What is the primary function of a stall fence on an aircraft wing?

What is the primary function of a stall fence on an aircraft wing?

• A. Barrier on the wings which temporarily prevents a stall from spreading to the wingtip.
• B. Device that changes the wing's camber.
• C. Guard that prevents bird strikes.
• D. System to accelerate airflow.

Answer: (A)

Stall fences work by controlling how air moves along the wing’s span at high angles of attack. Air tends to flow from the wing root toward the tip along the surface, which can cause a stall to begin near the root and then propagate outward or vice versa. A stall fence acts as a vertical barrier that disrupts that spanwise flow, making the wing stall first inboard (near the root) and minimizing the quick spread of stall toward the wingtip. This helps preserve aileron effectiveness and results in a more predictable stall behavior. They don’t alter the wing’s camber, they aren’t designed primarily to guard against bird strikes, and they don’t speed up airflow—in fact, they intentionally modify the flow to prevent undesirable spanwise movement.

Stall fences work by controlling how air moves along the wing’s span at high angles of attack. Air tends to flow from the wing root toward the tip along the surface, which can cause a stall to begin near the root and then propagate outward or vice versa. A stall fence acts as a vertical barrier that disrupts that spanwise flow, making the wing stall first inboard (near the root) and minimizing the quick spread of stall toward the wingtip. This helps preserve aileron effectiveness and results in a more predictable stall behavior.

They don’t alter the wing’s camber, they aren’t designed primarily to guard against bird strikes, and they don’t speed up airflow—in fact, they intentionally modify the flow to prevent undesirable spanwise movement.