LSA specs [Archive] - AviationBanter

September 23rd 06, 05:34 PM

wrote in news:1159025421.579979.9980
@i42g2000cwa.googlegroups.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
>

Take a real good look at the profile of the Sonex airframe.... looks
suspiciously like an airfoil doesnt it???

--
-- ET >:-)

"A common mistake people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools."---- Douglas Adams

Kyle Boatright

September 23rd 06, 06:01 PM

> 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-6A%20Final%20APR.pdf

KB

.Blueskies.

September 23rd 06, 06:21 PM

Any flap is considered a high lift device. An LSA can have flaps, but the stall speed clean is what is the determining
factor for the 45 knot (52MPH) limit. Seems that the powers that be do not want to require pilots to operate any but the
most basic flight and engine controls. Even a LSA 'amphib' with wheels on the floats cannot change the configuration
while in flight - the wheels need to be fixed either extended (for land takeoff and landing) or retracted for water
takeoff and 'landing'.

"Kyle Boatright" > wrote in message . ..
:
: > 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-6A%20Final%20APR.pdf
:
: KB
:
:

Montblack[_1_]

September 23rd 06, 06:41 PM

("Kyle Boatright" wrote)
> 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-6A%20Final%20APR.pdf

Interesting site!

http://cafefoundation.org/v2/research_aprs.php
"Aircraft Performance Reports"

(From CAFE Home page)
For over 25 years the aviation enthusiasts at the (C)omparative (A)ircraft
(F)light (E)fficiency Foundation have been carefully measuring personal
aircraft performance with innovations in flight testing. Their passion for
this stems from the thrill of working with state-of-the-art aircraft and the
geniuses who create them.

Montblack

Paul Tomblin

September 23rd 06, 06:44 PM

In a previous article, ".Blueskies." > said:
>most basic flight and engine controls. Even a LSA 'amphib' with wheels
>on the floats cannot change the configuration
>while in flight - the wheels need to be fixed either extended (for land
>takeoff and landing) or retracted for water
>takeoff and 'landing'.

The makers of one flying-boat style LSA (memory says Mermaid or Merlin or
something like that) have gotten a waiver that allows Light Sport pilots
to get special training to operate the gear.

--
Paul Tomblin > http://xcski.com/blogs/pt/
I got accused of being humorless last night. I'm considering quoting
Lieutenant Commander Data: "Perhaps the joke was not funny."
-- Alan Rosenthal

[email protected]

September 23rd 06, 08:24 PM

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-6A%20Final%20APR.pdf
>
> KB

September 23rd 06, 09:41 PM

wrote in
ups.com:

> 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
>

Which part of my post that indicated the fuselage of the Sonex is a
lifting body confused you??? Steve Wittman is said to have won a bet or
two with the same issue on the Tailwind. I have not done it, but plug
the same numbers in for the Tailwind and see what pops out.

--
-- ET >:-)

"A common mistake people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools."---- Douglas Adams

Kyle Boatright

September 23rd 06, 10:27 PM

"ET" > wrote in message
...
> wrote in
> ups.com:

<<<snip>>>

> Which part of my post that indicated the fuselage of the Sonex is a
> lifting body confused you??? Steve Wittman is said to have won a bet or
> two with the same issue on the Tailwind. I have not done it, but plug
> the same numbers in for the Tailwind and see what pops out.
>
> --
> -- ET >:-)
>
> "A common mistake people make when trying to design something
> completely foolproof is to underestimate the ingenuity of complete
> fools."---- Douglas Adams

Can you find a credible test of the Tailwind's stall speed on the web? I've
looked for one, but without success. The CAFE report in the "members"
section of the EAA site doesn't show the stall speed, although the text
discusses stall speed testing. I seem to remember that Tailwinds with the
stock pitot/static system have an inaccurate ASI at low speeds, showing much
lower airspeed than actual.

A buddy who owned a Tailwind described it as a fast airplane, but with
"mean" low speed characteristics.

I don't buy into the theory that Tailwinds or Soni (?) gain much lift from
the fuselage. The aspect ratio of a fuselage is too small to generate a lot
of lift.

KB

[email protected]

September 23rd 06, 10:31 PM

No part confused me. I just have a hard time believing that a fuselage
can accomplish 50 percent of the lifting force of the total body. Yes
I know that some lift comes off of the fuselage on planes, especially
the tailwind as you suggest and the hyperbipe type of designs, but I
didn't think the Sonex fuselage shape was that much different than most
other 2 seat SBS types, including the RV-6. I'll take this into
consideration, though I'm still not convinced that the fuselage lift is
what puts the Sonex into the LSA category.

Neal

ET wrote:
> wrote in
> ups.com:
>
> > 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
> >
>
>
> Which part of my post that indicated the fuselage of the Sonex is a
> lifting body confused you??? Steve Wittman is said to have won a bet or
> two with the same issue on the Tailwind. I have not done it, but plug
> the same numbers in for the Tailwind and see what pops out.
>
> --
> -- ET >:-)
>
> "A common mistake people make when trying to design something
> completely foolproof is to underestimate the ingenuity of complete
> fools."---- Douglas Adams

Peter Dohm

September 23rd 06, 10:34 PM

"ET" > wrote in message
...
> wrote in
> ups.com:
>
> > 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
> >
>
>
> Which part of my post that indicated the fuselage of the Sonex is a
> lifting body confused you??? Steve Wittman is said to have won a bet or
> two with the same issue on the Tailwind. I have not done it, but plug
> the same numbers in for the Tailwind and see what pops out.
>
> --
> -- ET >:-)
>
> "A common mistake people make when trying to design something
> completely foolproof is to underestimate the ingenuity of complete
> fools."---- Douglas Adams

Quite true. Lifting bodies can generate a lot of lift, and airfoils vary
wildly in their maximum coeficient. Also, there is nothing in the LSA
rules, or any others that I can think of, to require that an aircraft be
able to maintain level flight at stall speed--so drag coefficient is not a
factor.

Peter

Peter Dohm

September 23rd 06, 10:59 PM

"Kyle Boatright" > wrote in message
. ..
>
> "ET" > wrote in message
> ...
> > wrote in
> > ups.com:
>
> <<<snip>>>
>
> > Which part of my post that indicated the fuselage of the Sonex is a
> > lifting body confused you??? Steve Wittman is said to have won a bet or
> > two with the same issue on the Tailwind. I have not done it, but plug
> > the same numbers in for the Tailwind and see what pops out.
> >
> > --
> > -- ET >:-)
> >
> > "A common mistake people make when trying to design something
> > completely foolproof is to underestimate the ingenuity of complete
> > fools."---- Douglas Adams
>
> Can you find a credible test of the Tailwind's stall speed on the web?
I've
> looked for one, but without success. The CAFE report in the "members"
> section of the EAA site doesn't show the stall speed, although the text
> discusses stall speed testing. I seem to remember that Tailwinds with the
> stock pitot/static system have an inaccurate ASI at low speeds, showing
much
> lower airspeed than actual.
>
> A buddy who owned a Tailwind described it as a fast airplane, but with
> "mean" low speed characteristics.
>
> I don't buy into the theory that Tailwinds or Soni (?) gain much lift from
> the fuselage. The aspect ratio of a fuselage is too small to generate a
lot
> of lift.
>
> KB
>
>
>
>
>
It is also possible that your friend's plane was poorly rigged.

Some years ago, I saw a BD-4 that a guy had purchased and was trying to
repair sufficiently to complete. The biggest problem was that the fusalage
had a substantial twist. There can also be problems with a very heavy pilot
in a very small airplane--Steve Wittman was only a little bigger than Ken
Rand.

Peter

September 23rd 06, 11:14 PM

wrote in
oups.com:

> No part confused me. I just have a hard time believing that a
> fuselage can accomplish 50 percent of the lifting force of the total
> body. Yes I know that some lift comes off of the fuselage on planes,
> especially the tailwind as you suggest and the hyperbipe type of
> designs, but I didn't think the Sonex fuselage shape was that much
> different than most other 2 seat SBS types, including the RV-6. I'll
> take this into consideration, though I'm still not convinced that the
> fuselage lift is what puts the Sonex into the LSA category.
>
> Neal
>
> ET wrote:
>> wrote in
>> ups.com:
>>
>> > 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
>> >
>>
>>
>> Which part of my post that indicated the fuselage of the Sonex is a
>> lifting body confused you??? Steve Wittman is said to have won a bet
>> or two with the same issue on the Tailwind. I have not done it, but
>> plug the same numbers in for the Tailwind and see what pops out.
>>
>> --
>> -- ET >:-)
>>
>> "A common mistake people make when trying to design something
>> completely foolproof is to underestimate the ingenuity of complete
>> fools."---- Douglas Adams
>
Hrm,

Well, where can I get a copy of this spreadsheet?... either you've got
the wrong dimensions, or the spreadsheet is flawed.

The Sonex stalls clean at 46mph, and those are real verified numbers (no
I cant point you to a cafe study or anything but all builders on the
list who have actually flown one have verified their numbers..)

Is the airfoil type taken into account??

--
-- ET >:-)

"A common mistake people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools."---- Douglas Adams

Kyle Boatright

September 23rd 06, 11:30 PM

"ET" > wrote in message
...
> wrote in
> oups.com:
>
<<<snip>>>
>
> Well, where can I get a copy of this spreadsheet?... either you've got
> the wrong dimensions, or the spreadsheet is flawed.
>
> The Sonex stalls clean at 46mph, and those are real verified numbers (no
> I cant point you to a cafe study or anything but all builders on the
> list who have actually flown one have verified their numbers..)
>
> Is the airfoil type taken into account??
>
>
> --
> -- ET >:-)
>

The Sonex numbers are believable, but absolutely DO NOT trust performance
figures provided by builders. Pitot/Static systems are notoriously
inaccurate at low airspeeds and owner/builders are notoriously optimistic in
their performance reports. In addition, without very expensive and
sensitive test equipment, you're not going to get accurate figures. There
isn't a CAFE report on the Sonex, so unless Sonex Ltd. has invested the time
and money to conduct private tests, my guess is that accurate testing simply
hasn't been done.

KB

J.Kahn

September 24th 06, 12:50 AM

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
>

You are not missing anything Neal. The Sonex stall numbers are plainly
bogus. I will venture that Monnet is using indicated stall speed, not
true. That way he can say anything he wants because who knows what the
installation errors are. The calculated stall for the Sonex is 51-52
mph clean at 1100lbs, using the formula that is the basis for
certificated aircraft and assuming a Cl max of 1.6-1.7 for the NACA
64-415 airfoil.

The proof of the pudding? Monnet has contradictory information right on
his site. Go to the Xenos part of the site and look at the claimed
stall, which in this case DOES agree with the standard calculation.
With 158 sqf of wing area it is 44mph, which is right on the money.
Whereas the Sonex stalls clean ONLY 2 MPH FASTER with 60 sqf LESS wing
area! How can this be??? It's magic! Nah, he just fudged the numbers.
Airfoil differences do not account for this as the variation in Clmax
values of a point up or down have surprisingly small effects, maybe 1
mph for each point above or below 1.6.

For when you don't have software available, just a calculator, memorize
the simple formula in your head and apply it to any aircraft's specs you
come across to assess their accuracy:

Sea Level Stall in Kts = Sq root of: [(295 x Gr Wt) Divided by (Clmax x
Wing Area)]

Multiply by 1.15 for mph.

Assume 1.6 for the Clmax. Almost all airfoils are between 1.5 and 1.7,
which gives a 1 mph or so variation up or down relative to 1.6.

That is not to say that the Sonex is not a very clever design.

John

[email protected]

September 24th 06, 11:35 AM

The Roncz spreadsheets were published in Sport Aviation from February
1990 thru January 1991 ( I believe ). The one I am referring to ran in
the March 1990 issue. I'm not at the house at the moment but I'll
check when I get home and verify.

Neal

ET wrote:
> wrote in
> oups.com:
>
> > No part confused me. I just have a hard time believing that a
> > fuselage can accomplish 50 percent of the lifting force of the total
> > body. Yes I know that some lift comes off of the fuselage on planes,
> > especially the tailwind as you suggest and the hyperbipe type of
> > designs, but I didn't think the Sonex fuselage shape was that much
> > different than most other 2 seat SBS types, including the RV-6. I'll
> > take this into consideration, though I'm still not convinced that the
> > fuselage lift is what puts the Sonex into the LSA category.
> >
> > Neal
> >
> > ET wrote:
> >> wrote in
> >> ups.com:
> >>
> >> > 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
> >> >
> >>
> >>
> >> Which part of my post that indicated the fuselage of the Sonex is a
> >> lifting body confused you??? Steve Wittman is said to have won a bet
> >> or two with the same issue on the Tailwind. I have not done it, but
> >> plug the same numbers in for the Tailwind and see what pops out.
> >>
> >> --
> >> -- ET >:-)
> >>
> >> "A common mistake people make when trying to design something
> >> completely foolproof is to underestimate the ingenuity of complete
> >> fools."---- Douglas Adams
> >
> Hrm,
>
> Well, where can I get a copy of this spreadsheet?... either you've got
> the wrong dimensions, or the spreadsheet is flawed.
>
> The Sonex stalls clean at 46mph, and those are real verified numbers (no
> I cant point you to a cafe study or anything but all builders on the
> list who have actually flown one have verified their numbers..)
>
> Is the airfoil type taken into account??
>
>
> --
> -- ET >:-)
>
> "A common mistake people make when trying to design something
> completely foolproof is to underestimate the ingenuity of complete
> fools."---- Douglas Adams

[email protected]

September 24th 06, 12:12 PM

Is it possible that maybe it all could be just an interpretation of the
LSA rule? I mean does the "aircraft" have to be LSA legal or does the
"flight" have to be LSA legal? Say the Sonex could indeed stall at 51
mph ( flown solo in a lightweight condition ). Technically the
"flight" would have a max gross takeoff wt.and stall conditions that
would satisfy the LSA rule. But then if you loaded the aircraft to
it's max. designed takeoff weight and then it couldn't meet the 51 mph
stall speed, then it couldn't be flown under LSA rules. In other
words, flown solo, yes you're LSA legal, but flown at max design, no,
you're not legal. Could this be what the Sonex guys are doing? You
know.......I could just call Jeremy and ask him.

Neal

Richard Riley wrote:
> On Sat, 23 Sep 2006 19:50:36 -0400, "J.Kahn"
> > wrote:
>
> >For when you don't have software available, just a calculator, memorize
> >the simple formula in your head and apply it to any aircraft's specs you
> >come across to assess their accuracy:
> >
> >Sea Level Stall in Kts = Sq root of: [(295 x Gr Wt) Divided by (Clmax x
> >Wing Area)]
> >
> >Multiply by 1.15 for mph.
> >
> >Assume 1.6 for the Clmax. Almost all airfoils are between 1.5 and 1.7,
> >which gives a 1 mph or so variation up or down relative to 1.6.
> >
> >That is not to say that the Sonex is not a very clever design.
>
> Yeah, I ran it the other way and got a CLmax of 1.623 at 1100 gross
> and 52 mph.
>
> That's ambitious for the 64-415 clean. Not flatly false, just at the
> top end of achievable in the real world. And it's got a flat bottomed
> fuselage, so that will fudge stall speed down a little. (Not like the
> DreamWings, a few years back, that was claiming speeds that meant a
> CLmax of 4). I wouldn't bet it's that good, but it's plausible.
>
> The key is that it's still just legal for LASt - the min stall speed
> is 45 knots, or 51.8 mph.
>
> It's entirely possible that the builders are reporting accurate
> speeds, but aren't getting those speeds at full gross weight. They
> claim an empty weight of 620 lbs, useful load 480, 16 gallons of fuel.
> So, 96 lbs of fuel and two 192 lb occupants. Let's assume our
> reporting pilot is flying alone and he has 3/4 full tanks. That puts
> him at a gross of 884. If the 1.6 (and change) CLmax is true, he'll
> stall at 46 (and change) mph. Throw in a little pitot error and it's
> very believable.

J.Kahn

September 24th 06, 03:47 PM

wrote:
> Is it possible that maybe it all could be just an interpretation of the
> LSA rule? I mean does the "aircraft" have to be LSA legal or does the
> "flight" have to be LSA legal? Say the Sonex could indeed stall at 51
> mph ( flown solo in a lightweight condition ). Technically the
> "flight" would have a max gross takeoff wt.and stall conditions that
> would satisfy the LSA rule. But then if you loaded the aircraft to
> it's max. designed takeoff weight and then it couldn't meet the 51 mph
> stall speed, then it couldn't be flown under LSA rules. In other
> words, flown solo, yes you're LSA legal, but flown at max design, no,
> you're not legal. Could this be what the Sonex guys are doing? You
> know.......I could just call Jeremy and ask him.
>
> Neal
>
>
> Richard Riley wrote:
>> On Sat, 23 Sep 2006 19:50:36 -0400, "J.Kahn"
>> > wrote:
>>
>>> For when you don't have software available, just a calculator, memorize
>>> the simple formula in your head and apply it to any aircraft's specs you
>>> come across to assess their accuracy:
>>>
>>> Sea Level Stall in Kts = Sq root of: [(295 x Gr Wt) Divided by (Clmax x
>>> Wing Area)]
>>>
>>> Multiply by 1.15 for mph.
>>>
>>> Assume 1.6 for the Clmax. Almost all airfoils are between 1.5 and 1.7,
>>> which gives a 1 mph or so variation up or down relative to 1.6.
>>>
>>> That is not to say that the Sonex is not a very clever design.
>> Yeah, I ran it the other way and got a CLmax of 1.623 at 1100 gross
>> and 52 mph.
>>
>> That's ambitious for the 64-415 clean. Not flatly false, just at the
>> top end of achievable in the real world. And it's got a flat bottomed
>> fuselage, so that will fudge stall speed down a little. (Not like the
>> DreamWings, a few years back, that was claiming speeds that meant a
>> CLmax of 4). I wouldn't bet it's that good, but it's plausible.
>>
>> The key is that it's still just legal for LASt - the min stall speed
>> is 45 knots, or 51.8 mph.
>>
>> It's entirely possible that the builders are reporting accurate
>> speeds, but aren't getting those speeds at full gross weight. They
>> claim an empty weight of 620 lbs, useful load 480, 16 gallons of fuel.
>> So, 96 lbs of fuel and two 192 lb occupants. Let's assume our
>> reporting pilot is flying alone and he has 3/4 full tanks. That puts
>> him at a gross of 884. If the 1.6 (and change) CLmax is true, he'll
>> stall at 46 (and change) mph. Throw in a little pitot error and it's
>> very believable.
>

Any numbers quoted for speeds are always based on the published max
gross weight (maximum certified wing loading in other words) unless
otherwise stated. That fact that the Sonex may stall at 46 mph solo is
not relevant for the purposes of whether it meets LSA requirements.
And the speeds that builders see are generally meaningless since ASIs
are very inaccurate at these speeds and usually read 5-10 mph low.

I find it puzzling that Monnet uses a viable stall speed claim for the
Xenos but not for the Sonex. While the Sonex does meet LSA requirements
(just), the claimed stall speed of 46, which is normally assumed to be
for max gross, is simply mathematically impossible. I think you may be
on to something though. If someone was to question his claimed stall of
46 he will probably state that it's for solo weight but that's not
stated on his site and is misleading.

Does the LSA rule have anything to say about advertised stall speeds?
Can they be indicated or at less than gross without notation in ads?

John

[email protected]

September 24th 06, 06:07 PM

John,
I hear what you're saying, but with all that's been said here, and
investigated via spreadsheets, etc., I still don't think the Sonex can
stall near the LSA requirement at max gross wt. and no flaps which
means it is not LSA qualified. And just for grins, I looked up the
figures for the CT Flight Design ( which is a popular seller ) and
guess what. IT doesn't meet the LSA criteria. And I also looked up
the new Vans RV-12 "LSA" and you guessed it....IT doesn't meet the
stall speed criteria ( at least not on paper...I don't think it has
flown yet.) So I'm convinced that something is amiss. I'll keep
researching.

Neal

J.Kahn wrote:
> wrote:
> > Is it possible that maybe it all could be just an interpretation of the
> > LSA rule? I mean does the "aircraft" have to be LSA legal or does the
> > "flight" have to be LSA legal? Say the Sonex could indeed stall at 51
> > mph ( flown solo in a lightweight condition ). Technically the
> > "flight" would have a max gross takeoff wt.and stall conditions that
> > would satisfy the LSA rule. But then if you loaded the aircraft to
> > it's max. designed takeoff weight and then it couldn't meet the 51 mph
> > stall speed, then it couldn't be flown under LSA rules. In other
> > words, flown solo, yes you're LSA legal, but flown at max design, no,
> > you're not legal. Could this be what the Sonex guys are doing? You
> > know.......I could just call Jeremy and ask him.
> >
> > Neal
> >
> >
> > Richard Riley wrote:
> >> On Sat, 23 Sep 2006 19:50:36 -0400, "J.Kahn"
> >> > wrote:
> >>
> >>> For when you don't have software available, just a calculator, memorize
> >>> the simple formula in your head and apply it to any aircraft's specs you
> >>> come across to assess their accuracy:
> >>>
> >>> Sea Level Stall in Kts = Sq root of: [(295 x Gr Wt) Divided by (Clmax x
> >>> Wing Area)]
> >>>
> >>> Multiply by 1.15 for mph.
> >>>
> >>> Assume 1.6 for the Clmax. Almost all airfoils are between 1.5 and 1.7,
> >>> which gives a 1 mph or so variation up or down relative to 1.6.
> >>>
> >>> That is not to say that the Sonex is not a very clever design.
> >> Yeah, I ran it the other way and got a CLmax of 1.623 at 1100 gross
> >> and 52 mph.
> >>
> >> That's ambitious for the 64-415 clean. Not flatly false, just at the
> >> top end of achievable in the real world. And it's got a flat bottomed
> >> fuselage, so that will fudge stall speed down a little. (Not like the
> >> DreamWings, a few years back, that was claiming speeds that meant a
> >> CLmax of 4). I wouldn't bet it's that good, but it's plausible.
> >>
> >> The key is that it's still just legal for LASt - the min stall speed
> >> is 45 knots, or 51.8 mph.
> >>
> >> It's entirely possible that the builders are reporting accurate
> >> speeds, but aren't getting those speeds at full gross weight. They
> >> claim an empty weight of 620 lbs, useful load 480, 16 gallons of fuel.
> >> So, 96 lbs of fuel and two 192 lb occupants. Let's assume our
> >> reporting pilot is flying alone and he has 3/4 full tanks. That puts
> >> him at a gross of 884. If the 1.6 (and change) CLmax is true, he'll
> >> stall at 46 (and change) mph. Throw in a little pitot error and it's
> >> very believable.
> >
>
> Any numbers quoted for speeds are always based on the published max
> gross weight (maximum certified wing loading in other words) unless
> otherwise stated. That fact that the Sonex may stall at 46 mph solo is
> not relevant for the purposes of whether it meets LSA requirements.
> And the speeds that builders see are generally meaningless since ASIs
> are very inaccurate at these speeds and usually read 5-10 mph low.
>
> I find it puzzling that Monnet uses a viable stall speed claim for the
> Xenos but not for the Sonex. While the Sonex does meet LSA requirements
> (just), the claimed stall speed of 46, which is normally assumed to be
> for max gross, is simply mathematically impossible. I think you may be
> on to something though. If someone was to question his claimed stall of
> 46 he will probably state that it's for solo weight but that's not
> stated on his site and is misleading.
>
> Does the LSA rule have anything to say about advertised stall speeds?
> Can they be indicated or at less than gross without notation in ads?
>
> John

[email protected]

September 24th 06, 09:11 PM

Richard,
I'll be out of town for the next 3 days. If I can't get a copy to
you before I leave tomorrow, I'll get it to you as soon as I get back.
BTW...Roncz was using a CL of 1.5

Neal

Richard Riley wrote:
> On 24 Sep 2006 03:35:02 -0700, wrote:
>
> >The Roncz spreadsheets were published in Sport Aviation from February
> >1990 thru January 1991 ( I believe ). The one I am referring to ran in
> >the March 1990 issue. I'm not at the house at the moment but I'll
> >check when I get home and verify.
> >
>
> If you could email me a copy I'd like to go through and see what his
> assumptions are. He may be listing a CLmax of 1.4 or so - which would
> be a reasonable, conservative number. Going backwards through it,
> both J.Kahn and I get a 45 knot LSA legal stall at gross, assuming a
> CLmax of 1.6 and a smidge. 1.6 is ambitious but plausible.
>
>
> Richard (atsign) riley *d0t* net

September 24th 06, 10:27 PM

wrote in
ups.com:

> John,
> I hear what you're saying, but with all that's been said here, and
> investigated via spreadsheets, etc., I still don't think the Sonex can
> stall near the LSA requirement at max gross wt. and no flaps which
> means it is not LSA qualified. And just for grins, I looked up the
> figures for the CT Flight Design ( which is a popular seller ) and
> guess what. IT doesn't meet the LSA criteria. And I also looked up
> the new Vans RV-12 "LSA" and you guessed it....IT doesn't meet the
> stall speed criteria ( at least not on paper...I don't think it has
> flown yet.) So I'm convinced that something is amiss. I'll keep
> researching.
>
> Neal
>

Well then guess what, the spreadsheet is what's flawed. I guarantee CT
(the best selling LSA by far) and Vans, and the Pete Buck know what they
are doing far better then the developer of your spreadsheet...

3 real world examples of planes that clearly meet the LSA specs but do not
meet it "on paper".

Do it for the SportStar (http://www.evektoramerica.com/sportstar.html) and
the StingSport (http://www.sting.aero/) while your at it... I bet you all
the money in my pocket they won't "compute" either, and the spreadsheet is
flawed.

--
-- ET >:-)

"A common mistake people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools."---- Douglas Adams

J.Kahn

September 25th 06, 02:39 AM

ET wrote:
> wrote in
> ups.com:
>
>> John,
>> I hear what you're saying, but with all that's been said here, and
>> investigated via spreadsheets, etc., I still don't think the Sonex can
>> stall near the LSA requirement at max gross wt. and no flaps which
>> means it is not LSA qualified. And just for grins, I looked up the
>> figures for the CT Flight Design ( which is a popular seller ) and
>> guess what. IT doesn't meet the LSA criteria. And I also looked up
>> the new Vans RV-12 "LSA" and you guessed it....IT doesn't meet the
>> stall speed criteria ( at least not on paper...I don't think it has
>> flown yet.) So I'm convinced that something is amiss. I'll keep
>> researching.
>>
>> Neal
>>
>
> Well then guess what, the spreadsheet is what's flawed. I guarantee CT
> (the best selling LSA by far) and Vans, and the Pete Buck know what they
> are doing far better then the developer of your spreadsheet...
>
> 3 real world examples of planes that clearly meet the LSA specs but do not
> meet it "on paper".
>
> Do it for the SportStar (http://www.evektoramerica.com/sportstar.html) and
> the StingSport (http://www.sting.aero/) while your at it... I bet you all
> the money in my pocket they won't "compute" either, and the spreadsheet is
> flawed.
>

Forget about spread sheets. The simple formula in my earlier post...

<Sea Level Stall in Kts = Sq root of: [(295 x Gr Wt) Divided by (Clmax x
Wing Area)]

Multiply by 1.15 for mph.

Assume 1.6 for the Clmax. Almost all airfoils are between 1.5 and 1.7,
which gives a 1 mph or so variation up or down relative to 1.6.>

....works like a charm. I used it on the Sting sport and sure enough it
comes out to 44kts just as advertised.

Use it on the Sonex and you get 45 kts. Different airfoils will
increase or decrease that by about 1kt.

John

Peter Dohm

September 25th 06, 02:56 AM

"J.Kahn" > wrote in message
...
> ET wrote:
> > wrote in
> > ups.com:
> >
> >> John,
> >> I hear what you're saying, but with all that's been said here, and
> >> investigated via spreadsheets, etc., I still don't think the Sonex can
> >> stall near the LSA requirement at max gross wt. and no flaps which
> >> means it is not LSA qualified. And just for grins, I looked up the
> >> figures for the CT Flight Design ( which is a popular seller ) and
> >> guess what. IT doesn't meet the LSA criteria. And I also looked up
> >> the new Vans RV-12 "LSA" and you guessed it....IT doesn't meet the
> >> stall speed criteria ( at least not on paper...I don't think it has
> >> flown yet.) So I'm convinced that something is amiss. I'll keep
> >> researching.
> >>
> >> Neal
> >>
> >
> > Well then guess what, the spreadsheet is what's flawed. I guarantee CT
> > (the best selling LSA by far) and Vans, and the Pete Buck know what they
> > are doing far better then the developer of your spreadsheet...
> >
> > 3 real world examples of planes that clearly meet the LSA specs but do
not
> > meet it "on paper".
> >
> > Do it for the SportStar (http://www.evektoramerica.com/sportstar.html)
and
> > the StingSport (http://www.sting.aero/) while your at it... I bet you
all
> > the money in my pocket they won't "compute" either, and the spreadsheet
is
> > flawed.
> >
>
> Forget about spread sheets. The simple formula in my earlier post...
>
> <Sea Level Stall in Kts = Sq root of: [(295 x Gr Wt) Divided by (Clmax x
> Wing Area)]
>
> Multiply by 1.15 for mph.
>
> Assume 1.6 for the Clmax. Almost all airfoils are between 1.5 and 1.7,
> which gives a 1 mph or so variation up or down relative to 1.6.>
>
> ...works like a charm. I used it on the Sting sport and sure enough it
> comes out to 44kts just as advertised.
>
> Use it on the Sonex and you get 45 kts. Different airfoils will
> increase or decrease that by about 1kt.
>
> John

And the old graphs in the Dover Edition of Theory of Wing Sections look like
a CLmax of a little more than 1.6 can be achieved--plus whatever the
fuselage shape might ad.

Don't get me wrong. At 6'1" and 200#, I don't fit in the plane; and I
really don't like it anyway. I just don't have a problem with the specs;
and there have been plenty of designs over the years for which I do have a
problem with the specs.

Peter

J.Kahn

September 25th 06, 03:57 AM

Peter Dohm wrote:
> "J.Kahn" > wrote in message
> ...
>> ET wrote:
>>> wrote in
>>> ups.com:
>>>
>>>> John,
>>>> I hear what you're saying, but with all that's been said here, and
>>>> investigated via spreadsheets, etc., I still don't think the Sonex can
>>>> stall near the LSA requirement at max gross wt. and no flaps which
>>>> means it is not LSA qualified. And just for grins, I looked up the
>>>> figures for the CT Flight Design ( which is a popular seller ) and
>>>> guess what. IT doesn't meet the LSA criteria. And I also looked up
>>>> the new Vans RV-12 "LSA" and you guessed it....IT doesn't meet the
>>>> stall speed criteria ( at least not on paper...I don't think it has
>>>> flown yet.) So I'm convinced that something is amiss. I'll keep
>>>> researching.
>>>>
>>>> Neal
>>>>
>>> Well then guess what, the spreadsheet is what's flawed. I guarantee CT
>>> (the best selling LSA by far) and Vans, and the Pete Buck know what they
>>> are doing far better then the developer of your spreadsheet...
>>>
>>> 3 real world examples of planes that clearly meet the LSA specs but do
> not
>>> meet it "on paper".
>>>
>>> Do it for the SportStar (http://www.evektoramerica.com/sportstar.html)
> and
>>> the StingSport (http://www.sting.aero/) while your at it... I bet you
> all
>>> the money in my pocket they won't "compute" either, and the spreadsheet
> is
>>> flawed.
>>>
>> Forget about spread sheets. The simple formula in my earlier post...
>>
>> <Sea Level Stall in Kts = Sq root of: [(295 x Gr Wt) Divided by (Clmax x
>> Wing Area)]
>>
>> Multiply by 1.15 for mph.
>>
>> Assume 1.6 for the Clmax. Almost all airfoils are between 1.5 and 1.7,
>> which gives a 1 mph or so variation up or down relative to 1.6.>
>>
>> ...works like a charm. I used it on the Sting sport and sure enough it
>> comes out to 44kts just as advertised.
>>
>> Use it on the Sonex and you get 45 kts. Different airfoils will
>> increase or decrease that by about 1kt.
>>
>> John
>
> And the old graphs in the Dover Edition of Theory of Wing Sections look like
> a CLmax of a little more than 1.6 can be achieved--plus whatever the
> fuselage shape might ad.
>
> Don't get me wrong. At 6'1" and 200#, I don't fit in the plane; and I
> really don't like it anyway. I just don't have a problem with the specs;
> and there have been plenty of designs over the years for which I do have a
> problem with the specs.
>
> Peter
>
>
>
Yeah I'm 6' and 200 and the Sonex was a very tight fit. At Osh I
commented on the lack of head room for a long torso type like me and he
said "sit in the middle". Yeah right.

[email protected]

September 25th 06, 11:46 AM

The good news is that I think we're zeroing in on the problem. I'll
compare the formulas with the Roncz spreadsheet and the formula John
suggests and see where the difference is. You're right in that these
competent designers are coming up with figures that all suggest the
stall speeds can be achieved with a smaller wing, but I wouldn't go so
far as to say they're any better than John Roncz. I believe he is
responsible for most of Rutan's airfoils which have been proven to do
pretty much what they said they'd do. I'll report back what I find.
Thanks for the good discussion.

Neal

ET wrote:
> wrote in
> ups.com:
>
> > John,
> > I hear what you're saying, but with all that's been said here, and
> > investigated via spreadsheets, etc., I still don't think the Sonex can
> > stall near the LSA requirement at max gross wt. and no flaps which
> > means it is not LSA qualified. And just for grins, I looked up the
> > figures for the CT Flight Design ( which is a popular seller ) and
> > guess what. IT doesn't meet the LSA criteria. And I also looked up
> > the new Vans RV-12 "LSA" and you guessed it....IT doesn't meet the
> > stall speed criteria ( at least not on paper...I don't think it has
> > flown yet.) So I'm convinced that something is amiss. I'll keep
> > researching.
> >
> > Neal
> >
>
> Well then guess what, the spreadsheet is what's flawed. I guarantee CT
> (the best selling LSA by far) and Vans, and the Pete Buck know what they
> are doing far better then the developer of your spreadsheet...
>
> 3 real world examples of planes that clearly meet the LSA specs but do not
> meet it "on paper".
>
> Do it for the SportStar (http://www.evektoramerica.com/sportstar.html) and
> the StingSport (http://www.sting.aero/) while your at it... I bet you all
> the money in my pocket they won't "compute" either, and the spreadsheet is
> flawed.
>
> --
> -- ET >:-)
>
> "A common mistake people make when trying to design something
> completely foolproof is to underestimate the ingenuity of complete
> fools."---- Douglas Adams

Peter Dohm

September 25th 06, 03:40 PM

I believe that John Roncz is also responsible for the airfoil on the RV-9
and RV-9A, which also have a low stall speed.

Peter

> wrote in message
ups.com...
> The good news is that I think we're zeroing in on the problem. I'll
> compare the formulas with the Roncz spreadsheet and the formula John
> suggests and see where the difference is. You're right in that these
> competent designers are coming up with figures that all suggest the
> stall speeds can be achieved with a smaller wing, but I wouldn't go so
> far as to say they're any better than John Roncz. I believe he is
> responsible for most of Rutan's airfoils which have been proven to do
> pretty much what they said they'd do. I'll report back what I find.
> Thanks for the good discussion.
>
> Neal
>
> ET wrote:
> > wrote in
> > ups.com:
> >
> > > John,
> > > I hear what you're saying, but with all that's been said here, and
> > > investigated via spreadsheets, etc., I still don't think the Sonex can
> > > stall near the LSA requirement at max gross wt. and no flaps which
> > > means it is not LSA qualified. And just for grins, I looked up the
> > > figures for the CT Flight Design ( which is a popular seller ) and
> > > guess what. IT doesn't meet the LSA criteria. And I also looked up
> > > the new Vans RV-12 "LSA" and you guessed it....IT doesn't meet the
> > > stall speed criteria ( at least not on paper...I don't think it has
> > > flown yet.) So I'm convinced that something is amiss. I'll keep
> > > researching.
> > >
> > > Neal
> > >
> >
> > Well then guess what, the spreadsheet is what's flawed. I guarantee CT
> > (the best selling LSA by far) and Vans, and the Pete Buck know what they
> > are doing far better then the developer of your spreadsheet...
> >
> > 3 real world examples of planes that clearly meet the LSA specs but do
not
> > meet it "on paper".
> >
> > Do it for the SportStar (http://www.evektoramerica.com/sportstar.html)
and
> > the StingSport (http://www.sting.aero/) while your at it... I bet you
all
> > the money in my pocket they won't "compute" either, and the spreadsheet
is
> > flawed.
> >
> > --
> > -- ET >:-)
> >
> > "A common mistake people make when trying to design something
> > completely foolproof is to underestimate the ingenuity of complete
> > fools."---- Douglas Adams
>

September 25th 06, 04:24 PM

wrote in
ups.com:

> The good news is that I think we're zeroing in on the problem. I'll
> compare the formulas with the Roncz spreadsheet and the formula John
> suggests and see where the difference is. You're right in that these
> competent designers are coming up with figures that all suggest the
> stall speeds can be achieved with a smaller wing, but I wouldn't go so
> far as to say they're any better than John Roncz. I believe he is
> responsible for most of Rutan's airfoils which have been proven to do
> pretty much what they said they'd do. I'll report back what I find.
> Thanks for the good discussion.
>
> Neal
>
OK, well not that those folks are "better then" Roncz, but that his formula
is obviously flawed when it comes to these smaller aircraft, or perhaps it
is being mis-applied here?

--
-- ET >:-)

"A common mistake people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools."---- Douglas Adams

rpellicciotti

September 25th 06, 07:43 PM

[email protected]

September 25th 06, 08:58 PM

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

[email protected]

September 26th 06, 04:48 PM

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