Definition
A failure to properly control the airplane's total energy state — the combination of altitude (potential energy), airspeed (kinetic energy), and engine power (chemical energy being converted to thrust) — resulting in too much or too little energy for the current phase of flight. Mismanagement of energy is a leading causal factor in loss-of-control accidents, runway excursions, stalls, and unstabilized approaches.
Plain English
Letting the airplane end up with the wrong combination of height, speed, and power for what you're trying to do — for example, too high and too fast on final, or too low and too slow on a go-around.
Context Anchor
You will see this idea in discussions of takeoffs, climbs, approaches, landings, go-arounds, and any situation where the pilot must keep the airplane at the right speed and height.
Derivation
Mismanagement comes from mis-, meaning wrong or badly, and manage, meaning to handle or control. Energy comes from a Greek word meaning activity or work. In flying, the word points to the airplane’s ability to keep moving, climb, descend, slow down, or speed up.
Why Pilots Care
Uncorrected low energy can lead to a stall or hard landing; excess energy can cause runway overrun or loss of control during flare.
Grounding Statement
If the airplane is too slow and low on final, or too fast and high close to the runway, the pilot is dealing with an energy problem.
Intuition Check
Do not think of energy here as a vague feeling of motion or force. In this context, it means the airplane’s practical combination of speed, height, and power, and whether that combination fits the situation.
Example Sentence 1
Arriving at the final approach fix 500 feet high and 20 knots fast is a classic example of mismanagement of energy that often leads to a long, unstabilized landing.
Example Sentence 2
High energy on a short runway forced a go-around rather than forcing a landing that could end in an overrun.