Good write up Brian. ?I'm sure you probably already know this, but copper fuel lines are typically not an OK thing to do. ?The only exception to that is the little 1/8" primer lines as they only have fuel pressurized in them momentarily when you stroke the primer (or only when priming if you have an electric primer). ?As you found this week, even with loops in them, copper lines are prone to breakage due to vibration and work hardening from the vibration. ?The rule of thumb here is that you don't use a copper line where it always has either fuel flow through it, or fuel pressure that could become a flow should the line break. ?
I thought I would look that up in AC43.13. ?It says surprisingly little about the fuel lines them selves, so now I'm wondering where it is that I learned that so many years ago? ?However, I would count this as a very valuable lesson to builders, as we could very well have been reading about Brian disappearing in a ball of flame. -Jeff Scott Los Alamos, NM > ----- Original Message ----- > From: brian.kraut at eamanufacturing.com > Sent: 07/24/13 01:27 PM > To: KRnet > Subject: Re: KR> broken fuel line and lessons learned > > Hopefully will actually work this time. > > > Just returned from a flight to Mobile yesterday and back near > Jacksonville, FL today. Was going to make my normal stop about 20 miles > south of the airpark for fuel, but after my decent I found that it was > broken at 3,000' and a thin scattered layer around 600' after showers > just moved through the area. I made a non-eventful landing with the > normal electric boost pump on in downwind and turned off just after > landing. During taxii back I noticed a fuel flow going way up and > stopping about 20 GPM. Made a quick taxii for the hanger and noticed a > slight fuel smell so shut down quickly just before the hanger. After > pulling it inside starter to take the cowl off and noticed a small fuel > puddle under the plane. The builder of this plan was smart to put about > a 1/8" drain hole in the low part of the cowl to keep any leaking fuel > from pooling in the bottom of the cowl and I strongly recommend that > everyone do that. > > After I got the cowl off I noticed that the copper fuel line that runs > from a fitting on the mechanical fuel pump to the firewall mounted fuel > pressure sender was broken off right where it comes out of the AN flare > fitting from the mechanical fuel pump. A quick blip on the electric > boost pump that is right before the mechanical pump confirmed my fear > that it shoots out of the small hole inside the copper line like a > squirt gun and much of it winds up spraying on the exhaust pipe. That > was enough to make me cringe. > > I will admit that I did not look at the fuel pressure gauge during my > pre-landing check. Skating around the low clouds on downwind had me > looking outside which was probably the best place for me to be looking > at the time. Not sure if I would have seen the lack of pressure on the > gauge because I don't know if the break occured when I turned on the > boost pump or maybe right as I landed or during taxii. > > It was a fairly smooth landing so I really don't that that small bump is > what broke the line. I generally don't notice much of an increase in > fuel pressure with the electric pump on, but I do see an increase on the > flow meter from the pulsing of the pump. I do regularly check for fuel > leaks in fuel system by turning on the boost pump while the engine is > not running and confirming that it holds pressure for several minutes > with no fuel flow showing on the meter after the pumps is shut off. I > did that just a few weeks ago and thoroughly checked for leaks with the > electric pump on during the condition inspection, so might have been a > small crack leaking a bit, but not not for very long. Anyway, I am > always looking at my fuel flow and it did not go up until just after > landing. > > I am very thankful that the line did not break and start a fire in > flight. Nothing like a small fuel line becoming a spraying blowtorch > with low ceilings and visibility. > > > Several lessons learned. > > The solid copper line did have several loops in it to make it flexible, > but no more solid lines in the pressurized section of the fuel lines for > me. It will be replaced with a flexible stainless armored aircraft fuel > line before the next flight with fire braid over it. All my other fuel > lines are this way with the exception of the aluminum primer line, but > that line is not under constant pressure. If I built this plane it > would have been that way from the start because I would have thought > about it when I installed it. Being as it was already there I never > really thought about it. > > I can't reach my fuel shutoff in flight without taking off the seatbelt. > ?I had been planning on adding some type of remote actuation to the > lever. That will be done before I leave for Oshkosh. Been in a burning > aircraft on the ground before. Don't want to be in a burning aircraft > in the air(nor on the ground again, but certainly not in the air). > > Next time I notice a weird indication I will take action immediately. I > should have shut down the engine and turned off the fuel as soon as I > noticed the high flow rate. Taxiing back to the hanger thinking "hmmm, > flow meter acting funny again, but just flew 400 miles so plane must be > fine" was not the right move, especially when it would have been very > easy for me to walk a thousand feet to my house and tow the plane back > with my truck. > > Hopefully others can learn something from this and prevent a story > without a happy ending. > > _______________________________________________ > Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search. > To UNsubscribe from KRnet, send a message to KRnet-leave at list.krnet.org > please see other KRnet info at http://www.krnet.org/info.html > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change > options
