Definition
A condition of flight in which the aircraft is neither speeding up, slowing down, nor changing direction. All forces acting on the aircraft — lift, weight, thrust, and drag — are in balance, so velocity (both speed and direction) remains constant.
Plain English
The airplane is flying at a steady speed in a straight line, with no change in how fast it's going or which way it's headed.
Context Anchor
Seen in straight-and-level flight, instrument flying, and discussions of how the flight instruments behave when the airplane is stabilized.
Derivation
From 'un-' (not) plus 'accelerated' (from Latin accelerare, 'to hasten'). In physics, acceleration means any change in velocity — including speed or direction. So 'unaccelerated' means no change in either.
Why Pilots Care
Simplifies lift, drag, and performance equations by removing acceleration variables.
Grounding Statement
Picture the airplane holding the same speed, same altitude, and same direction with no growing trend on the instruments.
Intuition Check
Do not read “accelerated” as only “speeding up.” If the airplane is turning, climbing, descending, speeding up, or slowing down, it is not in unaccelerated flight.
Example Sentence 1
In unaccelerated flight, lift equals weight and thrust equals drag.
Example Sentence 2
Performance tables assume unaccelerated flight when calculating true airspeed for a given power setting.