Ed Cesnalis Posted February 20, 2014 Report Posted February 20, 2014 I recently had a fuel issue and we talked about it. I picked a poor name for the thread so it got deleted to not give the wrong impression. Subsequently I found that my vents were off by 30 degrees so today I added 25 gallons and made the vents face forward and then flew for 2 hours. My fuel usage was even again, 5-gallons from each side without much trying. The vents on a CTSW if not strait seem to make a difference.
Anticept Posted February 20, 2014 Report Posted February 20, 2014 On any aircraft that you can use both tanks simultaneously, if there is a pressure differential between the tanks, it will drain unevenly. The vents have to be positioned carefully.
Runtoeat Posted February 21, 2014 Report Posted February 21, 2014 Hi Jacques. When new, the vents had green dots on them to signify this was the forward face. It was a green "sticky" and is probably gone on older CTSW's or CT2K's. My 2006 still has them. FWIW, the vents on the CTSW has a skirted top, kind of like a tuxedo coat, with longer tail positioned to the rear. I assume this skirt catches airflow and produces a slight pressurization of the fuel tank. If one skirt is positioned forward, this either doesn't provide the pressurization or even produces low pressure while the correctly positioned one on the other tank is providing pressure. This will cause uneven fuel usage from the tanks.
Jacques Posted February 21, 2014 Report Posted February 21, 2014 Hi Granpa Dick, thanks for the info on the green dot. My 'vintage' 2005 didn't have that. Turning the vents is how I manage my fuel burn left side facing forward and the right at ~30° leaving more fuel(weight) in the right wing as I don't have the ailerons / rudder trims.
Mike Koerner Posted February 22, 2014 Report Posted February 22, 2014 I'm not sure why your 2005 doesn't have the green dot when my 2004 does. Mike Koerner
FlyingMonkey Posted February 27, 2014 Report Posted February 27, 2014 If you turn the vent backward don't you have the potential to create slight negative pressure and suck fuel out the vent?
Jacques Posted February 27, 2014 Report Posted February 27, 2014 maybe,,,,never tried it and have no intention but I don't need a green dot to tell me which way it goes, simple logic..my name is not Barnath
FlyingMonkey Posted February 27, 2014 Report Posted February 27, 2014 Hi Andy, Back in 2007 when I was doing wing fuel flow test I clocked each vent 90 degrees to test them. There is no real appriable difference. To fuel doesn't get sucked out and the pump makes sure it flows. That said the green dot or more open side of the fuel vent should be forward. Good to know, thanks!
Runtoeat Posted February 28, 2014 Report Posted February 28, 2014 Hmmmm, maybe Jacques has an interesting thought.....if one has one tank that consistently feeds faster than the other, turn the vent on this side to lesson the pressure induced from the vent skirt. As Roger indicates, the effect @ 90 degrees is not noticeable but maybe the effect when @ 180 degrees may result in slower flow from the "HI" flow side?
Runtoeat Posted March 1, 2014 Report Posted March 1, 2014 Roger, when do you find time to sleep? One of these times I'm going to come up with something you haven't tried!
Anticept Posted March 2, 2014 Report Posted March 2, 2014 Here is a picture of a fuel cap vent for an SW. It does not change any fuel feed properties, but it does keep any fuel from sloshing out when full. Nothing attached.
WmInce Posted March 2, 2014 Report Posted March 2, 2014 Here is a picture of a fuel cap vent for an SW. It does not change any fuel feed properties, but it does keep any fuel from sloshing out when full. https://picasaweb.google.com/116835195307984673307/CTFlierFuelCapVentsAndWingHoseAccess Here are two more pictures of holes drill to access the rubber hose for the fuel tank outlet fitting up by the fuel sight tube. Notice the fuel injection clamp with an Allen head. This makes life easy for whom ever needs to get back in here for the life of the plane. Done with a Dremel tool. Also notice the white air hoses on the bottom of the hole. I protect these with the blade of a putty knife while grinding out the hole. When done just use a piece of Bolus tape over the hole like the wing root tape. Pics were not viewable.
WmInce Posted March 2, 2014 Report Posted March 2, 2014 https://picasaweb.google.com/116835195307984673307/CTFlierFuelCapVentsAndWingHoseAccess?authuser=0&feat=directlink Does this work? Bingo!
Doug G. Posted March 2, 2014 Report Posted March 2, 2014 Odd, I can see them with either address on my phone. (Android)
Rogerck Posted August 22, 2014 Report Posted August 22, 2014 Like many, I've had uneven fuel tank usage. The left tank has consistently used more. My fuel vents are always placed forward and the green dot is in the correct place related to the higher part of the cap skirt. Part of my preflight includes blowing through the fuel vents to make sure there is air passage when I'm checking the gas level (fuel caps off). The amount of blowing pressure has felt about the same. Recently, I reversed my routine and sucked a small amount of air through the vent caps and noticed a small difference in air flow under a low pressure draw. For the heck of it, I switched the vent tubes on the wings. Now the right tank uses more fuel. I'm guessing at low pressure fuel draw, there is enough of a difference in fuel vent air passage to result in uneven gas flow. Does anyone know if the tops of the vent caps can be removed to visually check the vent hole? I don't want to force anything here.
Rogerck Posted August 23, 2014 Report Posted August 23, 2014 Hi Roger, I understand you've done a fair amount of testing with the fuel vents, but in my particular case, when I switched the vent tubes the fuel usage changed with the vents. That seems pretty telling. Is it possible to remove the upper portion of the vent to view the vent orifice? Roger Kuhn
WmInce Posted August 23, 2014 Report Posted August 23, 2014 Yesterday, I realigned my vent posts on my CTSW fuel caps (green dot forward). They were a bugger to turn, had previously been over tightened. Thank you Roger Lee for your suggestions to free them up, it worked perfectly. After backing off the lock nut on top, around the shaft vent post, I used a small pair of vice grips around the shaft post to unscrew it, being careful not to collapse the shaft. Following the realignment, I also blew air through the cap bottoms'. The pressure on both caps was about the same. All that withstanding, my tanks have not been emptying evenly either. My method of fuel balance is trim control and adjusting bank angle.
FredG Posted August 23, 2014 Report Posted August 23, 2014 Bill, I had more fuel in one tank than the other after a long flight until my mechanic checked and corrected the slight tilt of my Dynon. If the Dynon is not level in comparison to the wings, then flight with the ball centered results in one wing flying slightly higher than the other wing. Fuel will simply flow downhill in that case, and result in uneven volumes at the end of a flight. Don't know if you have checked for this.
Tom Baker Posted August 23, 2014 Report Posted August 23, 2014 In most parts of the country you can just look at the wing tips and see if you are level. I do this to make sure my wings are level when going cross country on autopilot, and I don't worry about the ball.
Jim Meade Posted August 23, 2014 Report Posted August 23, 2014 In most parts of the country you can just look at the wing tips and see if you are level. I do this to make sure my wings are level when going cross country on autopilot, and I don't worry about the ball.Tom, I've been told to do this before and have never felt it worked for me. Probably a good idea for those who can make it work. I had a fuel imbalance problem on a long trip recently. I was careful to trim to keep the ball centered. Checked yesterday and found the ball considerably off level, so I adjusted the Dynon and the muchroom and it is much better. (I need to get my SkyView in and solve this problem). A month or so ago, I was doing some work on the panel and found a piece of wood had been fashioned into a crude shim and placed under the mushroom where it fits on the tunnel. I'm betting now that that shim was to tilt the muchroom up so the Dynon ball was level, as I never noticed it to be badly out of level before.
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