FAA Airline Transport Pilot (ATM)Transport Aerodynamics and High-Altitude OperationsMedium
A pilot extends the flight spoilers (speed brakes) in cruise flight to increase the rate of descent without accelerating. What is the primary aerodynamic effect of deploying the spoilers in this configuration?
- AThey decrease lift and increase drag, allowing a steeper descent without gaining excessive airspeed
- BThey increase both lift and drag equally, having no net effect on descent profile
- CThey primarily affect roll control and have negligible effect on lift or drag
- DThey increase lift and decrease drag, allowing a faster descent at the same airspeed
Show answer & explanationAnswer & explanation
Correct answer: A. They decrease lift and increase drag, allowing a steeper descent without gaining excessive airspeed
Spoilers disrupt airflow over the wing's upper surface, which spoils (reduces) lift and significantly increases drag. This combination allows the pilot to increase descent rate or steepen the approach path while controlling airspeed, since the loss of lift and gain in drag counteract the tendency to accelerate in a descent.
Why the other options are wrong
- B. Spoilers don't increase lift at all; they spoil it, hence the name.
- C. While some spoilers assist roll control, flight/speed spoilers primarily affect lift and drag for descent/speed control.
- D. This is the opposite effect; spoilers reduce lift, not increase it.
Spoilers/Speed Brakes
Spoilers are panels on the upper wing surface that, when deployed, disrupt airflow to reduce lift and increase drag, used for descent control, speed control, and roll augmentation.
- Reduce lift by disrupting upper surface airflow
- Increase drag, aiding descent without airspeed gain
- Also used symmetrically for descent, or asymmetrically to augment roll
Memory trick: Spoil the lift, boost the drag