Back side of the power curve describes a flight regime where flying slower actually requires more power, not less. It is the counterintuitive zone where the normal relationship between speed and power reverses.
How It Works#
Every aircraft has a speed called L/D max (best lift-to-drag ratio speed). At this speed, the aircraft flies most efficiently. Above L/D max, reducing power slows the aircraft as expected. Below it, something different happens.
At low airspeeds, the wing must fly at a high angle of attack (the angle between the wing and the oncoming air). This generates a large amount of induced drag (drag created as a byproduct of producing lift). Induced drag rises sharply as airspeed drops, overwhelming every other force.
To maintain level flight at these slow speeds, the pilot must add power to overcome the extra drag. The slower the aircraft flies, the more power it demands. This is the back side of the power curve, sometimes called the region of reversed command.
Think of it like pushing a car uphill with a steeper grade around every corner. The slower you go, the harder you have to push just to keep moving.
Example in Aviation#
A student pilot is flying a stabilized approach and lets the airspeed decay below the target. The aircraft starts to sink. Instinctively, the student pulls back on the controls to arrest the descent, which raises the nose and slows the aircraft further. Now the aircraft is deeper into the back side of the power curve. Drag increases, sink rate worsens, and the aircraft needs a significant power addition immediately to recover.
Without prompt throttle input, this situation can deteriorate into a stall close to the ground, where recovery altitude is dangerously limited.
Why It Matters#
The back side of the power curve is responsible for a significant number of approach and landing accidents. Pilots who do not recognize it tend to respond with back pressure alone, which makes the situation worse. The correct response is always power first, then attitude adjustment.
Student pilots encounter this concept during slow flight training. Understanding it builds the instincts needed to manage energy on approach, especially during go-arounds and short-field operations where precise airspeed control is critical.
Key Takeaways#
- Below L/D max, flying slower requires more power, not less.
- Induced drag is the dominant force in this regime.
- Pulling back without adding power deepens the problem.
- This hazard is most dangerous during approach and landing phases.
- Power first is always the correct initial response to unexpected sink at low speed.