To ensure adequate maneuvering margins, flight spoilers must not be extended in-flight at airspeeds below which value?

• A. Ref + 10
• B. Vref
• C. V2
• D. 250 KIAS

Answer: (A)

Extending flight spoilers changes the wing’s lift and drag, which directly affects maneuvering margins and stall protection. When spoilers are out, you have less lift to help stay in control, so you want enough airspeed left to preserve roll and pitch authority and a safe stall margin. The standard rule uses Ref (landing reference speed) plus 10 knots, giving a safety buffer so that, even with lift dumped, the airplane still has adequate control and margin. Extensions below this margin can reduce lift too much for the current conditions, making precise control and safe descent more difficult.

Vref alone would remove that extra margin, as would V2 or a fixed high speed like 250 KIAS, which aren’t the required safeguard for spoiler deployment in flight.