skippydiesel

My Sonex started its life in Gippsland - seems to be a hotbed of Sonex/Rotax.

Very nice Blue, I would point out that: Sonex have only very recently "recognised" Rotax 9 engines for installation in their aircraft, so I wonder how good their data is? To the best of my knowledge Sonex do not have or ever had, a Rotax powered airframe, with which to arrive at the above figures. Sonex are so slow to adopt Rotax, that they are only now coming up with a suitable engine mount for future kits My Sonex Legacy/Rotax 912ULS will easily achieve (Max load): 1500 fpm in Climb Out, 80-100 knots, - I am still working on best climb speed. 130 + Knot True (150 mph) at 3000 ft, 5200 rpm, @ 15L/hr 147 knots indicated 150 + knots (173 mph) at 5450 rpm, 5500 ft, still working on the fuel but believe its 18-19L/hr If you are wondering about the accuracy of the above air speeds,- the pitot/gauge system has been independently tested and a range of errors noted: Indicated/Corrected Air Speeds in Knots 40/48.5, 60/66, 100/103, 120/123 140/142, 150/152, 165/166 PS - For me, speed itself, is only an indicator of airframe efficiency, when powered by the same/competing engines. Sonex recognise engines to 130 hp however it must be obvious to all, that while the speed may be greater, with such an engine, so is the fuel consumed to arrive at that speed. I want to travel in my Sonex , so fuel consumed per hour for a given speed will determine my power setting for near best range - I think my Rotax will do this for me. Do you think the tendency of US small aircraft manufacturers, to express their aircraft performance, in mph might be because it always looks better than in Knots???😈

RFguy, "The discussion is aircraft invariant" This phrase intrigued me - what is the meaning of ".....invariant"?? Looked it up - means not changing. So your statement could be read as - The discussion is aircraft not changing. Tad cryptic don't you think? Being short of what few brain cells I was born with, I still do not understand. Please explain?

From poor memory (will need to check on next flight) MAP around 22"

So - for one comment, within many, you refuse to engage - Me thinks that puts all your commentary in doubt😈 I think you will find that Rotax 5-5300 rpm is about 75% power.

RF , Your logical presentation is heading in the right direction however some possible holes (I stand to be corrected): "Prop spins a bit slower on the Rotax, that's worth a few % in efficiency. The Rotax prop spins a lot slower (a little over 2100 rpm at 75% cruise, to the Jab (guess) around 2700 rpm) and is not only more efficient it tends to be quieter - important in Europe now and in Australia in the future (fly neighbourly) Rotax torque 128 NM @5000 rpm gives it an advantage in TO/Climb out. Rotax runs lean in cruise. Jab runs compatratively rich, costing perhaps 5 to 10% in fuel " - My current Rotax aircraft seems to be delivering about 15 L/hr, 5200 rpm at 130 knots indicated - how would a Jab compare? AT 2000 hours, Rotax has had a gearbox service @ 1000h maybe about a grand, - 1200 hrs if run on ULP Both have had two sets of plugs. - will need to check but I think Rotax recomend 200 hr/set of plugs = 10 sets Both have had 1 set of hoses - Rotax rubbers replaced every 5 years of service and likely at least twice as much hose involved - must be more costly than Jab Both have had 40 x oil and filter changes. - Rotax recomend an oil change very 100 hrs (when run on ULP) so this would be 20 oil changes, compared with Jab X 80? (at today's prices, this is a difference of about $2,000) The rotax fuel consumption is worth a bit, at 2000 hours, youve probably put 1 litres more per hour into the 2200 = 2000 litres = $4000 more ! and proportionaly more for the 3300 6 cylinder.$6000. - seems to me your fuel consumption for the Jab is a tad optimistic - More likely up to 5 l/hr difference (could easily be a 10,000L difference or $23K today, for 98 RON). My feeling is the 2200 you end up costing about the same as the rotax, Nice thought and the 3300 end up costing quite alot more - but you have a far more powerful engine that can do 115 hp all day. True but this does not take into account the higher torque delivered by the Rotax at 5-5200rpm which I assume means a more efficient prop delivering the same/more thrust at 75% cruise.. Note: I have focused on the Rotax 912ULS , as I have no experience with the 912UL, comparing it with the little I understand of the Jab 3300

I do not dismiss other opinions - where I have something to contribute, I do. Scathing - for sure! where such a response is warranted. Much depends on the logical progression of the writers case - if it doesn't sound right, it possibly isn't. If there are large gaps/omissions, the writer is either poorly informed or so biased he/she is unwilling to acknowledge information that does not support their assertions, alongside those that do ie not a balanced argument. It is a shame that our debates, so often seem to, degenerate into personal attach.

Faith is a wonderful thing. Those that have it, are often blind to any other reality and so happy in their world. 😈

I note that my questions/observations have neither been answered or challenged. It seem a little unbalanced that I can be taken to task over a spelling mistake but when I ask some searching questions/observations regarding statements made, I am somehow "having a go at a few people lately"😈

Thanks for the spelling lesson. I have made my apology.

I have no idea what you are referring to - please elaborate. How is this" having a go"????

I have no idea what you are referring to - please elaborate.