Which value represents the stall speed when flaps up and power off?

Which value represents the stall speed when flaps up and power off?

• A. 149 knots
• B. 43 knots
• C. 55 knots
• D. 48 knots

Answer: (D)

Stall speed in the clean configuration with power off is the minimum airspeed at which the airplane can fly level without stalling. With power off, there’s no thrust to help climb or stay up, so you must rely on aerodynamic lift alone. When the wings are in the flaps-up (clean) configuration, the wing’s lift at a given angle of attack is lower than it would be with flaps extended, so the stall occurs at a higher speed. Stall speed also rises with weight and any increased load factor, but for a typical light aircraft at normal gross weight, the clean-stall speed sits in the upper 40s to around 50 knots indicated. That’s why 48 knots is the best match for the stall speed with flaps up and power off. The other values don’t fit this common range: 149 knots is far beyond stall speed for a small airplane, 55 knots is higher than the usual clean-stall speed, and 43 knots is more characteristic of a flaps-down condition or a lighter weight.

Stall speed in the clean configuration with power off is the minimum airspeed at which the airplane can fly level without stalling. With power off, there’s no thrust to help climb or stay up, so you must rely on aerodynamic lift alone. When the wings are in the flaps-up (clean) configuration, the wing’s lift at a given angle of attack is lower than it would be with flaps extended, so the stall occurs at a higher speed. Stall speed also rises with weight and any increased load factor, but for a typical light aircraft at normal gross weight, the clean-stall speed sits in the upper 40s to around 50 knots indicated. That’s why 48 knots is the best match for the stall speed with flaps up and power off. The other values don’t fit this common range: 149 knots is far beyond stall speed for a small airplane, 55 knots is higher than the usual clean-stall speed, and 43 knots is more characteristic of a flaps-down condition or a lighter weight.