stall speed at gross

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stall speed at gross

Postby KWK » Sat Oct 14, 2017 6:10 pm

Have any builders established using GPS the clean stall speed at gross of their Sonex/Waiex?

The nominal wing loading of the Sonex is higher than average among the LSA, so the fuselage must be providing some of the lift.
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Re: stall speed at gross

Postby gammaxy » Sun Oct 15, 2017 12:31 pm

I never set out to measure this number to the precision you want, but I did find a gross-weight flight where I performed two stalls and I flew in enough directions that I believe I can estimate the wind speed.

Aircraft weight: 1125lbs (took off at 1150lbs and burned ~25lbs of fuel; this flight was performed at greater than Sonex's recommanded gross weight for the Aerovee engine.)
Density altitude: 4000ft
Tailwind during the stall: 7mph (my greatest uncertainty, but I did record GS and TAS while flying around in several circles, so feel like this is a reasonable estimate)
Minimum GPS ground speed during the stalls: 43mph (35mph IAS)
Estimated clean stall TAS: 50mph (43mph+7mph)
Stall speed corrected to sea level density altitude: 50mph * sqrt(1.088/1.225) = 47mph

Sonex lists the clean stall speed as 46mph. I feel like my estimate of 47mph agrees remarkably well with theirs. Both are comfortably within the LSA rule of 51mph.

Here's a recent quote from John Monnett about the fuselage lift:
“They’re basically a box with a lifting body that’s created by a smooth canopy and cowling transition. That contributes tremendously to its performance at both low-speed and high-speed operations.”


I'd be interested in seeing a comparison against other more rounded fuselage designs.
Chris Madsen
Aerovee Sonex N256CM
Flying since September 2014
Build log: http://chrismadsen.org
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Re: stall speed at gross

Postby KWK » Thu Oct 19, 2017 12:27 am

47? I'd have bet it was closer to 51. Impressive performance. Thanks for the info.
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Re: stall speed at gross

Postby mike.smith » Fri Oct 20, 2017 8:37 pm

At 950 lbs (aerobatic weight) my stall speed is 26 kts indicated. There is probably some pitot error due to a high angle of attack, but I can keep flying straight ahead with rudder, and it won't start nosing down until 26 kts. At that weight I break ground on take off at 36 kts indicated.
Mike Smith
Sonex N439M
Scratch built, AeroVee, Dual stick, Tail dragger
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Re: stall speed at gross

Postby Darick » Mon Oct 23, 2017 10:02 pm

Is that with any flaps down?
Darick Gundy
Sonex #1646
N417DG
Taildragger, Aerovee, center stick, Prince P-Tip Prop
MGL E1, F2, V6 radio, Sandia Xponder, Reserve lift indicator (AOA), iFly 520
First flight! 10/21/2017
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Re: stall speed at gross

Postby mike.smith » Mon Oct 23, 2017 11:55 pm

No flaps.
Mike Smith
Sonex N439M
Scratch built, AeroVee, Dual stick, Tail dragger
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