Stall Speed Discussion

[mhcrowder]

We completed our stall speed testing quite awhile ago but after our flap handle issue discussion I thought it might be nice to discuss stall speeds. I got some comments back saying our speeds were on the high side. We have done Airspeed calibrations as well. We moved our Static Port due to this testing for better AS correlation.

Our empty weight came in at 824 lbs at 10.85" CG

We did Stall testing at the four corners:
Heavy Forward: 1393 lbs at 12.7" CG
Light Forward: 1059 lbs at 12.2" CG
Heavy Aft: 1516 lbs at 15.5" CG
Light Aft: 1123 lbs at 15.5 CG

We also did testing at the four flap settings of 0, 15, 30, 40 degrees

Our stalls ranged from a high of 55 mph when Heavy Aft and no flaps to 41 mph when Light Forward and full flaps.

Our normal landing configuration is 2 Notches or 30 degrees of flaps. In that configuration out stalls came in from 43-51 mph depending on weight and CG.

Do these numbers seem "normal"? We do have Steve Henry's leading edge cuff and VG's installed. Always have so, don't know how it would fly otherwise.

==
Michael Crowder
Ed Bodette
Highlander N371EM

[kenryan]

Just Aircraft claims 36 mph at 1320 pounds and 40 degrees of flaps. By that measure, yours seem high.

[BDA]

Michael you said "light and forward" was 41. What was the number for light and aft cg, or light and mid cg? That should give you the slowest stall.
How did you have it trimmed?

Do you have VGs?
Flap gaps seals?

[danerazz]

My plane is really nose-heavy (until I added ballast). The flight characteristics at the forward edge of the envelope are “interesting.”

Actually feels like the tail is losing effectiveness as opposed to wing stalling if trying to 3-point the landing. It is not what I call “comfortable.”

After adding ballast so I am near the middle of the envelope when light the flight characteristics are much closer to what I expect from an airplane.

I would expect your lowest stall speed to be light, with an AFT CG.

[BDA]

Yes, "interesting" is right!
or unpredictable is another word.
If I lighten up for a competition and forget to ballast, I may be short or I may be long - by a lot.
When light with forward CG, the tail gives up (tail stall with max elevator deflection) and sink rate increases greatly - so I have to have a lot of throttle in (more airspeed over the tail) to keep the tail down, but also makes landings longer.
The good thing about forward CG is - I am never at forward, always hauling something, so forward cg gives me a larger envelope for load capacity.
Sucks I have to add ballast weight for competition, but that is not what the plane was built for.

[mhcrowder]

Here's our Stall Speed Matrix...

Heavy FWD (CG@12.7, Gross 1393) No Flaps 54mph, 1st Notch 51mph 2nd Notch 48mph 3rd Notch 47mph
Light AFT (CG@15.5, Gross 1123) No Flaps 47mph, 1st Notch 46mph 2nd Notch 43mph 3rd Notch 42mph
Heavy AFT (CG@15.5, Gross 1516) No Flaps 55mph, 1st Notch 52mph 2nd Notch 51mph 3rd Notch 50mph
Light FWD (CG@12.2, Gross 1059) No Flaps 47mph, 1st Notch 46mph 2nd Notch 43mph 3rd Notch 41mph

We do do have both VG's, Flap Gap Seals, and Steve Henry's Leading Edge Cuff

VG's are about 5" back, measured along the top edge, or about 6.5% - 10.7% of chord (front to back of VG)

Our stalls are very benign. With stick all the way back, we usually get no nose break just altitude loss. We can ride that down picking up a wing with the rudder if it dips. Maybe we're just running out of tail authority.

[BDA]

Michael, I don't see where you mentioned your power setting for these stall speeds.
Is this power off?
1,800?
1,200?
The propwash over the tail makes a big difference with these planes. My 1,200rpm stall is MUCH different (faster) than my 1,600 rpm stall.
The only time I will care about stall at idle power is after an engine failure. Other than that, I will be landing w enough power to keep the nose up (slow), and fly level. My typical slow approach is a 1,300rpm decent, with flare to 1,600 rpm level flight over the numbers at 30 mph, then to 18-1900 rpm at 20 mph, dragging the tailwheel until I reach my touchdown point. (smooth surface STOL landing)

Tundra landings are a whole different thing. Some of the same stuff, but with more swearing and sweating.

[Tralika]

Tundra landings are a whole different thing. Some of the same stuff, but with more swearing and sweating.

Don't forget the teeth grinding.

[BDA]

Ya, had to tighten my rudder cables this year. The teeth grinding is part of the back arch - brake stomp, stretches those cables right out.

[mhcrowder]

Yes, speeds listed were at power at idle.... 1800RPM on a Rotax engine.