Propeller Overspeed

In aviation, a propeller overspeed occurs when the propeller's rotational speed exceeds its safe operational limits, often due to a governor malfunction or a sudden increase in engine power, potentially leading to propeller damage or failure.

Here's a more detailed explanation:

What it is:

A propeller overspeed happens when the propeller, usually connected directly to the engine, starts turning too fast.

Causes:

• Governor Malfunction: The primary propeller governor, also known as the Constant Speed Unit (CSU), is responsible for maintaining a constant propeller speed. If this governor fails, the propeller can overspeed.
• Loss of oil pressure: If the oil pressure decreases significantly but there is still sufficient engine power, the propeller can go several hundred RPM above redline.
• High-speed airflow: In a propeller aircraft, an overspeed can occur if the propeller is forced to turn too fast by high-speed airflow while the aircraft is in a dive.

Consequences:

• Propeller damage: Overstressing the propeller blades and hub can lead to failures that can break the propeller apart.
• Engine damage: In some cases, an overspeed can lead to engine damage or failure.

Safety Measures:

• Immediate throttle reduction: If an overspeed occurs, immediately reduce the throttle to idle.
• Best-glide airspeed: Set best-glide airspeed and start looking for a place to land.
• Check oil pressure: Check the oil-pressure gauge, as many prop overspeeds result from broken oil lines or oil starvation.
• Plan for a landing: Plan for a landing as soon as practical.