Sport Pilot Talk

Congratulations, Paul!!!

That's totally awesome. Just looking at it makes me want to run out and get a tailwheel endorsement.

The adventure continues!

On takeoff this morning, after a perfectly normal preflight and run-up, the engine started running quite rough immediately after takeoff. Since I still had more than half the runway ahead of me, I closed the throttle, descended, and performed an uneventful precautionary landing. I taxied off the runway, and did another uneventful (4000 RPM) run-up. Then, setting the parking brake and supplementing it with brake pedal pressure, I did a full-power run-up. Static RPM was making only about 5000 (I had previously seen more like 5200), and the roughness returned.

I taxied back to the hangar, uncowled, and began troubleshooting:



Suspecting something in the fuel system, I drained samples from both wings and the gascolator -- no debris detected. I then removed the gascolator, and checked it for contaminants -- again, nothing found. I removed the carb drip trays and, one at a time, pulled the float bowls to check the carb floats (a known issue with the 912ULS). Finding no debris on the float bowls, I proceeded to "weigh" the floats by observing how high the floated when the bowls were filled with fuel. Three of them looked normal (horizontal pin level with the fuel). The fourth was definitely heavy - the pin was well below the surface of the fuel.

I called my wife, and reported the situation. She said, "you know there have been ongoing problems with Rotax carb floats. You should have carried a couple of pairs with you when you went to pick up the plane." Dammit, why does she always have to be right?

Fortunately, I have a friend who runs a Rotax shop about 90 miles away from where the plane was sitting (he was, in fact, a classmate of mine in a bunch of Rotax maintenance courses I've taken over the years). He had floats in stock, and another pilot based near him was in fact driving to my current airport this very evening. Short version: I got the new floats installed, drip pans back in place, and leak check satisfactory with fuel selector valve open and electric fuel pump running, all before dinner.

Tomorrow morning, I plan on another full-power run-up. If it's smooth and makes proper static RPM, with no fuel leaking, I'll recowl and go flying. Stand by for a further report.

Hope the heavy float was it. Am I right in visualizing that that results in a slightly richer mixture on the side with the heavy float, since it takes more fuel to close the needle into the seat?

My two or three rough running events were likely due to momentary blocking of the main jet by debris. Sometimes the debris drops back into the float chamber, only to get sucked back up with the fuel flow and vibration of a full power takeoff. And sometimes it eventually gets sucked through the main jet never to be seen again. The latter possibility makes a certain diagnosis problematic.

This whole ROTAX float fiasco is really unfortunate. I’m thinking just weighing them every annual, which I just started doing, is still a reasonable precaution. At l least until they settle on a final, final, FINAL revision!

drseti wrote:The adventure continues! . . . . .
Fortunately, I have a friend who runs a Rotax shop about 90 miles away from where the plane was sitting (he was, in fact, a classmate of mine in a bunch of Rotax maintenance courses I've taken over the years). He had floats in stock, and another pilot based near him was in fact driving to my current airport this very evening. Short version: I got the new floats installed, drip pans back in place, and leak check satisfactory with fuel selector valve open and electric fuel pump running, all before dinner.

Tomorrow morning, I plan on another full-power run-up. If it's smooth and makes proper static RPM, with no fuel leaking, I'll recowl and go flying. Stand by for a further report.

Thank you for the report. Hopefully, those new floats will do the trick. Be sure the last 3 numbers of those floats are "189." Those are the latest and greatest iteration. So far, they have the best reviews and reputation.

It has been my experience that the heavy floats have a bigger effect on how the engine runs a lower power settings when you need less fuel.

FastEddieB wrote: This whole ROTAX float fiasco is really unfortunate. I’m thinking just weighing them every annual, which I just started doing, is still a reasonable precaution. At l least until they settle on a final, final, FINAL revision!

Well weighing the floaters has been part of the Rotax inspection checklist since 2015.

3Dreaming wrote:
Well weighing the floaters has been part of the Rotax inspection checklist since 2015.

Well, did not make it onto my checklist until this year. They checked out fine, so no harm, no foul!

FastEddieB wrote:Am I right in visualizing that that results in a slightly richer mixture on the side with the heavy float, since it takes more fuel to close the needle into the seat?

Bingo!

Just got down from a lengthy test flight, and she's running like a top.

FastEddieB wrote: Hope the heavy float was it.

Yep, it was.

You'd think after all this time, they'd have fixed such a trivial issue. Why can't they just switch to brass floats?

Warmi wrote:Frankly , it would have made for a very nice LSA if it weren’t for a absolutely ridiculous price that is being asked for another mostly metal LSA that doesn’t do anything better than half a dozen other LSAs - what exactly do you get for $ 220k that you cannot get with, say $160k Sling 2 or a Flight Design ?

Different mission. You get a great useful load, a very wide cabin, and extremely comfortable seats. A waste of money if you're just going around the pattern or hopping from place to place but if you spend hours doing cross country you'll find that most other LSA won't fit your mission, especially if you're a large person. It's like a Cessna 182 vs a Cirrus SR20. Similar performance but one of them you wouldn't dare take an 8 hour trip in.

The $160k Sling2 is a nice airplane but I can barely fit in it. I'm a big guy. No way I could spend more than an hour or two in one.

fatsportpilot wrote:You'd think after all this time, they'd have fixed such a trivial issue. Why can't they just switch to brass floats?

A bit of history.

Our BING’S are the same basic design as the BING’s used on BMW “Airhead” motorcycles from 1970 to 1997. Their floats looked like this:



That worked well enough on a motorcycle, since even when leaned over in a turn, g-forces were straight down. But for a plane in a slip or skid, fuel sloshing to one side or the other could force the needle into the seat prematurely. I’m pretty sure that’s why they went to the split float arrangement for aircraft use, such that either float independently could stop the flow of fuel into the float bowl at the right level.

I am a little fuzzy as to why a single heavy float in our ROTAX’s causes a problem. The force needed to raise the needle and stop the flow is really minuscule, and it seems like either float by itself could accomplish it, which I thought was the idea between split floats in the first place. But I’m sure there’s an explanation.

fatsportpilot wrote:

Warmi wrote:Frankly , it would have made for a very nice LSA if it weren’t for a absolutely ridiculous price that is being asked for another mostly metal LSA that doesn’t do anything better than half a dozen other LSAs - what exactly do you get for $ 220k that you cannot get with, say $160k Sling 2 or a Flight Design ?

Different mission. You get a great useful load, a very wide cabin, and extremely comfortable seats. A waste of money if you're just going around the pattern or hopping from place to place but if you spend hours doing cross country you'll find that most other LSA won't fit your mission, especially if you're a large person. It's like a Cessna 182 vs a Cirrus SR20. Similar performance but one of them you wouldn't dare take an 8 hour trip in.

The $160k Sling2 is a nice airplane but I can barely fit in it. I'm a big guy. No way I could spend more than an hour or two in one.

I am not a small guy either - 6 feet and 220 lbs ...and frankly none of these planes are good for more than say 2 hours but maybe that’s just me..

fatsportpilot wrote:

Warmi wrote:Frankly , it would have made for a very nice LSA if it weren’t for a absolutely ridiculous price that is being asked for another mostly metal LSA that doesn’t do anything better than half a dozen other LSAs - what exactly do you get for $ 220k that you cannot get with, say $160k Sling 2 or a Flight Design ?

Different mission. You get a great useful load, a very wide cabin, and extremely comfortable seats. A waste of money if you're just going around the pattern or hopping from place to place but if you spend hours doing cross country you'll find that most other LSA won't fit your mission, especially if you're a large person. It's like a Cessna 182 vs a Cirrus SR20. Similar performance but one of them you wouldn't dare take an 8 hour trip in.

The $160k Sling2 is a nice airplane but I can barely fit in it. I'm a big guy. No way I could spend more than an hour or two in one.

They are all allegedly capped at 120kts and 1320 MAUW, so, how is a Bristell any better than the rest of the LSA fleet, not counting interior space or hi end interiors? Is a Bristell certified in another configuration to carry more weight, like a SLING?

fatsportpilot wrote:You'd think after all this time, they'd have fixed such a trivial issue. Why can't they just switch to brass floats?

Or 21st-century fuel injection!

Beautiful airplane, by the way.