# Reducing CL-CD Ratio

> Means to reduce lift-to-drag ratio (Spoilers and Airbrakes).

- **Subject:** 081 — Principles of Flight
- **Section:** 081-01 — Subsonic Aerodynamics
- **Topic code:** 081-01-10
- **Last reviewed:** 2026-04-01
- **Author:** Pablo Asensio Martínez
- **HTML version:** https://pilotsyllabus.com/en/principles-of-flight/subsonic-aerodynamics/means-to-reduce-the-clcd-ratio/

---

## 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.

---

Free study notes from pilotsyllabus.com. Not a substitute for training at an approved ATO.