Chocks
Wedge-shaped blocks placed against an aircraft's wheels to prevent unintended movement while parked.
Full Definition
Chocks are physical restraints — typically made of rubber, aluminium, or polyurethane and wedge-shaped — placed against the main landing gear wheels of a parked aircraft to prevent inadvertent movement due to wind, slope, or inadvertent engine power. The placement and removal of chocks are defined steps in the aircraft turnaround sequence. 'Chocks in' signals that an aircraft has arrived at stand and chocks are in place; 'chocks out' signals the aircraft is cleared for movement. These phrases are used in block time calculations. Editors should note that 'chocks' is always plural in operational usage when referring to the devices, and 'chocks in/out' is set terminology that should not be paraphrased.
Usage
Usage note: 'Chocks in' and 'chocks out' are fixed operational terms used in block time recording and turnaround management; do not paraphrase. 'Chocks' is always used in the plural when referring to the physical devices.
In Context
- "Block time is recorded from chocks in to chocks out for all commercial movements." — Airline Operations Manual
- "Ground crew must confirm 'chocks in' to the captain before the parking brake is released." — Turnaround Coordination Procedure