Fuel mismanagement happens pretty regularly, even in the simplest of fuel systems. I've seen it happen in a Cessna with dual gravity feed tanks. The more parts you add to your fuel system, the more complex it's going to be. It is important to have easily seen, highly visible fuel indicators.
One of the more common mistakes I see in gravity fuel systems is to have a fuel or vent line that has a point where the line goes back uphill at some point in the line. That becomes an air trap in a fuel line that will stop the flow of fuel. A slight uphill run in a vent line will become a fuel trap that will prevent the tank from venting properly and can cause fuel flow to stop. I have seen both types of failures multiple times. In one case, the owner was just amazed that I was able to fix his intermittent engine failures with a simple 2 minute rerouting of the fuel line between his gascolator and carburetor. Fuel traps in vents are harder to find, but will eventually show themselves. I unknowingly built one into the vent line for the header tank on my KR. It took over 1200 hours years for it to show itself. It would not fail in flight thanks to the ram air I have on the vent line, but when I overflowed the tank through the vent on the ground, the vent line trapped a tiny amount of fuel and would not allow the tank to vent and killed the engine on the ground. Another interesting issue I see is placing the vent line in an area that can draw negative pressure at certain speeds. That can also stop the flow of fuel. I saw one GlasAir pilot wreck the plane after starving for fuel due to blowing his checklist and leaving the fuel selector on the 5 gallon header tank. He was being hurried by a jump plane behind him that was wanting to get off the ground. He glided for some distance and wrecked the plane with 42 gallons of fuel in the main tank because it never occurred to him to practice an emergency checklist ahead of time, so when the engine quit, it didn't occur to him to look under his elbow at the fuel selector. Clearly a pilot training issue. The pilot was out over Puget Sound when the engine quit, and his brain quite literally froze up with panic at the thought of ditching into the cold water. It is critically important to both understand your fuel system and to have an action plan for what tasks you will perform if the engine fails. The simpler you make the checklist, the more likely you are to remember it when you are overloaded and everything has gone wrong. Electric Fuel pumps (Facet) will almost certainly allow fuel to slowly backflow through them. Check valves often times will still leak back as well. So if you are going to use a transfer pump to a header tank, make sure the transfer line outlet is at the very top of the header tank. Facet does make a line of pumps with a check valve in them to prevent backflow. I haven't personally tested one yet, so can't say how effective they are. -Jeff Scott Cherokee Village, AR > > Supplemental reading: > > In light of the recent and very successful off-airport landing in a KR2, the > FAA posted an initial finding; > (https://www.asias.faa.gov/apex/f?p=100:96:16319109398827::::P96_ENTRY_DATE, > P96_FATAL_FLG,P96_MAKE_NAME:02-AUG-19 ) > "AIRCRAFT RAN OUT OF GAS AND LANDED ON PACIFIC COAST HIGHWAY." > > I think there was gas in the airplane, just not where it could make its way > to the engine. If so, this certainly isn't the first time as many incidents > have occurred in aircraft with complex fuel systems and multiple valves in > the design. AOPA has several articles online about this issue. Quote from > https://pilot-protection-services.aopa.org/news/2018/september/01/runnin-on- > empty > > "Running out of gas in the air is not quite as simple as it might seem. > Running out of gas is referred to by the NTSB as "fuel exhaustion." There > are also accidents, called "fuel starvation," that occur when there is still > gas in the tanks that doesn't reach the engines. This can be due to things > like improperly set fuel selector, water contamination, or cross feed > errors. Fuel exhaustion accounted for 56% of fuel-related accidents while > fuel starvation was responsible for 35% of these accidents. Other incidental > incidents complete the package." Elsewhere in that quoted article, AOPA says > these types of incidents happen 2 or 3 times per week. > > > > John Bouyea > KR-2S - 709 TTAF > OR81/ Hillsboro, OR > 2015 KR@MMV Gathering CoHost > > _______________________________________________ > Search the KRnet Archives at > https://www.mail-archive.com/krnet@list.krnet.org/. > Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change > options. > To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org > > _______________________________________________ > Search the KRnet Archives at > https://www.mail-archive.com/krnet@list.krnet.org/. > Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change > options. > To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org > _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. 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