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trisager

Couple of questions

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What a nice airplane! Looks good and flies well, what else can you possibly ask for? :Applause:I do have a couple of questions, perhap someone out there knows the answer:* Is the inverter modeled? I can't find it anywhere ...* On page 5 of the checklist document there is a table with takeoff power limits. How to read the last column (labeled "Tq Limit")? The numbers in that column don't seem to correspond to the torque gauge ...* Is there some trick to pulling the prop lever back into the feathered position? I can't get it to go all the way back.

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Tom,1. I couldn't find a reference to an inverter in the RW Grand Caravan manual, which suggests there isn't one.2. The TQ Limit column refers to the maximum OAT at which the engine will still be able to produce max torque for the given altitude. Above that temperature, and you won't be able to get 1865 ft/lbs. Essentially, the table is telling you that between the two temperatures, you'll get reduced torque, but you're still okay to take off (assuming everything else is good).3. Haven't tried feathering the prop.

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2. The TQ Limit column refers to the maximum OAT at which the engine will still be able to produce max torque for the given altitude. Above that temperature, and you won't be able to get 1865 ft/lbs. Essentially, the table is telling you that between the two temperatures, you'll get reduced torque, but you're still okay to take off (assuming everything else is good).
Got it now - thanks!

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Guest BeaverDriver

I "thought" I got the prop back into the Feather position once, but I've not been able to do it again (I was setting up FSUIPC at the time and I was able to bounce it in once or twice). I think it's possible, but I can't figure out how to do it.Thanks for the info on the Inverter question. I've been looking for that too. It's not in the RW manual? Again, if RW C208 pilots tested this, did they not pick up on this during beta? That one's pretty obvious.Thanks too for the info on the torque settings - I was unclear about that myself.

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Regarding prop settings: did anyone notice that the prop animation/model is in the feathered position regardless of the prop lever position when the engine is off?

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Guest BeaverDriver

Kurt may want to confirm this, but the C208 prop automatically goes into feather position on shutdown. A number of turboprops do this. Not sure if you can change that by a prop setting when the engine isn't running since you don't have any oil pressure going into the governor. So, I think this is correct.

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Thanks. I'm learning more and more... just too bad that information about intricacies like that needs to be found out by forum exchanges and not through the documentation that comes with the aircraft.

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Guest BeaverDriver
Thanks. I'm learning more and more... just too bad that information about intricacies like that needs to be found out by forum exchanges and not through the documentation that comes with the aircraft.
Amen to that! A POH would have been really handy.

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Amen to that! A POH would have been really handy.
Grand Caravan Pilots Information Manual can be found here.
Beta Mode is the engine operational mode in whichpropeller blade pitch is controlled by the power lever. Thebeta mode may be used during ground operations only.

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Thanks, Ken! Beat me to it!The Caravan's prop actually does go into feather on shutdown, as do all of the various PT6-powered aircraft. It's designed this way because the PT6 is a free turbine, so putting the pro in feather will stop the rotation quicker once the engine is shut down, and minimizes windmilling in windy conditions. Glenn's right, the prop governor run on engine oil, which is pressurized only when the engine is running. So, during start, the prop blades will match the commanded pitch once the engine oil reaches sufficient pressure...so you put the prop lever fully forward prior to start.

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After looking at this charts (thanks for the link, BTW) the cruise performance seems way too poor: according to the manual I should have had a cruise speed of about 160 KTAS, I could barely reach 140 KTAS, and I wasn't looking at the ITT which was out of limits of a good 20°, and my weight was 1000 pounds less than the chart reported (chart is at max weight). Something seems wrong, doesn't it? Cheers

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After looking at this charts (thanks for the link, BTW) the cruise performance seems way too poor: according to the manual I should have had a cruise speed of about 160 KTAS, I could barely reach 140 KTAS, and I wasn't looking at the ITT which was out of limits of a good 20°, and my weight was 1000 pounds less than the chart reported (chart is at max weight). Something seems wrong, doesn't it? Cheers
Absolutely agree, I'm also having troubles building speed past 130-140kts. I also find the "drop like a rock" tendency when the power is cut below 500lb torque a little extreme, the airplane noses over and loses airspeed like crazy. I realize that the Caravan is a bit nose heavy, but that much drop seems a bit unrealistic, though correct me if I'm wrong, I've certainly never flown a 208.

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Working on some config tweaks that should help the problem with the underpowered engine.As for the drop off in airspeed when you pull the power back, that's exactly what I'd expect for a PT6-powered airplane. Let's say that you've set your prop RPM to 1900 (which is max for this bird), and you're in level flight with 1200 ft/lbs on the TQ meter. When you push the power lever forward, you're increasing fuel flow to the engine, which increases turbine RPM. This, in turn, tries to increase the speed of the propeller. As the prop shaft speed tries to increase above where the prop governor (controlled by the prop lever) is set (1900 RPM), the governor increases the pitch of the prop blades, so that there is more air resistance to the rotation of the prop, maintaining the rotation at 1900 RPM but with more torque applied to the prop shaft. This produces more thrust, and also reduces the drag induced by the propeller, since the airflow coming from the front of the prop encounters less resistance as it flows through the prop.On the other hand, if you pull the power lever back, you are reducing fuel flow to the turbine, which now produces less power. Less power through the gear box to the prop shaft will tend to slow the rotation of the prop...but the governor again works to maintain the commanded 1900 RPM, this time by REDUCING the pitch of the prop blades. This means that the blades are now cutting the air more efficiently, edge-on to the rotation of the blades. But, now the flat of the blades offers more drag for the forward motion of the aircraft. This is what causes that rapid deceleration when you reduce the torque. After you get used to it, you'll rely on it as part of your landing technique.Incidentally, if you pull back too much, you'll go below Flight Idle, which may cause an engine overspeed and a loss of control.

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Guys, if you want to try, I spent the last hour playing with the parasite_drag value in the cfg, which is originally set at 1.5. The value 0.8 gives the best results I could obtain. I checked about everything, from the take off roll with and without flaps, max climb and cruise climb. Cruise settings are almost perfect with 0.8. The cruise climb is a bit too much improved, I get higher FPM than expected, but I thought it could arise...on the other hand all other values are correct. I didn't touch the ITT settings, because that would mean playing with the air file, not gonna do that. If other can try this value (or other values if you think this one is not good enough) and report your thoughts here, that would be nice and helpful, until we wait for a reply/fix from the developer. Now, I gotta go to sleep! ;)Cheers

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Absolutely agree, I'm also having troubles building speed past 130-140kts. I also find the "drop like a rock" tendency when the power is cut below 500lb torque a little extreme, the airplane noses over and loses airspeed like crazy. I realize that the Caravan is a bit nose heavy, but that much drop seems a bit unrealistic, though correct me if I'm wrong, I've certainly never flown a 208.
Is there a solution to this? Personally I find it annoying even if it is realistic.Thanks in advance guys.

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Absolutely agree, I'm also having troubles building speed past 130-140kts. I also find the "drop like a rock" tendency when the power is cut below 500lb torque a little extreme, the airplane noses over and loses airspeed like crazy. I realize that the Caravan is a bit nose heavy, but that much drop seems a bit unrealistic, though correct me if I'm wrong, I've certainly never flown a 208.
I also noticed this little extreme drop..!Maybe we can ask FEDE to take a look why it drops like that below 500LB

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Guest 413X3

It is realistic, it happens because the large surface area of the prop which turns into an air brake when rotating so slowly.

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It is realistic, it happens because the large surface area of the prop which turns into an air brake when rotating so slowly.
thanks, initially it was a shock but now when u expect it it is beter managed and actually not that bad as u know it is going to happen.

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