When SEAT BLTS switch is AUTO, under what conditions do the seatbelt signs illuminate automatically?

• A. Cabin altitude above 10,000 ft
• B. Landing gear extended
• C. Flaps greater than 0 degrees
• D. All of the above

Answer: (D)

In AUTO mode, the seat belt signs are controlled by three sensors: cabin altitude, landing gear position, and flap position. If cabin altitude climbs above 10,000 ft, that signals a safety requirement for passengers to be seated with belts fastened. If the landing gear is extended, the aircraft is in a configuration where quick changes or turbulence could occur and belts should be worn. If the flaps are greater than zero, the aircraft isn’t in clean cruise, indicating a phase of flight where belt use is prudent. Since any one of these conditions can happen on its own, the signs illuminate automatically under any of them, so the correct answer is all of the above.