Poor performance in icing conditions?

[meese91]

I just departed in wonderful -2°C and -RASN, i.e. proper good icing conditions. My first departure in icing conditions with the KA, I was pleased to see the ice slowly build on the flight surfaces while on ground. At the holding point, having only a few hundred pounds payload and 1900lb fuel, I completed one cycle to deice my surfaces (confirmed visually that they were, waited for light to extinguish), then departed. Vr at about 105, pitch slowly up to 10°, no increase in altitude. Increased to 11-12°, speed holding pretty much at blue line, and VS started to slowly build to about 300ft/min. Gear up, verified flaps was never anything but up, and rate increased slowly to 500fpm. Luckily no terrain around, continued the climb watching for ice buildups, cycling the anti-ice as appropriate. Managed to get to IAS 160 and 500fpm, kept that until passing the cloud layer tops at around 5000ft. The second I was out of the clouds, without any further deicing done, the rate increased from 500fpm to the more appropriate 2000ish at pitch 08-09 and 95% torque. It was like someone suddenly threw out a few tons of payload.

Has anyone else found insane levels of drag in icing conditions without actually being contaminated severely?

[KenG]

Tomas will have to answer this one. However, since you were on the ground it sounds like you may have built up icing aft of the protected surfaces.

Also if you took off into severe icing or SLD (supercool large droplets) you may have exceeded the deicing capability.

I know we had a huge discussion of the effects of icing and Tomas will have to tell us what exactly was implemented.

[Taguilo]

Hi,

I think what you experienced is severe ice buildup on the ground, triggered by P3D icing system, not ours.
P3D includes a severe icing model in which aircraft performance is clearly affected. The weak point of this systems is what you actually experienced: as soon as you leave the severe icing layer, ice effect on aircraft performance vanishes in a few seconds, which is not much realistic.

The KA includes a custom icing model, which in part also depends on P3D icing slider in wx menu, but not exclusively. Additional wx conditions may produce ice buildup, despite P3D slider position. However, severe icing (extreme) is triggered by slider in severe position, so you will notice, as Ken commented, ice formation beyond the boots and towards the inner wing; also thick ice on winglets. That is a dangerous situation that must be avoided; when encountered, flying away of the layer as soon as possible is the only safety action.

It seems what you got was a combination of our custom model and P3D severe model.

Tomas

[meese91]

Thanks for the explanation. Are there any settings in P3D or ActiveSky that will reduce/stop this effect? Operating in Norway at winter is bound to present conditions like these often and regularly, which is of course managed with some type IV fluid, so any tips on allowing winter ops without disabling real wx would be appreciated.

[jarek]

You may experiment with Options->Cloud Options->Maximum Cloud Icing in ActiveSky. Something between 50 and 75% is a good starting point. 100% is the default.