Explain the concept of stall margin in approach configuration with landing flaps.

• A. Stall margin = current approach speed minus stall speed in the same configuration; smaller margin increases stall risk.
• B. Stall margin = stall speed minus current approach speed in the same configuration; larger margin increases stall risk.
• C. Stall margin is a constant value regardless of configuration.
• D. Stall margin equals climb speed minus stall speed.

Answer: (A)

Stall margin is the amount by which your current airspeed exceeds the stall speed in the present configuration. In approach with landing flaps, the stall speed is lower than in clean configuration, and the current approach speed is chosen for a safe descent. So the margin is computed as current approach speed minus stall speed in the same configuration. A smaller margin means you’re closer to the stall and the stall risk is higher; a larger margin provides more safety.

The other ideas aren’t correct because stall margin should reflect the speed difference within the same configuration (not a reversed subtraction), it isn’t a constant value independent of configuration, and climb speed is not relevant to approach/stall margin.