The minimum speed when speed brakes are extended is equal to Vref plus how many knots?

The minimum speed when speed brakes are extended is equal to Vref plus how many knots?

• A. Vref+10 knots
• B. Vref+15 knots
• C. Vref+20 knots
• D. Vref+5 knots

Answer: (B)

When speed brakes are extended, the airplane experiences more drag and a slight loss of lift effectiveness, which narrows the margin above stall and can reduce elevator authority. To keep a safe cushion above stall while you’re on the approach, the minimum speed with speed brakes out is set at Vref plus 15 knots. Vref is the reference landing speed tied to stall speed in the landing configuration, so adding 15 knots accounts for the extra drag and potential gusts, preserving control and stall margin. The other options would either give too little margin, risking a stall, or be unnecessarily slow, which isn’t desirable for a stable approach.

When speed brakes are extended, the airplane experiences more drag and a slight loss of lift effectiveness, which narrows the margin above stall and can reduce elevator authority. To keep a safe cushion above stall while you’re on the approach, the minimum speed with speed brakes out is set at Vref plus 15 knots. Vref is the reference landing speed tied to stall speed in the landing configuration, so adding 15 knots accounts for the extra drag and potential gusts, preserving control and stall margin. The other options would either give too little margin, risking a stall, or be unnecessarily slow, which isn’t desirable for a stable approach.