Definition
Devices fitted to a parked airplane's propeller to prevent it from being rotated by wind, vandalism, or unauthorized handling while the aircraft is unattended. They typically clamp around a blade or the spinner area and physically block the propeller from turning.
Plain English
A lock you put on the propeller when the airplane is parked so it cannot spin or be tampered with while no one is watching it.
Context Anchor
Seen during postflight securing, preflight inspection, and aircraft storage at a tiedown or parking spot.
Derivation
Propeller comes from the Latin idea of “driving forward.” Security means protection against unwanted access or use. Locks are fastening devices that keep something from being opened or moved. Together, the term points to a lock used to protect the airplane by restricting propeller movement.
Why Pilots Care
Prevents wind-driven propeller rotation that can damage the engine or injure people near the aircraft.
Intuition Check
Do not assume a propeller security lock makes the propeller safe to handle. It is mainly a parking and anti-theft device, not permission to pull, push, or lean on the propeller.
Example Sentence 1
Before leaving the airplane on the ramp overnight, the pilot installed the propeller security locks along with the control surface gust locks.
Example Sentence 2
During the preflight walk-around the student removed the propeller security locks and stowed them in the baggage compartment.