Plain English Meaning

Valves that make sure things happen in the right order when the landing gear goes up or down — doors first, then gear, then doors closed again — so nothing tries to move through something that's still in the way.

Full Definition

Hydraulic valves in a retractable landing gear system that control the order of mechanical events during gear extension and retraction, ensuring that gear doors and gear legs operate in the correct sequence. They prevent the gear from attempting to move while the doors are still closed, and prevent the doors from closing on partially retracted gear.

Context Anchor

Seen in discussions of retractable landing gear systems, especially gear extension and retraction with gear doors.

Derivation

‘Sequenced’ comes from the Latin sequi, meaning ‘to follow.’ A sequence is a set of things that follow one after another in order. So sequenced valves are simply valves that act in a set order rather than all at once.

Why Pilots Care

Proper sequencing avoids mechanical and keeps the gear system reliable during and .