What does it mean when the handle is down and the lock indicator is green?

When the handle is down and the lock indicator is green, it indicates that the door is locked, and the vent flap is in the closed position. This configuration is crucial for ensuring that the aircraft's cabin remains secure and that pressurization is maintained during flight.

A locked door signifies that it cannot be opened from the outside, which contributes to safety and security protocols. Additionally, when the vent flap is closed, it prevents air from flowing through the venting system, which is necessary for proper cabin pressure management.

This combination is particularly important during critical phases of flight, such as takeoff and landing, where aircraft integrity is paramount. In other scenarios, such as when the handle is up or the lock indicator is not green, the implications for door and flap status would differ and thus not align with the situation described in the question.