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The Iceman Cometh


MarkHurst

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I have been experimenting with icing in the Twin Otter and I thought I would share some stuff I have found useful. First off, if anyone has tried the icev10 gauge by Charles Owen, I have installed this in my VC to give me a visual indicator of ice buildup without needing to use the pop-up checklist. But this gauge doesn't just display an indicator, it also simulates additional icing effects, notably the accumulation of freezing rain and interference with the flight controls (simulating wing and tailplane stalls) when the ice load gets too high. Although the Twin Otter accumulates ice in freezing rain conditions, it appears just to be treated the same as regular ice, so you can get rid of it by operating the de-icer boots (or leaving them on Auto). (I'm sure Finn will correct me if I have this wrong!) The icev10 simulation doesn't shed freezing rain ice unless you fly out of the freezing conditions, which makes things much more of a challenge.

You can get the icev10 gauge by searching all the regular places for 'icev10.zip'. Unfortunately the original has a bunch of problems, which I have fixed by tweaking the XML file. I have attached that file to this message - all you have to do is install the gauge from the original zip file, then copy my XML file over the original one. (You will need to rename the attachment to 'IceWarning.xml' as I can't attach a file here with a '.xml' suffix.) You can install the gauge as a 2D panel if you want, but I have managed to pop it into the VC by putting it on top of the transponder. It covers up the altitude readout but that's no real loss.

post-28045-0-98594500-1434566769_thumb.j

To get the gauge here you need to add a line to the [VCockpit01] section of panel.cfg:

gauge16=ICE!IceWarning, 8, 441, 120, 60

You will notice that the position numbers are the same as those of the transponder gauge, so you can experiment with putting it in other places instead. It works over the clock too. It would be nice to get this in place of the stall warning but I don't know how to do it.

Although this now sort of works with the Twin Otter you will find that the Twin Otter de-ice functions do not shed FSX-accumulated ice, which I think tells us that the Twin Otter's structural icing model is entirely internal. So you will need to make sure you operate the FSX de-icing functions too if you want to dump the ice. You can just map different buttons or keys to do this but if you use LINDA as I do, you can add the requisite commands to the Lua functions so that they operate both the Aerosoft de-icing functions and the FSX ones. I have done this and I have also attached a file with the mods in so you can see what is required. If you are going to do this I suggest you integrate these functions into the full LINDA library file for the Twin Otter, which you can find linked from this post.

Finally, if you look closely at those Lua functions you will see I have also called the 'engine de-ice' function for each engine whenever the intake de-ice or inertial separator are switched on. This is the same control that operates the carb heat in a piston-engined aircraft and it has more or less the same effect, which is to cause a drop in power (about 15% in the Twin) Otter. I think this hit makes it more realistic and it means there is now a trade-off in using the engine de-ice functions. (Otherwise you might as well just turn them on and forget about them.) I have otherwise found that the engine icing failures and precautions work well in the Twin Otter and that you definitely need to use them!

I think that's it, so maybe you will be inspired to try your own experiments. If you want to see some of my experiments, check out the following two videos. You can find a playlist for all my 'close up' videos here.

IceWarning.xml.txt

icefun.lua.txt

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Hallo Mark,

nice feature for the Twotter; thank you for your work!

I´m using the icev10 gauge by Charles Owen in a few other aircrafts, but couldn´t manage it to work in the Twin Otter.

Thanks to your effort it´s now working in that fantastic aircraft too.#

Best wishes

Rainer

BTW: Fantastic flightdeck and nice videos

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Hallo Mark,

I´m using your XML-script too; but I´ve just done one flight with it and not in icing conditions. So, cannot report anything about how it works; but I will try and see (and report back).

Is there something special to look at to be interesting for you as the modificator?

Best wishes Rainer

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Is there something special to look at to be interesting for you as the modificator?

Not really, just that it does what it needs to (you should at least see the indicator 'indicating'!) It would be good to hear what happends if you fly on without doing anything about getting rid of the ice.

One shortcoming to note is that until you touch the de-icing controls the internal (Aerosoft) ice load will be pretty much in step with the FSX one and so the cockpit gauge will show more or less what the checklist page does. However, when you operate the de-icing boots (Aerosoft controls), the Twin Otter sheds its ice load gradually. This is not like the FSX control, which sheds all the ice immediately. It appears the Aerosoft de-icing boots don't shed the FSX-accumulated ice at all (or maybe it does when the inernal ice load falls to zero, I did not check that). I am not sure if the implications of this but I would expect that the aircraft will continue to carry the FSX ice load (and any performance penalty it incurs) until such times as you fly out of the icing and the ice melts naturally. Maybe this performance penalty is small compared to the drag added and removed by the Aerosoft icing model.

I don't think these are great limitations in practice. You should regard the cockpit gauge as a reliable warning of (1) when you have flown into icing conditions and (2) when you're going to start having problems controlling the aircraft.

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