The Constant Speed Propeller

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The Constant Speed Propeller
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Introduction

• Describe how power is controlled with a Constant
  Speed Propeller
• Describe how the speed of the propeller is set
  and controlled
• State the limitations on the engine and propeller
• Describe the 2 elements of a Constant Speed
  Propeller Unit
• Describe the failure modes of the Constant Speed
  Propeller

3
Objectives

• State how to control power and engine RPM with a
  constant speed propeller
• State the limitations of RPM and engine power
• List the 2 main elements of a Constant Speed
  Propeller system
• Explain how the Pitch Change Mechanism and the
  Speed Governor work
• State the failure modes of the Constant Speed
  Propeller

4
Engine and Prop Controls
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Manifold Air Pressure (MAP)
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Control of Power (Low Power)
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Control of Power (High Power)
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Control of RPM (High RPM)
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Control of RPM (Low RPM)
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Control Indications
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MAP Change with Altitude
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Take Off and Climb
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Cruise
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Limitations

• The Slingsby Firefly T67M-Mk2
• The MAP must not exceed hundreds of RPM 4
• i.e. If the RPM is 2300, the max allowed MAP is
  27
• The RPM must not exceed 2700.

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Two Main Elements

• Speed Governor
• Senses speed of the engine
• Provides pressurised oil, hydraulic lock or a
  path to sump for oil to the pitch change
  mechanism
• Pitch Change Mechanism
• Changes pitch of the blades depending on the oil
  pressure from the Speed Governor

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Speed Governor
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Speed Governor RPM Control
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Speed Governor and Pitch Change Mechanism
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Pitch Change MechanismDecreasing Pitch
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Pitch Change MechanismHolding Pitch
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Pitch Change MechanismIncreasing Pitch
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Failure ModeUnderspeed

• Underspeed
• Caused by excessive pitch
• Loss of oil Pressure
• Failure of speed governor
• Failure of Pitch Change Mechanism
• Actions
• Check oil pressure
• Check MAP above 15 If not open throttle
• Exercise RPM through whole range
• Refer to checklist

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Failure ModeOverspeed

• Overspeed
• Caused by excessively fine pitch
• Speed Governor failure
• Pitch Change Mechanism failure
• Actions
• Use throttle to keep RPM within limits
• Leave RPM control at mid range
• Reduce speed 80kts
• Refer to failure checklist

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Summary

• How power is controlled with a Constant Speed
  Propeller
• How the speed of the propeller is set and
  controlled
• Limitations on the engine and propeller
• The 2 elements of a Constant Speed Propeller Unit
• The failure modes of the Constant Speed Propeller

25
Questions

• State how to control power and engine RPM with a
  constant speed propeller
• State the limitations of RPM and engine power
• List the 2 main elements of a Constant Speed
  Propeller system
• Explain how the Pitch Change Mechanism and the
  Speed Governor work
• State the failure modes of the Constant Speed
  Propeller