An airplane with an effective lift area of \(25 \mathrm{~m}^{2}\) is fitted with airfoils of NACA 23012 section (Fig. 9.23). The maximum flap setting that can be used at takeoff corresponds to configuration (2) in Fig. 9.23. Determine the maximum gross mass possible for the airplane if its takeoff speed is \(150 \mathrm{~km} / \mathrm{hr}\) at sea level. Find the minimum takeoff speed required for this gross mass if the airplane is instead taking off from Denver (elevation approximately \(1.6 \mathrm{~km}\) ).

Data From Fig. 9.23

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3.5 (3) 3.48 3.0 2.5 CL 2.67 Configuration 3. Double-slotted flap 2. Slotted flap 2.0 CL 1.5 1.52- 1. Clean (no flap) 1.0 0.5 T 3.5 3.0 2.5 2.0 CL 1.5 1.0 0.5 -505 10 15 20 Angle of attack, a (deg) (a) Lift coefficient versus angle of attack 0 0.05 0.10 0.15 0.20 0.25 0.30 CD (b) Lift-drag polar