Definition
The airspeed at which an airplane in level flight requires the least amount of engine power to maintain altitude. Below this speed, more power is needed to overcome the increased induced drag of high angles of attack; above it, more power is needed to overcome the increased parasite drag of higher speeds.
Plain English
The speed at which the airplane needs the smallest throttle setting to keep flying level. Fly slower than this and you need more power; fly faster than this and you also need more power.
Context Anchor
Seen in discussions of slow flight, airplane attitude, and how pitch and power affect altitude control.
Why Pilots Care
This speed maximizes time aloft on a given quantity of fuel, which matters during holding patterns or fuel-critical situations.
Grounding Statement
Picture slowing in level flight: at first the airplane needs less power, but after this speed, going even slower makes it need more power again to stay level.
Intuition Check
Do not read this as the airplane's lowest safe speed or the lowest throttle setting. It means the speed where the least power is needed to remain in level flight.
Example Sentence 1
During the endurance demonstration, the instructor reduced airspeed to the minimum power required speed and noted the low throttle setting needed to hold altitude.
Example Sentence 2
Maintaining minimum power required speed during the long cross-country leg improved fuel endurance without sacrificing altitude.