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Questions about anti icing and de icing


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You might start with the type of aircraft -- light single, biz jet or... ???

 

However if ice is starting to form, I'm going to look for a way out while I'm activating whatever anti-ice or de-icing equipment I have, which usually means heading for warmer temps or clear skies, or both. Icing deforms the airfoil, in addition to adding weight to the aircraft, and can affect handling, as well as stall speed. It adds drag, too. So all those bad things.

 

A note about the boots, though: a certain amount of ice has to form on the boots before you activate them, since they're just a device to break the ice off. If they're running constantly, the ice will build up on them in a way that won't break off, negating their value.

 

Heaters usually need to be started early, as they don't have enough power to melt off a thick accumulation, at least not very quickly.

 

But all that being said, get out of the ice. A typical light aircraft won't climb very well in icing, at least not enough to get above it. Jets might, depending on conditions, but if it's warmer below with enough altitude to continue the flight, that's probably the place to go.

 

Again, the aircraft type and performance and anti- and/or de-ice equipment play a big part in your decision.

 

Larry N.

As Skylab would say:

Remember: Aviation is NOT an exact Science!

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A lot of aircraft don't have flashing lights to warn of icing conditions (at least in the Sims). Either buy a cheap ice-pick or if you know that you will be heading into icing conditions, get those anti-icing heaters on in advance.

Still thinking about a new flightsim only computer!  ✈️

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While climbing I switch on the pitot heat between +10 and +5 degrees C, before it gets even colder.

I switch on the engine anti ice just before freezing. between +5 and +2 C.

 

Sometimes in my haste to climb I forget, and suddenly notice the airtemp is already -10 or lower. I then switch it both on, but also descend, to where the air is warmer. Sometimes as low as 10.000

 

I haven't seen anti-ice boots on fsx planes. In real planes they are rubber "bags" on the front of the wing. When you notice ice buildup, you inflate them, and that breaks the ice apart. (as long as the ice is not too thick yet.)

The airflow over the wing then blows the ice away.

 

Only a small number of aircraft type have them. The dash 100 I think does.

This video shows a look at an engine, with part of the leading wing edge and deice boot showing.

[sIGPIC][/sIGPIC]
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There is an excellent little gauge that makes the icing effects in the sim much more realistic. You have to install it yourself, and make a few changes to the plane's .air file as well, but it's not excessively difficult.

You can find it in the Flightsim Library HERE. I installed it in the default C208, and it seems to do everything it advertizes it will.

If you want relatively real icing in FS9 or FSX, I suggest giving it a try :)

Have fun!

Pat☺

[sIGPIC][/sIGPIC]

Had a thought...then there was the smell of something burning, and sparks, and then a big fire, and then the lights went out! I guess I better not do that again!

Sgt, USMC, 10 years proud service, Inactive reserve now :D

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  • 2 weeks later...

In real life, icing distorts the airfoils and adds weight, not always in a balanced manner, so if there's very much of it (and "too much" varies with the aircraft) the aircraft's handling is changed, often in such a way that the autopilot can make things worse because it's designed for a very specific way of handling, and a human can adapt to the changes much better. And the anti/deicing systems don't always get rid of all the ice -- they generally just increase the amount of time you have to escape the icing, either by climbing or descending to warmer air or by turning around back to warmer air (if it's still there and reachable).

 

To read about (among other interesting things) an extreme case or two, get Ernest K. Gann's Fate Is The Hunter, an excellent account of his days flying for American Airlines from the late 1930s to the mid 1950s. Icing encounters, engine problems, maintenance/structural problems and much more are touched on, as they affected his life and career. And you learn a lot of history, especially aviation history, and get a very interesting background perspective on WW II, as well as a bit on the Berlin Airlift and the Korean War.

 

Larry N.

As Skylab would say:

Remember: Aviation is NOT an exact Science!

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Thanks for the link -- that's very interesting, indeed. I could almost "see" the ice building up and imagine the sloppy controls.

 

Larry N.

As Skylab would say:

Remember: Aviation is NOT an exact Science!

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  • 2 months later...
Bad idea to simply generalize this as even the NTSB said that bridging can occur.

Furthermore the AFM of the plane is your valid guidance concerning the use of the boots.

 

There seems to be a fundamental absence of understanding - or rather lack of explanation - of the different roles played by anti-ice and de-ice systems. For the sake of clarity De-ice is applied whenever and wherever ice occurs, whether or not it is visible. Anti-ice will be used to prevent ice build up in the first place, and so will usually be applied in the presence of the risk if icing, whether occurring or not, visible or not...

 

For this simple reason inflating boots CANNOT be an anti-ice measure - they require sufficient ice build-up so that the inflation breaks the ice off - obviously and exclusively a de-icing tool. So whoever the `they` are that Captain Andy refers to in his post #6 are being misrepresented.

 

Thermal heating can be both an anti-ice and/or a de-ice measure and is often found as an alternative to inflating boots on empennage. These, and the typical wing-weeping systems found on many GA aircraft ARE anti-ice measures. Stall vane and pitot heat, and of course carb heat, are typical thermal measures, and it is advised to switch these on wherever the risk of icing is present - and the risk may be different for different control systems - the venturii effect of pressure activated systems like carburettors causes icing at far higher ambient temperatures and humidity than straightforward impact systems such as stall vanes or tubes. Pitot heat in most aircraft (but not all) is applied whenever the aircraft is in the air, which is why it is normally a `yellow` item in most checklist and warning systems.

 

IRL the primary anti-ice measure is not to fly there in the first place. Pilots are taught to recognise the elements that contribute to risk of icing and so to avoid them. Descending to warmer air or climbing out of the icing zone is the primary solution, no matter that anti-ice or de-ice systems are fitted. All that either does is buy the aircraft operator time to make and effect the correct resolution.

 

Where pilots cannot avoid, or unexpectedly encounter icing then only de-ice or leaving the icing area is going to help, as if anti-ice measures have been applied as they should have been by the PIC (otherwise he/she shouldn't be flying in the first place) then the onset of icing tells that pilot to remove themselves and their aircraft from the icing zone as its more than an anti-ice system can handle.

 

Modern aircraft can be certified for Flight Into Known Icing (FIKI) but that does NOT imply continuous operation in such a zone, it simply is buying time for the operator to decide whether to go up, down, left, right or back the way they came. Nothing more. Such aircraft will often carry anti-ice and de-ice in a combination, which is why it is vital to understand what should be used, and when. There is a substantial difference in where and when these measures are used, not based on the empennage but on the system itself. So while inflatable leading edge boots are a de-ice measure, used later into the icing event, bleed air edge heating is an anti-ice measure and should precede the arrival in the icing zone, or switched on in anticipation.

 

Finally, it's worth understanding why certain aircraft are fitted with certain systems and their capabilities.

 

I'm not aware of any aircraft manual that advises use of inflating boots at the first sign of icing. Perhaps our `Captain` can provide a couple of examples as I can't see how disrupting the airflow for no good reason makes things safer? What I suspect is being referred to will be systems that are either anti-ice fluid (wing weeping), internally heated electrically or via channeled bleed air.

 

Finally, rather than continuing de-ice and anti-ice practices in a single topic, if further clarification is needed perhaps we might revert to separate topics for each as clearly there is massive potential for confusion and crossover in the various systems and what they do and some replicate the layout and format of ant-ice systems but are actually de-icing tools, and vice versa.

 

For now, I hope this suffices and look forward to the clarification from our OP.

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