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Which of the following signs could potentially indicate that the clutch of your main transmission drive system requires servicing? Select three of the provided answers.

1. Excessive brake-shoe dust around the clutch component.
2. Higher than normal main transmission oil temperature during operation
3. Abnormal vibrations during rotor engagement
4. Main rotor run-down time during shut down takes much less time than normal
5. Abnormal vibrations at 100% rotor RPM

  • A

    1, 3, 4

  • B

    1, 3, 5

  • C

    3 and 5 only.

  • D

    1, 2, 3, 5

Refer to figures.
Generally, the clutch facilitates the engine starting with minimal inertial loading, ensuring that the gearbox engages only after reaching a certain RPM.

The clutch is located between the engine and the main transmission.

It operates within an oil environment which is essential for cooling and proper functioning, consisting of a set of shoes that connect to a drum casing and are driven by the engine.

Centrifugal force keeps the shoes engaged with the drum, enabling power transmission.

As a result, the engine experiences reduced load during the startup process, apart from driving the standard components such as generators and pumps.

More specifically, the centrifugal clutch operates automatically and becomes more effective as the speed increases.

On the other hand, when the engine's rotational speed falls below the equivalent rotational speed of the rotor, the centrifugal clutch disengages, allowing the rotor to spin freely, which is crucial for autorotation during an emergency landing.

Regarding the signs:

  • Excessive brake-shoe dust around the clutch component will indicate issues with the transmission system.
  • Unusual vibrations during rotor engagement might indicate issues with the clutch. A malfunctioning or worn-out clutch can cause improper engagement, resulting in vibrations that can be felt during the engagement process.
  • A shorter run-down time for the main rotor during shutdown could be a sign that the clutch is not disengaging properly. This could be due to wear or malfunction in the clutch, leading to an incomplete disconnection between the engine and the rotor system.

Therefore, the correct answer is “1,3,4”.

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