converting coefficient of lift to airspeed in knots
Thread Starter
Joined: Jul 2006
Posts: 52
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From: N37 56.3 E023 56.7
converting coefficient of lift to airspeed in knots
Hi there!!
I think I could use a little bit of help here as I'm trying to solve a lift problem from an ATPL book but nothing is working out...
Given:aircraft weight 588600 N
wing area 105m2
density,standard sea value 1225 kg/m3.
coefficient of lift 0.384
What is wanted is to calculate the airspeed for this coefficient of lift.
The funny thing is that at the end of the chapter you can find the solution which is 300 knots,the sad thing is that there is no explanation how this number occured...
Best regards
I think I could use a little bit of help here as I'm trying to solve a lift problem from an ATPL book but nothing is working out...
Given:aircraft weight 588600 N
wing area 105m2
density,standard sea value 1225 kg/m3.
coefficient of lift 0.384
What is wanted is to calculate the airspeed for this coefficient of lift.
The funny thing is that at the end of the chapter you can find the solution which is 300 knots,the sad thing is that there is no explanation how this number occured...
Best regards
Joined: Oct 2003
Posts: 76
Likes: 0
From: California (Highway Patrol)
Assuming level flight, LIFT = WEIGHT,...........
Lift Coefficient (CL) = L / (1/2 x rho x V^2 x S)
rho = density of air at sea level I guess (cant remember off hand, but might be something like 1.22506 I think - its been a while)
V = velocity (m/s)
S = wing area (includes portion "masked" by fuselage)
L = Weight = M x g (g = 9.81, M = Mass)
My calculator dont work, but give this a try!!!
FP
Lift Coefficient (CL) = L / (1/2 x rho x V^2 x S)
rho = density of air at sea level I guess (cant remember off hand, but might be something like 1.22506 I think - its been a while)
V = velocity (m/s)
S = wing area (includes portion "masked" by fuselage)
L = Weight = M x g (g = 9.81, M = Mass)
My calculator dont work, but give this a try!!!
FP
Joined: May 2003
Posts: 412
Likes: 0
Giorgino, the value for density at standard sea level is not 1225 kg/m cubed, but 1.225 kg/m cubed. Using L = W = 588600 Newtons, and the formula L = .5 * rho * S * Cl * V squared, the value for V comes out as 154.4 meters/sec. This converts to 300 nm/hour.
Hawk
Hawk
