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Fuel exhaustion with 4.5 gallons in one wing


tennesseect

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No one said that...I point out that in the emergency described in this thread the SW went engine out on a fuel starve.  That can't happen in the CTLSi as long as at least one of the dual fuel pumps are still working.

Just trying to understand the fuel system diagram you posted - thanks, by the way.

 

There's a single "block" with a fuel line in and a fuel line out. Yet it's marked "Fuel Pumps" in the plural. Does the accompanying description clarify multiple fuel pumps within that "block" and how they are arranged?

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I crudely drew in the vectors the fuel follows when slipping causes the right tank to empty first.  Fuel is motivated to flow towards the engine as well as the left wing tip as long as fuel is ported.

 

Remaining unported fuel is also shown.  The point of failure is the inboard fuel pickup on the left tank, due to slipping the remaining fuel is not available, carbed or injected.

 

post-6-0-50552400-1464726850_thumb.jpg

 

In the injected model the pilot would need to understand how to locate and recover his fuel or his engine will quit as well.

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Another thing to remember is the CTLS has a inboard tank baffle with flapper valve to help keep the fuel at the pick up point in the tank. Because of that a quick slip is not going to un-port the tank as quickly as it does with the CTSW.

 

Two thoughts Tom,

 

  1. The baffles don't actually work except for very short term. At least that's my understanding of the state of the art of high wing baffles.
  2. The same en-route slip that emptied the high tank will already have unported the low tank.  This could happen if your route is due west and you land strait in 27.  No turns or intentional slips needed.

Because of point #2 you really want to know where your fuel is.  Believe me when your engine quits it will take you time to become aware.  First you will see 2 dry sight tubes, then you will feel panic build.  At some point you should realize that you need to move your slip skid ball slowly from one side to the other and discover where the remaining fuel is hiding.  Once it appears its pretty intuitive to keep it there.  If you can see it so can your engine but it might take a little time.

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Two thoughts Tom,

 

  1. The baffles don't actually work except for very short term. At least that's my understanding of the state of the art of high wing baffles.
  2. The same en-route slip that emptied the high tank will already have unported the low tank.  This could happen if your route is due west and you land strait in 27.  No turns or intentional slips needed.

Because of point #2 you really want to know where your fuel is.  Believe me when your engine quits it will take you time to become aware.  First you will see 2 dry sight tubes, then you will feel panic build.  At some point you should realize that you need to move your slip skid ball slowly from one side to the other and discover where the remaining fuel is hiding.  Once it appears its pretty intuitive to keep it there.  If you can see it so can your engine but it might take a little time.

 

1. The baffles do have a flapper type check valve of sorts to trap the fuel inboard. The design is to quickly allow the fuel to be moved inboard and keep it from quickly being able to move back outboard.

2. I agree that an en-route slip will move fuel from one side to the other. That is why I manage my fuel to keep it balanced side to side. As for the straight in approach, that is somethin I typically don't do, unless instructed to do so at a towered airport.

 

My personal rule is that I don't take off even on a short flight with less than 5 gallons per side. There has been only a handful of times that I have landed with less than 10 gallons on board. The lowest I have been on landing is 5 gallons, but only because I was closely watching the fuel I had 2.5 gallons in each tank. While I know the OP's 4.5 gallons was more than required to meet the FAA minimums it really is not enough fuel for the CT's fuel system, especially if the fuel has not been kept in balance.

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  • 3 weeks later...

But as others have pointed out, it actually *can* happen if a simple light bulb fails.  

 

There are four lights...are they all burning out at the same time?  How about losing both mags at the same time?

 

Flight Design designed the product...maybe you guys should give them a call instead of second guessing them?

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  • 2 weeks later...

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

 

 

Why does this have to be about fuel?  You need other things besides fuel to make an engine run.  Spark for instance.  

 

For the first time, my engine quit on short final with plenty of fuel in the tanks.  It turns out one of my ignition modules had an intermittent failure and at idle the engine quit.  It was just diagnosed at this annual and replaced.

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For the first time, my engine quit on short final with plenty of fuel in the tanks.  It turns out one of my ignition modules had an intermittent failure and at idle the engine quit.  It was just diagnosed at this annual and replaced.

I would have expected it to continue to run on one module if there were no other discrepancies.

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Your engine should not quit on one module. You prove this every time you do a mag drop check. Loss of a module will show up on a mag check with an 800-1000 rpm loss. If your engine quit then both modules had to have issues. Many even loose the starting circuit of one module and the other will still start the engine.  That's been proven on all the websites that support Rotax engines and most never know one is bad until the second one gives up.You have a dual ignition system just so if one died the other will run the plane. If you lost one module and also have an excessively low idle rpm then that might be a maybe only because of the compression of the ULS engine.

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That seems reasonable.  It may have been the combination of low idle and the bad module.  It certainly surprised me.  I landed, turned off, started the engine, and taxied back to the hangar.  Like it was an everyday occurrence.  LOL.

 

I heard they put the last non-soft start module that Lockwood had in as a replacement. 

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Better than moving the stickers next to the fuel sight tubes, I like to mark the tubes themselves at known amounts each time we do the wing inspection and replace the sight tubes.  Every tube is different.  Mine are now marked at 4.5 and 9 gallons per side, and I know the very top of the tube is 10.5 gallons.  Your mileage may differ.  WF

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