A Condition Lever is a pilot actuated control which is located within the throttle quadrant of a turboprop engine equipped aircraft. It is utilised to control some functions of both the propeller and the engine. These functions vary from installation to installation.
Functions of the condition lever can include any of the following:
Fuel cut-off. Most condition levers incorporate a fuel cut off position. Selection of this position will result in fuel to the engine being electrically or mechanically shut off resulting in engine shut down due to fuel starvation. In some installations, this condition lever position is rendered non-functional by the weight on wheels switches anytime that the aircraft is not on the ground. The condition lever must be moved from cut-off to the "run" ("start/feather" in some cases) position when starting the engine
Propeller feathering. Dependant upon the installation, the condition lever feather position can also be the engine start position. Conversely, for many propeller / engine combinations, the feather position is also a fuel cut-off position which is active both in the air and on the ground.
Propeller un-feathering. This position, when fitted, is usually a "spring-loaded", momentary on position which is used to start the propeller feathering pump to drive the propeller blades out of the feather position. It is used to initiate the air-start sequence for an engine that had been previously shut down.
Low idle/high idle selection. Low idle is a ground selectable position which may be used when desired to select an alternate fuel schedule reducing both engine and propeller RPM for ground operations, thus saving fuel and reducing noise. In some aircraft, this function has been transferred to dedicated "low speed" selector push buttons.
Propeller speed control. Fitted for propellers which have more than one rotational speed setting available. The condition lever may have two or more detents corresponding to specific RPM settings (i.e. Takeoff, Climb and Cruise settings) or the lever may allow setting the propeller RPM to any value within an allowable range.