Definition
The region of slow flight, below the airspeed for minimum power required, where flying slower actually requires more power, not less. In this region, induced drag rises sharply as airspeed decreases, so maintaining altitude at a slower speed demands a higher power setting. Pitch and power roles also reverse from normal cruise: pitch primarily controls airspeed and power primarily controls altitude.
Plain English
It is the slow-speed range where flying slower needs more power, not less, because drag goes up as the airplane gets closer to its stall speed.
Context Anchor
Seen in slow-flight, approach, and elevator-control discussions, especially when learning how pitch and power work together at low airspeeds.
Derivation
The 'power required curve' is a graph of how much power the airplane needs to maintain level flight at each airspeed. The curve dips to a minimum and then rises again at slower speeds. The rising left half — slower than the bottom of the curve — is the 'backside.' The name simply describes its position on the chart.
Why Pilots Care
Operating here without adding power produces an unintended descent or stall; recognizing the region allows the pilot to apply the correct power response immediately.
Grounding Statement
Picture the airplane flying slowly with a higher nose attitude: if it gets slower from there, it may need more engine power just to hold altitude.
Intuition Check
Backside does not mean the rear of the airplane. Here it means the slow-speed side of a power-required graph, where less speed requires more power.
Example Sentence 1
On short final at a high angle of attack, the airplane was operating on the backside of the power required curve, so the instructor used throttle to control the descent rate and pitch to control airspeed.
Example Sentence 2
On final approach the pilot allowed speed to decay into the backside of the power required curve and applied immediate power to arrest the sink rate.