Definition
The path of an airplane's total energy state over time, considering both its altitude (potential energy) and airspeed (kinetic energy) together, and how those quantities are changing as a result of pitch, power, and drag inputs.
Plain English
The way an airplane's height and speed are heading together, treated as one combined picture rather than two separate things.
Context Anchor
Seen in energy management discussions, especially when visualizing how an airplane moves between climbing, descending, speeding up, and slowing down.
Derivation
Energy comes from the Greek 'energeia,' meaning activity or work being done. Trajectory comes from the Latin 'trajectoria,' meaning a path across. Together the phrase describes the path that the airplane's working energy is taking — not just where it is going through the air, but where its altitude and speed are heading.
Why Pilots Care
It shows pilots how to perform precise altitude and speed changes efficiently without unnecessary power adjustments, improving safety and control during training and normal flight.
Grounding Statement
Picture an airplane on final approach. If it is descending toward the runway and the airspeed is also bleeding off, its energy trajectory is heading downward in both senses — losing height and losing speed at the same time. The pilot sees this as one combined trend, not two separate gauges.
Intuition Check
Do not read energy trajectory as just the airplane’s path through the air. Here, it means the direction its speed-and-altitude condition is changing.
Example Sentence 1
On a stabilized approach, the pilot monitors the energy trajectory to ensure the airplane will arrive at the threshold at the right height and the right speed.
Example Sentence 2
The pilot used the energy trajectory concept to descend at constant airspeed by trading altitude for kinetic energy.