This morning my wife and I drove out to French Valley Airport in Murrieta/Temecula CA. I took my wife for a ride to get some fuel and do a run-up of the engine. It was around 90ºF when I finally made it to the runway so the engine was running a little hot, but all looked good so I ask her to get out and I proceeded to the runway. I slowly added throttle and it responded well so I applied full boost power (115%) and then pulled back on the stick slightly at around 55 knots and just like that I was flying. The handling was very good. Pretty sensitive on the controls so it took a little getting used to. I wanted to fly more, but I noticed the oil temperature was jumping up to around 250ºF and then back down to around 190ºF which seemed a bit odd. My thought was a bad connection or faulty temperature sensor, but I didn’t want to risk damaging the engine so after only one lap in the traffic pattern I set it back down to further investigate.
Also to note was that after driving out to the fuel at the far South end of the field with a stop at another fuel station (that didn’t seem to work) I had some difficulty starting the engine. It cranked and tried too start, but would die. I thought maybe a lack of fuel so I tried adding choke, but no luck. I then took the opposite approach (too much fuel) and turned off the fuel pumps and set the throttle to idle and was able to get it to start after one or two attempts. After a bit of research it seems this is a know issue with the 914 when it’s hot outside. It will start up cold fine and will also start right after shutdown, but if you wait 5-10 minutes then it won’t start very easily. You then need to wait 30-45 minutes to let it cool and it then starts. The theory is that fuel in the carburetor bowls vaporize and there is also fuel vapor in the plenum chamber and that causes the engine to be too rich so it won’t start. Someone noted that turning off the fuel pumps prior to shutdown, letting the engine start to run rough due to lack of fuel and then kill it with the ignition will help minimize the issue. I’ll give it a try sometime and see how it goes.


Getting some AVGAS, there’s no Mogas on the field so using AVGAS for the testing.

Run up is done and all looks good.



A few more photos from the first flight day.
UPDATE 7/29/2022
I had a few issues since the first flight. One was that the oil temperature would be in the normal range (around 210ºF) and then suddenly jump up to over 250ºF in a split second. All other temperatures (EGT, cylinder temps, and oil pressure were perfect). While I’m not that great with engines I know a liquid (oil in this case) can’t actually heat up that fast. I figured it may be a bad connection to the sensor or a bad sensor rather than an actual over temperature issue. In any case I did treat it like it was actual and did what I could to fly while seeing what could be done to keep the temps in the normal range. It was indeed sporadic and not much could be done on the aircraft (lower RPM, more coarse prop setting, etc.) to bring temps down. I opted to keep the flights short where the temperatures were in this high range. I had check teh wiring and all seemed good. I decided to swap the oil temp with one of the cylinder temp sensors since they are the same and to see if the issue would follow. A run of the engine on the ground showed normal temps across the board so issue seemed better, the cylinder temp that I moved the sensor to was also normal. I also decided to disconnect the return line from the oil cooler and force in some oil with a syringe, just to make sure there was plenty of oil in the cooler… it seemed like there was as only a small bit was added until it came back out the thermostat where the line was disconnected. In any case so far the temps seem OK. They go up to around 235ºF after a bit of climbing after take off, but cool after going into cruise.
The other issue I had was the plane to want to bank to the left if I let go of the control stick. If I held pressure (to the right) to neutralize the ailerons the plane flew straight. To me it seemed like something weird with the ailerons. I checked all the rigging and also that the wing angles (wash out) all matched between teh left and right wings. I lowered the left flap about 5mm and it maybe helped a little, but was hard to tell. TAF said to add a trim tab to the right aileron which I really didn’t want to do… I wanted to find the reason for why the left wing was dipping, but reluctantly I added the trim tab and it does fix the problem. So for now I’ll keep it with double sided tape. Maybe something will come to mind to check.
In any case the plane flies very well. I’m getting used to the prop and the noises the plane makes. It’s very responsive and climbs like crazy on take-off.

The trim tab I made for the right aileron. I’ll need to get it painted and then rivet it on, but for now it seems to fix the left roll issue. To the life of me I can’t figure out why it wants to roll to the left though.
UPDATE 8/4/2022
After a few flights I noticed that the fuel pressure would very briefly spike up to around 5.3-5.4 PSI (Normal is 3.6). It would quickly come back down to normal, but didn’t seem right. I also noticed that the fuel pressure would sit around around 4.1 PSI when idling on the ground so I decided to adjust the fuel pressure regular down by 0.5 PSI. The adjustment is done by turning a set screw on the bottom of the regulator (CCW to decrease pressure, CW to increase pressure). So far it seems better. It has only spiked up maybe once or twice on the last 3 flights. It may also be that the UMA differential sensor isn’t working completely accurately when the airbox pressure gets higher. The fuel pressure sits pretty steady at 3.6 PSI while idling, but seems to fluctuate in a wider range when airbox pressure gets high or it could be the regulator over compensating for a change in airbox pressure. I think the engine should have data on the airbox pressure so maybe I can see if there are any sporadic readings of airbox pressure.
UPDATE 8/5/2022
Well the fuel pressure issue remained on my first flight today. For the second flight I figured I should make sure all was good with vacuum connections, etc to the fuel pressure regulator. All seemed good, but I noticed a little white residue around one of the brass fitting into the airbox. I put a wrench on the fitting and it was a bit loose so I tighten a bit so it was snug (there’s probably a proper torque value, but for now will do). This was a fitting installed by teh factory and had torque seal on it so not sure why it was loose. Anyways I figured it wouldn’t really help that much… boy I was wrong. The next flight the fuel pressure was nice and steady on teh ground as usual. I took off and started my climb up to 6000ft into the test area (about 5 miles East of French Valley Airport (F70). Watching the fuel pressure gauge I noticed vert small fluctuation between maybe 3.9 and 4.2 PSI (in flight the pressure seems to go up a bit from 3.6PSI). The whole flight which was a bit over an hour I expected it to jump at least once or twice, but no it stayed in a very small range. I flew 3 more times all about an hour each and same thing so it seems like the large fluctuation in the fuel pressure has been resolved with the tightening of fitting.
I’m still messing with the K factor on the FT-60. I had set it to the default 68000 and was reading very low (3.1gal/hr in cruise at 31 MAP and 5000RPM – 75% power). It’s been a bit difficult to accurately set it because the fuel gauges are so in accurate. They’re only somewhat accurate when parked on the ground so that’s what I’ve been trying to use as a basis for how much fuel was used and then compare that to the fuel calc page on the GDU. I think I’m getting close now though. I set it to 55000 and will test on Sunday. The Garmin manual has a calculation for adjusting it… Corrected K-Factor = ( [G3X reported fuel used] x [previous K-factor] ) / [actual fuel used]. I’ll see if I can accurately determine “actual fuel used” and then this should help get me much closer, then it may just need some small adjustments to get it perfect.
UPDATE 8/7/2022
I’m at 23 hours now so in 2 more hours I need to do my 25 hour inspection which is mainly an oil change and going through the plane and just making sure all is good. I’m going to try to get the 25 hours tomorrow morning so I can start the inspection later in the day and do the oil change on Tuesday and then hopefully get some flying in on Tuesday evening. The plan is to wrap up the 40 hours by Saturday or Sunday and bring the plane home to Torrance. The plane has been flying really great. My #3 EGT is a little high so that would be nice to fix, but it’s within spec so I’m not super worried about it. I think the carburetor is a little lean so I need to verify the placement of the circle in the carburetor. I also have a buzzing sound in the cabin at certain RPMs which I think might be something with the rudder pedals. I sounds like a washer or bolt vibrating. Once again it’s really just an annoyance and nothing major so if I can fix it then I will otherwise it may just be something on the squawk list that will eventually get resolved some day.
One thing that is slightly important is that I have the newer cylinder heads (suffix -01 as they are called), this is identified by having the temperature sensor on the top of the cylinder head rather than on the bottom. I knew this and I read it quite a few times in the Rotax Installation Manual, but it suddenly dawned on me that the newer placement of the cylinder temperature sensors also means that they are not measuring cylinder head temperature, but instead coolant temperature. What this means is a reduction in the max temperature on the sensor gauge reading displayed on the GDU from 275ºF to 248ºF and technically it should read “Coolant Temperature” instead of “CHT”, but since I used the CHT pins on the GEA there’s no way to change the label. I suppose I should move them to one of the Misc Temperature pins that can have a custom label and then label it as “Cylinder 2 Coolant” and “Cylinder 3 Coolant”. The reduction in max temp didn’t do anything since the temperatures where always well below that, but the Rotax Manual stressed that you need to make this change and also notated that they are coolant temperatures and not CHT readings. The later I’m not really sure how I’ll implement. Anyways I thought it was interesting and funny that I have looked at that verbiage and never really caught on above the change in what the sensors are actually measuring.
UPDATE 8/9/2022
Today I did the 25 hour inspection. The inspection has many points (listed in the Sling POH, propeller manual and the Rotax maintenance manual) that I’ve already been checking after each flight, but I did a bit more involved look at a few things like verifying the torque on the spar bolts, the engine mount bolts, etc. I also did a check on the prop for cracking and wear on the trust bearings. The last bit of the inspection was to go over the engine and do an oil change. Everything looked good and the oil change went fine. The only issues that I found was that the water cooler must have been touching the exhaust so it melted a bit of the top and a few fins. I adjusted it and there’s now about 1/2-3/4″ of clearance which isn’t great, but should keep it from touching. I’ve also been checking it before each flight to make sure it’s not any worse. I’ll do a proper fix when I get the plane back home in a few days. The other thing to note was that looking at all the plugs, most were a sooty black which means that the engine is running too rich. I don’t think there is a simple mixture adjustment on the carbs so I’ll have to look into how that is adjusted. This could also have happened prior to my setting up the carbs and doing the carb sync, but most likely not. I cleaned the plugs so I should be able to find that out at the 50 hour.
UPDATE 8/12/2022
The past few days was just getting time in the plane and making sure all was working as expected. Today marks 40.2 hours of time on the plane so I made my log book entry and will be flying the plane back on Sunday to Torrance. I have a few remaining issues, but they are mostly just annoyances and not critical to safety. First issue is that the oil temperature slowly climbs up to 238-240ºF on climb out over around 3000ft. The work around has been to set the propeller to 5000 RPM (cruise), pull the throttle to 31 MAP and lower the nose a little to get 80-85 KIAS. The oil temp then come down pretty quick, all other temps are great. After it reaches normal I haven’t seen any issue with climbs even at climb RPM (5500) so it’s a bit odd. I may try a new oil thermostat to see if maybe this one is not opening all the way. Second issue is that the fuel pressure seems to fluctuate. I thought I had this fixed, but it has come back up a few times since. When it’s behaving I see very steady press on the ground and once up to cruising altitude it fluctuations a bit between 3.5 and 4.2 (and typically hangs at 4.1) which is fine. When it gets crazy it will rise to 5.5 and then drop to 2.3 and then bounce around between that for a bit then settle back down. Since the UMA sensor is calculating the difference between airbox and actual fuel line pressure then it could be any of those 2 things that is fluctuating and causing the problem (or it could be an issue with the sensor itself). It may be heat related as well since it seems to happen after the plane has been flown a bit. So to figure this out I’ll have to rig up a sensor to look at airbox pressure and another to look at fuel line pressure and then when the UMA starts fluctuating I can see what exactly what is causing the fluctuation. I’ve eliminated the fuel pump and fuel tanks since it doesn’t matter which one I’m on when the fluctuation starts. I’ll also take look at the gascolator because that is common between both fuel feeds, maybe there’s some debris in there. Last issue is that the PDF heading sometimes shows yellow and says “miscomp”. SO far it’s only happened in a steep turn and on a fairly rapid descent (1500-2000FPM). I emailed G3 experts and they said it’s because the pitch roll is off on the ADHRS. The G5 doesn’t have the issue so I think that may be the case. I think that when I added in the backing plate to the ADHRS to get it to pass the vibration test I may have forgotten to redo the pitch/roll calibration or I did a crappy job of it. So I’ll just level the plane and do the calibration again which also means doing the compass (magnetometer) calibration as well.