Effects of changing propeller rpm on propeller pitch
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@ barit : ah ok, we talked two ifferent things- my fault. i referred to pitch loks which prevent the prop goeing into feather at shutdown - like described such installation exists at singleshaft installation to reduce drag at startup and is not necessary at a free turbine since the core engine does not care about drag from the prop.
you talked about locking the pitch inflight when the governor wents out to avoid a destructive prop overspeed.
@ jammed stab: i think you also refer with the pw100 series to pitch locks which prevent an prop overspeed when the governor fails- i have no experience on lets say an atr- but seeing them shutting down the prop always feathers there. beyond that- interesting statement on your floatplanes , never heard this but it maybe true that such special installations are made there. what i can say for sure is that when you shut down a land plane with the pt6a the prop will fully feather, you do not even have a possibility to prevent it from feathering.
barit may be right that the situation of a prop going into feather with loss of oil pressure may be valid only for an installation where springs force the prop to high pitch /feather and oil pressure forces it to low pitch ( pt6a e.g) . with double acting oil systems things may be different.
thanks for the interesting details gents !
you talked about locking the pitch inflight when the governor wents out to avoid a destructive prop overspeed.
@ jammed stab: i think you also refer with the pw100 series to pitch locks which prevent an prop overspeed when the governor fails- i have no experience on lets say an atr- but seeing them shutting down the prop always feathers there. beyond that- interesting statement on your floatplanes , never heard this but it maybe true that such special installations are made there. what i can say for sure is that when you shut down a land plane with the pt6a the prop will fully feather, you do not even have a possibility to prevent it from feathering.
barit may be right that the situation of a prop going into feather with loss of oil pressure may be valid only for an installation where springs force the prop to high pitch /feather and oil pressure forces it to low pitch ( pt6a e.g) . with double acting oil systems things may be different.
thanks for the interesting details gents !
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JammedStab:
Were I editing this class note, it would say: "Aerodynamic and centrifugal loads on the propeller..." -- and -- were I a betting man, I'd say the centrifugal load creates a greater pitch torque than the aero. There are a couple accident reports I could quote to support this statement.
"Aerodynamic loads on the propeller tend to drive the blades toward low blade angles... "
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JammedStab:
Were I editing this class note, it would say: "Aerodynamic and centrifugal loads on the propeller..." -- and -- were I a betting man, I'd say the centrifugal load creates a greater pitch torque than the aero. There are a couple accident reports I could quote to support this statement.
Were I editing this class note, it would say: "Aerodynamic and centrifugal loads on the propeller..." -- and -- were I a betting man, I'd say the centrifugal load creates a greater pitch torque than the aero. There are a couple accident reports I could quote to support this statement.
Thanks.
