Monday, July 26, 2010

Sizing to stall speed requirements


FAR 23 certified multiengine aeroplanes with Wto less than 6000 Lbs must have a stall speed of no more than 61 knots. The power off stall speed maybe determined from part 1, chapter 3, page 90 as:

Vs = {2(W/S)/ρCLmax}½   (answer is in feet / second)

Given the following details from the single engine design are already known; Wing profile NACA 747A415, a highly laminar flow wing with low drag profile but generates poor lift at slow speeds so CLmax (clean)   = 1.4 and CLmax (flap)   = 1.8 With a Mean Aerodynamic Chord (MAC)    = 1300 mm and a proposed increase in span to 9 meters then;
(S) surface area = 120 sq.ft
(W/S) = 16.5 Lbs/sq.ft

Sea Level
5000 ft
Stall Clean  (Vs)
59.0 kts
63.6 kts
Stall Flap     (Vso)
52.1 kts
56.1 kts

No comments: