"Handling Upgrade" for "Pre-D Model J230s"?

·         John Womer

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I own and fly a 2010 J230-SP (assembled by Jabiru USA from Australian "kit").

Having started my flight training in a Diamond DA-40F where the rudder pedals are basically used as footrests in flight, it took me a little while to develop my ""stick and rudder" skills. Once I did, I fell in love with the way my plane handles.

The J230-D arrived in the U.S.A. a couple of years ago (manufactured by Jabiru South Africa with avionics and other finishing touches done by Jabiru USA). A big selling point of the new model is its "aerodynamic enhancement to the design of the vertical tail surfaces for nearly-effortless coordinated handling" in addition to better directional stability.

A while back, while doing my regular monthly check for manual updates, service bulletins, and advisories on the Jabiru USA and Jabiru Australia websites, I was interested to read about the upgrades to improve the handling of the J170s (those not fitted with the "fat tail fin").

I understand that the longer tail boom on the J2xx/4xx series provides greater inherent directional stability than the J170, but I'm curious... Has there be any thought to trying a larger ventral fin on pre-D Model J230s to see whether it would improve their directional stability and reduce rudder inputs as well?

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2010 J230-SP

·         Doug Smith

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Hi John,
I'm sure there's been *some* thought put into it but it never went any further than casual "what if" sessions.

It is a balance: as you increase the fixed area of the tail your directional stability tends to improve but unless you increase rudder size proportionally the power of the rudder will decrease. This can be a problem, particularly in crosswind take-off or landings where the big tail can cause the plane to "weather cock" into the wind and run off the runway if the rudder isn't big enough. Bigger tail feathers mean more drag too and, ultimately an efficient aeroplane demands that you reduce losses like that as much as possible.

Last but not least, we like that way it flies now!

Best Regards,
Doug.