Sivuperäsin

Sivuperäsin, known in English as a tailplane or horizontal stabilizer, is a crucial component of an aircraft's empennage. It is typically a fixed wing-like structure located at the rear of the fuselage, positioned behind the main wings. The primary function of the sivuperäsin is to provide longitudinal stability, meaning it helps to keep the aircraft flying straight and level. It accomplishes this by generating a small amount of downforce, which counteracts the tendency of the aircraft's nose to pitch up or down due to aerodynamic forces.

The sivuperäsin consists of a main airfoil section and, on many aircraft, a movable control surface called an elevator. The elevator, attached to the trailing edge of the sivuperäsin, can be deflected up or down by the pilot to control the aircraft's pitch. Increasing the angle of attack of the elevator will cause the tail to move down, pitching the nose up, and vice versa. The size and shape of the sivuperäsin are determined by the overall design of the aircraft, including its size, speed, and intended mission. Larger and faster aircraft generally require larger tailplanes to maintain adequate stability.

In some aircraft designs, particularly those with very high speeds or specific aerodynamic requirements, the entire sivuperäsin may be movable, acting as a single control surface. This design, often referred to as a stabilator or all-moving tailplane, provides more direct control over pitch. The sivuperäsin is a fundamental element in achieving stable and controllable flight.