Devices fitted on the aircraft braking system designed to prevent the locking of the wheels when the aircraft brakes are applied. The normal arrangement is to have a flywheel in contact with the landing wheel. When any of the landing wheels slows down at an abnormal rate such as in the case of an incipient skid, the brake pressure to the wheels is released automatically, thus preventing their locking. This arrangement is especially useful with bogie undercarriage units, where the same amount of braking force is applied simultaneously to all wheels in the same bogie unit but the loading on each of the wheels may be different. Also called an antiskid unit.