Reducing CL-CD Ratio

081-01-10Pablo Asensio Martínez2026-04-011 min

Purpose

Sometimes pilots need to increase Drag (to descend stepeer or slow down) or destroy Lift (to ensure weight is on wheels during landing).

Spoilers

Plates on the upper surface of the wing that spoil the smooth airflow.

  • Flight Spoilers / Speed Brakes: Can be extended symmetrically in flight.
    • Increase Drag significantly.
    • Decrease Lift.
    • Used for emergency descent or slowing down.
  • Roll Spoilers: Operate asymmetrically (one side up) to assist ailerons in banking.
  • Ground Spoilers (Lift Dumpers): Extend fully on touchdown.
    • Primary purpose: Destroy Lift. This puts weight on the wheels, making wheel brakes effective.
    • Secondary purpose: Increase aerodynamic drag.

Airbrakes

Dedicated drag-producing surfaces (e.g., tail cone, fuselage panels).

  • Difference from Spoilers: Airbrakes increase Drag without significantly affecting Lift (ideally). Spoilers definitely affect Lift.
Written and reviewed by

Pablo Asensio · 2026-04-01

Aeronautical engineer. Passed the thirteen EASA ATPL(A) theoretical knowledge exams studying from these very notes. Writes and reviews each topic against the Part-FCL Learning Objectives.

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