Flying Bozo Posted September 5, 2011 Report Share Posted September 5, 2011 I was trying to drain my right side tank (CTSW) to stop a very slow leak at the wing root so that it would not drip until I got it fixed. Roger is going to repair it as soon as I bring it down to him in Tucson and I thought that draining the right tank would be possible. However, as I drained the tank with a siphon hose I was also draining the left tank too. I mistakenly thought that with the fuel shut of the tanks would not cross drain. They do. So it is not possible to only drain one tank unless I am missing something. Has anybody had any similar experience with this happening? Roger can you weigh in on this? Larry Flying Bozo Cottonwood, AZ Link to comment Share on other sites More sharing options...
Roger Lee Posted September 5, 2011 Report Share Posted September 5, 2011 Hi Larry, The tanks are connected and they will both drain and or one will seek the level of the other tank. It is an open circuit. Butttttt there is a way to only drain one tank. Use a pair of hose pinch pliers and clamp off the other side. I do it all the time. Clamp it where the fuel line comes out of the "A" post down in the engine compartment up in the corners of a CTSW. Or just drain them both. Link to comment Share on other sites More sharing options...
chanik Posted September 5, 2011 Report Share Posted September 5, 2011 Indeed, if you look at the FD Parts assembly manual you can see that the T-connection is before the fuel shutoff valve so the tanks will still cross drain. It's all behind the firewall down near the fuel shutoff handle Link to comment Share on other sites More sharing options...
Runtoeat Posted September 5, 2011 Report Share Posted September 5, 2011 Roger, thought that I'd add that those with CTLS will not have the same hose setup as CTSW and cannot pinch off fuel at the fire wall. The CTLS fuel lines run down the pillar and then into the inside of the cabin and not out to the engine. I beleive that the CTLS fuel flow can be stopped at a chosen wing by pinching off the short hose up at the wing root that connects to the pillar fuel tube but can't verify this. Link to comment Share on other sites More sharing options...
Tad Olmsted Posted September 5, 2011 Report Share Posted September 5, 2011 Dick, It can be done the same way, but the fuel lines are inside the cabin above your knees up against the firewall. I use the same technique as Roger. This is needed during an inspection and or replacement of the wheel/brake. We've all jacked up one side and then a few minutes later we smell and then see gas coming from the fuel vents. Link to comment Share on other sites More sharing options...
Roger Lee Posted September 5, 2011 Report Share Posted September 5, 2011 Hi Dick, I never touch the hoses up by the site gauges because if they get damaged replacing them is absolutely a nightmare. I'm with Tad, pinch the CTLS hoses in the panel, those are easy to replace if you accidentally damaged one.. Link to comment Share on other sites More sharing options...
Flying Bozo Posted September 5, 2011 Author Report Share Posted September 5, 2011 Thanks for all the great input. That answers a lot of questions. Larry Flying Bozo Cottonwood, AZ Link to comment Share on other sites More sharing options...
chanik Posted November 27, 2011 Report Share Posted November 27, 2011 This is more a question for the mechanics, but how hard would it be at add a 3-way fuel selector like this to the CT? http://www.aircraftspruce.com/catalog/eppages/fs20tYPE4.php Link to comment Share on other sites More sharing options...
Tad Olmsted Posted November 27, 2011 Report Share Posted November 27, 2011 Easy... but an LOA would be required, W&B etc... Link to comment Share on other sites More sharing options...
chanik Posted November 27, 2011 Report Share Posted November 27, 2011 Well, not for me and my ELSA, but if it is easy, I'm tired of the fussy cross feed thing and this is a 4-way with L,R,both positions. What sort of connections should it be? 3/8" hose? male? Looking closer there are alot of options. http://www.andair.co.uk/system/index.html http://www.andair.co.uk/pdfs/FS20.pdf They also have an extension version that might adapt better Link to comment Share on other sites More sharing options...
Mike Koerner Posted December 4, 2011 Report Share Posted December 4, 2011 The ELSA folks can do what they want... but Flight Design will not provide a letter authorizing a change to a Left/Right fuel valve for our LSA planes. They don't think selector valves are safe. Indeed, general aviation accident statistics show innumerable cases of fuel starvation caused by the pilot forgetting he has the fuel switched to one tank or the other and proceeding to run it dry. Flight Design avoided adding to this statistic by eliminating the selector entirely and interconnecting the two tanks upstream of the shutoff valve. They even went one step further by putting the ignition key under the shutoff valve actuation lever so that there is no way you can takeoff with the valve shut. This is another potential source of accidents as it takes several minutes (at least in our planes) to empty the fuel lines downstream of the shutoff. That trick will be hard to duplicate with a rotary Left/Both/Right/Off switch. Unfortunately, interconnected tanks also mean that unless we fly perfectly coordinated, which is difficult to do, we'll run out of fuel on one side before the other. Fortunately, this only matters on a particularly long flight legs, or if our lack of coordination is particularly egregious. And the resulting fuel imbalance is easy enough to correct by flying uncoordinated in the other direction for a few minutes. Furthermore, even if left uncorrected, emptying the fuel in one wing will not necessarily result in premature engine shutdown since sloshing of fuel in the other wing will tend to keep the vertical fuel feed lines full; again unless we're sustaining uncoordinated flight or trying to burn the very last gallon of fuel in the tanks. And finally, in the newer CTLS model the issue has been further addressed with baffles that make it less likely that the engine will shutdown due to a fuel imbalance. However, it remains disconcerting to the pilot to see one wing emptying prematurely. A fuel selector valve is not a good solution to the fuel imbalance problem. When you switch to the tank with more fuel in it to drain it down to the level of the lower tank, the aircraft is just as susceptible to fuel starvation due to uncoordinated flight as when one wing is completely empty. Indeed, this would only exasperate the situation by leaving the aircraft susceptible for a longer period of time. The underlying problem is that our wings don't drain as easily a Cessna's because they have less dihedral. But we don't want to change that... The flat wing gives us improved handling and performance. Another problem with our interconnected tanks is that parking the plane with one wing low allows fuel to transfer from the high wing to the low one. This creates a lateral weight imbalance and, if the tanks near full, causes fuel to pour out the low wing's vent; wasting fuel, staining the finish on the low wing and creating a fire hazard. Still, I consider these minor inconveniences compared to putting the plane in the trees because I took off with the fuel lever in the off position or forgot to switch the valve back to both after balancing the fuel load. Yet, I believe there are solutions for each of these problems which provide about the same level of safety and tolerance for pilot error as the factory configuration. First, for the fuel overflow problem; if we ganged two fuel shutoff valves on the existing fuel shutoff lever so they both actuate together, one valve being for the right tank and other being for the left, and relocate the interconnection to just downstream of these valves, then we could eliminate the transfer of fuel while parked on a slope by merely lowering the fuel shutoff lever. Looking at the actuation mechanism and mounting of the existing fuel shutoff valve, it seems fairly easy to mount a second valve forward of it and gang the two together. Second, to address the fuel imbalance issue, we could add a very small electric motor driven fuel pump with a timer circuit set to run the motor just long enough to transfer one gallon of fuel from one wing to the other. The timer could be actuated by a two-way momentary switch and configured such that the motor polarity, and thus direction of fuel transfer, depends on the switch input. Further, the switch could be arranged such that pushing it to the left transfers fuel from the right wing to the left, and pushing it to the right transfers it the other way. This arrangement would assure that the pilot cannot accidently leave the transfer pump on. And because the transfer of fuel is not a flight-critical function; a failure of the pump would not be a safety issue. The addition of an indicator light and circuit breaker would allow the pilot to shut the pump off in the event of a failure of the timer circuit. Mike Koerner Link to comment Share on other sites More sharing options...
chanik Posted December 4, 2011 Report Share Posted December 4, 2011 Actually, the need to park pefectly level when full is my main complaint. Ganging two shutoffs on the individual tank lines does seem the better solution. Link to comment Share on other sites More sharing options...
Jim Meade Posted December 4, 2011 Report Share Posted December 4, 2011 I was told by someone at Lockwood that as long as there was fuel covering the intake on one tank the plane would not run out of fuel. The discussion to date seems to indicate that if you run out of fuel in either tank the engine will be starved. Is there a definitive reference for the company answer on this question? References and sources, please. Link to comment Share on other sites More sharing options...
Roger Lee Posted December 5, 2011 Report Share Posted December 5, 2011 Hi Jim, It was on the FD website 3 years ago. Written by FD Germany. It addressed the uneven fuel flow and dry tank. It isn't there any more. All of us old CT guys can tell you what you want to know as it was a debate 4 years ago and had finally died out. You can get low enough on fuel to be empty in one tank and be flying uncoordinated and slosh the fuel to the outboard side of the tank with fuel that level is low enough. Number one reason that flying with excessively low fuel or bare minimums is not a bright idea. This is not unique to our plane it is like that in other aircraft GA and LSA. It is due to the flat design of the fuel tanks and that's all. Link to comment Share on other sites More sharing options...
Jim Meade Posted December 5, 2011 Report Share Posted December 5, 2011 Rpger. I'm looking for the reference or citation to the specific question of whether of whether the engine quits if you have fuel in one tank and none at all in the other. Lockwood said it would fly. The guy I talked with said he personally did it. I'd like to see something in print from FD that said yes or no to that issue. Link to comment Share on other sites More sharing options...
Roger Lee Posted December 5, 2011 Report Share Posted December 5, 2011 Hi Jim, I have done it once too. Nothing in writing any more. You would have to call FD and see if they still have the original article. Link to comment Share on other sites More sharing options...
Jim Meade Posted December 5, 2011 Report Share Posted December 5, 2011 Well, if you did it, too, then I'm confused as to the concern about running low on fuel while not perfectly coordinated. It would seem to me that it's a non-issue as to how much is in which tank? Am I confused? Link to comment Share on other sites More sharing options...
Roger Lee Posted December 5, 2011 Report Share Posted December 5, 2011 Hi Jim, It does make a difference. If you empty one tank and only have something like 3 gals. in the other side you could fly uncoordinated enough to push that 3 gals to the outboard side of that tank and make the plane think it is total empty. That would be a bad situation. If you were clever enough and high enough you would put the rudder peddles to the other side which would move the ball the opposite direction which would bring that 3 gals. back to the inboard part of the wing and then you could do a re-start. Altitude and seeing where the fuel is would be the key. panic would make it a real mess. Remember this; The fuel will follow the ball. If you want fuel to go to the left then put the ball to the left. If you want fuel to go right then put the ball to the right. Still the best policy is never try to fly somewhere with low or bare minimum fuel. Link to comment Share on other sites More sharing options...
FredG Posted December 5, 2011 Report Share Posted December 5, 2011 Jim, It would take some real effort to cause the problem. The key issues are the the tanks are always connected to each other, the tanks are relatively flat and have no internal baffles, and the fuel line connects to the tank at a location close to the cabin. The airplane would have to be flying with one wing low (uncoordinated) for a long time and without much fuel in either tank. The fuel in the high wing would slowly drain to the low wing. The high wing would eventually run dry. Fuel in the low wing would pool at the low end of the tank (towards the wingtip) and, sooner or later, the fuel drain (at the end of the tank closest to the cabin) will no longer be covered with fuel. At that point, the airplane still has some fuel onboard, but given the low wing, it is pooled in the end of the tank away from the cabin and would not be available to the engine. If the wings were leveled, fuel would again cover the fuel drain and be available to the engine, even if it were in one tank. Just the opinion/experience of one CT owner. Fred Link to comment Share on other sites More sharing options...
Jim Meade Posted December 5, 2011 Report Share Posted December 5, 2011 Fred, Thanks for the clear explanation. It makes perfect sense. It gives me the information I need to manage the fuel. I agree with Roger that the best policy is to never fly with low or bare minimum fuel. In my own personal opinion, I want to be landing with 5 or more gallons left in the tank. That fits a number of missions I have. Others might prefer more. Link to comment Share on other sites More sharing options...
Mike Koerner Posted December 5, 2011 Report Share Posted December 5, 2011 Jim, What I said agrees with what you heard. In fact, I took this one step further saying the fuel only needs to cover the outlet on one side intermittently, "sloshing" across it, to keep the engine running. But if you continue to fly uncoordinated in the same direction after one wing is completely empty, once the fuel in the other gets low enough (how low depending on the degree of uncoordination) the fuel still on board will never make it to the outlet. Again, I don't think this is a problem. I'm not going to fly my plane that close to empty or that uncoordinated. But I think it would be a problem if you added a fuel selector. You wouldn't just be worrying about coordination at the end of very long leg, you'd have to worry about it any time the selector was on something other than "both". Also, if you ever do get to the point, by whatever twist of fate or stupidity, that there is no fuel showing in either side, and you don't want to land immediately on whatever is below you, I wouldn't try to fly perfectly coordinated. I would be too concerned that I might not be able to that and thus would be leaving some fuel in the outboard section of one wing or the other. Instead I would periodically rock the plane from a slight side slip in one direction to a slight side slip in the other. This would force any remaining fuel to the outlet and thus keep the vertical fuel lines full for as long as possible. Again, I don't think this is a problem. I have never been in this situation and never intend to be. But it's still worth considering. One more time, I don't think fuel management in a CT is a problem. In fact, I think this is, by far, the safest aircraft I have ever flown. All of this is my own opinion and I should have introduced it as such - sorry. The two ideas presented, ganged fuel shutoff valves and an motorized fuel transfer pump on a timer, are my own and have not been disclosed previously. There was a discussion of some aspects of fuel management on a previous CT forum some time back, but I don't have a perfect recollection of that discussion and have no way to recover it. Roger Lee posted a letter from Flight Design on this forum that also addresses fuel management, that in response to a question from you on May 21 of this year. In that letter Flight Design explains why they don't have a selector valve (people leave it in the wrong position), common vent, header (though I think the vertical fuel lines act as a heater to some extent), or a direct line between the tanks. Most of the discussion in that thread is centered on keeping the ball centered and making sure the indicator is level in the first place. Roger also makes the observation that you shouldn't run your tanks down to where there is just a gallon or two remaining (here, here). I believe there was another letter from Flight Design that discussed successful performance tests with one wing completely empty or shut off, but I am unable to locate it now. You would not expect this to be a problem... as long as the flight is coordinated and there is sufficient fuel in the other wing. Mike Koerner Link to comment Share on other sites More sharing options...
Mac Bowden Posted August 1, 2012 Report Share Posted August 1, 2012 All CT owners received notification from the British CAA of a Proposed Mandatory Directive which sometime later this month will become mandatory to implement. It confirms that some CTs have run out of fuel due to fuel imbalance and they give clear directive on the remedy. SB131 CT fuel system ISS 1_CT2K &.pdf Link to comment Share on other sites More sharing options...
Roger Lee Posted August 1, 2012 Report Share Posted August 1, 2012 Hi Mac, Interesting. we have talked about this and had these same conclusions back in 2007. I'm surprised it has taken this long to come out with this in the UK. No one should be flying a CT with only 5L on board. That's a little more than 5 qts. That is absolutely asking to get bit in the butt big time. I would have to ask that pilot what he was thinking or not. We have discussed this on this very forum about running a tank dry and having as much as 2-3 gals in the other wing and if flying slightly uncoordinated as the publication points out then that good fuel will be moved to the outboard side of that tank and make it totally unusable and the plane will think it is totally dry. 5L is not even the required amount here in the US for the extra 30 min. required by the FAA for day VFR flights Our panels may not be perfectly lined up so if your ball is dead in the middle of the lines you may still be slightly out of trim which would give you problems in the scenario listed in the publication. Fuel management is an on going check during a flight and it was sorely mishandle in the publication flight. My personal minimums is 3 gals in each wing, then it's time to fill no matter what. if fuel is disappearing from a sight tube it's time to transfer fuel in flight by flying with 1 full ball out to the low fuel wing and that's if there is enough in the other wing to transfer, otherwise why aren't you already on the ground re-fueling. Link to comment Share on other sites More sharing options...
Mac Bowden Posted August 2, 2012 Report Share Posted August 2, 2012 yes I agree with you Roger. The thought of flying with 5 ltrs of fuel in each wing is crazy. My anxiety level rises as soon as I get near 20 ltrs in each wing. The end result for us over here now is an annual drain test and another unsightly placard in the cockpit. On a lighter note, we've just come through one of the worst summers on record, rain, rain and more rain with most fly-ins cancelled so I envy you your dry sunny climate! Link to comment Share on other sites More sharing options...
Roger Lee Posted August 2, 2012 Report Share Posted August 2, 2012 Hi Mac, So come on over to Tucson, AZ and enjoy some drier climate. Plenty of CT's here to fly and friends to with them. Hotels, food and fuel are cheaper here too. So when do I book you? Link to comment Share on other sites More sharing options...
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