Learn what aircraft chocks do, when crews fit and remove them, how they differ from parking brakes, and the ground-safety mistakes to avoid.
Aircraft chocks are sturdy wedges placed against an aircraft’s tyres to stop it rolling while parked. In Aviation & Real-World Flying, ground crews use them during parking, loading, servicing, maintenance and some engine operations. They are removed only after the aircraft is ready and authorised to move.
What do aircraft wheel chocks actually do?
A wheel chock is an external physical barrier that prevents a tyre from rolling forwards or backwards. Chocks are commonly fitted in pairs around one or more wheels, although the required wheels and arrangement depend on the aircraft, apron and operator’s procedures.
Aircraft chocks are made from materials such as rubber, moulded polyurethane or wood, often with a rope joining the pair. Their size and shape must suit the tyre: a small automotive chock is not adequate for a large aircraft wheel. Our explanation of landing-gear wheels, brakes and struts covers the components that chocks secure while the aircraft is parked.
Chocks do not make an aircraft immovable under every condition. Excessive thrust, a steep slope, strong wind, ice or an incorrectly sized chock can cause the tyre to climb over it or the chock to slide.
When are aircraft chocks used?
Chocks are used whenever an unattended or serviced aircraft needs a positive safeguard against rolling.
- After arrival: Once the aircraft has stopped and ground personnel are cleared to approach, chocks are fitted and reported as “chocks in”. The flight crew may then release the parking brake if the aircraft and operator permit it.
- During a turnaround: Chocks normally remain in place while passengers, baggage, cargo and fuel are handled, or while external ground power is connected and used.
- During maintenance or storage: They provide a restraint while people work on or around the aircraft. Long-term outdoor parking may also require tie-downs or other approved measures.
- During some engine operations: Aircraft started in place may remain chocked until removal is requested. High-power ground runs require approved restraints and procedures; ordinary chocks alone are not sufficient protection.
- On sloping or exposed parking areas: Additional chocks may be required, but they cannot compensate for an unsuitable parking position.
Not every aircraft is chocked in the same place. A light aircraft may be secured at a main wheel, while a transport aircraft may use the nose gear, main gear or both. The aircraft manual and local operating procedure decide the correct arrangement.
How are aircraft chocks fitted and removed safely?
Chocks must be handled in a controlled sequence because approaching the wheels too early or removing them without another restraint can let the aircraft move.
- Confirm that approach is safe. Wait until the aircraft has stopped and the responsible crew member or marshaller has given the required clearance. A stopped propeller or an applied parking brake is not, by itself, permission to approach.
- Select the correct chocks. Use the specified size, material and wheel positions for that aircraft and surface.
- Place them correctly. Position the chocks ahead of and behind the tyre as required, keeping ropes clear of brake assemblies, hydraulic lines and landing-gear mechanisms. Do not hammer a chock tightly beneath a tyre.
- Report their status. The ground crew should clearly communicate “chocks in” before anyone relies on them as the aircraft’s restraint.
- Remove them only on command. Confirm that the parking brake is applied, a tug has control or another approved restraint is in place. Report “chocks out” and stow them clear of the movement area.
If the aircraft has rolled against a chock and trapped it, do not pull, kick or reach beneath the tyre. The cockpit crew or tug operator must first move the wheel slightly away from the chock. Suspected hot brakes require a separate safety procedure and an exclusion area around the wheel; ground personnel should not approach merely to fit chocks.
Are chocks the same as the parking brake?
No. The parking brake holds the wheels through the aircraft’s braking system, while chocks physically obstruct tyre movement and do not depend on hydraulic pressure remaining available.
They are often used together during the handover between cockpit and ground crew. On arrival, the parking brake normally holds the aircraft until chocks are confirmed in position. Before departure, the brake or tug must take control before the chocks are removed. Some operators release the parking brake after chocking, particularly during longer stops or when brake cooling is a concern, but that is procedure-dependent.
Why can an aircraft move even when chocked?
Chocks fail to restrain an aircraft when their size, placement or operating conditions exceed what they can safely handle.
- Wrong size or orientation: The tyre can climb over a chock whose face is too low or poorly matched to the wheel.
- Only one direction restrained: A single chock may stop forward movement but leave the aircraft free to roll backwards.
- Slippery or broken surface: Water, ice, loose gravel or contamination can let the entire chock slide.
- Excessive force: Engine thrust, a steep gradient, towing loads or severe wind can overcome normal wheel chocks.
- Poor positioning: A chock left too far from the tyre allows momentum to build before contact.
The remedy is to unload the chock safely, reposition or replace it, and add the restraint specified by the aircraft or operator. Nobody should step into the projected path of a wheel to correct a chock while the aircraft is moving.
How do chocks work in flight simulators?
In flight simulators, chocks may be functional ground equipment, a visual animation or simply unavailable, depending on the aircraft add-on. Some models prevent movement while chocks are fitted; others connect their visibility to the parking brake without simulating a separate physical restraint.
Our downloadable Tiger Moth for FSX and Prepar3D is a practical example with animated wheel chocks and parking-brake interaction. If an aircraft seems held by its brakes rather than its chocks, especially when moving the yoke or pedals, use our guide to diagnosing unwanted simulator brake inputs before assuming the ground equipment is at fault.