FAA Airline Transport Pilot (ATM)Transport Aerodynamics and High-Altitude OperationsEasy
A pilot extends the wing leading-edge slats prior to landing. What is the primary aerodynamic benefit of this high-lift device?
- AIt reduces induced drag during high-speed cruise
- BIt increases maximum lift coefficient and delays stall to a higher angle of attack
- CIt increases Vmo by strengthening the wing structure
- DIt increases the wing's critical Mach number for faster cruise
Show answer & explanationAnswer & explanation
Correct answer: B. It increases maximum lift coefficient and delays stall to a higher angle of attack
Leading-edge slats re-energize the boundary layer over the upper wing surface, allowing the wing to reach a higher angle of attack before airflow separation occurs, which increases CLmax and lowers the stall speed for approach and landing.
Why the other options are wrong
- A. Slats are a low-speed device and do not function during high-speed cruise.
- C. Slats have no effect on structural speed limits like Vmo.
- D. Critical Mach number relates to compressibility at high speed, not slat function at low speed.
Leading-Edge Slats
Movable leading-edge high-lift devices that extend to re-energize airflow over the wing, increasing CLmax and delaying stall to a higher angle of attack.
- Used primarily during takeoff and landing at low speeds.
- Increase CLmax, allowing lower stall speeds.
- Work by smoothing airflow over the upper wing surface at high AoA.
Memory trick: Slats slow the stall, letting the wing bite a bigger bite of air