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softreset

(Another) Taxi question - Prop Question

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I just got done going through 3 years worth of taxi-related discussions in this forum but I was unable to find my answer. At the advice of one individual (to just taxing around for an hour) I tried that this morning at KBNA and after almost 90 minutes and almost 400 lbs of fuel, I never quite got it dialed in.

 

I'm aware of the turboprop modeling issues within FSX. I have FSUIPC (registered) friction module and I'm very comfortable taxing multiple A2A props, Flight1 & Carenado turboprops. But I'm struggling to get the Twin Otter tackled. After dialing up my torque for breakaway power and rolling the power back completely to idle one of two things happens:

 

- I continue to accelerate for several hundred feet (even with zero power and a sub 10psi torque reading)

- I come to a complete stop

 

For troubleshooting purposes, I've disabled all weather. Although I intend to typically fly with ASN.

 

What I'm trying to figure out and understand is the relationship of prop setting to taxi speed/control. I've gotten pretty comfortable taxing the aircraft at 3-6 kts ground speed and keeping it within that range. But the moment I give it more power (to taxi in a more reasonable 10-15 kt range I get the speed runaway). I have an axis for prop and power and I understand the need to move it slowly and deliberately as there's a delay in spool up & down. But even once the power settles at around 10-15 psi on the torque gauge I can still be cruising down a taxiway at 30+ kts within moments of breaking away.

 

My question, that I couldn't find in the manual, quick start guide or in one of those forum posts:

 

- Where should be prop % be set at while in ground operations?

 

I turned on cockpit tooltips and I've had the best luck in the 19-24% range or basically right above the point where the game engine puts my props into feathered (and spikes the torque). But whether I'm at 23% or 93% my runaway speed is still intermittent.

 

Thanks!

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11 hours ago, softreset said:

- Where should be prop % be set at while in ground operations?

 

 

As far as I know the prop levers should be fully forwards. The prop levers only control the prop pitch within the governed range, which you should not be in while on the ground. In real life the props are in the beta range at low power settings and the pitch is controlled by the power levers rather than the prop levers. Hence you should see that the prop levers only have any effect once the prop RPM rises into the green arc (75%+). In practice I don't think this is all really simulated, so I just do what you do - huge burst of power to break away, particularly on non-hard surfaces, and then taxi at idle with little bursts to keep me going if necessary or to get around tight corners.

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6 hours ago, MarkHurst said:

 

 

As far as I know the prop levers should be fully forwards. The prop levers only control the prop pitch within the governed range, which you should not be in while on the ground. In real life the props are in the beta range at low power settings and the pitch is controlled by the power levers rather than the prop levers. Hence you should see that the prop levers only have any effect once the prop RPM rises into the green arc (75%+). In practice I don't think this is all really simulated, so I just do what you do - huge burst of power to break away, particularly on non-hard surfaces, and then taxi at idle with little bursts to keep me going if necessary or to get around tight corners.

 

Mark,

 

Thanks. By the way, I thoroughly enjoy your YouTube series. I'm on episode 5 of the home cockpit build and working my way through it. I specifically watched the propeller video explanation prior to posting. After also watching numerous real world flights, I agree, the prop setting is full forward the entire time on the ground. I saw a couple videos where it appears to be at about 80% but it's never in the 20-30% range like I've experienced. I was mostly successful with a taxing at KJAU last night with the propellers at full forward, I just need to figure out a better FSUIPC sequence coming out of reverse as the torque has a tendency to spike and I go from 15 kts ground speed up to the low 30s before I begin to apply brake pressure.

 

It's pretty clear that this particular aircraft functions like an FSX turboprop but unfortunately different than the other turboprops I've been flying in FSX. So I need to learn how it works, rather than trying to handle it like I think it should operate. A wonderful experience, though, it will be a great route fulfiller on FSEconomy.

 

Thanks!

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1 hour ago, softreset said:

I just need to figure out a better FSUIPC sequence coming out of reverse as the torque has a tendency to spike and I go from 15 kts ground speed up to the low 30s before I begin to apply brake pressure.

 

Glad you like the videos - I am up to 41 now, although the last six or seven have been a bit of a wild goose chase!  Anyway, I agree - you just need to figure out how the Twin Otter behaves and work to that. Let's not kid ourselves this is like real life - I watched a cockpit video of the Twin Otter engine start and it was a lot more involved than the simulated start!

 

As for coming off reverse, you might have a look at my old Turbine Toucan videos (numbers two and three, I think), which show how to do it for that aircraft using FSUIPC. The Toucan is so powerful it can actually take off again before the engine spools down! Although I use analog control for the reversers on the Twin Otter I think the principle will still work. From memory, for the Toucan I programmed a 'throttle cut', then a single 'decrease throttle' action to put the pitch very slightly into reverse. All this can be triggered by the Saitek lever coming out of a bottom detent.

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4 hours ago, MarkHurst said:

As for coming off reverse, you might have a look at my old Turbine Toucan videos (numbers two and three, I think), which show how to do it for that aircraft using FSUIPC. The Toucan is so powerful it can actually take off again before the engine spools down! Although I use analog control for the reversers on the Twin Otter I think the principle will still work. From memory, for the Toucan I programmed a 'throttle cut', then a single 'decrease throttle' action to put the pitch very slightly into reverse. All this can be triggered by the Saitek lever coming out of a bottom detent.

 

Indeed, I watched that last night as well regarding the programming of the action on button release. I too have the Saitek lever so I'll look into tweaking it.

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