Vertical stabilizer

A vertical stabilizer, vertical stabiliser, or fin of an aircraft, missile, bomb, or car are typically found on the aft end of the fuselage or body, and are intended to reduce aerodynamic side slip and provide direction stability. It is analogous to a skeg on boats and ships. On aircraft, vertical stabilizers generally point upwards. These are also known as the vertical tail, and are part of an aircraft's empennage. This upright mounting position has two major benefits: The drag of the stabilizer increases at speed, which creates a nose-up moment that helps to slow down the aircraft and prevent dangerous overspeed; and when the aircraft banks, the stabilizer produces lift which counters the banking moment and keeps the aircraft upright in the absence of control input. If the vertical stabilizer was mounted on the underside, it would produce a positive feedback whenever the aircraft dives or banks, which is inherently unstable. The trailing end of the stabilizer is typically movable, and called the rudder; this allows the aircraft pilot to control yaw. Often navigational radio or airband transceiver antennas are placed on or inside the vertical tail. In all known trijets (jet aircraft with three engines), the vertical stabilizer houses the central engine or engine inlet duct.