Ground-adjustable propeller
A ground-adjustable propeller is a simple type of aircraft variable-pitch propeller where the blade angle can be adjusted between pre-set limits of fine and coarse pitch. As its name implies, a ground-adjustable propeller may be adjusted only when the aircraft is on the ground and when the engine is not running.
Ground-adjustable propellers, which are mostly used on light and very light aircraft, are much cheaper and lighter than more sophisticated and versatile in-flight-adjustable propellers. A ground-adjustable propeller allows pitch changes to be made, although not in flight, to optimise the aircraft for current payload and flying conditions.
Adjustment
To adjust the propeller, the blades are loosened in the hub, a new angle set and then the hub tightened. The process is one of compromise, and of trial & error. After a flight, if, say, climb seemed too sluggish, the pitch angle may have been set too coarse and would need to be made finer. Alternatively, if the aircraft reached take-off speed quickly but struggled to reach a comfortable cruise speed, the pitch would need to be coarsened. The person making the adjustments would be advised to do so in small increments until a satisfactory outcome were reached.