
how fast does an ultra light plane have to be going to take off?
does anyone have an idea to figure how fast an ultra light plane needs to be going to take off? wingspan 30 feet max..max weight about 450 (including pilot)
Well 1st of all, more info about the wing is needed.
What is the wing lift surface area?
What is the maximum coef of lift of the wing?
I can go through a simple example that makes several common assumptions:
Wing aspect ratio = 10 --> wing area = 90 sq ft.
Make an assumption to the coef of lift during takeoff (at a certain angle of attack with full flaps) --> let's say it's Cl = 1.5
So now we can calculate the velocity where the wing's lift force equals the aircraft's weight of 450 lb:
L = 1/2 p V^2 Swing Cl
where p = density of air = .00237 slugs/ft^3
and V = velocity (ft/sec)
V = sqrt ((2 L)/(p Swing Cl))
V = 53 ft/sec = 36 mph
This is the air speed where lift = weight, the take off velocity should be at least around 20% higher than this ~ 45 mph to ensure a stable climb and minimize risk of stall or spin.
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