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My CTLSi, with tanks full, measures about 17 gallons on each side with the dip stick.  Is that measuring total fuel in the wings (usable and unusable combined) or total fuel in the plane including the header tank (usable only)?  I believe it's the former, as I think the wing tanks have the same capacity in the CTLS and CTLSi.

 

Also, when I set the Dynons on full fuel, it goes to 33 gallons.  This isn't the full fuel nor is it the useful fuel.  Is this mis-configured in the setup?  Assuming the answer's yes, how do I re-configure it?

 

Thanks much.

 

Andy

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The 17 gal on each side dipstick does not include the header tank.  I think the Dynons are assuming 1gal unusable.  How to reset them I don't know but I'm sure if you call Dynon support they can tell you.

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That depends on if your dipstick is calibrated. Most people (pretty much all of GA) do NOT have calibrated sticks for their specific airplane; it's approximated, which is good enough.

 

Calibrating means draining your tanks with a leveled airplane from the gascolator or other point which is NOT in the fuel tank, then adding measured amounts of fuel, dipping, and making appropriate markings on the stick. Draining it first via the gascolator will leave unusable in the wings and is fine for the purposes of calibrating a dipstick (mechanics: not acceptable for weighing!). Unusable fuel should already be part of the W&B of the airplane, so don't worry about it. (This has been the case since the 70's). I suggest consulting the manual to find out what the procedure is.

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Are you sure? I have dipsticks from FD too, and there's no indication that they are calibrated. To be honest, I haven't been looking that hard though, it would be neat if they did.

 

Usually MFG and tool suppliers sell sticks that are for specific types (for 172Ps, PA-28-161s, etc), not specific aircraft. It really doesn't make much of a difference in small planes of the same type. With big ones, however, the geometry differences can become large enough that calibrating equipment can become a necessity, even to the point of measuring specific tanks.

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Mine looks like it came from Flight Design.  Technically it's metal, T-Shaped, with the calibrations etched into it.

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Part of the problem with the FD joysticks is that they will read different fuel levels if they are put in the tank at different places in the fuel filler. I always place mine against the back of the filler. That at least adds some consistency. No guarantee of accuracy.

There have been a number of people on the forum who have calibrated their sight tubes. I suppose you could do the same with the dip sticks. As they are I wouldn't put too much trust in them.

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The dipsticks are more than close enough. If you are trying to split hairs you may get in trouble. Make sure you always have enough fuel and if you have to ask yourself if you have enough then you don't. Always error on the plus side.  Either add more or make a stop. Why even worry.

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Ran out of fuel at 4500 feet and I assure you the plane flys beautifully without the engine.Fortuantely. Had my Iphone and took a picture of the panel showing 12.5 gal of gas and 2.5 hours of flight time .In Iowa we have a road every mile and simply landed on a black top road and hitched to a gas station and completed the trip.I was mystified as to how this could happen and had laughed at the in competence of running out of fuel in a plane.When I filled the tanks the following day and started to taxi I smelled fuel.When I checked the fuel caps to insure they were tight I noticed fuel flowing off the back of the wing.Comparing the fuel caps and inspecting for damage I noticed that the black o rng under the cap was missing allowing the fuel to flow out of the full tank.When I returned home I found the o ring on the ground where the fbo had fueled the plane.My mechanic replaced them after noticing that the missing one had expanded and could be displaced trying to replace it.I had visually inspected the tubes in cockpit ,turned on the master confirmed 14 gal ,checked tanks fuel in both,with 7 in the right.I am also meticulous about input.Finally the trips are always about the same in usage and yet it was clear fuel had been lost that didnt flow through the instruement meter.Faa suggested that the caps be made part of the inspection process.

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Mine looks like it came from Flight Design.  Technically it's metal, T-Shaped, with the calibrations etched into it.

 

You mean the graduations? I'm not trying to be a smartass, just getting on the same page :-)

 

A calibrated fuel dipstick would be one where the graduations are are tested and marked according to that very specific airplane. No two airplanes are alike, but with CTs, the differences are so small that it's not going to be a big deal (UNLESS YOU DO FUEL TANK REPAIRS! Then you most definitely want to make sure the indicator being used is still acceptably accurate!)

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Skywalker,

 

Use the force of the sight tubes.  They are not wrong.  If you see fuel, you have fuel, if you don't see fuel, you should have already landed.

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The CTLSi has a total fuel capacity of 17.2 gallons per wing and 1.6 gallons in the header tank (36).  The total useable fuel is 16.7 per wing and 1.1 from the header tank (34.5).

 

The Dynon fuel computer menu is where fuel quantities are set.  Press FULL to have SkyView recall a previously programmed amount of fuel . See the SkyView System Installation Guide for information about how to set this value as a preset.

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So, how does that translate to the accuracy of the stick?

 

I answered the question originally asked by the person starting the thread.

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Sounds like a 17 gallon dipstick would be total fuel in the tank including unusable.  If you have to worry about the 1/2 gallon of fuel at the bottom of the tank, you're way to low on fuel.

 

I understand that 1/2 gallon in the tank is low on fuel.  In 2,400 hours of flying, prior to owning the CT I've never flown a plane with under 1 1/2 hours of fuel, although in a different world, flying in weather and much longer distances.  In my CT, the quantity of unusable fuel is about 1/3 of an hour of flying.  Misunderstanding whether the various forms of measurement (the dip stick and sight tubes) include or don't include the unusable fuel can have a meaningful impact on my fuel margin of safety.  Hence my original post.

 

Andy

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No matter what you see on the dipstick at least 1/2 gallon of what you read will not be useable in each wing.  And of the 1.6 gallons in the header tank, only 1.1 gallons are useable.

 

The sight tubes, arguably are an unreliable way to estimate actual fuel. One should NEVER fly if no fuel appears in the sight tubes. And by extension no flight should be taken if just the header tank shows fuel. 

 

The use of the fuel computer is also pretty useless, IMHO.  I don't bother using or relying on it at all. 

 

If flying less than an hour, I just make sure fuel is visible in the sight tubes.  If flying a cross country (2 hours or more) I dip the wings and add fuel accordingly.  If flying a long cross country of over 6 hours I top off the wings.  And take Decalin with me in case I need to refuel with 100LL.

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Fuel management in a CT is very easy.  If the both sight tubes are at half, you have about ten gallons and should be thinking about landing.  If both tubes are a quarter full, you have about 5 gallons and should already be on the ground, IMO.  

 

If one sight tube is empty and the other is half full or less, you have to be careful to not unport the full tank in a turn to that side.  Probably best to not let it get to that point.  You can adjust the fuel in the wings by flying with the more full wing up.  That will generate higher head pressure on that side and preferentially feed from that tank and transfer some fuel to the low wing.

 

If you have an EFIS with fuel management functions, they are great for fuel planning, but IMO the tubes have to remain the primary fuel device since they can't be wrong.

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I don't fly CT's, but I rarely takeoff with less than full tanks.  I usually top the tanks after each flight.

 

I don't know what you are flying, but the CT fuel capacity is 34 gallons.  That's way more than needed to fly around the local area.  I usually fly with 15-25 gallons for those short flights.  If I'm traveling, I will have 30+ gallons.  I will rarely fill the right wing to the top, as more than 15 gallons in that wing will sometimes slosh out the vent onto the wing.  Only seems to happen on that side, probably because that wingtip sits an inch or two lower than the other one on the ground.

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I don't know what you are flying, but the CT fuel capacity is 34 gallons.  That's way more than needed to fly around the local area.  I usually fly with 15-25 gallons for those short flights.  If I'm traveling, I will have 30+ gallons.  I will rarely fill the right wing to the top, as more than 15 gallons in that wing will sometimes slosh out the vent onto the wing.  Only seems to happen on that side, probably because that wingtip sits an inch or two lower than the other one on the ground.

 

Andy, just want to point out 2 things.

If the fuel is getting on the wing in flight, then you are likely flying a little crooked.

If you have a wingtip that is setting lower than the other on the ground by 2" or more you likely have a slightly bent landing gear. If that is the case make sure you are complying with SB-ASTM-CTSW-02 at your condition inspections. You should be doing this inspection anyway.

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Maybe this is "old school," but I generally don't see much reason not to keep the fuel tanks topped off.

 

 

Well, if I did in my Sky Arrow, I'd be forced to offload fuel any time someone over about 160 lbs wanted to fly.

 

Even in my Cirrus, "to the tabs" gave a lot more loading flexibility than full tanks, and still enough range for most flights.

 

Tankering excess fuel around is seen by even some "old school" pilots some as inefficient.

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Maybe this is "old school," but I generally don't see much reason not to keep the fuel tanks topped off.

 

Topping is standard practice, yes.  The AIM points out that topping will keep condensation down.  I don't do it because I live in a super dry climate and am hangared.  And I always check fuel before each flight (gascolator).  One practice I have gotten into is to fuel the day before a flight to give any water in the fuel a chance to get to the bottom of the system.

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Topping is standard practice, yes.  The AIM points out that topping will keep condensation down.  I don't do it because I live in a super dry climate and am hangared.  And I always check fuel before each flight (gascolator).  One practice I have gotten into is to fuel the day before a flight to give any water in the fuel a chance to get to the bottom of the system.

 

The composite tanks don't foster condensation.

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...

 

If you have an EFIS with fuel management functions, they are great for fuel planning, but IMO the tubes have to remain the primary fuel device since they can't be wrong.

 

:thumbs_up-3334:

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Maybe this is "old school," but I generally don't see much reason not to keep the fuel tanks topped off.

 

With the CT half to just over half on fuel will give the endurance of many "old school" airplanes.

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