RMIT飞行训练课件－Constant Speed Unit

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Constant Speed Unit
Aim
• To gain an understanding behind the
operation and use of a variable-pitch
propeller (CSU)
Application
• When flying a CSU aircraft
• C182 or PA44
Overview
• Revision
• Definitions
• Principles
• Considerations
• Air Exercise
• Airmanship
Revision
• Fixed-Pitch Propeller
– Same rotational velocity (RPM), different
forward speed
Low Speed
Higher AoA
High
Speed
Lower AoA
Revision
• Fixed-Pitch Propeller
– Same forward speed, different rotational
velocity (RPM)
High rotational velocity
Higher AoA
Low rotational velocity
Lower AoA
Revision
• With a fixed pitch propeller
– If the aircraft is put into a climb, what will
happen to the RPM with a fixed power setting?
– If the aircraft is put into a descent, what will
happen to the RPM with a fixed power setting?
Definitions
• CSU
– Constant Speed (propeller) Unit, is a type of
propeller that has a variable blade angle
– It is called constant speed unit because the
propeller can be set to a certain RPM and
stay there with an increase or decrease of
power.
• Governor
– A mechanical device that keeps the propeller
at a set RPM, by means of springs and
flywheels
Definitions
• Propeller Governor Cut-away
Definitions
• Fine pitch
– Small blade angles, used at
low airspeeds
• Coarse Pitch
– Large blade angles, used at
high airspeeds
• Feather
– When the blade chordline is
parallel with the aircraft’s
relative airflow
• Pitch Stops
– Variable pitch propellers are
typically limited to angles
between 15 and 25.
Between these stops
(fine/coarse pitch stops) the
propeller acts as a CSU. At
the stops it becomes a fixedpitch
propeller.Governor
Blade
Angle
Definitions
• CTM
– Centrifugal twisting moment is the force acting on the blade,
trying to turn the blade towards a fine pitch
• ATM
– Aerodynamic twisting moment is the force acting on the blade,
trying to turn the blade towards a course pitch
Definitions
• Manifold Pressure (MAP)
– Is an indication of engine power, measured in
inches of Mercury (“Hg)
Principles
• Efficiency
– Fixed pitch propellers have only one blade angle, which equates
to efficient operation at only a certain airspeed.
– Variable pitch propellers can change the blade angle, so that the
blade angle can be the most efficient through all stages of flight
Principles
• Varying airspeed
– At Low airspeeds the blade angle is small, therefore
fine pitch
– At hight airspeed the blade angle is large, therefore
coarse pitch
Principles
• Change of Power
– Pitch lever controls the blade angle
Principles
• Pitch Adjustment
– Pitch lever is attached to a speeder spring
– This adjusts spring tension which sets RPM
• Various systems:
– Non-Feathering Systems (Single Engine Aircraft)
• McCauley Non-Feathering System (C182)
• Hartzell Non-Feathering System (PA28R)
– Feathering System (Multi-Engine Aircraft)
Principles
• Hartzell System
Principles
• McCauley system
Principles
• Once a certain RPM is selected, the CSU senses a
deviation from the set RPM and adjusts the blade angle:
– Straight and level flight, open throttle, propeller will coarsen
– Raise the nose, IAS will decrease, propeller pitch will be finer to
stop RPM reducing
– Descent or dive, IAS will increase, propeller pitch will coarsen to
maintain RPM
Considerations
• Pre-Flight
– Check for leaks and secure blades.
• Ground Operations
– Important to do propeller check to get warm oil into
hub to ensure serviceable system.
• Failures
– In Single engine, speeder spring fails, flyweights will
fly out, making propeller go to coarse pitch stop.
– Oil pressure failure, propeller will go to fine pitch stop.
Air Exercise
• Changing Power
– As a rule of thumb, keep MAP below RPM!
– Use power settings (MAP and RPM) as
shown in POH (5-21 to 5-30)
– Stay within limits as per POH
• Increasing Power
– Pitch up, Power up.
• Reducing Power
– Power down, Pitch down.
Air Exercise
• Taxiing
– Aircraft is at the fine pitch stop, so it will act as a fixed
pitch propeller
• Take-off (POH 4-15)
– Propeller is at the fine pitch stop, so the propeller will
act as a fixed pitch propeller – immediate power
available
• On Final Approach (POH 4-17)
– Pitch full fine
– Undercarriage down and locked
– Flaps
Air Exercise
Airmanship
Airmanship
• Pre-flight inspection
– Check for oil leakage
• Power changes correct
• Smooth coordinated power usage
• Thorough checks

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xy8701

谢谢楼主，我正准备去RMIT读书