Definition
A target airspeed equal to 1.4 times the airplane's stalling speed in the landing configuration (gear down, full flaps, power off). Used as a recommended approach speed on the base leg of the traffic pattern, providing a margin above the stall while the airplane is configured for landing.
Plain English
A speed that is 40% faster than the slowest speed at which the airplane can still fly with the gear and flaps down for landing. It gives the pilot a safe cushion above stalling while turning toward the runway.
Context Anchor
You will see this in traffic pattern and landing discussions, especially when setting a safe speed on base leg before turning final.
Derivation
VSO is a standard FAA airspeed reference: 'V' for velocity, 'S' for stall, and the subscript 'O' for the landing configuration (gear and flaps fully extended). Multiplying it by 1.4 gives a working speed that is 40% above stall.
Why Pilots Care
This speed margin reduces the risk of an inadvertent stall during the turn to final while still allowing time to configure the airplane for landing.
Intuition Check
Do not read 1.4 VSO as a fixed speed for every airplane. It is a multiplier applied to that specific airplane’s VSO.
Example Sentence 1
On base leg, the instructor asked the student to slow to 1.4 VSO before turning final.
Example Sentence 2
With a slight headwind, the student adjusted pitch to maintain exactly 1.4 VSO throughout the base leg.