Future Improvements  

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Jabiru Aircraft
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22/05/2018 6:53 am  

Future Improvements   1 year 2 weeks ago#528

·         Harry Smithard

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Hi guys

I'm a proud owner of a J120 and absolutely love this little plane.

I have noticed that the LSA industry is moving towards turbocharged engines and reflexed flaps to get that last bit of speed and altitude performance. Has Jabiru considered some of these options?

I,d be interested to hear everyone's thoughts

Regards
Harry

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Future Improvements1 year 1 week ago#529

·         Doug Smith

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Hi Harry,
Glad to hear you're enjoying the 120... I've a bit of a soft spot for those myself!

The LSA regs in most countries limit the stall speed for the aircraft in the clean (no flap) configuration. Generally speaking there's no way to achieve that sort of stall speed other than to have a thumping big wing... which of course was the intent of the people writing the rules: for a given aircraft weight, the bigger the wing the slower the cruise speed and the slower the speed the lower the energy and the lower the energy the safer the aircraft are in a crash; one of the cornerstones of LSA categories. Of course you can fiddle around the edges with clever wing sections (and wing plans), variable props and reflexing flaps but it's a case of diminishing rewards; I'm reminded of the old racing truism - "How fast do you want to spend?" And that spend might be engine life, payload, real-world practicality, operational complexity, toughness or even just old-fashioned money.

From a technical point of view, reflexing flaps wouldn't work terribly well on a Jabiru wing; used correctly in the right circumstances they would give a handful of knots - but the difference would be pretty small and to date they've not justified the extra complexity and certification work that would be needed. We have looked into different wing sections a few times and there would be better gains to be had there but at the cost of stall handling and ease of rigging.

For now the certification cost of fuel injection (not to mention the cost of the system itself), combined with a higher degree of complexity mean it's not on the immediate agenda. Turbocharging in this category of aircraft doesn't strike me as a great idea due to our generally low operating ceiling (reducing the relevance of high altitude intake pressure normalisation), limited payloads and allergy to complexity.

Best Regards,
Doug.


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