RMIT飞行训练课件-PROPELLERS螺旋桨
**** Hidden Message ***** PROPELLERS<BR>Aim<BR>• To understand the principles and<BR>considerations in a propeller producing<BR>thrust.<BR>Application<BR>• All stages of flight where the engine is<BR>running<BR>Overview<BR>• Definitions<BR>• Principles<BR>– Effect of Airspeed<BR>– Effect of Rotational Velocity<BR>– Blade Twist<BR>– Efficiency<BR>• Considerations<BR>• Airmanship<BR>Definitions<BR>Blade<BR>• an aerofoil which<BR>converts engine<BR>power into thrust.<BR>Definitions<BR>Blade Face<BR>• the flat side of the blade<BR>• What you see from the cockpit<BR>Blade Back<BR>• the cambered side of the blade.<BR>Definitions<BR>Blade Angle<BR>• the angle between the blade chordline and the plane of rotation.<BR>Angle of Attack<BR>• the angle between the chordline of the blade and the relative airflow.<BR>Definitions<BR>Helix Angle<BR>• the angle between the resultant velocity of<BR>the blade and the plane of rotation.<BR>• Sometimes Referred to as “advance<BR>angle”<BR>Definitions<BR>Fixed Pitch Propeller<BR>• A propeller which the blade angle or<BR>“pitch” cannot be changed<BR>Definitions<BR>Torque<BR>• resistance to motion in the plane of<BR>rotation.<BR>• “Rotational Force”<BR>Definitions<BR>Engine Rotation Force<BR>• Force that turns the propeller<BR>Propeller Torque<BR>• Produced by the drag of the propeller<BR>blades<BR>• Opposes the Rotation of the Propeller<BR>Principles<BR>For Constant Propeller RPM<BR>• Propeller Torque = Engine Rotation Force<BR>• Propeller Torque > Engine Rotation Force<BR>– RPM Decreases<BR>• Propeller Torque > Engine Rotation Force<BR>– RPM Increases<BR>Principles<BR>• Effect of Airspeed<BR>Principles<BR>• Effect of Rotational Velocity<BR>Principles<BR>• The combination of the forward velocity<BR>and rotational velocity creates a helical<BR>motion of the propeller through the air.<BR>Principles<BR>Principles<BR>• Geometric Pitch is the theoretical forward<BR>distance<BR>• Effective Pitch is the ACTUAL distance<BR>travelled<BR>Principles<BR>Fixed Pitch Propellers<BR>• For a given rotational Velocity there is only<BR>one forward velocity in which the propeller<BR>operates most efficiently<BR>Considerations<BR>• Propeller Damage<BR>• Propeller Fatigue<BR>• Efficiency<BR>Airmanship<BR>• Always perform thorough pre-flight<BR>inspections on the propeller.<BR>• Handle the engine smoothly.<BR>• Low power settings on ground to avoid<BR>damage.<BR>Review<BR>• Which side of the propeller do we see from<BR>the cockpit?<BR>• What happens to the angle of attack when<BR>we increase RPM?<BR>• Why do we have “Blade Twist”? 收藏学习!感谢楼主:handshake 收藏学习!感谢楼主
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