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The Beechcraft Turboprop – PT6
Propeller Auto-Feather System
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Auto-Feather Purpose: The purpose of the auto-feather system is to to provide an automatic quick feathering of a single propeller during the critical stages of flight – Take-off and Go-Arounds in particular.
peration: The operational modes consists of: !. Arming the system ". Automatic operation of the system in " distinct stages #. Testing the system on the ground $efore flight.
Arming !. Arming the system is accomplished $y the selection of the %Auto-Feather Arm& s'itch $eing placed to the on position. ". (hen armed the electrical paths are completed from a single Auto-Feather circuit $reaker through the arm s'itch to the po'er lever s'itches. #. (hen the po'er levers are moved for'ard past the s'itch point )*aries 'ith aircraft model – typical +, g/ the electrical path is delivered to the nside high pressure torque s'itch 0. 1ince the engine is running the torque system 'ill have provided more than the high pressure torque s'itch is set at – thus the high pressure and lo' pressure torque s'itches are in the %Pressure& positions. 2. (hen the Po'er 3ever is advanced and the s'itches are activated the system 'ill no' $e %Armed& This is indicated through the annunciator $eing controlled $y the %Arm 3ight 4elay&. 5. The electrical po'er is delivered to the %ffside Feathering 6ump *alve 4elay& 7. The ground for the Feathering 6ump *alve 4elay& is open at the %nside& 3o' Pressure 1'itch. 8. The system is no' %Armed& - each 6ump *alve 4elay $eing po'ered through the ffside high pressure s'itch circuit.
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peration: !. (hen an engine fails 'ith the Po'er 3evers in the for'ard position )9igh Po'er/ the torque 'ill drop very quickly. ". (hen one engine torque reaches a value ust less than the high pressure s'itch; the s'itch activates and removes po'er from the offside 6ump *alve 4elay. #. At the same time it 'ill remove po'er from the offside annunciator indicating the autofeather function is not availa$le for that engine. 0. (hen the torque pressure drops $elo' the lo' pressure s'itch setting the s'itch activates and provides a ground for the onside 6ump *alve 4elay. 2. The relay 'ill activate and dump propeller oil control pressure allo'ing the propeller to feather. 5. nce a single high pressure s'itch is activated 'ith lo' pressure; the offside is automatically inhi$ited. 7. The system can $e reset $y starting the engine and once the torque is a$ove the high pressure s'itch setting and the po'er levers are for'ard of the s'itch activation points. 8. The system is dis-armed $y retarding the po'er levers $elo' the s'itch activation points. This means for e
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Testing
!. A test s'itch is provided for the testing of the Auto-Feather system on the ground under very much reduced po'er settings. ". The test s'itch $ypasses the Po'er 3ever s'itches – this means that the requirement to have the Po'er 3evers at a very high setting is negated. #. >ach engine is tested individually to ensure correct system operation. 0. The Arm s'itch is selected to the on position. 2. ?oth Po'er 3evers are advanced to give ust over the required 9igh Pressure s'itch torque. 5. @f the system is 'orking correctly $oth Auto-Feather Annunciators should $e illuminated. 7. Then one engine po'er is reduced to under the high pressure s'itch setting $ut a$ove the lo' pressure s'itch setting. At this point the Auto-Feather Armed annunciator on the offside engine should e
!. The only rigging requirement is for the position of the Po'er 3ever s'itches. An easy 'ay to check is to complete a po'er run on the engines and using a strip of masking tape dra' a line on the tape that corresponds to the correct g speed of the engine. After shutdo'n this can $e referenced to check the po'er lever s'itch activation point and determine if any adustment is needed.
by FreeBee is licensed under a Creative Commons Attribution 3.0 International License
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by FreeBee is licensed under a Creative Commons Attribution 3.0 International License
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by FreeBee is licensed under a Creative Commons Attribution 3.0 International License
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by FreeBee is licensed under a Creative Commons Attribution 3.0 International License
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by FreeBee is licensed under a Creative Commons Attribution 3.0 International License
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by FreeBee is licensed under a Creative Commons Attribution 3.0 International License
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by FreeBee is licensed under a Creative Commons Attribution 3.0 International License
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by FreeBee is licensed under a Creative Commons Attribution 3.0 International License
