I almost LOST my Airplane in a Wind Storm / And it needs your Help.

[@DocmurdocFPV]

I have seen this before on the 2 strokes with 2 bladed props, what is happening is on the ground the center part of the prop due to the higher pitch near the hub is aerodynamically stalling while running up due to having to pitch it to keep it under a certain static RPM. But once you accelerate the aircraft and have airflow moving through the prop disc the center section of the prop is no longer stalling but biting into the airstream causing more load on the engine resulting in a lower overall in flight engine RPM. Look up the Arnold AR-5, they ran into this exact same issue on that aircraft with a similar engine and prop configuration.

[@gettinsmeegy]

How does prop mass affect things? Is the engine over spinning the prop during static testing because it's so light? If the engine ran fine (despite temp issues) with the other prop, changing the prop shouldn't change how the engine normally runs. Have you tried reducing pitch on the prop?

[@DocmurdocFPV]

@@gettinsmeegy Prop mass is not the issue here, it is the percentage of the prop disc that the physical blades take up. Remember everything is a trade off, you can increase the width of the blades allowing you to lower the overall pitch to keep things equal or lengthen the blades again allowing you to lower the overall pitch or go to a 3 bladed prop with a slightly smaller diameter and slightly less pitch. All 3 of these options have different tradeoffs. Such as when you go with bigger diameter and less pitch you give up a little top speed but gain takeoff and climb performance. With a smaller diameter 3 bladed prop you give up a little takeoff and climb performance but gain a little on the top speed side. You just have to decide where you want to make the tradeoff and compromise to your satisfaction for the type of flying you are intending on doing. With Jonas' situation I believe a slightly wider blade with the same length pitched slightly less will get him closer to the sweet spot for power and climb performance on that engine and airframe setup. He is only losing about 400 rpm from static to flight, so he is close to the sweet spot for that engine and airframe from what he showed in the video.

[@gettinsmeegy]

@@DocmurdocFPVI hadn't thought about prop width... What happens if Jonas reduces pitch a little bit to optimize rpm?

[@michaelogrady3249]

I agree. Sounds like prop partially stalled. Less drag.

[@DocmurdocFPV]

@@gettinsmeegy That will allow the prop to be less stalled on the ground with the result of higher static RPM on takeoff and allow the prop to bite less once he is flying resulting in a higher flight RPM but with the trade off of better climb but less top speed. From the video I think if he had a slightly wider E-Prop the same length and then pitched it for the correct static RPM he will get the best out of that engine and performance in the air.

[@regardtcoetzee]

Jonas, the rpm problem you're having is 99% due to the e-prop. We've tested the e-props on the rotax 912 uls, 914 and 915 engines and found that on all of them we would get 200-300 rpm higher while static but the moment that you start to move and the prop "bites" the rpm drops down. On the 915 you can actually hear and feel the prop cavitate and make a loud screaming sound and after a couple of seconds into the ground roll it becomes quiet, the plane accelerates and the rpm drops.

[@danbarone7643]

Hummm, sounds like maybe when the prop is static the section nearest the hub is aerodynamically stalled, then as airflow starts moving over the prop it loads properly and reduces rpm. I’ve never experienced this phenomenon, but sounds logical. I can’t think of any other reason why static rpm’s would be higher than flight rpm’s. If this is the case, I would adjust the pitch to get proper rpm’s during climb.

[@danbarone7643]

One more thought. I had an IVO on my hawk, it’s claim to fame was that the flexing of the blades made it act like a constant speed prop. Static, under high aerodynamic load, pitch would flex out of the blades, then when you would get into cruise flight the prop would unload and pitch would flex back in and give better cruise speed. Maybe that is what is happening with your static and flight rpm’s.

[@JonasMarcinko]

That is good to know about the e-props. Thanks!

[@craigdowden4788]

Yes that was my thought too. The e prop is high aspect ratio (like a glider wing). So it is effectively cavitating at run up allowing the engine to rev higher. Try adjusting (reduce) the pitch to achieve the desired airborne RPM.

[@ellenorbovay5226]

I think the temperature indicates its too lean. You may want to go up one, two or even three more sizes on the main jet. You saw an improvement when you raised the needle up (lowered the clip) so that indicates it was too lean. With two stroke engines you want to jet them just below rich, so go up on the main jet size until the plug turns blackish and it's a little rich (you'll hear the motor run rich), then back off to one size leaner. Two strokes are very sensitive to fuel-air mixture, they need fuel to cool, and if they are too lean, they melt the piston. That's why you start rich and move towards lean very carefully.

[@coggersl1]

You already proved the issue...its the new prop. All that pitch has your centre section stalled, when your relative airflow increases with airspeed, it unstalls, causing lift (and drag!) on the blades giving you an RPM drop. Eprops are really performant for this reason...you are getting all the engines power at flying speed right across the blade length.

[@guybougard8495]

Hello, Actually, these props, like e-prop, are constructed to make the pitch to increase when flying. If you go on their website, they explain why by organising the carbon fiber direction they are able to do that. I fly a lot with Duc props and it's the same: statict rpm are a few hundreds higher than in flight. It's why you really can adjust the static rpm to max power; you will gain in T/O distance and on cruise speed. I am test pilot for Sonaca aircraft and soon for Stemme who are using these props.

[@JonasMarcinko]

Interesting! Thanks for the info!

[@marcdouton6226]

Jonas, there is no problem! The r-props is designed to stall at take-off. Set your pitch to reach the proper rpm in flight. For now you pits h is simply too high. Don’t touch your carb settings ! Cheers

[@chrisatty]

Great to watch your and your friends, tinker with engine issues, ex bush pilot/Airlines/ corporate jets/ retired/ 26500 hours, best fun was , single pilot, 19-21 years old bush flying in Tanzania, East Africa. 5 pilots, in 2 years lost 2 pilots flying into cloud and high ground. Happy days.

[@rumbear1]

Great video! Great to see you at Reno! This is exactly what I was referencing when we chatted... your videos are working the problems and finding solutions. Doesn't matter if it is a hay baler, para-glider on snow skis or an airplane motor with wings! Stay frosty and have fun!

[@HeeHawHighlander]

The above comment by Docmurdok is correct. We experienced this year’s ago on a friend’s Kolb Slingshot. 582 68” Warp paddle blades. Static runs were 6250 rpm indicated. On take off roll the engine would fall flat on its face. The blades are at a lower angle of attack as speed increases and when they quit stalling it over loaded the engine. Compounding Dave’s issue was a 2 1/8” analog tach that read higher than actual rpm and made us think we were getting more power than we were. Dang thing was reading 6800 when rpm was actually 5800. If you are running the little analog tach, I strongly suggest you add a digital “tiny tach” to insure you have a correct tach reading. Take some pitch out until she’s happy.

[@sterlingmadsen8900]

Jonas, i am no mechanic and certainly no aviator (with only 25hrs of fixed wing flight, and THAT was 40 yrs ago !) So I'm just shooting in the dark here BUT..... Since you have that other 3 blade carbon prop for the Capella, maybe you could put that on and see if that creates more air flow into/onto the motor maybe to fill down the motor temps??? And THANK YOU Sylvia for giving us another TOO TINY peek at Ava ! THIS PART of your lives is at least, if not MORE INTERESTING (to ME at least) Is she getting close to saying things like Mama/Dada or close to walking maybe ? I hope you'll include more of that in your future videos.... PLEEEEEEEEEEEEASE ???....!👍!🥰!👍!

[@DevilDolphin734]

When Jonas uploads, you watch. Nice video.

[@JonasMarcinko]

Thanks!!

[@OtterFlys]

Similar to what Docm…. Said, high pitch of that prop required due to not enough cord (blade area) , prop stalling when static, then unstalls in flight and prop starts 'biting'. Not really a big deal if it performs ok. But more cord would fix. I’m thinking that prop was designed for a lower HP engine. Just my best guess.

[@barrysimmons5489]

Could that cylinder be running too lean?

[@jwoodyr1]

FYI - Airplane propellers operating in air cannot "cavitate". They can stall, fully or partially, but they cannot cavitate. Cavitation is a phase change (phase = solid, liquid and gas) in the fluid caused by a local reduction in static pressure. For boat and submarine props operating under certain conditions, the water actually boils (liquid to gas phase change) at low temperatures because the pressure drops so low on the front side of the blades. That boiling creates bubbles or "cavities" in the water - hence the name, "cavitation".

[@oneninerniner3427]

Correct; what many people call cavitation of a marine propeller is actually ventilation.

[@holenwegchristophe1971]

I actually live 10 min away from the factory and I have known the owners for some time. I have seen them developing this propeller, and (I don't know if that's the real thing that happens here, but) they advertised for a "constant speed propeller effect" from the blade profile and maybe the way it deforms with changes in AOA. Seems consistent with your issue and the performance measured in T/O and cruise. I hope it helps! Safe flights

[@JohnArmstrong-ui8zq]

Great vid! Thanks Jonas! As many others have pointed out, it looks like the prop is stalled at static rpm and low speeds. Probably designed for a polini or moster with less power. I’d try a borrowed ivoprop sized for that engine, you’ll have airflow at the hub for cylinder cooling as well. Blue skies!

[@JamesGood]

Well edited, great fun to watch! Thanks for sharing the journey.

[@SnowAndrews]

Feels very like a fuel-flow issue. Engine going LEAN as flow reaches it's upper limit.

[@randallbrack2130]

I would suggest the following... number one consider what the gentleman said concerning the fuel pump. That could be a key source. Number two consider going with some fuel hose that might be a shade bigger to give you more volume and flow of the fuel from the tank to the pump to the engine. if you do not have any spices in the line where you use fittings those fittings could be restricting some of the fuel flow. The less splices you have and more of a pure feed line that you might have can help greatly. Also maybe consider some form of calling over the nose cone and the engine similar to a piper pup To restrict drag on the body of the plane. Then lastly, possibly, another type of prop that would be like a power prop that would give you just a little more pitch and volume of air or thrust. Just some thoughts

[@randallbrack2130]

That should have said splices in the lines with any type of reducing fittings that could restrict the flow of fuel

[@friedclutch97]

Regardless of your findings with the E-Prop cavitation post... Rule out the following for hot CHT.... With a warmed up engine, smoke test the engine. In the automotive industry we use a smoke machine to look for intake system leaks. In a 2 stroke you need this test to check the front crank seal and the case seal. Any leaks will throw you a case of wierd problems. even an exhaust flange leak. Any leaks at all from the carb base gasket to the exhaust will have you chasing your tail forever.

[@dlrowle]

love this channel you gave me the bug for sure, Question have you ever flown a gyroplane, WOW that looks like a blast I want one or two.

[@danbarone7643]

I ran a Rotax 503 in a CGS hawk for a few years. If your front crankcase seal is leaking it would explain the front cylinder running hot. An intake manifold leak on the front cylinder would do the same thing. If you unload a two stroke in the air, such as, lowering the power to descend, it’ll run hot, but that happens on both cylinders. That’s why I keep thinking it’s an air leak on the front cylinder. If your spark plugs don’t have that nice tan color you need to find out why or suffer an engine failure at some point. 3 out of 4 pilots that fly a Rotax 2 stroke have had an engine failure and 95% of those failures are due to improper operation. As far as the rpm issue, I’m somewhat stumped at the moment. One thing I’m pretty sure of is that flying at 40-50mph is plenty fast enough to get proper cooling. Every ultralight on the market climbs at 40-50mph with no problem. One question I have is, you mention your cht is high but never mention egt. Do you have an egt gauge ? To me, egt is much more important when running a 2 stroke. It tells you what the engine is doing in that moment( Rich or lean). I’m really curious what is causing the rpm issue.

[@tomcoryell]

Your response makes the most sense to me. Something is causing a lean condition. It can almost only be that.

[@johnsuttles3475]

I'm not an airplane mechanic nor a pilot, just a 75 yr old licensed engineer with a passion for learning. Read all the comments which appear to have alot of great first hand knowledge and apparent validity. I am touching on my first thoughts on the high head temp. Using the original prop, seems if the cooling air scoop was ~8"-10" wider and only open on the front face near the ends, it would grab air from behing the active thrust portion of the prop beyond the propeller hub.

[@dalethorburn6626]

I took a look at Lycoming for inspiration and found this list of possibilities. I know you and the crew have already considered most everything. (• Oil supply insufficient • Low grade of oil • Malfunctioning oil temperature gauge • Clogged oil lines or strainers • Inadequate air for cooling (cowling inlet/outlet areas) • Ineffective engine baffling installation • Improper oil cooler installation • Excessive blow-by (worn or stuck rings) • Failing or failed bearing Similarly, a high cylinder head temperature condition can be caused by some of the same things that affect your oil temperature. A few additional possibilities may also have to be explored: • A malfunctioning CHT gauge • Inadequate air for cooling • A poor baffling installation • Improper ignition timing • Wrong grade of fuel

[@peterkelseyferryair2396]

Jonas, Hopefully this will make you understand the query you have with the E-Prop giving you less RPM in Flight than you can get Statically. EXTENDED SPEED RANGE (ESR) EFFECT At E-PROPS, the term "ESR effect" is used to refer to a fixed pitch (or ground adjustable pitch) propeller whose behavior is very close to that of a variable pitch propeller, i.e. a strong thrust at all engine RPM. ESR Effect This ESR effect has the following characteristics: it induces very little gap between the static rpm and flight rpm, which makes it possible to maintain high power at takeoff. Thanks to the hollow profiles, capable of more lift, the blades are not stalled, and therefore it allows to have a very strong take-off thrust. Don't forget: what makes the plane take off, and what we are looking for, is not engine RPM, but thrust With an ESR effect propeller, the full throttle engine speed remains almost constant. But beware: just because a propeller keeps the same RPM all the time doesn't necessarily mean it has the right efficiency... => A propeller can be "Constant Speed" without having this ESR effect, whereas a propeller with ESR effect is necessarily "Constant Speed". Some examples : - take-off : engine full throttle 5400 RPM - max speed 200 km/h : engine full throttle 5500 RPM In this case, the gap between 0 km/h and 200 km/h is only 100 RPM. For comparison purposes, a standard propeller (not ESR) can have a gap up to 1000 RPM between take-off and max cruise speed. The ESR effect can improve the performances at take-off, because then the engine is running very near of its max RPM, and provide all its power during take-off. Some E-PROPS models allow to have more RPM at take-off than in flight... From technical point of view, there are different solutions to obtain this ESR effect : - narrow chord with classic profiles - pitch reduction at low speed by blades deformation (difficult to obtain) - narrow chord with special profiles, in order to avoid the stall of the blades => it is the case of the E-PROPS Increasing the diameter reduces the ESR effect. Decreasing the number of blades restores the ESR effect. COMPARATIVE CURVES (THRUST and RPM) between an E-PROPS ESR effect propeller and a standard propeller thrust esr effect in thrust % (100% = an optimal variable pitch propeller) the thrust of the E-PROPS propeller with ESR effect is always above the thrust of a standard propeller thrust esr effect indicated RPM in % of the maximum engine RPM during take-off, the RPM of the E-PROPS propeller with ESR effect is always above a standard propeller In the case of stalled blades, the loss of performance may be higher than the power gain. Therefore, optimization of the curve "max thrust / speed" is essential when designing the propeller. When attempting to reduce an aircraft’s take-off distance, thrust between 40 and 80 km/h is much more important than that between 0 and 40 km/h : - while the aircraft is increasing from 0 to 40 km/h, its average speed is only 20 km/h; the distance made remains low (ex: 16 m in 3 sec) - between 40 and 80km/h, the average speed is 60 km/h: this is where the runway length is "consumed" (ex: 60 m in 3.5 sec) For E-PROPS propellers, static thrust measurement is not relevant, as they are designed to achieve full thrust during take-off, not in static.

[@KDAero]

Almost for sure, you need to repitch your E-prop. It acts different than a normal one. It is almost like a somekind variable pitch at a speed, 'cos blades do twist a little.

[@JonasMarcinko]

Hmm 🤔 interesting. I’ll give it a try. Thanks!

[@jerrydelyea5820]

Hi Jonas. I wonder if you re pitch for slightly over where you want to be while static and see it might drop to your desired in flight? Good luck, live the air bike!!

[@ArionRaine]

Your drop off is due to carb float height. Check its set properly. It needs to be set lower so more fuel is made available in the fuel demand chamber (the bowl). People often overlook float height. It is the main fuel metering function. If it isnt right, increasing jet size will have zero effect, as you found out, as the inlet fuel (controlled by the float height) will not be able to keep up. The RPM drop is very common on 2 strokes if fuel mixture isnt correct. I find it odd that the 2 stroke guru you called has never had that happen. Its the primary "gauge" we look for in 2 stroke tuning when we dont have any instruments.

[@stevekincaid]

I don't like the way your exhaust is pointed to the left. I wonder if the exhaust tip is in a high pressure area when flying causing back pressure. Can you run a test without the muffler?

[@eclipso104]

Jonas, have you checked for an air leak ? Fuel is not the only way to run lean. The lean condition van cause heat issues and too much air can cause this. You could have a leak in the case or the intake. Any extra air on the engine side of the carb will cause issues. You'd need to devise some block off plates. Check out how my friend and his dad did it here kzbin.info/www/bejne/nH3FameamNaBeZosi=H9uLZDqsccaMdKdk Also, all the suggestions about the vent tubes is right too. If the tubes are in the air stream it can cause issues. You need to be sure the open end of the tubes are being block from the airstream.

[@mikekopf1173]

Your prop is probably cavitating on the ground. Set your pitch based on 'in flight' rpm data. The in flight rpm is more accurate than static on the ground. Once you have it set correctly for in flight, I would not worry too much about the static rpm on the ground. I am an A&P and this is my best guess. If it were my plane, this is how I would do it. Blue Skies.

[@oneninerniner3427]

It's stalling

[@okgo8315]

Do be careful messing with jets, its very easy to hole a piston. Good luck getting it sorted👍

[@LuMaxQFPV]

Float bowl vents/fuel angle in bowl is different on ground vs in the air.

[@OSWCrosshair2002]

Stay safe, buddy. Got be around for your wife and that new baby.

[@timadams3489]

I like the ram air idea maybe using a large shop vac exhaust..........work out extra weight of the shop vac and how to power the shop vac.........🤪

[@AerialPhotogGuy]

Jonas, @regardtcoetzee said almost exactly what I was going to say, the prop is cavitating while static but biting the air in-flight. As for cooling, I would also recommend making an air scoop that extends out into the airstream of the prop (preferably to the side). Most airplanes with cowlings have a similar air scoop that direct the prop air into the heads.

[@oneninerniner3427]

It's stalling

[@flybluecollar]

I have heard that E props are designed to work almost like a constant speed prop, and the RPM does change. I’m not 100% sure but I would look into it. Good luck, keep up the great videos.

[@Ronbc000]

From my motorcycling days. Is there a chance that the carb is fuel boiling, upsetting mixture strength, lean mixture = increase cylinder temps? A rubber or remote carb mount may alleviate the problem. Also are you using the recommended manufacturer's carb intake filter? Cheers 👍

[@joeroscillo4015]

Great seeing you flying, even though that craft looks a bit on the sketchy side! Pretty sure your solution is close at hand! You always figure thing out!

[@experimentalaircraftandmor531]

Per e-props you do not adjust the propellers to static RPM, you adjust them to max flight RPM. Because the propeller cord is so small, it cavitates in the air under static thrust, and you can even tell when you’re taking off that as your speed increases across the ground, you will feel the surge when the propeller finally bites more air. Ignore static RPM, and use in flight max rpm.

[@patrickheavirland3599]

Good morning from Minnesota! Great episode!

[@dennisjay3277]

It could be a fuel pump but I'm leaning towards a faulty fuel cap. I'm thinking the cap is creating a minor vacuum in the tank. The cap is partially plugged and the pump is pumping faster than the air is flowing into the tank. That would lean out the front cylinder and raise the temperature. Next look for a collapsed fuel line or a restriction.

[@JonasMarcinko]

I did try that I just didn’t show it. Took the fuel cap off completely in flight and no change. I’ll try the ram air to the fuel cap and see if that does anything.

[@franciscoaloureiro]

On 2-stroke gas RC planes I sometimes struggled to get a good tune in the air even though it would be good on the ground. The most common problem was positive dynamic pressure at the intake often making the mixture way too lean causing detonation, loss of power, and high cylinder temps. To deal with this I usually make cowlings that stabilize the pressure to near atmospheric at the carb inlet.

[@JonasMarcinko]

Interesting! Good to know.

[@gregwelch6658]

Does that e prop have more vibration than the heavy prop? Perhaps it’s a torsional issue. Can you achieve the higher rpm inflight with the 8lbs prop? 8 vs 2 lbs can have a huge impact on torsional vibration.

[@GudmundurAlfredsson]

e-Prop work like this. Its increase pitch as speed comes up.

[@jimchuk8511]

I had a 447 single carb in my Himax yrs ago. Ran a three blade !VO 60" prop. Free air cooling, using the aluminum scoop that California Power Systems sold. It worked fine, and I never had high CHTs with it. Many others say the prop is cavitating or stalling on the ground, and that is what I think as well. I would set the prop so that it's right in the air. Mind the EGTs though so you don't cook the engine.

[@ancienttelligence5161]

Im going to guess, and I could be completely wrong, that is due to the extreme pitch of that skinny little prop so that once its got air speed over it, its biting to much air and reducing your rpm. Good luck hope you figure it out!

[@martineronn2257]

Could it possibly be the prop stalling when static? You were pitching up several times before flight if i remember right. Increase in pitch would not change rpm significantly if the prop is already stalled. An rpm drop when flying would make sense then. Have you tried reducing the pitch slightly?

[@Eddiey43]

Hey Jonas the rpm issue is 100% e-prop thing I’ve fitted about 8 of them on already flying LSA planes techam, savanha, savage cub all with 912 rotax they will do 5500/5800 static and as soon as you have 20knots/40 on the nose they drop and will max out at 5000/5200 rpm it’s got something to do with how there made and how the air effects the blade. Think of it as an automatic constant speed prop.

[@CS_247]

Nice to see you doing crazy stuff with airplanes again!

[@krissfemmpaws1029]

At first I was thinking lean fuel. Then it dawned on me you are flying with carbon fiber prop. My theory, pulling hard on the groung the prop flattens to a finer pitch so you get the RPM. But in the air it doesn't have the load so it doesn't flatten to a flatter pitch so you don't get the same RPM as on the ground. Look at your scoop it looks too small for good cooling at low speed. As I remember the free air scoops had about twice as big of scoop opening them what you are using. The bummer is some of the products you use to be able to get for the 2 cycles 10 to 15 years ago are hard to find now. By the way what size tires are you running now? Blessing Kriss

[@JonasMarcinko]

Good theory! It seems to make sense. Good to know. I need to make the scoop larger. I’m running the Nanco smooth tires.

[@RevUnstableBoy]

prop could be stalling. prop is a wing. at the high pitch, the prop has exceeded the AOA and has stalled somewhere on the length. that stalled section is not making lift (thrust) and therefor less induced drag. when you are moving forward. the AOA decreases and you start getting more thrust, but added drag, slowing the RPMs

[@marknapier2236]

Check the venting of the float bowls. If they are in disturbed air the pressure can vary greatly with airspeed. On my kitfox I took to venting them into the top side of the air filter. Also used the Hacman to control EGT's but that's another story. For me, the bigger issue is the inspections and maintenance needed to keep that 2-stroke going. Get behind and the engine can quit with no warning.

[@Airplanefish]

It was fine before switching propellers. Preventative maintenance is good but not the issue in this case

[@flyaerovoltz]

Love the video! thanks so much for the love with the Aerovoltz Decal! you are the best! fly safe my friend! Kiss that baby!

[@Mindcrime13]

I would check for components that might expand with height related to fuel. Also would check for possibly cracked fuel lines or the brass where the gas line goes in, Float bowl height, fuel pump pressure, fuel pump/line blockage, etc.

[@danblumel]

We've had crazy weather in northern Utah and South Eastern Idaho recently. 1 inch of rain the other day in Preston, ID.

[@Scott-ol9zs]

what

[@brentdykgraaf184]

Remove the carburator plunger and lower the clip one notch...this raises the needle for more fuel. Lean is hot. Do a plug check. While tied down run wide open and shut it down. Pull plugs.. white is lean..black is rich...brown is fastest sled in town...snowmobile that is.

[@homestuff2949]

I woud love to see the rc plans fly

[@TheHighDesertLife]

Need to do dual carbs so you can tune each cylinder and get your jetting perfect,

[@311ytc]

1) Change out your fuel filter if you haven't already. Always look for a 2nd "hidden" fuel filter (sometimes inside of the fuel tank). 2) If you're using a mechanical fuel pump, switch out to electric. Also, check the tiny filter screen just inside the fuel inlet nipple. That can get clogged and you would never know unless you remove the inlet nipple and sprayed it out. Also consider that you may have debris in your fuel system from old gas or old lines (or corrosion in the tank). The system behaves fine on the ground but after a while the fuel gets churned up the debris starts clogging up that screen. I haven't worked on rotax engines but I have had a similar problem on an older boat engine using a high pressure fuel pump. 3) Is there something blocking or holding back the throttle cable? 4) It could be something related to your exhaust system (exhaust pipes too narrow or too long). Don't underestimate restrictions in exhaust flow, 5) It sounds like you opened up the air intake but could there be something inside mechanically blocking air from getting in? Good luck. I hope this helps.

[@OneAV8]

Glad to see the aviation vids coming back!

[@Doug_Morgan]

My first thought was the airflow around the air filter as well.

[@peterbarry7595]

I missed it --WHICH engine is it? One guy told me--- rebuild/thoroughly clean the carb. That is Cheap and easy. Try another carb if you can. Spray 'engine starter' spray around seals, and carb boots etc --- to check for leaks. Replace fuel pump, mount properly, and isolate from heat and vibrational. New fuel line. Sending units and install locations and guages can ALL be wrong. All are cheap and good maintenance anyway. All comments on prop seem like good bet --first prop blocked air flow perhaps, new Eprop may be flexing differently under static and flying conditions.... why not fly it and do not overheat at max RPM taking off (although some gurus say these engines over heat just below max throttle even more...?) Fly around and really watch RPM and temps. Let us know!

[@aaronhartley5644]

My e-prop does the same thing. It's the prop!

[@John-N797]

Hey Jonas, after reading a number of comments here, I realize I come here just to see you and yours do your thing!!! I have no idea what everyone else is talking about. I feel like I entered a calculus class by mistake instead of my history class. Am I alone or there are others like me?😂

[@Mbell3568]

That thing looks terrrifying

[@chaseallen953]

Need more pitch, lower pitch makes it run lean. Also, if you have room, flip your gearbox 180 and that will let better airflow to the cylinders.

[@aero_nwa]

I’m not sure how flipping the gearbox would affect his thrust line… I’ve got a rotax with the flipped box like you’re talking about

[@garygrimm892]

this may sound crazy take the muffler off and shake it if it rattles you have a baffle broke loose and blocking the exgaust i have seen this happen several times and make shure you run the highest octane gas you caan as it will cool off EGT & cylinder head temps and a good Synthentic oil will cool CHT also

[@JonasMarcinko]

Interesting!

[@coreybeaty8528]

Try putting a 90 in your air intake, or build your self a ram air box for the outside of your air filter. I think you were on to the idea with the rushing air forming a vacuum. I don't think its the filter but the 90 degree angle of the throttle body to the flow of the air. It may be forming a partial vacuum on the inside of the carb at the opening of the throttle body that is why the air filter did not change any thing. The jets in your carbs work the same way pulling more fuel in depending on the speed of the air moving through the throttle body. You could make a cheap ram air box out of sheet metal. later if it works make something nice out of fiberglass or something!

[@coreybeaty8528]

For example all the harleys with cone air filters use a 90 to orient the nose of the cone into the flow of air so they dont create a vaccum i dont see why airplanes would be any different

[@jossderaadt7844]

Could it be float level with tail down vs level flight?

[@JonasMarcinko]

Good point! 🤷🏻‍♂️

[@pkane5472]

You should have asked your followers a long time ago! They absolutely have the answers!

[@JonasMarcinko]

Right! It’s awesome to get all this feedback.

[@jeremylynn8631]

I'm going straight KZbin comments section on this one.... Looks like your wings could drop an inch or so in the front, they look they have too much pitch, too much lift! Then the motor use Lucas 2 stroke oil, it's designed to keep air cooled motors low temp. And it looks like your muffler/exhaust needs to be more restrictive! Not enough back pressure at high RPMs with the wind blowing and creating a vacuum out the tailpipe. Then also if you don't have a choke or a crappy one, make sure to install a good one to play with the air fuel mixture when cruising at, "altitude," or the lack there of! Lol. And that #1 cylinder, close the gap on the spark plug ever so slightly to create a colder plug. And I'm sure u run nothing but NGK brand, right??? Especially on a 2 stroke, that's all I would ever run! And instead of getting a bigger fuel pump, if possible try to increase the fuel lines up one size. I bet your pump has enough force, but the size of line may be only allowing so much volume to enter the motor/carbs. Higher pressure isn't always the answer, especially on a small motor. But honestly I feel the wings are pitched just a hair too much, and the airplane is fighting itself to get on that smooth even keel plane! Wish I could be more help, but I'm just some guy randomly showing up to your channel after being absent for about a year, and have no clue about anything going on in that engine compartment! God bless, and just because u almost died and met him, doesn't mean u get to use his name in vein! JONAS! 😉🤔

[@Mister510]

Do you have an EGT gauge? Trying to sort and tune a two stroke without EGT is maddeningly frustrating! I don't think it's running out of fuel as it doesn't miss, and it hasn't melted the pistons.... yet. You don't want ram air into the carb or ram air into the fuel tank, either will make the engine's mixture air-speed-sensitive and you DO NOT want that! I don't know shit about airplanes, I know two stroke tuning from racing snowmobiles. That said, I think the load on your prop is higher when it's moving forward thru clean air. If you need all the RPM for power when flying set the pitch to achieve it, and add a rev limiter if needed so you don't hurt it on the ground?

[@mulveymotorsports69420]

For your temp issue I can suggest over jetting your carb for about 12.5:1 afr for 87 octane. And there is the chance that the prop being so thin with so much pitch could be cavitating which would cause your ground runs to over rev like crazy but once you have the air flow of flight would load the piss out of your engine and bog it down, marine outboard engines do this a lot when you put to tall of a prop on a really strong engine. Or it could be similar to the effect of putting your hand on a vacuum cleaner and it revving up from the lack of load. Just spitballing, good luck!!

[@oneninerniner3427]

Stalling

[@whoanelly737-8]

Great video!

[@JonasMarcinko]

Thanks!

[@trnpsycho]

Try doing your static runups with the tail off the ground. Basically, take out the stalled prop and see if it works out.

[@moesky5246]

I think that the prop is cavitating on the ground due to the high pitch. I would try to knock down the pitch a few degrees,and fly it... that's how we set-up our racers in 428 Q-500 moesky

[@lonewolf56308]

Could it be cavitating at slow speeds?

[@edbennett6922]

My thought. the prop is creating its own vacuum setting still causing cavitation. Thus giving false readings for pitch. Try taking some of the pitch back out of the prop and checking rpm during flight instead of setting still on the tarmac.

[@oneninerniner3427]

Ok , but aeronautical props don't cavitate. They stall. Boat props cavitate. Cavitation is air bubbles bursting on the surface of the low pressure side of the prop in water, mostly on high hp engines. Most people mistakenly call ventilation cavitation. Ventilation is somewhat similar to an aero prop stalling, it's what happens to some boat setups like in a tight turn when the prop sucks surface air into the prop and then loose bite of the water. Just sayin ok

[@edbennett6922]

Okay my mistake but in theory it is still the same thing happening. The prop is not getting enough bite

[@DTMinimax]

I had this issue with my plane and I installed forward facing fuel vents on my caps. My tanks were drawing a small vacuum during flight and even though I was running a pump it was still just slightly starving. May not apply to you but wanted to at least mention it.

[@JonasMarcinko]

Thanks for sharing. makes sense.

[@LuMaxQFPV]

Vibration!! Carb is experiencing an additive vibration/resonance from the engine at cruise rpm, affecting the needle valve. I had this happen on my '75 AMC Gremlin years ago! LOL! seriously, it's gotta be nasty vibes messing with the needle assy. (All the dynamics change in flight with the vibrations, and the carb bowl is at a different angle in flight too, vs ground.)

[@2031dj]

the funky chicken!!! ha ha ha

[@AdamCourville]

Could also be the pipe cooling off as you get moving. (Not the EGT but the actual average temp of the entire expansion chamber as a whole). When you cool a 2 stroke expansion chamber the resonating sound waves slow down and matches up to a lower RPM where it moves the most air/fuel mixture. When the prop is stalled (static rpm test) it isn’t moving as much air as when it is moving through the air thus not cooling the pipe as much. Once you get moving it is cooler which makes peak power at a lower RPM. I have a video on my channel where I inject water into a home made expansion chamber on my outboard and you can see the cooling water affect the rpm of the motor. In my case I was below the range that the pipe worked and injecting cooling water lowered the RPM that peak power is made… then after I accelerated through that rpm range I shut the water off and it accelerated more. Basically, if you cool the exhaust on a 2 stroke, you lower the peak power rpm.

[@dvx3700]

ive had overheating on air cooled engines in the past and some (not all) have been fixed by having the air intake on the cowl smaller than the air outlet. as the air expands with heat it can flow through the lager lower pressure outlet and not stall the airflow in the cowl system

[@buzzypeterson1147]

Don’t watch the temps that close. Don’t let an indication take you away from flying the plane. I’d try a new probe and a new gauge before I’d be messing with props. Cool it with fuel. It’s most likely a mixture or jetting issue rather than air. I’d be checking the plugs on the back cyl. If that one has hunker up plugs and your using that for comparison then you’ve got a jetting issue. The cargo plane I flew would dump fuel to cool the engine. It won’t be air man. Check the back plugs first. Then try switching proves if you have 2 chts. See if the back one is then hot. My money is on bad indication. By the way, the 503 is a good engine. If you ask me, you’re afraid of it and worrying too much about indicating. Don’t let what the gauges tell you make you crash. Just fly her. Once you’re up there, that’s not the time to get all spooked by an indication. (Which may or may not be accurate)

[@buzzypeterson1147]

With the prop, if it’s higher static that means the relative wind isn’t helping to increase rpm. That’s a pitch issue. To me it sounds like you need more pitch. The flatter you go the higher the acceleration. But will be slow in cruise if it’s flat. Controllable props you always take off with the prop as flat as you can get it. Then bring in pitch at cruise.

[@phil3921]

I had a very similar issue with a car once (yes I realise it stays on the ground!). It would rev perfectly when static but as soon as I tried to drive anywhere it would take a Month of Sundays to even reach 30 mph! It turned out to be the mesh fuel filter Inside the fuel pump!! We did all sorts to fix it before hand but a firmed had a light bulb moment, asked me to pop the bonnet disappeared for about a minute and then said give that a go and that was it! Anyway just in case it helps.

[@waynep343]

Does the fuel pump hold pressure. Ever deal with automotive electronics. Gm fuel tank pressure sensors have been used to measure minute pressure changes. So you can monitor minute air pressure changes. Ford egr back pressure tranducers are a single sensor to measure pressure differential . Just thoughts. Maybe you have a friend in HVAC. With the dual inlet pressure gauge for measuring air flow.

[@Sledrentca]

This happened on my first Avid 582 with an Ivo prop. The prop would stall slightly until I got a little speed and then it would catch air and pull the engine down a couple hundred rpm. It happens the same on my 912 Kitfox with a warp drive

[@jameschupp2230]

What is your fuel Pressure? Before take off and during?

[@CentralPaRcFlying]

At full throttle, pitch down, do you get any increase in RPM?

[@negrildoc]

I don’t know but I love the baby

[@AV8R_1]

I see some comments on here about the E-props causing some issues. I ran a 6 blade Excalibur e-Prop on a 100HP 912 ULS without any issues at all. Talk to Larry at Evolution Trikes in Zephyrhills FL. He has TONS of experience installing, adjusting, and flying e-props over several years on multiple rotax powered aircraft. I'm certain he can give you excellent feedback.

[@aero_nwa]

On my rotax 377 (smaller bore 503/447) the gearbox is flipped 180 degrees compared to yours which lets more air from the prop cool the cylinders

[@makotanko2994]

I’m going with something with your fuel lines, maybe the wind is pulling a line and causing it to collapse at high speeds in the air. (Not an airplane dude or mechanic).

[@ginahillenbrand8595]

I notice when you are doing your ground runs you are tail low. The RPM is dropping when the tail is lifted. How is your carbonator float situated. Can the change in geometry be the cause?

[@travisw9071]

Parallel electric fuel pump? (Thinking of Ben Kairys Kolb crash too) Thats my plan with my project anyway.. other than that theres some great comments! 1. Check case for air leaks 2. fuel system re-design 3. Prop pitch more or less (I wanna see this theory!) 4. Get a rotax mechanic recommendation from Hal Stockman

[@Silverloo2525]

repower it man. Don't risk it anymore.

[@ClassyTurtleProductions]

I had a jet ski that would run great when hooked up to a hose but wouldnt run when set in the lake. never figured it out so I sold it. good luck

[@rsbrehm]

I was thinking somehow you are getting a vacuum in your fuel tank. An issue with air flow into the tank as the pump attempts to pull harder on it, causing a vacuum?

[@davidnelson4707]

if the jets have been changed have a look at the venturi in the carb . some carbs can be have the ventures changed