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Purpose of wing fences

Aviation Mechanic Airframe (AMA) practice question 4 of 16 on Flight Controls. ACS element AM.II.C.K11 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONWhat is the purpose of wing fences on an airplane?

  1. AThey reduce the drag caused by wingtip vortices
  2. BThey obstruct spanwise airflow on the wing
  3. CThey increase wing area during landing
Show the answer and explanation

Correct answer: B. They obstruct spanwise airflow on the wing

  • A — incorrect Reducing the drag associated with wingtip vortices is the function of winglets.
  • B — correct Wing fences are vertical plates on the upper surface that obstruct spanwise airflow and prevent the entire wing from stalling at once.
  • C — incorrect Increasing wing area to change lift on takeoff and landing is the function of flaps.

BACKGROUND

Wing fences are flat metal vertical plates fixed to the upper surface of the wing. They obstruct spanwise airflow along the wing and prevent the entire wing from stalling at once, and they are often attached on swept-wing aircraft to prevent the spanwise movement of air at high angle of attack. Their purpose is to provide better slow speed handling and stall characteristics. Winglets, by contrast, are the near-vertical extension of the wingtip that reduces the aerodynamic drag associated with wingtip vortices, lowering fuel consumption and extending range. A canard wing is a small wing or horizontal airfoil placed ahead of the main lifting surfaces, and it may be fixed, movable, or designed with elevators.

STUDY TIP

Group the wing features by what each one fixes: fences for spanwise flow and stall behavior, winglets for induced drag, canards for pitch and lift ahead of the wing.

KEY POINTS

  • Wing fences are vertical plates on the wing upper surface.
  • They block spanwise airflow and keep the whole wing from stalling at once.
  • Winglets cut wingtip vortex drag; canards sit ahead of the main wing.

SOURCES

  • sources/ama-airframe/ch02.txt "Wing Fences"
  • sources/ama-airframe/ch02.txt "Winglets"
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SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-31B Aviation Maintenance Technician Handbook – Airframe, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.