Definition
The acceleration produced by Earth's gravity on a free-falling object near the surface, with a standard value of approximately 32.17 feet per second squared (9.81 meters per second squared). In aviation energy and performance calculations, it is the fixed value used to relate an airplane's mass to its weight and to convert between potential energy (altitude) and kinetic energy (speed).
Plain English
A fixed number that describes how strongly Earth pulls things downward. Pilots use it as the unchanging value behind weight, climbs, descents, and energy trade-offs.
Context Anchor
You see this term in the chapter that explains the airplane as an energy system, especially when altitude is treated as stored energy that can be exchanged for speed or distance.
Derivation
From Latin gravitas, meaning weight or heaviness, and constant, meaning unchanging. The name simply says what it is: the unchanging value of how heavy gravity makes things feel near Earth's surface.
Why Pilots Care
Correct use of the value keeps energy calculations accurate for altitude-to-airspeed conversions and safe glide distances.
Grounding Statement
Drop any object near the ground and it speeds up by about 32 feet per second every second it falls. That rate is the gravitational constant.
Intuition Check
Do not confuse this with pilot “G-load” or with a changing force you feel in a maneuver. Here, gravitational constant means the standard gravity value used in a simple energy formula.
Example Sentence 1
When the airplane descends, potential energy converts into kinetic energy at a rate governed by the gravitational constant.
Example Sentence 2
When trading altitude for airspeed the pilot relies on the gravitational constant remaining fixed throughout the maneuver.