Elevator

An elevator is a hinged control surface on the horizontal stabilizer (tail). Deflecting the elevator trailing-edge-up produces a downward force on the tail, pitching the aircraft nose-up and increasing angle of attack. Deflecting trailing-edge-down does the opposite.

The elevator’s effectiveness depends on the tail volume coefficient — the product of tail area and moment arm (distance from wing to tail) divided by wing area and mean chord. A longer fuselage with a smaller tail produces the same pitching authority as a shorter fuselage with a larger tail, but with different dynamic characteristics: the longer-arm configuration responds more sluggishly but damps pitch oscillations better, while the shorter-arm version is more agile but less stable.

Trim and elevator deflection

In steady flight, the elevator maintains trim — the condition where pitching moments sum to zero. The center of gravity position determines how much elevator deflection is needed for trim: a forward CG requires more up-elevator (trailing-edge-up) to balance the nose-heavy moment, which generates a downward force on the tail. This “trim drag” — the drag from the tail producing a net downforce instead of zero or positive lift — is one reason that CG position matters for cruise efficiency.

On conventional fixed-wing UAVs, the elevator is driven by a single servo. On delta wings and flying wings that lack a horizontal tail, the elevator function is handled by elevons on the trailing edge of the wing.

Some UAVs use a full-flying tail (stabilator) — the entire horizontal surface rotates rather than having a separate hinged elevator. This provides more powerful pitch control per unit area but requires more precise center of gravity management because the surface is more sensitive to deflection.

Related terms

• Aileron — the roll control surface
• Rudder — the yaw control surface
• Elevon — the combined pitch/roll surface on tailless aircraft
• Trim — the equilibrium condition the elevator maintains
• Center of Gravity — the balance point that determines elevator trim requirement