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Guest LSangiovanni LIML

What's the purpose of Auto-feather?

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and Prop-Sync?Can anyone please enlight me?Thanks in advanceLuigi ;-)

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In the real world, auto feather is a feature where incase an engine quits while in flight the prop will automatically go to full feather lessening drag from the dead prop and workload on the pilot during the emergency. Prop sync is a feature where each prop is running at exactly the same rpm and rate. In other words if you were to stop the props completely and they were in sync then the blades would be in the exact same position for each prop...I.E. one blade up two down. If you have ever been at your local airport and had the chance to watch a turboprop taxi out and runup then you may have noticed an annoying wah wah sound comming from the props as the pilot did the runup...this is the sound of an out of sync prop. I believe insync props increase effieciency, speed, and climb rate. I hope this has helped some for your understanding.:)

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Since a non-running propeller produces about the same drag as a disc with the same diameter (!) and would stall (and finally crash) the plane, the propeller blades of more advanced engines are able to be twisted 90 degrees around their longitudinal axis. This way, the pilot (or an automatic device) can turn the blades so that only the sharp edges of the blades are presented to the oncoming airflow, thus reducing drag tremendously. Autofeather is when some device automatically feathers the propeller in case of an engine cutout.Synchronizing the propellers means to synchronize the revolution rate and orientation of the propellers if the aircraft has two or more of them. So, synchronized engines don't differ significantly from each other, they behave equally. This meliorates the overall flight performance since the pilot doesn't need to adjust each engine separately to get the engines running uniformly.Hope this helps.Andreas

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An unfeathered prop WILL NOT stall and crash a plane, but it does make flying the plane a LOT more difficult. Another main reason for feathering the prop is that, in an unfeathered state with the engine not running, the force of the air on the prop will cause it to "windmill", which causes a LOT of damage to the engine, especially on free-turbine engines (like the PT6s on King Airs). With the prop in feather, the prop remains stationary, and prevents the prop/engine from turning, which reduces the asymmetric drag and prevents engine damage.Prop sync has no effect whatsoever on the performance of the airplane, it is there to prevent the audible resonance that out of sync props cause (the wah-wah sound mentioned earlier). Prop sync is never used on takeoff, because if there is an engine failure, the props will try to sync, and BOTH engines will slow down. Next time you are flying on a twin prop, listen for the resonance on takeoff, and you will understand why the sync is there. Nobody would want to listen to the resonance for an entire flight without going absolutely crazy.As a side note, some aircraft have syncrophasers as opposed to synchronisers. A synchrophaser differs in that it staggers the blades (if you took a snapshot in flight of a plane with the synchrophaser on, the props would look like this -x-O-+- ). This is done to prevent 2 blades from passing the fuselage at the same time, which reduces noise inside the airplane. Class dismissed! :D

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Hi friends,thanks a lot for helping.cheersLuigi ;-)

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