Empennage

Qu'est-ce que l'empennage ?

The empennage (pronounced em-peh-NAHJ) is the complete tail assembly of a fixed-wing aircraft. It typically comprises the vertical stabilizer (fin), the horizontal stabilizer, the rudder, and the elevator. The term comes from the French word for the feathers of an arrow — an apt metaphor, since the empennage stabilizes the aircraft in flight just as fletching stabilizes an arrow in its trajectory.

Fonction et objectif

The empennage provides aerodynamic stability and directional control about two axes. The vertical stabilizer damps yaw motion (nose swinging left or right), keeping the aircraft pointed along its flight path. The movable rudder, hinged to the trailing edge of the vertical stabilizer, allows pilots to deliberately yaw the aircraft — essential for coordinated turns and crosswind corrections during landing.

The horizontal stabilizer counteracts pitching moments generated by the wing and center-of-gravity shifts. On most modern jets, the entire horizontal stabilizer is adjustable (a trimmable horizontal stabilizer, or THS), allowing precise pitch trim across the flight envelope. The elevator, hinged at the trailing edge, provides additional short-term pitch control.

Types et variantes

• Conventional (cruciform) tail: The most common configuration, with the horizontal stabilizer mounted at the base of the vertical fin. Found on the Boeing 737, Airbus A320, and most commercial jets.
• T-tail: Horizontal stabilizer mounted at the top of the vertical fin, raising it above engine exhaust and flap wake. Used on the Boeing 727, McDonnell Douglas MD-80, and Bombardier CRJ series. T-tails must avoid the "deep stall" condition where the horizontal surface is blanketed by the stalled wing.
• V-tail (butterfly tail): Two angled surfaces replace both the vertical and horizontal stabilizers. Rare on commercial aircraft but used on some Beechcraft Bonanza models.

Exemples notables

The Airbus A380 features one of the largest empennages ever built, with a vertical stabilizer nearly 15 meters tall — taller than a four-story building. Its trimmable horizontal stabilizer spans 30.4 meters. The Boeing 787 empennage incorporates carbon-fiber-reinforced polymer throughout, saving significant weight compared to aluminum equivalents.

Composants associés

The empennage attaches to the aft section of the fuselage. On rear-engined aircraft (e.g., Boeing 717, Embraer E-jets), the empennage must be designed to handle proximity to engine exhaust, and the auxiliary power unit (APU) is typically housed in the tailcone immediately behind the empennage structure.