The plate type of capacitance transducers are known for reading pretty inaccurately due to the sloshing in the tanks. The feedback I have heard is that they work just fine on the ground, but as soon as the plane is moving and bouncing around the fuel gauges become relatively useless. If someone else has been flying with them and has a different experience, I'd sure like to hear it.
I did install capacitance gauges in my KR. I used the transducers from Westach, which are a 1/4" aluminum tube with a wire suspended in the center that is used to measure the capacitance. I found the tube type transducers to be accurate and work quite well in rough air. I have had a history of the Westach transducers losing the ground where the ground wire is riveted onto the 1/4" tube with a cheap pop rivet, but addressed that issue by wrapping and zipping them down tight with some .020 safety wire. I've been flying with these gauges in my KR for 15 years now. It's worth noting that the more modern Westach transducers come with the ground wire already wrapped around the tube at the rivet. Craig, my fuel system is set up similar to yours with a 9 gallon header and two 6 gallon aux tanks that get transferred to the header. Maybe it's just me, but in 900 hours I have never failed to look at the fuel gauge and transfer fuel from the wings to the header. In fact, it is rare for me to ever allow the header to go below 1/2 tank until after the wing tanks are dry. However, I have forgotten to shut off the tranfer pumps a few times, so was pumping excess fuel to the header which was sending it overboard. Don't try to over think it as all the warnings can become a distraction. You may find yourself responding to warnings that may not necessarily be as critical as just flying the plane first. The only annunciator I have in my plane is the traffic proximity warning on my PCAS. That's one that gets my attention, but after more than one near miss while in cruise flight, I want it to get my attention. Jeff Scott Los Alamos, NM ----- Original Message ----- From: Craig Williams Sent: 02/11/12 04:36 PM To: KRnet Subject: Re: KR> annunciators box Mark You may want to look at Jim Weirs (June 2000 kitplanes) design for a capacitive fuel gauge. It's what I am going to use. No moving parts and no need to ever go back in the tank. It also has an alarm for low fuel. That will be useful for me because I do not plan on having and external fill capability on the mains, all fuel goes through the aux and transfers to the mains via a pump. http://www.rst-engr.com/kitplanes/ Although I will have the low fuel alarm I decided to build the timer circuit to alert me every hour to transfer fuel. The 0-200 will burn my mains down to half full each hour. Then I flip on the pump switch and watch the gauge climb back to full and shut her off. (<2 min) If fuel won't transfer then I have one hour to fix it or land. Craig www.kr2seafury ________________________________ From: Mark Langford <m...@n56ml.com> To: KRnet <kr...@mylist.net> Sent: Saturday, February 11, 2012 2:44 PM Subject: Re: KR> annunciators box The reason I have a fuel transfer LED (and it's just green and doesn't flash) is purely for information that the pump really is getting power, and that it shuts off automatically when it's supposed to, after about three minutes. I agree that the automatic level switch makes a lot of sense, but I've got two dead fuel level sensors in two different tanks in my plane, both of which lasted a mater of weeks before they croaked, so I hope folks choose better than I did in that regard (Compac Engineering). I'd be tempted to find an automotive (either factory or aftermarket) level sensor that has the extra connection for a "low fuel" light, and use that to trigger a warning light, just like in your car. But I've found in my plane that I never, not once, ran the main tank out of fuel, for the reasons Matt mentioned....the fuel gauge in the header tank is something I glance at quite often, and when it drops to the point that it could hold another couple of gallons, I shoot it over there. The "fuel transfer" light is just to let me know if the pump is receiving power or not (and hopefully working). That's not to say that I didn't know what the gauge looked like when it was dead empty. Part of my annual inspection is to prop the tail up to flying angle and run the fuel out, to make sure the gauge is still accurate, and that I know how it looks just before it gets there. As much as I don't like fuel in the cabin, I have to admit that the Swift has a fuel system I could like in a KR. It has an aluminum "header" box that holds about a quart of fuel, right under the seats. It has a standpipe sticking out the top, into which a cork float twists a magnet that acts on a gauge that sticks out between the seats (like a boat fuel tank, I'm told). This aluminum box is plumbed to the two wing tanks, always receiving fuel from both tanks by gravity, and the fuel is then pumped from the aluminum box to the carb by a mechanical and/or electric pump. Gravity means no such thing as fuel left in either tank when it finally runs dry. This way, only one water/trash drain is needed. It's remoted to a pull knob at the firewall via cable. The fuel outlet runs through a large fine screen before it can be sucked out of the header and to the carb. Another advantage to this system is that replacing the gauge is easily done in minutes with four screws, from inside the cabin, and without even draining the fuel! Of course my Swift's gauge has been operating flawlessly for 65 years One of the many nice things about the EIS is the programmable fuel remaining. I have mine set to alarm at 2.3 gallons (more than a half hour at cruise), but then that is based on the assumption that I've been smart enough to empty the aux wing tanks into the header tank via fuel transfer. With the Swift system, that issue doesn't exist, and I'd only need two electric pumps (main and backup), rather than four (add a pump for each aux tank)... Mark Langford ML at N56ML.com website at http://www.N56ML.com -------------------------------------------------------- _______________________________________ Search the KRnet Archives at http://mylist.net/private/krnet/ to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html _______________________________________ Search the KRnet Archives at http://mylist.net/private/krnet/ to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html
