Did you know that the propeller is one of the most highly stressed components on your aircraft? During normal operation, the typical general aviation aircraft propeller will experience between 10 and 25 tons of centrifugal force! With all the forces at work on your propeller during flight, it stands to reason that the care and maintenance of your propeller should be a top priority.
One of the best ways to keep your propeller in good condition is by performing regular maintenance inspections to check for wear and damage. Along with visual inspections of your propeller, it’s important to check for proper blade tracking.
Your propeller blade tips should follow one another closely in the same plane of rotation. But if one of your propeller blades has been bumped, bent, or otherwise damaged, it will not track in the same rotational plane as the other blades.
To find out if your propeller is out of track, use this simple method:
First, chock the aircraft so it cannot be moved. Use best safety practices, ensuring that switches are off or grounding the magnetos to prevent the aircraft engine from starting while you rotate the propeller.
Next, remove one spark plug from each cylinder. This will make the prop easier and safer to turn. Rotate one of the blades, so it is pointing in the “down” position.
Place a solid object, such as a heavy wooden block, just under the tip of the blade. Use a pencil to mark the blade’s path on the wood. Leave the wood block in place and slowly rotate the propeller to see if the next blade “tracks” or aligns with the same mark on the block as the previous blade. The difference in blade track shouldn’t exceed the amount specified by the propeller manufacturer (usually the specified difference is 1/16 of an inch, plus or minus).
If you discover that a propeller blade is out of track, it could mean that the blade has been bent or damaged. It’s best to have an approved propeller shop address the problem right away. An out-of-track propeller can cause extra vibration and stress to the airframe and engine. Inaccurate tracking can also be a sign of premature propeller failure. Note: Never try to straighten a bent propeller blade yourself. Take it to a reputable propeller repair station.
A bent propeller blade could be caused by improper handling of the propeller itself, such as moving the airplane by pulling or pushing on the propeller. While propeller blades are made to be strong, you can cause some expensive damage by moving your airplane this way. It’s just not worth the risk—use a tow bar instead!
For more helpful propeller care and maintenance tips, check out Hartzell Propeller’s free video series.