Ekran and Rotor Anti-Ice

[Sm0k3y]

Correct me if I'm wrong, but I'm pretty sure that the de-icing setting has this switch in the up position, down is only dust protection.

 

No correction needed.

[159th_Viper]

Correct me if I'm wrong, but I'm pretty sure that the de-icing setting has this switch in the up position, down is only dust protection.

 

Aye - as said, Up is On. Always good to also confirm via the Message Lamps that it is engaged, as the Switch has 3 positions, the middle (off) position is by default also slightly up as opposed to fully up.

[Sm0k3y]

Can anyone answer as to why I only had 50% mission completion on Altitude?

 

All aircraft survived, although one did get hit by a SAM and had smoke bellowing out of his engines, but checking the mission in mission editor the only things that you loose points on are aircraft dying, supposed to get +25% each for each one of the four transports that make it back alive.

 

Could it be that my wingman didnt land? I got impatient waiting for him to land and he wasnt replying to RTB requests.

 

Im not a perfectionist and dont mind that I dont get 100% except for the fact that it wont show in the log book unless you do.

 

EDIT: Or could it have something to do with ATC saying "Use Extended" or "Use Alternate" shortly after getting clearance. I didnt know what that meant so I just waited for all four transports to land then landed on a free pad.

Edited November 7, 2009 by Sm0k3y

[ARM505]

Sorry, carrying on my question from above:

 

Yeah, I know WHY I need anti-ice IRL, but perhaps I should rephrase my question:

 

If you do NOT have anti-ice ON (rotor, engine, pitot, etc), and the temperature drops below 0 deg C (or whatever the modelled limit is) WHILST CLEAR OF CLOUD, will you get icing buildup? IRL, I've never, ever seen that (icing buildup in clear skies).

 

Put the other way, do you need both the following conditions to be TRUE for ice formation/engine performance degradation:

 

- temp below critical level (0 deg C is the obvious one, excluding compressability effects)

- be IN visible moisture (cloud, fog, mist, rain, etc)

 

I ask because I seem to recall losing an engine after the 'watch EKRAN' message myself, despite being clear of cloud, and a lot of the discussions here on this topic always end with the advice 'turn everything on when this message appears'. The thing is, I DON'T want to turn everything on - I'll have almost everything on as a matter of course, but the engine anti-ice I only want on if I really need it on, due to the performance loss incurred.

[EtherealN]

Yes, you can still get ice building up.

 

Being cloud free does not mean that the air is humidity free - what governs whether you get clouds basically is if the air is able to contain the water or if it condenses into clouds, normally this would happen at specific altitude (technically - pressure) points. As an example, fog can in some cases be completely the same as a cloud - just that you end up with the dewpoint right on the ground.

 

When you do not have clouds, it simply means it hasn't met the right temperature/pressure circumstances to condens the water.

 

Now consider what it is your airfoils actually do. Part of the job is deflecting air downwards, of course, another part works on differential pressures on the upper and lower surfaces. This means you might actually change the pressures with your rotorblades just enough to condens the water and the unfortunate part there of course is that this would be happening right onto surfaces you really want to be ice free - like your rotor blades or compressor blades. Pressure changes of this kind can also cause temperatures to change locally (ever seen how an air-driven pump can become frosty even in 30 degree heat?), wherefore the automatic systems will caution you to verify your anti-ice systems (engine, blades and pitot) already at 5 degrees.

[Frederf]

I think it is hard to get "clear air" ice on the airframe because the air is not moving around the airframe fast enough to drop the pressure-temperature enough to wring the water out of the air like a sponge.

 

The rotors and especially the engine are different, air is being pulled very fast around these parts and fast air means low pressure and temperature... all of a sudden visible moisture forms around these fast air flows and you get icing.

[ARM505]

Hmmm...this must be a helicopter specific thing then. In all my flying career (fixed wing), I've NEVER seen this occur on ANY surface of my aircraft (that I could see :) ), with one notable exception - carb icing (but that's a very specific case, given the other factors involved there). Nor is something like this described as a threat in textbooks, but perhaps I've just forgotten about reading it. Sorry to appear sceptical, I'm aware of the theoretical possibility and indeed the theory behind it, but since I've never ever seen or heard of it from my own personal experience or that of colleagues IRL, I find it slightly off-putting that it seems to occur 100% of the time based solely on temperature alone - or does BS somehow consider humidity too? I grant that 'trace' icing (EXTREMELY light coatings of icing) could have occured from this, but enough to literally shut down an engine?

Edited November 9, 2009 by ARM505

[EtherealN]

Well, icing on a turbine compressor is a pretty serious thing, even if it's pretty light ice.

 

Would have to get word from some of the people here who work on these specific engines to get something authoritative, though.

[AlphaOneSix]

I have a lot of hours of flying (as a flight engineer) in an Mi-17 with temps at or below 5C and we never turn on the anti-ice unless we have visible moisture, and we have never had ice buildup.

 

Oh and flying at 90 knots at -18C with the doors open and the cabin heater off....brrrrrrr.

[EtherealN]

Not that the cabin heaters would be much good with the doors open, would they? :P

[AlphaOneSix]

Not that the cabin heaters would be much good with the doors open, would they? :P

 

Not really, but even with the cabin doors open, the pilots would get nice and toasty. But if the guys in the back suffer, we all suffer!

[RvETito]

The EKRAN warning keeps coming because it's activated by the ice detection sensor, the rotor anti-ice system has only manual mode so the sensor would not know whether you've turned the blades heating on.

 

Same goes for the engine intake ice protection system. IRL ,or at least in civil helicopters powered by TV3-117VMA engines it's automatic - below 5'C it operates the anti-ice bleed valve. In case of failure of the automatic funstion there is always a manual mode available. In this case you have to pay attention on the ambient temperature since the system won't turn the bleed off if it gets warmer than 5'C and you might prety much overheat the intake. In BS the engine ice protection is only manual, I guess this is how it's done on the real thing.

 

The "Electrics on battery" warning in flight means both generators off. This is most probably due to low rotor RPM- they automatically disconnect from the AC busses at rotor RPM ~75%. Once you increase the rotor RPM above 80% they will come online again.

[Frederf]

Oh there's really an ice detection sensor? I thought it was even less sophisticated, measuring temperature and humidity and looking up if that combo of values fell in a danger zone in a big table.