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Vultee

Prop Feathering

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Does anyone know if the real caravan shuts down when the prop is placed in the feather position on the ground. Or do you have to use a combination of feather and fuel shut off with the fuel lever. I was looking at the engine shutdown procedure and they say to shutdown engine using the feather position to stop the engine from rotating excessively during shutdown. I was not sure if its really a two step process. First increase blade angle to high using prop lever (Feather) then use the fuel shut off to kill the engine. Then when the engine stops the blade angle being high keeps the prop from excessive rotation during shut down. I have to use the Ctrl F2 key to drive prop to feather even grabbing it in the virtual cockpit does not allow it to get past the stop on the quadrant. I also see no blade movement when moving the prop lever but this could just be the sim limitation for the c208. On another note speaking of blade angles is there a way to align the joy stick throttle so they go into the beta range correctly. Right now it seems the mechanical stop on the quadrant at flight idle is actually the ground beta range but visually the throttle is at flight idle but the power shift (big drop in airspeed in flight) shows the engine and prop are actually in the ground beta range. Is there a way to align this better and have the throttle (visually) actually go over the stop into the beta. Is there a way of tweaking the acft cfg file or will I just screw up all the acft engine performance and best just leave it alone and accept it the way it is. Either way is fine. Just wanted to see if some of these tech savvy guys/gals have figured out some adjustments to make this a bit more realistic. i do have to say though that the Carenado C208 is a great product and I have really enjoyed flying it with its quirks too.

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I don't know about your hardware settings, but on the real Caravan the prop is feathered, then the condition lever moved to cutoff- so yes a two step process


Dave Scalora

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Thanks for response. I have a CH Product yoke and pedals first generation that I'm using to fly the C208. I think there is a way to tweak the levers with the sim but not sure how to adjust. The controllers are basic calibrated that's it. I would like to be able to move throttles into beta on my yoke and on the acft. They kind of are at beta, but indicate flight idle on the plane visually at the gate. If that's just the way it is on this model I can live with that no problem. Also out of curiosity when the prop is feathered does the fuel shut off too. I know on some acft feathering also shuts off the fuel mechanically and electrically at the same time. That is what I was wondering about. It sounds from your response that the feathering moves the blade angle only and the the fuel is shut off from another process.

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Correct, feathering the prop only moves the blades, the condition lever mechanically shuts off the fuel. In fact you can run the engine with the prop completely feathered.


Dave Scalora

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A good friend of mine flies the 208B for Morningstar (a Fedex feeder located in Canada). In his 208, he cuts the fuel, then moves the prop lever into feather, as the engine is still spinning producing hydraluic pressure to move the blades. You are correct, if you don't feather, you get dirty looks from the rampie's as they can't move in a load/unload or fuel the aircraft until the prop safely stops (or slows down significantly). If you do not feather the prop, the engine and prop will eventually slow down losing hydraulic pressure and eventually feathering the prop (about 2 min I think after shutdown). This is why you don't see the blade angle change with the propeller stopped, because there is no hydraulic pressure causing the blades to change angle of attack. This is somewhat of a safety feature, as if pressure is lost in flight, you aren't stuck with a massive drag inducing device - yes the propeller actually produces quite a lot of drag! The prop feathers, and flight can continue until you lose speed, etc... Hope this helps!


Cameron Caldwell

CPL (A)

King Air 200 Pilot

 

 

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Thank you so much for the information. I'm trying to fly this bird as realistic as possible. I use the c208 a lot on my air hauler flights.

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With a controllable pitch propeller, turbine or piston, the propeller pitch is controlled by engine oil pressure against a spring.  A piston inside the prop hub is connected via control rods to the prop blades and this provides the movement.  Say for example you want to pull the prop back to 1650 for cruise, so you pull the prop lever back, this opens a valve in the prop hub allowing the spring pressure to push the piston farther into the cylander containing the engine oil, therefore pushing the oil back to the resivoir and reducing the oil pressure vs spring pressure.  This movement is transfered via the control rods increasing the pitch on the propeller and creating more rotational drag on the prop, therefore increasing the load on the engine and reducing engine speed.  So if the engine is not turning there is no oil pressure to control the pich of the prop and it does not move when you change the setting on the prop lever.

 

So in this case if you were to shut the engine off without feathering the prop first the drag on the prop blades would allow the engine to turn much more freely and take much longer for the engine to spool down.  Since oil pressure is present any time the oil pump is operating (which is any time the engine is turning since it's connected to the compressor shaft) there is oil pressure pushing against the feathering spring pressure and trying to maintain a low pitch/high RPM condition.  Since the prop is connected to a PT6 via the turbine shaft only it spins very freely and would take decades to stop on it's own (ok decades is an exxageration but it would take quite a while.)

 

So in the PT6 you feather the prop before moving the condition lever to cut off (or shortly after) to add the drag to the prop and slow it much faster, allowing the prop to stop sooner, to make it safer for everyone involved.

 

 

I hope my low caffene explanation works, let me know if you have any questions.

 

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