What are the typical signs of boundary layer separation on a wing during a stall and how is it detected?

What are the typical signs of boundary layer separation on a wing during a stall and how is it detected?

• A. Signs include loss of suction peak near leading edge, a flatter pressure distribution, and possibly local flow visualization; stall warning devices detect onset.
• B. Signs include increased suction peak near leading edge and sharper pressure gradient.
• C. No signs are observable; stall is only theoretical.
• D. Separation occurs only at the trailing edge.

Answer: (A)

When a wing stalls, the boundary layer separates because the adverse pressure gradient along the upper surface becomes strong enough to overcome the attached flow. The typical signs are a loss of the suction peak near the leading edge and a flatter, more uniform pressure distribution over the upper surface. The flow often starts separating near the leading edge and then progresses aft as the angle of attack increases, reducing lift and altering the pressure field. In practice, flow visualization methods (like tufts or oil flow) can show where separation is occurring. On actual aircraft, stall warning devices monitor parameters such as pressure signals or angle of attack to detect the onset of separation and warn the pilot.

When a wing stalls, the boundary layer separates because the adverse pressure gradient along the upper surface becomes strong enough to overcome the attached flow. The typical signs are a loss of the suction peak near the leading edge and a flatter, more uniform pressure distribution over the upper surface. The flow often starts separating near the leading edge and then progresses aft as the angle of attack increases, reducing lift and altering the pressure field.

In practice, flow visualization methods (like tufts or oil flow) can show where separation is occurring. On actual aircraft, stall warning devices monitor parameters such as pressure signals or angle of attack to detect the onset of separation and warn the pilot.