Frequently Asked Questions:

Q: When and why should I have my propeller balanced?

A: Out-of-balance propellers cause vibration, which can lead to premature failure of components and contribute to one or more of the following:

• pilot fatigue
• leaky oil coolers
• cracked or broken exhaust manifolds
• sheet metal and cowling cracks
• broken or cracked engine and/or turbocharger mounts
• vacuum pump failure
• avionics, alternator, fuel control and engine wiring harness failures

Because of this, dynamic propeller balancing is essential for maintaining perfect propeller balance. Dynamic balance is concerned with the entire rotating assembly (engine and propeller) in its normal operation.

Q: How long will a dynamically-balanced propeller stay in balance?

A: Under normal use, the balance should be checked every 400-600 hours, or following propeller overhaul/repair or engine overhaul.

Q: How frequently should maintenance be performed, and what should I be looking for in the meantime?

A: A big part of preventing in-flight emergencies is to establish and adhere to a strict maintenance schedule. Propeller (and governor) overhaul periods deserve respect because what affects most propellers are not surface defects, but unseen internal corrosion. Never take your propeller for granted! Before you take off on that next flight, take the time to check it carefully. Here's what to look for:

• Is the propeller clean or covered in grime? (You can't determine the condition of a blade if you can't see it.)
• Are the blades scratched, pockmarked or nicked? This is a critical examination because blade separation starts with small stress concentrators in the metal. These stress concentrators weaken the metal.
• Are the blades tight in their sockets? Constant-speed propellers depend upon centrifugal force to seat the blades, but there should not be more than the slightest bit of movement.
• Check the propeller hub. With a spinner-fitted, it's often difficult to determine the condition of the hub, but you should be able to see the mounting hardware. Look closely for loose nuts or back-out bolts. Some propellers have oil-filled hubs to assist in detecting hairline cracks that might, otherwise, go undetected. Is there any evidence of red oil? If so, this must be investigated before flight.
• Is the spinner secure? A loose or off-center spinner can self-destruct in a few hours if not corrected. Grasp the tip of the spinner firmly and gently try to move it in a circular pattern -- just be careful not to overdo it because the spinner and backing plate can be easily damaged. That's why the aircraft should never be moved or lifted by, or pushing the nose of the spinner.

Got a question? Send it to us by email, by fax (717-560-4354), or snail mail (Sensenich Propeller Service, Inc., 519 East Airport Road, Lititz, PA 17543).