Aircraft icing

[Pin Head]

The aircraft we fly usually don't pick up ice in icing conditions as the airframe is so cold and bar near the engines which are warmer and allow melting we are really lucky to operate in the conditions that we CAN operate in.

Why then do we have wing anti ice on the LE devices?

[lomapaseo]

probably because you haven't come close to the appendix c edges of the icing envelop yet.

there is all kind of ice out there in a varitey of water droplets sizes and temperatures. When you finally get near the conditions like that plane in Buffalo you better hope your anti-ice is on and that the ice that does form is not on your critical control surfaces.

[Derfred]

To get rid of the ice when it accumulates on the leading edge.

[Pin Head]

Exactly but forgive my stupidness why just the LE of the wing and not say the LE of the elevator.

[B737900er]

Pinhead - what part of the airplane creates the most lift?
If your actively flying on the line I am worried :ugh:

[wanabee777]

Is is possible for the horizontal stabilizer to stall due to icing?

I honestly don't know.

[Centaurus]

Is is possible for the horizontal stabilizer to stall due to icing?


A Vickers Viscount crashed during tailplane icing shortly after landing flap was selected on final approach.

https://en.wikipedia.org/wiki/Linjeflyg_Flight_618

[Jet Jockey A4]

"Is is possible for the horizontal stabilizer to stall due to icing?

I honestly don't know."


Yes they can!

[lomapaseo]

Exactly but forgive my stupidness why just the LE of the wing and not say the LE of the elevator.

Mostly (not all) aircraft the wing LE is the most sensitive to contamination and is likely to contribute to stall long before the tail.

In spite of this there are always fresh arguments in some aircraft types whether the un-deiced tail contributed

[wanabee777]

Is is possible for the horizontal stabilizer to stall due to icing?

I honestly don't know.


Yes they can!

Then, are there aircraft out there that have STAB AI??

[MarkerInbound]

Baby DC-9s have tail heat (don't know about the Mad Dogs). You're supposed to cycle it every 20 minutes while in icing conditions and once before gear extension if you're in icing conditions.

[RVF750]

Most types do. It's just that most aircraft out there are from a very short list of those types...

The L.E. heat is useful but I've used it only once since I started flying the NG.

It concerned me coming from another well known ice magnet type....

Basically, and it is just a basic statement, you get the most icing from 0' to -14'.

Yes, in the descent you do have a very cold air frame, but the leading edges are treated to TAT airflow, not SAT.

Keep the speed up and you can keep the ice away. A generalism maybe but it has always worked for me.

[safelife]

My understanding is that during certification flights material is attached to the leading edges simulating the shape of the worst ice accretion to be assumed with moderate icing and a typical speed.
If the wing/stab profile still does ok aerodynamically it can go without anti icing.
Fokker 70/100 were quite suspectible and had full stab and vertical fin anti ice (and no bleed air left to run anything else :rolleyes:)

[Pin Head]

Thanks for the replies.

Nice post b737900, still talking rubbish I see.

Again in aviation there is no stupid question.

If it promotes flight safety then I can sleep easy at night.

[tdracer]

Just a clarification on 'conventional' airframe icing.

The risk is due to what is commonly called "supercooled droplets" - basically liquid water that is below freezing. When it hits a cold surface, it instantly freezes. At least according to the FAA regulations, 'conventional' airframe icing is a threat between +10 and -40 deg C, and below 23k (although it's been reported as high as 30k).

Ice Crystal Icing (ICI) is different - it's basically very small crystals of ice - typically at very high altitude (above 30k). ICI will simply bounce off cold surfaces, but can accumulate ice on warm (above freezing) surfaces because the crystals hit the warm surface, melt, then additional crystals cool the liquid water enough that it re-freezes and accumulates ice. Accumulations of ICI icing typically occur on surfaces between 0 and 20 deg. C. This is the issue that many engines have been having - ICI accumulates ice internal to the engine in areas where is normally too warm for ice to accumulate - when the ice sheds it can quench the flame (flameout) and sometimes damage compressor blades.