centered then you are slipping and tranferring fuel when the ball is centered.  

 

If you do not watch your fuel usage in flight and if you do not keep from transferring fuel due to your ball being off and your sight picture being hard to interpret then eventually you will have fuel in one wing only.

 

If you continue in this condition after one wing empties the other will unport and your engine will stop with fuel on board.

 

Fuel management in flight is fundamental.

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It seems like CT's are a bit quirky when it comes to getting even fuel flow.

 

As a bit of an aside, neither winds nor turning (as long as the turns are coordinated) should affect the rate the the fuel flow from either wing. Crosswinds themselves do not require trim nor affect the ball, and one could be in a right-hand "orbit" for hours, and as long as the turns were coordinated, fuel flow should not be affected.

 

Just bringing this up so that those things don't get blamed for an issue that must have another proximate cause.

 

Remember, the older planes are completely different than the new CTs with fuel injection and header tank.  Have run mine down to half a gallon with no issues.  Might be a carb or filter issue for the SW guy.  He should not be having 5 gallons on one side, none on the other EVER.

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Remember, the older planes are completely different than the new CTs with fuel injection and header tank.  Have run mine down to half a gallon with no issues.  Might be a carb or filter issue for the SW guy.  He should not be having 5 gallons on one side, none on the other EVER.

 

Your CTLSi has a header tank but it is no different otherwise.  Your CTLSi can run out of gas with 5 gallons on board or more.

 

If you fly in a slip and are transferring fuel, first the leading / high wing will empty first, some to the engine and the balance to the low wing.  If you continue in the same slip the remaining fuel will eventually all move outboard to the wing tip end of the tank behind any baffles and your header tank will empty and your will experience fuel starvation with fuel on board just like a CTSW or a CTLS that fails to fly level enough.

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Your CTLSi has a header tank but it is no different otherwise.  Your CTLSi can run out of gas with 5 gallons on board or more.

 

If you fly in a slip and are transferring fuel, first the leading / high wing will empty first, some to the engine and the balance to the low wing.  If you continue in the same slip the remaining fuel will eventually all move outboard to the wing tip end of the tank behind any baffles and your header tank will empty and your will experience fuel starvation with fuel on board just like a CTSW or a CTLS that fails to fly level enough.

 

Nope. 

 

The header tank has it's own fuel pump and drives fuel from the common header tank into the fuel injection system.  The wing tanks are still gravity fed to the header tank but since they both feed the header tank there is no way one wing can have fuel and the other empty and the header tank not have fuel unless fuel stops flowing from BOTH wings at the same time.  The fuel check of the header tank is done each preflight on the clear site gauge on the tank to make sure there is a reserve of fuel no matter what is in the wing tanks.  You can get an uneven amount of fuel about 2 gallons or so from one wing to the other from slip flying but the header tanks ensures that uneven feed does not affect the engine operation.

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Your CTLSi has a header tank but it is no different otherwise.  Your CTLSi can run out of gas with 5 gallons on board or more.

 

If you fly in a slip and are transferring fuel, first the leading / high wing will empty first, some to the engine and the balance to the low wing.  If you continue in the same slip the remaining fuel will eventually all move outboard to the wing tip end of the tank behind any baffles and your header tank will empty and your will experience fuel starvation with fuel on board just like a CTSW or a CTLS that fails to fly level enough.

 

I'm not saying it couldn't happen, nut you would have to work real hard to do it. It would take something like staying in a turn for an hour or something crazy like that.

 The CTLS had changes made to the fuel system to help prevent this from happening. They added a fuel tank baffle with a flapper valve to help keep fuel inboard to the fuel pick up. In addition to that the CTLSi added the header tank and selector valve. You can now use the selector valve to help keep fuel levels even. For the CTLSi all the fuel for the engine comes directly from the header tank. That 1.5 gallons provides plenty of time to change positions to get the remaining fuel out of a wing tank when fuel is getting low.

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I'm not saying it couldn't happen, nut you would have to work real hard to do it. It would take something like staying in a turn for an hour or something crazy like that.

 

 

 

Remember, it would have to be an uncoordinated turn for it to affect fuel flow.

 

In a coordinated turn the net forces still act straight down relative to the plane:

 

icon-forces-in-a-turn.jpg

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Nope. 

 

The header tank has it's own fuel pump and drives fuel from the common header tank into the fuel injection system.  The wing tanks are still gravity fed to the header tank but since they both feed the header tank there is no way one wing can have fuel and the other empty and the header tank not have fuel unless fuel stops flowing from BOTH wings at the same time.  The fuel check of the header tank is done each preflight on the clear site gauge on the tank to make sure there is a reserve of fuel no matter what is in the wing tanks.  You can get an uneven amount of fuel about 2 gallons or so from one wing to the other from slip flying but the header tanks ensures that uneven feed does not affect the engine operation.

 

Again no difference.  When you fly in a slip you add a 2nd vector for fuel flow to the low wing tip.  

 

  1. Inadvertently empty 1 tank by flying in a slip due to slip / skid ball calibration error.  This is easily tested, see my post above.
  2. Continue in the same configuration until there is no fuel at the port/fuel pickup located inboard.(because you don't bother to watch your fuel drain over time) Now all the fuel is at the outboard end of one tank and will remain there until slip is terminated. Gravity feed to your header tank cannot happen at this point and your engine will starve

The fact that you landed with empty wing tanks early on suggests that your ball calibration is good and you have not been prone to this scenario.

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I'm not saying it couldn't happen, nut you would have to work real hard to do it. It would take something like staying in a turn for an hour or something crazy like that.

 The CTLS had changes made to the fuel system to help prevent this from happening. They added a fuel tank baffle with a flapper valve to help keep fuel inboard to the fuel pick up. In addition to that the CTLSi added the header tank and selector valve. You can now use the selector valve to help keep fuel levels even. For the CTLSi all the fuel for the engine comes directly from the header tank. That 1.5 gallons provides plenty of time to change positions to get the remaining fuel out of a wing tank when fuel is getting low.

 

 

Tom,  

 

Cruising in a slip (likely because of slip/skid ball calibration error) will first cause 1 tank to empty and 2nd will cause the other tank to unport with fuel on board.  No turn or hour long turn needed.  Granted a left/right/both valve and paying attention would be another way to prevent fuel starvation due to slipping. It makes more sense to #1 confirm that you are or are not slipping.

 

I tested yesterday and today. 2.25 hours flying total.  

  • Saturday, flew 45 minutes with ball centered and all fuel came from right tank
  • Sunday, flew 1.5 hours with ball on right bar, not centered between bars, and fuel usage was even.

Prior to these flights I took off with 6 gallons in each wing.  I took off and configured for cruise and trimmed for a centered ball.  I then saw that my right tank's sight tube showed near 10 gallons and the left showed near one gallon.  I then trimmed to make my sight tubes read 5 gallons on each side and noted that my ball was on the right line.  If if fly with the ball on the right line my usage gets even.

 

It doesn't matter if you empty one tank first, you are still safe until the other tank unports.   After one tank is empty keeping the other ported becomes very important.

 

The most dangerous is a long strait in approach with a cross wind.  You could hold a slip that looks right visually and not even notice.  You must see fuel in at least one tank or this approach could cause your engine to quit given adequate time.

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When you are fuel critical. (It is likely 1 tank is dry if not both are below 15 minutes each.

  1. Keep fuel visible i at least 1 sight tube - use rudder trim
  2. Land ASAP
    • if no visible fuel then land on road or field or pull chute.
    • If fuel remains in 1 tank only fly in slip with that wing high to keep remaining fuel visible and accessable to engine.

 

If nothing else visually check your fuel on approach.  Fuel starvation with fuel on board is never necesarry and is always due to not paying attention.

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Tom,  

 

Cruising in a slip (likely because of slip/skid ball calibration error) will first cause 1 tank to empty and 2nd will cause the other tank to unport with fuel on board.  No turn or hour long turn needed.  Granted a left/right/both valve and paying attention would be another way to prevent fuel starvation due to slipping. It makes more sense to #1 confirm that you are or are not slipping.

 

I tested yesterday and today. 2.25 hours flying total.  

  • Saturday, flew 45 minutes with ball centered and all fuel came from right tank
  • Sunday, flew 1.5 hours with ball on right bar, not centered between bars, and fuel usage was even.

Prior to these flights I took off with 6 gallons in each wing.  I took off and configured for cruise and trimmed for a centered ball.  I then saw that my right tank's sight tube showed near 10 gallons and the left showed near one gallon.  I then trimmed to make my sight tubes read 5 gallons on each side and noted that my ball was on the right line.  If if fly with the ball on the right line my usage gets even.

 

It doesn't matter if you empty one tank first, you are still safe until the other tank unports.   After one tank is empty keeping the other ported becomes very important.

 

The most dangerous is a long strait in approach with a cross wind.  You could hold a slip that looks right visually and not even notice.  You must see fuel in at least one tank or this approach could cause your engine to quit given adequate time.

 

In the CTLSi it would have to be almost a 40 mile straight in approach.

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Remember, it would have to be an uncoordinated turn for it to affect fuel flow.

 

In a coordinated turn the net forces still act straight down relative to the plane:

 

icon-forces-in-a-turn.jpg

 

 

I know, straight out of the textbook.

The question is how do you know if you are coordinated while making the turn?

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In the CTLSi it would have to be almost a 40 mile straight in approach.

 

Why?

 

You could already have emptied one wing and unported the other prior to final all due to flying with a low wing and not realizing it because your ball is centered.  All you need from final in this case is to keep the fuel unported, it could happen in a fraction of a mile.

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1030.jpg

 

Or equivalent.

 

Or was that a trick question???

 

No trick question. Most of the CT's have the electronic equivalent, however many of them seem to be somewhat inaccurate. There are far to many people who report having unequal fuel flow while flying with the ball centered. I know my airplane on a long cross country needs to fly with the ball off center to get even fuel usage. However flying with the ball centered doesn't feel uncoordinated, and in most airplanes I have a pretty good feel for coordination.

The whole point is you might be relying on something that is giving you incorrect information, especially with the electronic ball.

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Why?

 

You could already have emptied one wing and unported the other prior to final all due to flying with a low wing and not realizing it because your ball is centered.  All you need from final in this case is to keep the fuel unported, it could happen in a fraction of a mile.

 

With one tank empty and the other un-ported you would still have 20-25 minutes of fuel in the header tank. There is a low fuel warning sensor in the header tank that should let you know that the wing tanks are not supplying any fuel with at least 10 minutes run time. That should give a person plenty of time to bank the airplane left and right to see if there is any fuel remaining in the tanks.

 

In my opinion you shouldn't be running that close on fuel anyway.

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I calibrated my CTSW at a wing removal/inspection a few years ago.  Drain both tanks to remove the wings.  Reinstall the wings.  Check for wings level by placing bubble level on center console.  Better to put a trammel bar across the wings and a level on this.  If not level, jack a wheel to make wings level.  Add a known quantity of fuel to each wing.  I add 6 gallons to each.  Put a tie wrap around the sight tube to mark where the 6 gallons level is.  Check the ball.  If necessary, correct this so it is centered.  Caution, the mushroom can and does move around so the ball may become inaccurate.  When the fuel shows equal distance from the tie wraps on the left and right sides, your CT has an equal amount of fuel in each tank.  When these show you are at "6 gallons", this is where you're at and you can estimate what fuel you have remaining by the relative distance the fuel is from the tie wraps.  An accurate fuel level and not one derived by guessing where the fuel level lines up to the tape that is alongside the sight tubes-which in themselves, may not have been installed accurately.  When the sight tubes are replaced, re-calibrate.

 

Andy, you're right.  Something isn't right about the gascolator draining fuel but the engine refusing to run until the empty tank is filled. This doesn't make sense to me either.

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when the plane is on the ground it is no longer in a sideslip so you get fuel at the drain point . It does take a bit to get the fuel through after getting air in the pump and lines . As mentioned before , it  actually not possible to use fuel from one tank before the other unless you are in a sideslip . It is easy to think you are in coordinated flight when you are not .

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No trick question. Most of the CT's have the electronic equivalent, however many of them seem to be somewhat inaccurate.

If I had a CT with an iffy electronic slip/skid, I would install a physical inclinometer somewhere, making sure it was level.

 

Some Cirrus owners have repurposed trailer leveling devices like this high on the panel:

 

419zLKBvNUL._AC_UL160_SR160,160_.jpg

 

Though aviation-specific inclinometers are not terribly expensive.

 

Install it with SuperLok or double-sided tape and I don't suspect an LOA would be required.

 

I really appreciate having mine mounted front-and-center by 3i on my Sky Arrow:

 

7425322402_1f33583a32_z.jpg

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If I had a CT with an iffy electronic slip/skid, I would install a physical inclinometer somewhere, making sure it was level.

 

Some Cirrus owners have repurposed trailer leveling devices like this:

 

419zLKBvNUL._AC_UL160_SR160,160_.jpg

 

Though aviation-specific inclinometers are not terribly expensive.

 

Install it with SuperLok or double-sided tape and I don't suspect an LOA would be required.

 

We CT owners have something far better, our sight tubes.  It takes a few seconds in flight when fuel is below 10 gallons total to confirm.  This can be done on virtually every flight and done en-route to keep fuel even so there is no issue on approach.

 

  • With the sight tubes the question of 'level' is taken out of the equation
  • The tubes confirm coordination in an error free manor, the left confirms the right.
  • The tubes show the net of all yaw forces that effect fuel flow not just level / gravity.
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