RMIT飞行训练课件－Constant Speed Unit

航空发表于 2010-9-10 09:24:37

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航空发表于 2010-9-10 09:24:49

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

猪也能飞 发表于 2013-10-28 19:20:45

感谢楼主万分感谢感谢万分

xy8701 发表于 2015-4-7 22:43:48

谢谢楼主，我正准备去RMIT读书

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RMIT飞行训练课件－Constant Speed Unit