Definition
Movable surfaces or panels on an airplane's wings designed to either increase lift at low airspeeds (high-lift devices, such as flaps and slats) or increase drag to slow the airplane and steepen the descent path (high-drag devices, such as spoilers and speed brakes). Many of these surfaces, particularly flaps, do both at once — they raise the wing's lift capability and add drag at the same time.
Plain English
Wing parts the pilot can extend to make the wing lift more at slow speeds, or to add drag and slow the airplane down. Flaps are the most common example, and they do a bit of both.
Context Anchor
Seen in discussions of how the pilot manages airplane energy with the throttle, elevator, and devices such as flaps during approach and landing.
Why Pilots Care
They give the pilot direct control over speed and descent angle in the critical low-speed phases of flight.
Grounding Statement
Extending a high lift/drag device changes how the airplane moves through the air, usually helping it slow down or stay controlled at a lower speed.
Intuition Check
“High” does not mean high altitude here; it means an increased amount of lift or drag. “Drag” means air resistance against the airplane’s motion, not dragging something along the ground.
Example Sentence 1
On final approach, the pilot extended the flaps to full, using the high lift/drag devices to fly slower and descend at a steeper angle.
Example Sentence 2
During the approach briefing the instructor emphasized when to deploy high lift/drag devices to stay on the glide path.