Actually, the CAFE numbers come out a little better than what Van
states as the performance figures for the RV-6. And the stall speeds
that Van posts are pretty much what J. Roncz predicts in his
spreadsheets, even though Van's are a bit better. But then again Van's
planes may be operating at a slightly higher CL than what Roncz uses.
Which leads me to believe that the spreadsheets are quite accurate.

This is why I'm having a hard time believing that the Sonex aircraft
meet the LSA rules as written. Even at the lightest version of their
aircraft ( Jabiru 2200 power and flown solo and no fuel ) the plane
would have a hard time meeting the stall requirements of LSA which
require max gross wt. figures with a 51 mph stall speed.

And my intention is to fully understand the LSA rules, not "down" the
Sonex aircraft or the people behind it. I believe the Sonex and its
people to be top notch, as do many others, evidenced by how many are
flying and continue to be built. They are reasonally priced,
economical to operate and good "all around" performers for their
power. And from what I have seen, several of the other "popular" LSA's
would have a hard time meeting the LSA specs. as I see them written.

Neal

Kyle Boatright wrote:
wrote in message
ps.com...
Could someone clarify something for me concerning LSA's. The websites
that have the detailed LSA aircraft limitations listed say that the
plane must have a maximum stalling speed of 51 mph at the maximum gross
takeoff weight WITHOUT the use of high lift devices.

I plugged the numbers for a Sonex into the John Roncz spreadsheets. (
Max Gross TOW of 1150 lbs, stall of 46 mph ) and it reports that I need
a wing area of 180 sq. feet. The Sonex only has 98 square feet of
wing. What am I missing?

Thanks
Neal

I *think* high lift devices are considered to be Fowler flaps, slats, slots,
etc. Everything I can find on the internet indicates that conventional
hinged flaps are allowed on LSA's.

If you look at something with a similar planform, more weight and more wing
area (an RV-6), you'll find that the CAFE foundation measured a flaps down
stall speed of 52 mph for an RV-6a, which is an indicator that a Sonex could
meet the 51 mph regulation.

http://cafefoundation.org/v2/pdf/RV-...inal%20APR.pdf

KB