Stall speed with flaps up is ______ and stall speed with flaps full is ______?

Stall speed is the minimum speed at which an aircraft can maintain level flight. It varies depending on the configuration of the aircraft, particularly whether the flaps are extended or retracted.

When the flaps are retracted (flaps up), the stall speed is higher because the wings have a reduced lift coefficient. This configuration requires a greater airspeed to maintain sufficient lift. The first part of the answer indicates that the stall speed with flaps up is 50 knots, which reflects a common performance metric for many small aircraft.

Conversely, when the flaps are fully extended, the stall speed decreases. This occurs because extending the flaps increases the lift coefficient, allowing the aircraft to generate lift at a slower speed. The value given for stall speed with full flaps at 40 knots represents this reduction. This information is consistent with typical aircraft performance characteristics, showing how flap configurations significantly impact stall speeds.

In summary, the correct choice correctly matches the expected relationship between stall speeds with various flap configurations, highlighting the significant role flaps play in aircraft performance during flight.