Definition
In a helicopter, pedal trim is the condition in which the anti-torque pedals are positioned so that the aircraft is in coordinated flight, with the slip/skid indicator (ball) centered and no sideward force on the airframe. It is the rotorcraft equivalent of keeping the ball centered in a fixed-wing airplane, and is achieved by applying the correct amount of left or right pedal pressure to balance main rotor torque at the current power setting.
Plain English
Pedal trim means using the foot pedals to keep the helicopter flying straight through the air, not sideways, with the little ball in the turn indicator centered.
Context Anchor
Seen in helicopter instrument flying when discussing trim systems that reduce pilot workload and help hold a steady attitude and heading.
Derivation
Trim' here means 'in proper balance or adjustment,' from the old English sense of arranging something neatly. Combined with 'pedal,' it points to the pedals being the control used to achieve that balance — just as 'rudder trim' would in an airplane.
Why Pilots Care
Reduces leg fatigue on long flights and improves precision when flying by reference to instruments.
Intuition Check
Pedal trim does not mean the pedals are decorative or optional. It means the pedal force is adjusted or held so the pilot does not have to fight the pedals continuously.
Example Sentence 1
After adding power in the climb, the pilot adjusted the pedals to restore pedal trim and recenter the ball.
Example Sentence 2
During the instrument approach, engaging pedal trim allowed the pilot to focus on pitch and bank without fighting yaw.