Touchdown protection deactivates 3 seconds after WOW senses ground or wheel speed exceeds what threshold?

• A. >40 knots
• B. '>50 knots'
• C. ">60 knots"
• D. ">70 knots"],

Answer: (B)

Touchdown protection is a safety feature that keeps certain ground-related protections held until the airplane is clearly on the runway and settled. It uses a weight-on-wheels signal or wheel speed to confirm that the aircraft has actually touched down and is rolling.

The threshold of 50 knots is chosen because it’s high enough to avoid triggering from a brief contact or a small bounce, yet low enough to confirm the airplane is truly on the ground and accelerating as it should. When wheel speed exceeds 50 knots, and after a short 3-second dwell to ensure the speed is stable, touchdown protection deactivates so normal ground operations—like spoiler deployment or autobrake interaction—can proceed normally. A lower threshold (like 40 knots) risks premature deactivation during a bounce or transient roll, while much higher thresholds (60 or 70 knots) could delay deactivation too long after landing, hindering normal ground behavior.