PROPELLER TRACK

An out of track propeller will suffer an imbalance caused by the Dynamic and Aerodynamic being out of balance.

Propeller track is the path followed by a blade segment in one rotation. If one blade does not follow in the same track as the others, its angle of attack and thus the thrust it produces, is different to the remaining blades, and vibration will result.

A simple blade tracking check would entail, chocking the wheels to prevent the aircraft from moving. Place a board under the propeller so the blade tip ‘nearly' touches it. Mark the board at the tip of the propeller, and then rotate the propeller until the next blade approaches the board...mark the second blade position. Repeat for all blades. It can be observed from the marks generated, the extent of tracking deviation between blades. The amount that blades can be out of track is specified in the relevant Aircraft Maintenance Manual (AMM).

For information only, an average ‘maximum' permitted deviation in track is 0.25 inches. Wherever possible the pointer should be attached to the aircraft structure to avoid the possibility of aircraft movement during the check.
Small propellers may be checked using a special mandrel, a surface table and a height gauge.