RFguy

Yes, the ATEC Faeta is a very good plane, also. skip, we're talking INDICATED airspeed for this question. My guess is ur talking 115 kts indicated at 18lph (translate to 134 kts at 8.5kfeet) Looking at W&B limits , the Vixxen has a little more utility of you want to carry stuff (but is not as fast as the ATEC)

I've only flown the centre Y stick Vixxen. comfortable.

that's crap skippy, 18 lph with 106 kias indicated is excellent. I dont know any other plane that will make that and land slow. AND carry 100 litres of fuel AND two people and 25kg bags, comfortable cabin width etc. SKippy, please list the airplane you speak of, and its useable load, endurance, cabin width etc

right. good one. so its not that the ULP goes stale, more that it becomes contaminated and changes, and develops unwanted characterists and afterproducts. The single Kwinana pipeline. golly. LOL. Seems the overiding advice is for bowser ULP- test if possible and otherwise immediately. and with AVGAS, we are paying for some care with the fuel. I've still heard plenty of suspect AVGAS stories. So what's the purity like then of "bulkfuel" (ULP) ? I guess you give yourself a fighting chance, depending on the supply chain, how it was bottled etc.

yeah. it's cruise speed is down though. the Vixxen can walk AND chew gum.

anyways ........ discussion is on truth or myth stale ULP. My current thinking is that the ULP becomes contaiminated by aircraft tanks, ethanol, etc

Kevin The LSA airplane I have liked most so far is the Aeroprakt A32 Vixxen. that is quite an impressive airplane. lands in the low 30s, heaps of rudder autho, 106 kts indicated at 18 lph , climbs like a scalded cat (for its category) . 5 hours of endurance and heaps of load capacity. That would be the plane I would buy if I had some coin.

Nice writeup OneTrack . Thanks for the effort on that major treatment.

I bring up the question on compatibility with the detergents, volatiles and additives question because of what I saw last weekend in the banana milkshake fuel drop (same colour as the tank) ! I have seen a fuel drop in same tank type from avgas sitting around in it with no such effect. Onetrack : IYO , How likely is ethanol fuel contamination into the premium unleaded fuel station supply ? If its not ethanol attacking the tank, then what is ?

Generally there is discussion on whether fibreglass tanks are ethanol compatible. I wonder if there is any issue with volatiles and detergent compatibility with said tanks , also. Note bulk fuel you can just buy 95 PULP, without the detergents and other marketing additives. That's probably what I would choose sans extra research.

front more black then rear ? enrichment circuit not slightly on ? I have heard of Bing carb enrichment shafts getting a bit sticky with the rubbers- causing enrichment never to truly disappear and runs hell rich. remove and pollish enrichment shafts and reinstall. No accidental carb heat ? no mouse in the intake ducts ? EGT drop on carb heat applied? EGT does as expected as WOT and as expected (gets hotter ) at cruise throttle ?

IF it was a 19 rego AND you built it you could change it in a heartbeat but being 24 Jabiru have to approve the change. So, that's unlikely..... Yes visiting people makes a difference, that was very obvious after a year of lockdowns... I'm happy to suggest something and document it. IE change to two flap switches, each above each throttle with a relay interlock. But we are getting off the "tell us about your last flight "topic- start another forum topic Jack to continue...

yes RON and MON, and AKI (RON+MON)/2 are different... I read they pushed the RR Merlin up to 30 lbs of boost at sea level on "150 octane".... rotax with its cool heads and moderately coolish bores the ULS (11:1) spec is min RON95 (AKI ~ 91) and 80hp (8:1) is min RON90 / AKI 90. chamber face of the rotax probably is ~ 130C for 110 coolant. Jabiru face is ~ 200C for 170 CHT sensor.

continuing on from above.. have been doing some reading about effects of mixture richness and detonation/preignition "D/PI". - chamber temperature (piston, cylinder, head ) is a strong driver of D/PI. - primarily, assuming the fuel is not junk, the reduction resistance to D/PI for rich mixtures primarily comes from the cooling effect of the rich mixture. Leaner mixtures dont provide the cooling benefit of the cylinder, piston, head, glowing bits... - Some engines , depending on their CC design and shape, and buildup, at some RPMs, will get 'still' regions in the chamber, where despite all the gas flying around , will not get gas flow to some regions, which can become hot spots with gunk. This is more common at low and idle RPM where gas velocities are low . I am sure there are others on this forum that can provide a more nuanced explanation. It is significant that AVGAS provides , for the purposes of describing knock resistance, both lean mixture equiv octane and rich mixture equiv octane (100/130).

you could reach over and operate from other side , its not that far, but my intention is to put DUAL switches with a simple relay interlock. pretty bombproof. Agreed the Vixxen (which I have flown) is very much instant flaps. Jack - you want 'detent' which needs a 3 microswitches (5 is best, 3 is OK) and a couple of relays. IE runs until hits first microswitch, then runs until hits second microswitch. does same in both directions. Microswitches on the actuator arm, or simply small magnets on the indicator cable driving reed relays (as microswitches). The jab still flys pretty well with all the flap out (note there was an SB later 200s that reduced the maximum flap deflection since beyond a certain point all it does is add drag, not lift)

I like the vernier electric flap. I can have a little bit more or a little bit less. and retracting from full flap in a go around is gradual. However !!!!! I am going to move my flap switch currently in that lower awkward centre positon to just above the LH throttle. (dont parallel it, since two reversing switches if they go in opposing positions will blow a fuse!) -- because roll/pitch hand is busy and you dont want to have to lean down there where its exciting.

agreed with you KG and Mike . fresh ULP is the best fuel for a Jabiru. Jabirus have a top end TBO of about 300-400 hours on avgas (without additive) . Anecdotally, adding Decalin Runup at about double the minimum dose reduces avgas buildup 90%.... Another anecdotal- I hear about more stuck rings and buildup issues in engines that are 'babied', and more so the 6 cyl jab, not the 4 cyl, presumably the 6 has plenty of power in hand for most users and users might back off below the 26 lph. I saw a 2200jab (800hours TSO) that was dieseling on shutdown last week. something glowing in the chamber (some of that gunk I guess), and the ULP was old- 75% of it in the 60 litre tank was 6 to 12 months old. the first fuel drop looked like a banana milkshake (same colour as the fibreglass inboard tank) as it hadnt moved in a while. subsequent drops got cleaner until it looked like ULP..... Cold compression was OK, (estimate in the high 60s) , But, it started quickly - kicked first revolution- no issue at all and did runups just fine. cant remember static RPM . suggested to the owner to drain it all, put a fresh tank of avgas is it and see what it does. (still, at 800 hours TSO it needs heads cleaned and rings /ring lands done) Mike, when I get the big jab flying again long XC likely at fill home with ULP95/98 (whatever has the lower RVP) then at destination, go to the bowser and fill to the tabs with avgas before parking.

how did you find landing it? stall horn blowing in the (steepening) flare ? ah I see instructor landed it. we look forward to the next installment.

Yenn : "will cause detonation." does? or will ?

good stuff !. good info for those searching. my MAP question came out because the carbs behave differently when there is any boost going on.... there is a SB about it soemwhere in the rotax doco. make sure you wear your chainmail-mesh suit near the prop..

Hi KG. I think you've interpreted that document incorrectly. mostly it seems to be orientated to engines cold starting and high revving.... They are talking about issues with vaporization at cold temperatures causing lean mixtures at cold startup (like a chainsaw etc revving to life at high revs and suffering pre-ig and detonation) it talks about the mixture going RICH : "Because the fuel carburetors and injectors operate on a volume metering system the higher density means that more fuel is introduced for a given volume of air and so the air fuel ratio is fuel rich. " This does not cause LEAN mixtures in moderately running warm engines. So, stale fuel does NOT cause lean mixtures under normal vaporization (engine warm) conditions. The reduced vapour pressure (stale fuel losing its volatiles) might cause difficulties in getting the correct mixture if the carb is unable to vaporize the mixture tdue to a very cold carby body. In fact the vapour pressure of AVGAS is about~ 40 to 50 kPa versus 60-80 for ULP... and we dont have vapourization problems with AVGAS.

Hi KG I cant see the evidence that 'stale fuel' causes the mixture to be lean anywhere. according to this BP publication, the usage actually riches up.... https://www.bp.com/content/dam/bp/country-sites/en_au/australia/home/products-services/fuels/opal-factsheet-storagehandling.pdf see the air fuel ratio reducing (getting richer)

914s are genuine complex beasts. could be alot of things. What is the MAP during this rough running ?

Hi onetrack. I didnt know 'drum fuel' was different from ' drum fuel' . Open drum. use drum. I assumed the only type of drum fuel is... comes in a drum from the oil company depot. please explain.

suggestion = @RHTRUDDER- please use more descriptive subject titles- this is not email with your mates ! (rather than '914' and 'hash') example "914 rough running 4800-5200rpm in ..... aircraft" "Hash interference on microair radio " etc