Why we have to use ANTI ICE Below 10 degree

[idisaid]

Is there any special reason
Why we have to turn on the anti ice sw on below 10 degree not minus degree?

[galaxy flyer]

Venturi effect in the inlet cold the entering air to 0C, so SAT of +10 might equal freezing conditions.

This is pretty basic stuff for a professional

GF

[EpsilonVaz]

Some of the most horrendous icing I've seen has been between 0 and +10C. As galaxy flyer said, basic stuff.

[Capt Claret]

10 degrees, but measured how?

On the Douglas/Boeing 717 it's 6 degrees, C, TAT. Even with an indicated TAT of up to 20C, I've seen quite large ice accumulation on th wiper arms & blades. A check of the OAT even at +20 TAT or more, can reveal sub zero temps.

[STBYRUD]

Yup, obviously 10° is TAT, not SAT! The temperature rise resulting from airspeed will obviously not be the same everywhere on the aircraft, but the indicated TAT should in principle be the highest apparent temperature anywhere on the plane, but local effects can of course mean that the actual temperature around ice critical parts is much lower.

[divinehover]

Icing range: +10 TAT to -40 SAT.

The numbers mean nothing without the SAT/TAT detail.

[mmrassi]

10 degrees, but measured how?

On the Douglas/Boeing 717 it's 6 degrees, C, TAT. Even with an indicated TAT of up to 20C, I've seen quite large ice accumulation on th wiper arms & blades. A check of the OAT even at +20 TAT or more, can reveal sub zero temps.

I think the point is whether the situation leads to Ice stick to engine inlets or not. Ice accumulation on windows doesnt necessarily shows hazardous Icing condition.

[Uplinker]

This is an extremely fundamental question. I sincerely hope that idisaid is not a professional pilot.

If the OP is already a pilot, why do they not know the answer to this question???????

Why was it not covered in their training??? How did they pass their exams?????

This really scares me.

[His dudeness]

Ah, the perfect people are having a go...

So you passed all exams ever with 100%....? If not, I´m "scared"...

[lomapaseo]

Many years ago we faced this same question throughout the industry, pilots, operators and manufacturers. So we brought in some science and to be sure we got the word across we all agreed to the same guideline to avoid confusing pilots switching from one aircraft to the next.

I'm happy to see from the discussion above that it's under control and in the general knowledge bank. I see no harm in questioning the issue as long as one follows the guideline at the same time.

[Uplinker]

Is that a dig at me dudeness? :D

Interesting. If the OP is a qualified pilot, do you really think it is OK that they do not know such a fundamental fact as the physics and temperature range of icing?

[de facto]

Guys,

Maybe he was asking about ground use of TAI?

Flying turboprops many years back,the aircraft was fitted with a TAT kinetic heating chart.
Basically at 250 kts,a TAT of 10c would give SAT of O degrees C.

Also on the ground,there is a drop of temperature as ambient air is sucked into the engine,i believe there was a discussion whether +5 c would be a more sensible restriction as the drop in temp was around 3c.,but no news.
The same for the WAI,should be used for example at less than 10c in visible moisture.(vis 1500m or less,rain..).
In any case,follow your aircraft AFM guidance.

[flydive1]

Ah, the perfect people are having a go...

So you passed all exams ever with 100%....? If not, I´m "scared"...

No, they were born knowing everything.

They never had to ask questions, they never had to be told anything;)

[His dudeness]

Yes uplinker that was mostly 'for you'.

You conclude something from basically one sentence and don´t know the context (or complete picture) - and the OP is likely a Korean, which means there could be a 'language thingy' lurking in the dark as well...

Sometimes even the most fundamental things are not obvious. Thats how the human brain works - ask the pilots of AF447 as one example....57 times the airplane told them "Hey guys I´m stalling" and still they asked "whats happening here"...

And turning your argument around, we should all have to pass at 100% and all imaginable questions should be asked. Cause, If you not know something, it might be dangerous and thus "scary". :ugh:

Even IF the OP has a 'knowledge gap', my experience is that the pilots that don´t ask questions are the ones on whichs plane I wouldn´t put my family on.

Have you HONESTLY never asked a question that in hindsight was "dumb" ?

I certainly have. Still I ask if uncertain or not in the know. Maybe I´m just dumb... or not as perfect as others ?

Don´t get me wrong, if a dude comes on an writes: yeah don´t know why we switch on at 10° and therefore won´t switch it on, THEN I´m happy to join in on a virtual slaughter...

[Uplinker]

You have got the wrong end of the stick, but perhaps I shouldn't have mentioned exams.

From the earliest flying in SEPs, pilots learn (or should learn) that carburettor icing can occur in air temperatures above zero degrees.

Does the SEP phase of ATPL training no longer occur, or are they all fuel injected engines these days? Does it not worry you that someone who might be a qualified line pilot (and this is all conditional - we don't know if he actually is), does not know that icing can and does occur from +10 degrees TAT and below? If so, what did his ground school and line training consist of? I would like to be assured that Korean pilots do understand icing, because my brother will be flying with them later this year.

If the OP is an interested non pilot or wannabe asking a question, then fine, but he says 'we' which implied otherwise to me.

I am happy to be proved wrong.

[Fly4Business]

Maybe I am too simple minded, but icing occurs at the wings of my flown aircraft mainly due to the abundance of water vapor. Temperature is secondary and only relevant for two things, how much water can be carried max in the atmosphere at a given temperature and what is the dew point temperature. Max vapor content of water in atmosphere goes exponential with temperature, so below a certain temperature there is no water in air anyways. Critical is the temperature area where there is enough amount of water vapor possible and physical effects can cause stickiness to the aircraft.

[de facto]

until ice crysals came about....

[harrryw]

One thing of learning in a Cessna.,..not that hard to forget the carb heat and have the instrutor not remind you. those splutters and stops are something you never forget.

[Fly4Business]

until ice crysals came about....
Ice crystals in the atmosphere won't stick easily at surfaces, worst is undercooled droplets ...

[de facto]

true but was answering in regards to his line 7 sentence,icing in the form of ice crystal is found at temperatures way below normal icing and do accumulate quite easily on engine surfaces such as compressors and can even block probes such as TAT ones.

[Capt Claret]

True mmrassi, but why would one ignore such indications? And my point was more that even at seemingly high temps, one can still encounter icing.

Anecdotally I've been told by a colleague, sitting in the rear of the cabin who could hear the change in "air noise" with the selection/deselection of anti ice, that there was still a significant rim of ice on the intake lip when the anti-ice was turned off.

General

Ice protection is provided by the airplane anti-ice systems.

NOTES: Icing can occur on the ground under the following conditions:

• OAT is less than 6°C (42°F), and
• Visible moisture is present (clouds, fog with visibility less than 1 mile, rain, snow, sleet, ice crystals, etc.) or,
• OAT and dewpoint are within 3°C (5°F) of each other or,
• When operating on ramps, taxiways, and/or runways where slush/standing water may impinge and freeze on exterior surfaces.

In flight, icing can occur under the following conditions:

• TAT is less than 6°C (42°F), and • Visible moisture is present, or

• Ice is built up on edges of windshield and other visible portions of the airplane.

[KTM300XC-W]

How about for the simple reason that people have spent years in university becoming specialists in their field (designing engines) and they've determined that it's required. Until you're as well versed in meteorology, fluid and aerodynamics just do it. We have people in our company that have barely passed high school yet are convinced that the Boeing engineered are idiots and completely wrong with regards to some of the ways we are supposed to fly the 737.

[lomapaseo]

I haven't followed this thread well enough to decide if their are arguments of points or just open discussions

For what its' worth. the general concept is to control the amount of ice that forms and/or sheds. It's pretty difficult in some icing conditions to eliminate all ice since mother nature throws all kinds of stuff at you.

On the subject of inlet ice, the available amount of heat at worst conditions permits ice formations up to a point where the insulating effects of the blanket of ice against the inlet skin causes enough heat load to dislodge a layer of ice. Such layer is suppose to be handled by the engine without affecting the flight.

There are many other effects going on relative to the aircraft and other surfaces but I am trying to stay within my interpt of the OP.

[mmrassi]

True mmrassi, but why would one ignore such indications? And my point was more that even at seemingly high temps, one can still encounter icing.

Well I had this discussion (Problem) with a Capt in one flight who was commanding to turn on the Anti Ice while we had TAT aroung +17°C which is well above, but he was concerned when He saw the icing on wipers. Despite I shown him the Notice in FCOM that bans pilots to use TAI above +10° he insisted on using that.
Now my point is what if our actions beyond the book, induce damage to a system, specially in a long period of time?!

[PW1830]

If you have time, and access to Boeing 747 manuals over the last 20 years or so, you can trace the evolution of current procedures to combat ice crystal icing on engines and TAT systems. Event,investigation,procedure,--another event,investigation ,procedure etc etc. Newer more efficient engines seem to be more prone so I don,t believe the latest procedures will be the last. Someone will be the guinea pig to initiate the next change!!

[ROKVIATOR]

Up to 30º c and low power settings ice formation can be seen for example in pistons engines.