Propeller System

Summary

The Diamond DA42 features a sophisticated propeller system with two three-bladed, constant-speed feathering propellers for each engine. The pitch of the propeller blades is controlled by a propeller governor, adjusting to maintain optimal RPM for different flight phases. The system, integrated with the electronic engine control unit (ECU), ensures consistent power and performance. In the event of engine failure, the propellers can feather to reduce drag and improve control, ensuring safe single-engine operations. The design relies on engine oil pressure and counterweights to achieve and maintain feathering, offering better control and efficiency.

Takeaways

• 😀 The Diamond DA42 is equipped with two three-bladed, constant speed, feathering propellers.
• 😀 The propellers are variable pitch and controlled by the propeller governor to maintain constant RPM during different phases of flight.
• 😀 The governor ensures the RPM stays constant despite changes in engine power or airspeed, optimizing engine performance.
• 😀 The propeller pitch control system is integrated into the Electronic Engine Control (EEC) system, managed by the Electronic Control Unit (ECU).
• 😀 Each propeller has a gear reduction ratio of 1.69:1, meaning the engine RPM is higher than the propeller RPM.
• 😀 The ECU adjusts propeller RPM based on the engine power level set by the pilot.
• 😀 The DA42's propellers are full feathering, counterweighted, and rely on oil pressure to adjust the blade pitch.
• 😀 The blades are driven to low pitch at high RPM when increased oil pressure is applied from the governor.
• 😀 The propellers can feather in the event of engine failure, reducing drag and improving performance.
• 😀 Feathering requires the engine power lever to be at idle and the engine master switch to be off, which dumps oil pressure from the governor.
• 😀 Counterweights on the propeller blades help move them toward the feathered position during an engine failure or loss of oil pressure.

Q & A

What type of propellers are installed on the Diamond DA42?

The Diamond DA42 is equipped with two three-bladed Mt constant speed feathering propellers, one for each engine.

How is the pitch of the propeller blades controlled in the DA42?

The pitch angle of the propeller blades is controlled by the propeller governor, which adjusts to maintain a constant RPM set by the pilot.

What is the function of the governor in the propeller system?

The governor ensures that the engine's rotational speed (RPM) remains constant across different power levels and airspeeds, optimizing engine performance.

What role does the Electronic Engine Control (EEC) system play in the DA42's propeller system?

The propeller pitch control system is integrated into the EEC system, which automatically adjusts the propeller RPM based on the engine's power setting.

What is the gear reduction ratio in the DA42’s propeller system?

Each propeller is geared down with a ratio of 1.69:1, meaning the engine RPM is higher than the propeller RPM.

What is the significance of the Feathering capability in the DA42’s propellers?

Feathering refers to adjusting the blade angle to minimize drag and the windmilling effect, improving aircraft control and performance, especially in the event of an engine failure.

How is the propeller feathering achieved in the DA42?

To feather the propeller, the power lever is moved to idle, and the engine master switch is turned off. This causes oil pressure to be dumped from the governor, allowing the counterweights to drive the blades toward the feathered position.

What is the role of counterweights in the propeller design of the DA42?

Counterweights are attached to each propeller blade to oppose the aerodynamic forces of a windmilling propeller, helping move the blades towards a coarse pitch when necessary.

Why is a constant supply of high-pressure engine oil crucial in the DA42 propeller system?

A constant supply of high-pressure engine oil is necessary to keep the propeller from feathering during normal operation and to enable feathering in the event of engine failure.

What happens if there is a loss of oil pressure or a failure in the propeller governor on the DA42?

In the event of a loss of oil pressure or failure of the governor, the propeller will feather automatically due to the counterweights and spring mechanism in the propeller hub.