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darthbrooklyn

Twin Otter Flight Dynamics question

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You are correct Ken.

The PT6A's of the Twin Otter has condition levers that are on / off only.

Finn

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The short answer is keep these two gauges out of the red zone at all time. Even on takeoff you should avoid overtorquing the engines. The torque gauges each have a slender red line on them. That is the limit of engine power you should command with the throttle levers.

Well, I'm amazed. I might have been doing the right thing all along :D

I noticed right from the start that the rpm gauge went over the red line at take off and stayed there all through the climb out. I thought 'this can't be good'. So, I experimented with the prop levers. Now, when I line up for take off, I set them so they are almost in a vertical position and then run the engines up. The prop speed peaks just under the red line and the turbine needle stays out of the red. I seem to get a better acceleration as well, Once the flaps are up and I'm in the climb out I set them to 85% and then start playing with the trim to give me the desired rate of climb (usually 800 fpm).

I only return the levers to the max settings when I've reduced the power and I know that moving the lever won't take me beyone the red line.

You get slightly better fuel consumption rates as well :D I suppose when 1.1 is released I'll have to relearn all this again :D:D:D

Kind Regards,

Cliff

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Okay then............. It's obviously fast approaching time someone wrote a tutorial for this splendid aircraft.

Who's up for it then....???

Kan-ichiro, thanks for the book reference - will search it out.

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Actually, according to pbearsailor (our resident actual Twin Otter pilot) he set 95% prop RPM for climb and then set 75% for cruise.

Cheers,

Ken

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Thanks for that Ken,

I've been doing other things with flight sims for a week so I'm running from memory here.

As you decrease the prop % rpm all goes well until about 70% - 75% when the noise increases and the prop % rpm just falls through the floor. I've not hung around to see what the aircraft is doing at this point because I've put the levers back where I found them :lol:

'Wasn't me! I never touched that!' :shock:

I'll have to have a go tonight. Having first got to a few thousand feet - just in case . . . :D

Kind Regards,

Cliff

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The propellers in the real Twin Otter's, as well as the Aerosoft versions, are only governered in the range from ~70% - 100%.

In the real twotter it works like this:

From ground idle to flight idle (approximatly the range where the beta range lights are on), the propeller blade angle are altered direct.

From flight idle (appr.) to full power, the propeller are governered by the propeller governor.

In the real twotter there are linkages between the propeller and the power lever that makes certain settings impossible.

That can´t be done in FSX, at least not when following the SDK.

Regards

Finn

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You are correct Ken.

The PT6A's of the Twin Otter has condition levers that are on / off only.

Finn

As mentioned in the Aerosoft manual: "....they actually have two settings, OFF when pulled fully back and ON in any other setting."

But it seems that fuel flow slowly decreases when pulling the levers aft. While having a GG rpm of 70 % and prop rpm of 50% with fuel levers fully forward, I get 62% GG and 20% prop with fuel levers shortly before cutoff.

Isn't that a high and low setting or did I get something wrong ?

What is it like in the real Twin Otter ?

Regards,

Andy

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In the real Twin Otter it´s only on / off.

As long as You make sure that the levers are either fully back (Fuel cutoff) or Full Forward, everything should be ok.

Regards

Finn

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The reason that you get a gradual decrease in power when moving the Twin Otter condition levers is probably due to how FSX handles turboprop modeling.

What's probably happening is that FSX is only set up for turboprops that have a flight and ground idle position on the condition levers (like the King Air), and it's not capable of properly modeling a turboprop engine that has only an on and off setting for the condition levers without using some invisible gauges or something similar.

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I think that's the point. Seems to be another limitation of the SDK, but as long as I know how to operate it correctly... no problem in this case, just move the levers fast enough and nobody will notice :wink:

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