LSA specs

I think I may have found my answer. It is located on page 42 of the
June 1990 edition of Sport Aviation. But first, I have found another
source of information. Currently on the EAA website are articles and
spreadsheets written by Mr. Neal Willford, a frequent contributor to
Sport Aviation. His formulas reach the same conclusions of the
formulas suggested by John Kahn. And John Roncz has TWO formulas. The
first one ( spreadsheet) reaches the same conclusions as do those of
John Kahn and Neal Willford. But his SECOND spreadsheet reaches a
conclusion that requires the plane to have more wing area. Here is his
explanation. I'll quote him here....I'm sure EAA won't mind.

" A couple of EAA'ers have noticed that if you plug the same
parameters into the first and second spreadsheets, you get different
answers for wing area required. This is true. The first spreadsheet
calculates wing area based on the AVERAGE lift coefficient of the wing.
The second is more sophisticated, and takes into account the fact that
the wing is not evenly loaded, and will begin to stall when any one
portion of the wing reaches its maximum lift capability. Ideally, you
want the root part of the wing to stall while the aileron part of the
wing still has not begun to stall, so that you can still operate the
ailerons. Thus, you end up adding a bit more wing area so that you can
protect part of your wing while the rest is stalled. You want to use
the AVERAGE lift coefficient of the wing to set your incidence angle,
while you want to use the second spreadsheet to set your wing area."

For this reason, I have always used Mr. Roncz's second spreadsheet to
calculate wing area and I was supposing everyone else was using this
theory also. I'm assuming that if you show the FAA a formula that is
widely used to calculate stall speed, as Mr Kahn and Willford are
using, that's good enough for them. Heck, I'd use the smaller wing too
if I were marketing a plane. As long as the ROC is sufficient, the
plane would be faster, lighter, easier and cheaper to build .

Thank goodness for guys like Neal Willford, John Roncz and Barnaby
Wainfain. What these guys know.......and more importantly, what they
are willing to divulge.

And Mr Wanttaja.....I think I may have found my missing wing area.

Neal


wrote:
Rick,
I really wish I could claim it is my spreadsheet. I've been
referring to the spreadsheets written for Sport Aviation by Jonh Roncz.
Upon looking at his spreadsheets closer, I remembered that he had TWO
of them that calculated stall speeds and they had different results for
stall speeds. He gave an explanation of why there are 2 different stall
speeds but I'll have to go back to the magazines and look it up to find
out exactly why. I think this may be the answer I've been searching
for. I'll try to do this tonite and reply. Thanks

Neal

rpellicciotti wrote:
wrote:
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

There's something very wrong with your spreadsheet. A quick sanity
check shows that a Cessna 172 doesn't have 180 sq feet of wing (it is
174 sq ft) and it carries four people, baggage, 320 pounds of fuel and
still manages a stall speed of 51 knots (no flaps, "R" model), only a
little higher than LSA requirements.

I have flown most all of the S-LSA aircraft and a lot of experimetals
that are LSA compliant. I am fairly confident that their figures are
not exaggerated.

Rick Pellicciotti
LightSportFlying.com