Ground Idle

Ground idle refers to a specific, lower engine speed setting used while an aircraft is on the ground, typically for taxiing, engine checks, or before takeoff, as opposed to the "flight idle" used during flight.

Purpose

Ground idle allows for reduced fuel consumption and noise pollution while the aircraft is on the ground.

Characteristics

• Lower Engine Speed: The engine operates at a lower RPM than during flight idle.
• Reduced Thrust: Ground idle generates minimal or no thrust, depending on the aircraft type.
• Propeller (Turboprop): In turboprop aircraft, ground idle typically involves a flatter propeller blade angle compared to flight idle, resulting in more drag and less thrust.

Turboprops vs. Jets

While jets may have multiple idle settings, the distinction between "flight idle" and "ground idle" is more prominent in turboprop aircraft.

Ground Running

"Ground running" refers to the operation of an aircraft's engines on the ground for functional checks, and thrust levels above ground idle should be applied symmetrically.

Safety

Engine operation above ground idle requires personnel to be clear of the aircraft.

Dangers of Flight with Power Below Flight Idle

Any operation of the power lever below flight idle while in flight must be avoided unless specifically permitted by the Aircraft Flight Manual (AFM).