aerosiam
Joined: 26 May 2008
Posts: 59
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 Posted: Sat Nov 19, 2011 11:35 pm Post subject: Allegro stall speeds |
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During a biennial with a CFI, the stall characteristics were tested. The plane is a 2006 Allegro 100 hp fitted with full span vortex generators plus VGs on the bottom trailing edge of the horizontal stabilizer. Weight was 500 kg or 1,100 lb. OAT 30 degrees C. The VGs are from stolspeed.com and were inexpensive and easy to install
The plane has a Dynon plus 2 ASIs fitted to 2 pitots. Both ASIs were poorly calibrated at the factory. There were carefully re-calibrated right thru the speed range with a manometer and are exactly in sync with the Dynon so IAS is also CAS.
Minimum speed
42 kts at half flap. With a little power, the plane maintained altitude and could perform gentle 10 degree turns. Aileron control was slow but positive.
Stall speeds power off (indicated and calibrated)
Zero flap - 42 kts
Half flap 15 degrees – 38 kts
Full flap 48 degrees – 36 kts
This confirms an approach speed with flaps at 50 kts. Touchdown speed in ground effect is about 34 kts
Stall behaviour
At all 3 flaps settings, the behaviour was the same.
The stick is back against the stop and the plane simply parachutes at about 400 ft/min pitched about 5 degrees nose up. There is no break or wing drop.
Deliberately moving the aileron sometimes provoked a mild wing drop, sometimes not.
Recovery is immediate as soon as back pressure is released and power applied. Height loss is negligible.
The stall warning worked correctly. There is almost no buffet presumably because the VGs prevent the usual separation at high angles of attack.
Difference with VGs fitted.
The slow speed and stall behaviour is very mild. There is more elevator and aileron control bite especially for take off, flare and landing. The nose wheel can be held off noticeably longer.
Without the VGs, typically there was a wing drop to the right.
The Allegro manual states the CAS stall speeds as 43 / 39 / 35 (at) 520 kg or 1,144 lb.
Before the VGs were fitted, I noted the stall speeds as 45 / 40 / 36.
I suspect Fantasy’s figures are a little optimistic. What results have other owners obtained when practising stalls?
Paul
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