Emergency landing this morning

[Walt]

Originally Posted by Nick

I have not seen a fuel filter with a built in bypass. While I'm not opposed to the idea, I would like to know if the bypass is being utilized.

Practically every filter I've seen has a relief spring to bypass a clogged filter.

[pjc]

Originally Posted by Planecrazy232

I’ve read a story similar to this in the past- only it was frogs in the dispenser nozzle. They found them in their tank after the dead stick. My S.O.P. since I read that is squirting .50c worth of gas next to the fuel pump before I put the nozzle near my plane. I do this everywhere I gas up. This just solidified my decision.

We fished 6-8 (small) frogs out of the fuel tank of our soaring club tow plane (a Pawnee). They found the (quickly dry) warm fuel nozzle a good place to spend the day apparently. Fortunately the fuel flow restriction was noticed on the ground during run up.

You never know what might kill you .... be careful out there.

Peter

[dhmoose]

Originally Posted by Walt

Practically every filter I've seen has a relief spring to bypass a clogged filter.

Thanks Walt! I had no idea that was a relief spring (Learn something new every day). So if I understand correctly, the fuel pressure builds up due to the clogged filter and the dark metal portion gets pushed back against the spring which allows that hole in front to be revealed...thus re-establishing fuel flow. Is that right?

Ingenious.

If this occurs, I assume that the pilot would not know it until the next condition inspection.

Thanks again.

[RONSIM]

The glider club at Zephyrhills, FL (KZPH) has a tow plane, Piper Pawnee. Pilots started reporting engine stumbling at high angle of attack. Nothing could be found, on the ground. After one close-call (nearly complete engine stoppage), the airplane fuel system was examined. Inside the fuel tank, approximately 12 tree frogs were found floating around (well preserved).

The fuel farm for the club used the typical fuel nozzle, with an open end. I seems that a frog would crawl in there and be dispensed with the next load of fuel. Apparently it took at least 12 fuelings before the frogs started plugging the tank outlet screen.

Yes, nature cannot be fooled!

Ron

[Tom @ N269CP]

In industry, its common practice for critical filters to be equipped with internal bypasses which will open at a set "cracking pressure". A 10 micron filter is very fine as far as liquid filters go, and is prone to plugging. You might consider installing a fuel filter with internal bypass set at a specific, repeatable differential pressure and then install a differential pressure switch at, say, 75% of said cracking DP connected to an alarm in your panel.

Wouldn't surprise me if there are small filters on the market incorporating the above features ready for wiring back to the panel.

[Sibirsky]

I’m glad it turned out to be a Happy Landing , makes want to check my fuel system now 1

[MikeyDale]

Good job getting down! I hate that you missed the party! Why not run 10 microns on the tanks too? Then maybe if one tank is contaminated, the other would still be usable.....Now excuse me while I go check my fuel nozzel to make sure the cap is on it!

[emsvitil]

Originally Posted by MikeyDale

Good job getting down! I hate that you missed the party! Why not run 10 microns on the tanks too? Then maybe if one tank is contaminated, the other would still be usable.....Now excuse me while I go check my fuel nozzel to make sure the cap is on it!

Pushing thru 10 microns is a lot easier than trying to suck thru 10 microns........

[daddyman]

Originally Posted by airguy

This happened to me this morning about 7am just after sunup, I'm still processing the details in my head, but here's the short version.

I was headed out to go see some friends up north, wheels up at first crack of dawn 6am this morning, and cruising along fat dumb and happy at 9500 on VFR flight following when I noticed that my AFR (air-fuel-ratio) was quite a bit leaner than I normally run it. I tweaked my mixture a bit to get it back where it should be, but my mixture control was significantly richer than it should have been for that condition. That made me take a good long look at the engine, specifically the fuel pressure - which normally runs 40-42 psi (SDS injected engine), and it was down around 29. I watched it for a few more minutes, 28. 27, 25. Definitely slowly dropping and my low fuel pressure alarm goes off. The engine starts to stumble, the AFR indicates 18 (way too lean), so I go full rich, AFR only comes up to mid-16's and my fuel pressure continues to drop. Of course I changed tanks, changed fuel pumps, changed injector boards, all the things you are supposed to do - and it didn't do anything.

That was enough, I kicked off the autopilot and keyed the radio, declaring an emergency with Center. I had a small short grass strip TE08 at my 2 o'clock and headed for that with the engine stumbling and bumbling and started descending. I was plenty close enough and high enough to deadstick it, so I pulled the throttle back to make a no-power approach - and the engine got happy again. Throttle back in, and it's not happy - back out and I get some power - about 10 seconds of this and I realize I've got about 30%-40% partial power - and that means I have options. I can almost maintain my current cruise altitude of 9500 on that.

I called Center and advised them I will be holding altitude with the partial power I have, and will attempt to overfly my known good grass strip in order to stretch my deadstick glide ring to include 77F, Winters Tx, with a paved runway and a least a fighting chance of some type of assistance. I would not have been able to do this if I was lower down - but at 9500 it was possible to include both airports in my deadstick range - so I made the decision to press on another dozen miles and try to milk the engine that far. This is exactly why I like to cruise high - it gives you time and options when things go bad.

It worked, I got within comfortable deadstick range of 77F, advised Center of my intentions, they gave me a number to call on landing and I switched to advisory. By the time I had copied down the number and gotten back on task, with the engine still happily making partial power, I was well high and had loads of energy to dissipate. I pulled the throttle all the way off (don't need it now - and can't trust it - so it no longer exists and I'm a glider) and made a few spacing turns, got into a good position for final on 17 with a 10 knot direct cross, declared intentions on the local frequency and used flaps to manage my energy for a delicious squeaker of a landing that, of course, nobody was around to see. Engine was still running so I taxied clear and shut down by the hangars.

First call was to Center on the number they gave me, advised them I was down safe, no injuries, no damage, and would have assistance on the way shortly and thanks very much. Zero drama there.

Next call was to my wife, you can pretty much guess how that one went. Next call was for help, and within 20 minutes I had a 172 loaded with tools airborne in my direction.

So - that was fun. Long story short, the cause was tracked down to a plugged 10-micron final fuel filter between my pumps and the injectors. My 30-micron pre-pump filters were dirty but not completely plugged - and the stuff in them was like muddy lint. Cleaned those out, reassembled, engine made excellent power and fuel system was doing its original thing again - so I took off and climbed in a circle over the field (with the 172 close by watching me) to about 7500 feet on my way to higher and then pointed it home. On arrival I pulled apart the entire fuel system and flushed the tanks - and found the smoking gun - which is why I'm sharing this here for you other guys that fuel yourself.

On my 125-gallon fuel transfer tank and pump, I have a 10-micron fuel filter prior to the hose, as most of us do - but I do not (yet) have any type of protection for the hose end - it is hung on a peg and open to the air. A mud-dauber had come in and started building a nest in the open hose end, and I didn't see it this morning when I was fueling my plane in the dark at 5:30, and pumped that nest into my left wing. On draining the wing tanks I ran the fuel into a filter funnel and found a fair bit of the evidence coming out of my left sump, so the chain of events is well established.

So - a good fuel system flush, another cleaning of the filters, another load of good fuel in the plane, and it's happy again. All's well that ends well - but the message here to you guys that fuel yourself with a home-brew fuel setup - PROTECT your stuff against insects. Those little buggers can kill you dead.

Way to go on your handling of your emergency. Good decisions all around.
Thanks for sharing.
Daddyman

[lr172]

Originally Posted by Tom @ N269CP

In industry, its common practice for critical filters to be equipped with internal bypasses which will open at a set "cracking pressure". A 10 micron filter is very fine as far as liquid filters go, and is prone to plugging. You might consider installing a fuel filter with internal bypass set at a specific, repeatable differential pressure and then install a differential pressure switch at, say, 75% of said cracking DP connected to an alarm in your panel.

Wouldn't surprise me if there are small filters on the market incorporating the above features ready for wiring back to the panel.

an interesting dilemma. I would ask Ross what size debris it takes to clog an injector. Having a relief spring only allows the debris to get to the next orifice to clog. In the OP's case, it would seem that a relief spring in the fine filter would have just allowed the debris to move forward and clog the injectors. It is also possible that the injectors could pass the fine debris passed by the coarse filter and the 10 micron caused a problem that didn't have to happen, assuming the 10 was causing the bulk of the blockage.

It would seem that larger filters or a cascading system with more layers between the coarsest to finest filter may be a better answer.

Larry