Definition
In aircraft flight controls, primary controls are those required to safely control an aircraft in flight — the ailerons, elevator (or stabilator), and rudder. Secondary controls are those that improve performance, reduce pilot workload, or enhance handling qualities — typically flaps, leading edge devices, spoilers, and trim systems.
Plain English
Primary controls are the ones you must have to fly the plane — they make it roll, pitch, and yaw. Secondary controls aren’t essential for flight, but they make flying easier or improve how the aircraft performs, like flaps for landing or trim to relieve control pressure.
Context Anchor
Seen when learning the parts of an airplane’s flight control system and how cockpit controls connect to moving surfaces on the airplane.
Derivation
‘Primary’ comes from Latin primus, meaning ‘first’ — the first-order, must-have controls. ‘Secondary’ comes from Latin secundus, meaning ‘following’ — controls that come after the essentials and support them.
Why Pilots Care
Knowing which controls are primary versus secondary helps a pilot understand priorities in training, troubleshooting, and emergencies. If a secondary system fails (like flaps), the aircraft is still controllable. If a primary control fails, it’s a serious emergency.
Intuition Check
Do not read “secondary” as “unimportant.” Secondary systems are not the main controls for pointing the airplane, but they can still be very important for safe and smooth operation.
Example Sentence 1
During the systems lesson, the instructor explained that the ailerons, elevator, and rudder are the primary flight controls, while flaps and trim are secondary.
Example Sentence 2
The checklist reminded the pilot to test both the primary and secondary systems during the preflight inspection.