Definition
The amount of engine power available beyond what is required to maintain level flight at a given airspeed and configuration. Excess power is what an aircraft uses to climb; rate of climb is directly proportional to the power excess divided by the aircraft's weight.
Plain English
The leftover engine power after the airplane has used what it needs just to stay flying level. That leftover power is what lets the airplane climb.
Context Anchor
Seen in aircraft performance discussions and rate-of-climb graphs, especially where the handbook compares power available with power required.
Derivation
Excess comes from the Latin excedere, 'to go beyond.' Power excess literally means power that goes beyond what is currently needed — the surplus available for climbing.
Why Pilots Care
It determines how fast the aircraft can climb and whether it can clear obstacles after takeoff.
Analogy
Think of power like income and level flight like the bills that must be paid first. Power excess is what is left over after those bills are paid; that leftover is what the airplane can use to climb.
Grounding Statement
If an airplane needs 100 horsepower to hold altitude and the engine is producing 140, the 40 horsepower difference is the power excess — and that surplus is what lifts the airplane upward.
Intuition Check
Power excess does not mean unused throttle or wasted power. It means power above what level flight needs, and that surplus is what makes climbing possible.
Example Sentence 1
At higher altitudes the engine produces less power, so the power excess decreases and the rate of climb drops off.
Example Sentence 2
As airspeed increases beyond that point, power excess shrinks and rate of climb drops.