RMIT飞行训练课件－Constant Speed Units
**** Hidden Message ***** RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 1<BR>CONSTANT SPEED UNIT<BR>Aim: To understand the principles behind the operation and use of a variable-pitch<BR>propeller (CSU).<BR>Application:<BR>- Anytime when flying an aircraft fitted with a CSU<BR>- C182 or PA28R<BR>Revision:<BR> Fixed-pitch Propeller<BR>- Same rotational velocity, low forward velocity = high AOA, and vice versa.<BR>Definitions:<BR> Fine Pitch<BR>- small blade angles, used at low airspeeds.<BR> Coarse Pitch<BR>- large blade angles, used at high airspeeds.<BR> Feather<BR>- when the blade chordline is parallel with the aircraft’s relative airflow,<BR>minimising drag.<BR> Pitch Stops<BR>- variable pitch propellers are typically limited to angles between 15 and<BR>25. Between these stops (fine/coarse pitch stops) the propeller acts as a<BR>CSU. At the stops it becomes a fixed-pitch propeller.<BR> Governor<BR>- once set, the governor maintains a constant propeller speed, therefore<BR>constant RPM. This is done through speeder springs and flywheels.<BR>Principles:<BR>- By employing a CSU, a more efficient blade angle can be obtained during<BR>most phases of flight.<BR>- Low airspeeds, blade angle small, therefore fine pitch.<BR>- High airspeeds, blade angle large, therefore coarse pitch.<BR>Brief 26<BR>RMIT Flight Training Constant Speed Unit<BR>RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 2<BR> Change of Power<BR>- pitch lever controls the blade angle.<BR>- throttle controls engine power, measured in inches of Mercury (“Hg).<BR>Termed manifold pressure.<BR>- once RPM is selected, the CSU senses deviation from the set RPM and<BR>adjusts the blade angle.<BR> Constant RPM, open throttle, coarsen<BR> Raise nose, IAS , finer pitch to stop RPM reducing<BR> Dive, IAS , coarser pitch to avoid overspeeding<BR> Pitch control lever is attached to speeder spring. This adjusts tension which<BR>sets RPM. Speeder spring attached to flyweights. These operate with<BR>centrifugal force, reacted by springs. Movement of flyweights adjusts oil<BR>control valve. Oil flows to hub, where its pressure manipulates a piston, which<BR>is mechanically linked to the blade root. Pressure equalises, valve shuts.<BR>Brief 26<BR>RMIT Flight Training Constant Speed Unit<BR>RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 3<BR>McCAULEY NON-FEATHERING SYSTEM. (C182)<BR>Brief 26<BR>RMIT Flight Training Constant Speed Unit<BR>RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 4<BR>HARTZELL NON-FEATHERING TYPE. (PA28R)<BR>Brief 26<BR>RMIT Flight Training Constant Speed Unit<BR>RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 5<BR>Considerations:<BR> Pre-Flight<BR>- check for leaks and secure blades.<BR> Ground Operations<BR>- important to do propeller check to get warm oil into hub to ensure<BR>serviceable system.<BR> Multi-Engines<BR>- following failure align blade with relative airflow to minimise drag.<BR>(Feathered engine).<BR> Failures<BR>- in Single engine, speeder spring fails, flyweights will fly out, making<BR>propeller go to coarse pitch stop.<BR>- oil pressure failure, propeller will go to fine pitch stop.<BR>Air Exercise:<BR> Changing Power<BR>- must always keep MP below RPM!<BR> Reducing Power<BR>- Power down, Pitch down.<BR> Increasing Power<BR>- Pitch up, Power up.<BR> On Final Approach<BR>- Pitch full fine<BR>- Undercarriage down and locked<BR>- Flaps<BR>Airmanship:<BR>- Pre-flight inspection<BR>- Power changes correct<BR>- Smooth coordinated power usage<BR>- Thorough checks<BR>Brief 26<BR>RMIT Flight Training Constant Speed Unit<BR>RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 6<BR>GOVENOR CUT-AWAY<BR>Brief 26<BR>RMIT Flight Training Constant Speed Unit
页:
[1]