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Resin nodules found in gascolator


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Good afternoon,

 

Yesterday I removed the bowl from the gascolator and found some crystaline nodules at the bottom of the bowl. There were approx four, about the size of a pin head. Removing and pressing them between my fingers rendered a very stickey resin like substance.

 

The previous day, when the plane was being returned from Arkansas, the pilot noticed a slight momentary reduction in RPM at takeoff. A few seconds later it cleared and the remaining trip from Ohio to PA was uneventful.

 

My dealer and manufacturer said that the fuel tanks were 10% ethanol acceptable. I've been running 93 octane Exxon with 10% ethanol since new. Aircraft and engine, Sting S4 and Rotax 912 ULS, 2012 model.

 

I have noticed this only once before with even smaller particles being found at the bottom of the bowl.

 

I'm now concerned that the ethanol is causing the resin in the tanks to break away. Is this minute amount of resin like substance something to worry about or may this be normal for new tanks?

 

The fuel does not sit for long in the tanks, so I believe phase separation can be ruled out. I'd dislike running 100LL both for the lead content and the cost (6.39).

 

The drop in RPM on takeoff may have been vapor lock as the temps were above 80*F and the pilot went to lunch for an hour while the plane was sitting in the heat. There was no ethanol in the tanks at this time. Mostly 93 octane ethanol free from KORK in Arkensas and some a 100LL added in Ohio where the momentary RPM reduction occured on takeoff. May be some water in the fuel from Ohio?

 

I've flow it twice since and had no RPM drop.

 

I'd appreciate any input on this matter.

 

Thanks,

Rich

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The drop in rpm could of been a blurb of water, or could be some debris in the carbs, temporarily clogging a jet. Does the Sting have a fuel filter in between the tanks and the gascolator? If so, I'd be looking there for signs of any issues with ethanol and your fuel tanks, or any other debris.

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Hi Rich,

 

I have seen in a few CT's what looks and feels like silicone. I have seen many other types of pin head debris in gascolator's so this may be normal. This is one of its jobs to help filter out small debris. It could have come from any where at this point. I would advise to pop the carb bowls off as it was demonstrated in the maint. section here on the forum and take a look in the bowls. You do not need to disconnect a lot of things to do this check. Debris in the bowls can do be a total blockage, but some times it just goes through with just a hiccup if it is small enough. I would just check the carb bowls and gascolator for now. Double check the gascolator in about 15 hours. My guess is the hiccup was a carb bowl issue and you just stumbled on the gascolator debris.

 

The vapor lock idea could have happened, but it only hiccuped because it was followed by cooler fuel. This is usually short and self limiting incidents.

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Hey Rich,

I have never had any of the issues that you mentioned on my S4. I also use Exxon mogas, but the station I use the ethanol content is in the range of 5-6%. I have had the gasculator checked numerous times and the only debris ever found was small amounts of carbon fibers that remained in the tanks during manufacture.

 

At my annual in January '13, I had the mechanic at KORK drop the carb bowls and there was a small piece of something in one of the bowls but it was heavy enough to never get into the fuel system. As I recall we thought it was there from day 1, maybe due to the manufacturing process.

 

To remove the carb bowls it takes a little work, and the way the mechanic did it was to actually remove the carburators/airfliter assembly and then remove the carb bowls.

 

I'm on my 3rd fuel pump and used to get low fuel pressures on take off regularly. You may want to run the auxilliary fuel pump just prior to take off just to make sure the fuel bowls are full and the system is pressurized.

 

I had 130 hours on the plane at my annual and have about 160 hours on it now.

 

Hope this helps.

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Dan,

 

Why three fuel pumps with such little time on the aircraft? Was yours originally equipped with the pumps that have just had the SB announced?

 

I spoke to Bill C and he believes it may have been vapor lock as Roger had mentioned. Bill suggests that on high temp days to run the aux pump for a few seconds before departure to push through any vapor that may accumulated. It may also pay doing a mag check at 4K on every flight of the day, not just the first, to remove any vapor. I will be applying both to my checklist.

 

I just read about a fatal accident that could have been prevented, had the pilot turned on the electric fuel pump when power was lost. Apparently, he never had the problem before and didn't give it a thought. That aux fuel pump is always on my mind and I hope I react properly if faced with a similar situation.

 

Thanks for your reply. Every bit helps.

 

Rich

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Just as an aside, I do a complete preflight and runup every leg of every flight.

 

I've never understood the logic of only doing it once a day, or anything other than every flight.

 

And most of the planes I've flown with boost pumps call for them to be on for takeoffs and landings.

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Eddie,

 

I definitely agree. For me, run-ups will now happen prior to every departure.

 

My aircraft has an electric Facet aux fuel pump, which I don't believe is considered a boost pump. It may over-power the floats in the carbs if ran together with the engine driven fuel pump and present a rich mixture which may cause a severe RPM drop or worse.

 

I don't want to mislead anyone on this as it's very important. Hopefully someone with more knowledge of the fuel system on the 912ULS will respond.

 

Rich

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My Sky Arrow has an electric boost pump, also a Facet. The engine is above the tank so one pump or the other better be working.

 

On the boost pump alone, the needle on the fuel pressure gauge barely makes it up to 2 psi, the bottom of the green arc. In normal flight with the pump off, it runs about 4 psi, the middle of the green arc.

 

For some reason, with both pumps on it still shows about the same 4 psi. I don't think there's a pressure regulator, so I'm not sure why the output of the two pumps is not cumulative.

 

My plane has also exhibited one very strange trait: often on climbout with both pumps on, it will show about 3 psi. When I turn the boost pump off, it will drop to very close to zero before climbing back up, usually beyond where it was before and settling at around the normal 4 psi. weird.

 

In any case, in any given plane I would give very large weight to what the POH checklist says to do, and not vary from tat without very, very good reason. But you sound like the kind of pilot that does that anyway.

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Eddie,

 

My POH states " Aux fuel pump as required " then goes on to say the folowing.

 

Warning-----"Operation of both the engine driven and the auxiliary fuel pump for take-off and landing is not recommended.

The combined pump output has been observed to overcome the carburator float valve fuel cut off, flooding the carburator, preventing full power engine operation or cause engine failure"

 

I have not been given an explanation of what "aux fuel pump as required" means, so, I just leave it off after I have primed the system prior to start up.

 

Rich

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Hi Rich,

 

Leaving the auxiliary fuel pump on for landings and take-offs is another old school hold over that came about from Continental's and Lycoming's. It's that old ugly word "tradition" again. Some how some day old school ideas should die away and some old school thinkers should learn to move forward with change with the newer engine and aircraft designs. In truth it has never been necessary for a Rotax, but non Rotax plane planners and builders came from those days and engines. It's there in case of a failure as a secondary device. The auxiliary facet pump should only add .5 psi to the system, but some of the older mechanical pumps didn't work that way and they over pressured. I have had planes with auxiliary pumps in a Rotax setup and only turned them on in the pre-flight to make sure they were operational.

 

I'm with your aircraft POH book description. It isn't necessary on landings and take-offs and if the needle valve in the carb goes bad you may be in a worse condition because it will flood the carb out on your landing or take-off and you won't know the cause because people rarely think in those terms.

 

Here is another situation where an individual will need to decide what side of the fence to fall on. It will boil down to a personal preference. I will say this that either way has been working out okay so far. Yes there have been some carb flooding issues and I also don't believe anyone has lost the Rotax mechanical pump on a landing or take-off.

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Interesting.

 

I should probably already know this, but...

 

...what kind of plane do you have?

 

As I said, in my installation the output of the two pumps do don't seem to be cumulative.

 

What are your fuel pressures, boost only, engine pump only, both together?

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Hi Eddie,

 

I think Rich has a Sport Cruiser. (?)

Some of the old Rotax pumps were affected by the electric pump being on and it did multiply the fuel pressure and there was even a bulletin that addressed this. Some of the Rotax pumps weren't affected. There is more than one Facet pump too so it would depend if you have the lower pressured model which is what you want. Some engines don't have the fuel re-circulation line which compounded the problem which still causes some engines today to have flooded carbs. The new style Rotax pump needs that re-circulation line. Rotax says the addition of the second pump shouldn't raise the pressure more than .5-1 psi. (.5 is normal and maybe hard to discern on an analog gauge) Some show no affect. The Rotax mechanical pump does a good job for high or low wing. That said; Rotax does like to see the auxiliary pump on all engine installations regardless of wing configuration. They should be plumbed in parallel with a check valve and not series. The new Rotax fuel injection has two electric pumps. Seems great unless you lost power.

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Roger,

 

For whatever reason, 3i chose to put the two pumps on the Sky Arrow in series.

 

And, for whatever reason, that does not seem to cause excessive fuel pressure.

 

Still, I can see if there was even a remote possibility that a pump failure could cause a blockage, that parallel would be a safer arrangement.

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Aux pump as required would be during landing. If the engine quits on approach its no big deal, but it may help with icing. Still, none of this is a problem with the 912i.

 

How would it help with icing?

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Aux pump as required would be during landing. If the engine quits on approach its no big deal, but it may help with icing. Still, none of this is a problem with the 912i.

 

Living on a moderately busy airport, I see lots of take offs and landings. For about half of them, an engine failure on approach would be a very big deal since they are low enough that they would never make the runway.

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Living on a moderately busy airport, I see lots of take offs and landings. For about half of them, an engine failure on approach would be a very big deal since they are low enough that they would never make the runway.

 

I see the same thing. My first engine was a 2-stroke and I didn't trust it. I have always cut the power to idle abeam the numbers. I fly as though an engine failure is far more likely when I retard the throttle than it is in cruise flight. I'm not sure how true it is.

 

The consensus on this forum leans towards 'whatever works for you' including power for approach and landing. I guess time will tell, we now are getting enough time to see various failures that were not common in the early years. It would be interesting to see someone pull the chute on final after making the pattern ( not that I wish that on anyone ).

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