Aircraft Propeller Systems Flashcards
Propeller
Rotating airfoil attached to jet engine through a reduction gear assembly. Used because it’s extremely efficient at low altitudes and air speeds. Has controllable pitch which provides forward and reverse thrust.
Propeller Slip
Is the difference between the geometric pitch of the propeller and it’s effective pitch.
Geometric Pitch
Distance a propeller would advance in one revolution in a solid medium. Is theoretical
Effective Pitch
Distance it actually advances. Actual
Blade Angle
Means of adjusting the load on the propeller in order to control engine torque and ultimately thrust.
4 types of Blade Angle
Zero Blade Angle, Positive Blade Angle, Negative Blade Angle, and Feather.
Zero Blade Angle
Occurs when blade is right angle to the propeller shaft. Not in position to produce power.
Positive Blade Angle
Occurs when blade is turned that leading edge is forwards and angles is increased.
Negative Blade Angle
Blade with leading edge rearward. Used to shorten landing roll.
Feather
Blade is turned so that leading edge is pointing fowards. Used when engine has been shut down inflight.
Propeller Efficiency
Propellers are responsible for absorbing power from the engine and converting the energy into aircraft forward motion. A propeller must be capable of changing its blade angle to adapt itself to varying flight conditions.
Thrust
Result of the shape and angle of the propeller blade. 80%, 20% lost in friction and slippage.
Barrel 3 main Functions
1) Retain the blades within the propeller assembly.
2) Transmit engine torque to the propeller blades.
3) provide means of attaching propeller to the engine shaft.
Dome
Mounted on the forward section of barrel assembly. Contains mechanism for changing propeller blade angles.
Spinner
Encloses the dome, barrel, and control assemblies in a streamlined housing.
