Mike Gearon

Still leaves me curious what Rotax rebuilders are finding on engine pull downs that makes some favor 100ll over mogas. My reading says without decalin additive 100ll is going to cause valve seat problems, sludge in oil and possibly detonation. Detonation obviously being a major problem. Decalin converts the lead, why one wonders do some LAME recommend 100LL in a rotax 912 and why isn’t decalin recommended as an additive if so. What experiences are they having that informs this recommendation? Roger Lee again responding to a question on decalin and Rotax response. I think I’ll just make Roger my Rotax guru and leave it at that seeing as he always has his hands on these engines insides. It isn't approved in writing. I classes and verbally they say okay. It's the Austrian's that would have to take it to task and run hundreds if not a thousand hours of test before they would put it in writing. It isn't a priority for them. In the US and other parts of the world real life experience has shown and proved Decalin isn't an issue and works to help scavenge lead deposits. Decalin like TCP is absolutely not a cure all for lead deposits. It only reduces the lead build up. Without these scavengers lead would build up worse than with their use. Anyone that has torn into a Rotax engine using leaded fuel can see the deposits instantly. If it cured all the lead problems then many GA aircraft using these products wouldn't have lead issues and owners like us wouldn't have to have 25 hr. oil changes because the scavengers would have completely removed the lead, but we all know that isn't the case. Decalin and TCP only reduce lead build up and by changing the lead additive TEL from an oxide to a phosphate. Cut and paste: "What is TCP Fuel Treatment and what does it do? TCP stands for tricresyl phosphate which is an effective tetraethyl lead (TEL) scavenger. During the combustion process, TCP chemically converts the TEL to lead phosphate, which is less conductive, thereby reducing spark plug fouling. TCP use does not impact the power provided by leaded fuel."

Okay 5200rpm seems to be the sweet spot for cruise based on what I’ve been reading and below and maybe mentioned by one or two pilots here. Bold at bottom via Roger Lee the most definitive. 5200 combining fuel economy with engine at favourable RPM for longevity. Rotax bulletin. https://legacy.rotaxowner.com/si_tb_info/serviceletter/sl-912-016.pdf Rotax bulletin 3.1.2 No WOT continuous below 5200 RPM and that’s what your ear/ feel is telling you when it labours down at 5000rpm WOT I was trying some 5000 RPM low MAP with consideration to fuel economy yesterday. Had my own personal runway rain cloud for landing so didn’t get a lot of time to play around. Pics yesterday below. Flying to commute so have to cop cross winds and rain within reason. Seems to be fairly dramatic drop in fuel consumption. 130kn 5400 rpm 27 map is some 22lph. Dropping map back to 20 and 110kn around 12 lph… I’ll test this more. Seems too big a drop in lph. 390nm trip and get there in 3 hours/ 66l or 390nm trip in approx 3 1/2 hours for 36l and save some 60-70 dollars or stretch a trip to avoid a refuel and get there at the same time with less dollars spent. Maybe… This provides a reason to run 5000RPM range lower MAP. However, is it easier on the engine based on Rotax 2000 hour tests? Don’t know. This lifted from Robert Lee in CTflier 2012. The Rotax 912 series engine was not designed to run under 5000 rpm. It was specially designed to run in the mid 5000's. Running in the 4000's will cause excessive vibration (no you can't feel it) to the engine and more heat. The jetting in the carbs is set up to run in the 5000's. Running in the 4000's with 100LL will absolutely cause more leading and faster. If you run a steady diet of 100LL run the engine around 5300-5400 in cruise to help keep the lead blown out. We are not talking about 4000 rpm to land or slow to look at something. That is intermittent. We are talking the most used or sustained throttle position that is important to the engine. Set your WOT to be around 5500-5700 for a ground adjustable prop (closer to 5600 is better). Use a cruise rpm of 5100-5400 rpm. Your Rotax 912 can really run at 5500 rpm all day 24/7 if you wanted. That said I see no reason to run at 5500 24/7 just because it burns more fuel, you don't go that much faster than 5200 or so and there is a little more wear at the higher rpms if it is a 24/7 run. My 2006 CTSW cruises around 135 mph at 5100-5200 depending on the days conditions. The 6 CT's at my field I have set up are about the same and yes they can go faster with more throttle in cruise. (i.e.5500 rpm) Can a CT fly faster at 5700 rpm WOT compared to 5500 rpm, yes. IF you set the prop to get 5700 rpm at your average altitude then it will run better at the higher altitudes because it will be able to get more rpm up high verses too much pitch causing it to bog down some at the higher altitudes due to loss of HP and torque to turn the prop at that particular pitch setting. The rule of thumb is a 3% loss of HP for every 1K ft. This from another forum. I guess I will share a few more tidbits about the Rotax that you won't find in print. In the manual it says to only run 5500-5800 rpm for up to 5 minutes. In truth it could run 5800 all day. It could actually hit 6200 rpm and not cause any damage. The engine probably won't float a valve until around 7000 rpm. Rotax set the 5500-5800 rpm and time limit as a liability safety margin. So now you can see that it was designed for higher rpms and running way down in the 4000's isn't great. That's almost like running a 3 speed manual shift car in 3rd. gear at 15 mph. Not quite that bad, but it makes my point.http://ctflier.com/public/style_emoticons/default/wink.gif From Roger Lee some 6 years back…. Hi Claus, I see you have a 1680mm (66 inch prop) ground adjustable prop. WOT means Wide Open Throttle. Since you do have a ground adjustable prop you usually want a prop pitch set to get a good overall balance performance. If anyone is over pitched there are ZERO redeeming qualities with over pitching. You lose out on everything. Typically a good rpm be to be setup for for a balanced performance envelope is 5600-5650 rpm at WOT (wide open throttle) at your average altitude in level flight. A prop getting 5200 on take seems a little under pitched and would get upwards of 5800 at WOT in level flight. Nothing really wrong with that. That gives you a good climb prop, but you would lose some speed and fuel economy. In other words you'll have to give it more throttle and rpm to do a decent cruise speed which in turn would eat up more fuel. Most guys are around 4950-5000 rpm at takeoff and that usually puts them in the 5600 range, Adding a little pitch back into the prop will also increase temps a small amount. Probably not much in your case. Your engine really isn't designed to run its life in cruise at 4500-4800 rpm. It is better to be over 5000 for cruise. Most of the guys I know here have there 912iS prop set up to get that 5600-5650 rpm and cruise around 5100-5400 with the average being 5200. Low cruise rpms is also causing you low engine temps.

Started writing the question with map and I changed to WOT. The strong opinions must be coming from somewhere and you’d think it would be the rebuilders who are aware of pilot habits. Mine at 2000 hours is going to be the 5400rpm WOT guy. The other obviously a 5000rpm with a known throttle habit/ setting that’s prob also less than WOT

Can I ask if we have anyone willing to discuss their experience of dozens of Rotax 912 rebuilds that have known operational conditions of… 4900/ 5000 rpm cruise WOT versus 5300-5450 rpm WOT Cross country pilots as one point fo comparison and school aircraft as another to compare equally. Same goes for Avgas versus Mogas. Proof must be in the eyes and measurements of the guys actually doing this. I lean on Robert Lee in USA as the guy doing this for decades. It’s 5400rpm approx cruise and Mogas. Anything else as detrimental. However, seeing as there is conjecture I’d really like to have more data based input.

Enjoying learning how your E Prop testing goes. 3kn is significant. 105 to 108 means efficiency gains for fuel economy even if you don’t need to get somewhere faster or of course when dealing with rough air. Rotax RPM also to be an endless debate at the 5000 range and the 5400RPM. My local Tooradin and Tyabb mob are for the better part firmly in the 5000 26 map camp. I was advised by Michael Coates the ex Pipistrel dealer to run the higher rpm because the rotax is labouring at 5k 26 map. It certainly sounds that way as you adjust the CSU back if all the way from 5800 take off to 5000k after climb out. Also. This guy has huge experience.…. https://www.rotax-owner.com/en/912-914-technical-questions/5405-cruise-rpm-in-912-motor

Thanks. I have thought of this. I see on the forum Mark will start his S21 when current project complete. I wish he was ahead. He’s quite comprehensive and we reviewed his S21 unpack method when doing our own. Helpful! There are I believe 20 plus S21 kits in Australia and at least a few flying. I suspect most of the post activity is taking place on Facebook Rans forums Australia and USA. I’ll look into doing both here and the book. 😀

I was considered a “young one” 12 years ago and sought after for the fire brigade on French Island. Now I’m dads army old and look keenly on the 50 y.o. + newer island residents for the CFA. You’re right though. We bring experience to a project. Move more carefully and thoughtfully with past experience in mind and get it done just as quick and maybe better. Here is an example. Front end loader drops logs onto the frame then as cut they fall into place. Wood frame placed at the garage and then picked up and lifted into the fireplace. Actually feels like I cheated myself out of a job.

I was flying in Alaska with an old bush pilot mid 2022. We headed up a narrow pass and remembering YouTube’s of pilots crashing in the Rockies as they lost ability to climb in mountain passes. I said “we don’t have a choice here do we, can’t turn around” We then did. A steep descending 180 degree turn around in a float plane!

Hey, that’s a great idea! I’ve been flying to the other pilot/ runway on French island every few days. It’s 15 min drive or 2 minutes flying. Of course we fly it! I take off and pretty much same. 50ft up I’m turning toward the east and not even over the bay. Had not occurred to me that this is also setting up EFATO back to a paddock instead of a bay! It will “occur” to me from now on! Nic and I flying today on S21 build errands. I think we will do some slow flying up high as you’ve indicated. See and seen! I always have the little Uavionics on now and iPad or phone open on avplan. Can end up throwing out 3 signals. The aircrafts transponder and iPhone and iPad if I’ve accidentally left avplan open on iPad. I expect to fly to Dubbo next week delivering Nynja to a buyer. Not far from you. Nic will follow and we return in the Blackshape. Well, Nic will take off way later. I’ll prob cruise up at 100kn and Nic is 145-150kn in the tandem Blackshape with retractable gear.

Picked up the rans S21 kit at Tooradin. Then the barge blew an engine. We made it back on last trip for at least a month very lucky. Build will be in a B&B we haven’t finished as in pic here. Pic of tv showing YouTube S21 build has island resident Steve to right of tv. I had no idea he was retired airforce and specialised in skins until he was watching the video with us. A great resource! Always amazed at our tiny 100 plus island population and their past lives.

I think of this problem like learning to ski. You really don’t want to push the weight into the front of the ski. It is so counterintuitive to push your weight forward down the slope you just finished tumbling down and now you’re trying again. Same happens again on your first black run steep slope. Some 300 hours plus hours in my muscle memory is stick forward and a glance at the ball just to double check nose is where it should be. I tried a 300ft turn emergency turn back in the Nynja some months back. In gliders you tap the altitude at 200ft and verbalise “ 200ft and safe to turn back to runway. At least in USA that’s what you do or fail checkride. Over the bay and I was bloody surprised to find the rudder tightening like it had a mind of its own. I was keeping the nose pointed well down for speed first. Still, I was shocked to see the ball well outside. Exactly the stuff we are taught to never do. Pulled it back to coordinated flight and never in danger. Still, a shock! No way would I have made it back to the beach and in a real emergency flying performance would I expect be significantly downgraded. Simple rules. Aviate, navigate… aviate it first at best glide and coordinated turn then navigate without a fixation on having to get to best landing site. I have no idea how often other pilots practise scenarios. I recite abort point and land ahead each flight as I was taught. I probably don’t practise enough in flight scenarios and never practised a BRS pull…. Next flight!

Same. I’m using an IPad. All works the same..I’d started to write a similar post then wasn’t sure exactly what F10 was asking because I noticed previous quotes where this was deftly handled…. Then, I went to delete and found you can’t so just removed my text then noticed you’d gone grrr in another thread about inability to delete. 😀 Yeah, it’d be nice to have a few minutes to delete. Understood though, the remnants remain in peoples email inboxes.

I flew home last light and yeah, you can see the dirty sky there. I’m burning off (pic below as I heaped the wood up after landing) and last night probably contributed to my dirty flying air for today. Should have RAA retractable endorsement this week if all goes to plan and CASA conversion from FAA still involves more hurdle jumping including my English language proficiency check. I’ve been trying to perfect English for 63 years now so should pass. Clip,was taken with iPhone in one hand and I’m surprised how close the fence and tea tree look. Feels higher. Pretty standard landing without a headwind. With headwind the aircraft is stopped by the shed/ hangar. Without it take a while to pull up on the downhill. I let it dissipate as much energy as possible with elevator all the way up and delay gently braking as long as possible. Tail wheel is the answer! Rans S21, Sinus Flex motor glider (long/ short wing interchange is 5 minutes 1 bolt each) and the quicksilver. Virus SW 121 will likely be sold when the tail wheel Pipistrel arrives later this year from USA. I’ll miss the Nynja……. It’s such a simple easy aircraft to fly. Plenty of nibbles at 48k but no takers yet. Wouldn’t want to be in aircraft sales. Sinus long wing tail wheel sold twice now and yet I still own it! IMG_0371.MOV

Rans S21 with 220hp UL520 and Garmin G3X. Stall 33kn and cruise 135kn with the 180hp so 200hp-220hp Ul520 will push it along a little faster. Particularly if we go the turbo 220hp option. VNE 187Kn so maybe a spread of 33kn stall to 150kn cruise. Take off is genuine STOL around 50ft or so. It’ll look a lot like this pic but maybe green main Color. Can’t decide. we have kit and waiting on new hangar build August/ September then start in. I’m mechanical and my 50/50 build partner is an electrics/ electronics whiz so it should work out 🙂 Visited Rans factory and their stand at OSH Kosh last year and plan a return this year to attend a heap of build forums. Huge knowledge input at OSH Kosh. Kit builder heaven and heaps of forums on safe flying.

I’ve just found this thread via Blueadventures and the E Prop. Didn’t realise you are the Australian agent. I was viewing the whole e prop install with some slight skepticism. Seemed too good to be true and I’d remembered the stolspeed prop comparison and mentioned that…..That was the extent of my knowledge until coming across this thread. Now I see what it’s all about. I fly two current aircraft and for some reason the Rotax gearbox clunk is more pronounced in the Nynja with Bolly. I actively hold the throttle back against stop with just left mag then shut down to minimise this. MT CSU prop without researching it could be lighter, there is no noticeable clunk. So, I get the lighter aspect from just this point of view. Then noise and vibration. Pipistrel is vastly quieter because of slippery frame. It’s like the difference of turning on noise cancelling. So, anything that can reduce the noise level is a huge bonus. Vibration is probably equal between both aircraft. Noticeable and of course reduced vibration equals more mechanically and possibly more people friendly/ reduced fatigue. CSU. I see you mention that above. I’ve not read the whole thread to this point. Will continue but wish to mention my experience with CSU in Pipistrel and upcoming S21 build. CSU in Pipistrel. I set it full fine for take off 5800rpm and pull the flaps and throttle back by say quarter quadrant 26 MAP and set 5400 rpm at around 100ft AGL. 1100-1200fpm climb out at 80kn. Cruise 130-135kn 5400 rpm 26 MAP. Reality is I could set it at 5400 on the ground just like the Nynja and never think about it again. I set it full fine for landing as POH but for a go around I’d be just as happy at the 5400rpm pitch and one less thing to think about climbing out and the go around indicates something went wrong snd you have a bit to think about deal with at that point. This brings me to the S21. We’ve (my build partner and I) decided to go UL520 and probably the turbo 220hp. UL USA say the turbo fits. If it was a choice between CSU benefits for tuning climb out and cruise or turbo then the turbo wins every time. It’s doing a way better job of dealing with air density, altitude and cruise performance as well of course as extra grunt on the climb out. Cost and complexity differences between turbo and CSU. I’m sure that’s a whole topic on its own. At first glance I’d say the turbo is less complex than a CSU and similar or less cost. I’m becoming an e prop fan. Pity they don’t make them for the higher hp aircraft!

At the end of the day it’s climb out FPM and cruise TAS showing consistently better figures over the old prop. Sounds like this is what is going on.

I was concerned looking at that claim of 130mph/ 113kn and how that could be achieved. Reviewed the extensive tests JG has done. I’ll list them here. E prop at the time was very similar. They’ve obviously been developing since.

I think it’s left stick preceding the right wing drop. FullSizeRender.MOV IMG_0355.MOV IMG_0355.MOV

5500rpm and 130mph or in our flying language……113knots…. I’ve left the Nynja exactly as Vince had the Boly ground adjust prop set. Climbs out nicely and WOT 5400-5500rpm is a very consistent 105kn.

Found the little USB. Testing on ferry. Probably too windy to fly later today and ferry captain is warning me we may not return from Phillip island this morning due to forecast 30kn winds. very interesting to see the green from Uavionics more up to date than the blue from Avplan. 700ft higher. 1.3nm further along on a course change. That alone is worth the wires and extra bits.

I’ve just noticed the other clever thing Harry from Iceland has done. The stock Skyranger throttle setup is in the way for entry/ egress. It’s easily bumped wide open by yourself or passengers and I’m probably not alone in finding it doesn’t hold TWO on it’s own. Harry has it solved. Throttle is retained at idle and isn’t in the way and can’t be bumped open. Throttle arm weight is downward and probably as such nicely balanced. Either that or he pegs it wide open. 😳 I’m pretty sure it’s idle. it’s probably the result of those 24 hour days and 24 hour nights and lots of thinking time. I’ve been to Iceland. Nice place to visit but….

So, that’s what’s going on! I was trying to work out why an obviously experienced pilot was asking! I’d love to have that last playback feature. A feature I really like on the Garmin is dual monitoring. Example, I was coming into King Island on Melbourne Center and monitoring King Island CTAF. Heard them talking about me the unverified VFR and then heard one of the 2 pilots also converging on King island at the same ETA. I’d have been way less informed without that feature. Because of dual monitoring I was able to have a site picture of the 2 transport aircraft and they were already talking about who’d be number one and two. I knew my ETA was the same and Melbourne was also telling the 2 I was same ETA. Made it really easy to let them know on CTAF that I’d meander down the coast at 80-90kn and let them go about their commercial business and tourist me would enjoy the view. I’d say to be completely honest it’s a very appropriate thread. I fly most days and 2 aircraft on CTAF are pretty easy. It gets more and more difficult as you add them. Weekend or monthly flights and you’d expect to be a bit rusty! I’m adding ADSB in as mentioned if I can find the f$#@ng little USB stick thing with a sucker on end. My wife claims to have not tidied it up! Add GoPros with headset wires, iPhone, extra phone with Telstra chip for country trips and IPad along with backup batteries for head set and wires to power stuff as needed and it makes you want to fly the quicksilver. Simple seat of the pants flying with a yaw string and airspeed indicator. Low, slow fun flying with the wind full on in your face and practically 360 degree vision.

That’s so detailed. He’s done an extraordinary job including the LED lights for flap indication on dash. radio up high has given him space on the dash for iPhone and iPad. Brilliant! I like the pilot and passenger heaters. Prob not needed in Australia if we aren’t flying winter in southern states. Just more water hoses and electrics to have potential problems. Iceland different story! I heard him mention thermostat. I have no idea if we have water or oil thermostats in 912. I just know they take ages to heat up and I do runups facing away from wind and opposite to what I’d do in air cooled engines. Learned to start the engine before doing anything else. Start then close door, seat belts and checks. Even then it’s just wait and wait for temp before takeoff.

Yesterday Nic and I flew to Tooradin on a shopping mission. During return we spotted a 3 day old fire flared up again and I called it in to our local CFA. Landed, drove to intercept the fire truck and 30 minutes later we were mopping up. Good public relations on French Island from that fire spotting. The fire was very close to escaping into bush to the west. There are occasionally aircraft that really abuse the privilege of the French Island training area and The 2 pilots based on the island were being blamed. For example my near neighbour recently asked why I had circled their house about 6 times. Was I trying to intimidate them? I felt terrible for her and apologised on behalf of the pilots responsible. Pics. Spotted the fire. 2 minutes later our ground crew had hangar doors and farm gates sorted and not long after that on scene! 3 hours later and dark and we were still spotting red glows and mopping up.