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Anti-ice in clear skies

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Hi,

 

If the temperature is, for example, -5 degress, should you use anti ice for takeoff even when the skies are clear and there's no clouds?

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No.

 

Icing conditions are generally defined as TAT below +10C *and* visible moisture (ie in rain/snow/hail etc, cloud, fog (visibility <1500m ish), standing water on taxiways/apron etc).

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Nope as there is no visible moisture in the air. The wing and/or engine anti ice system must be switched on when facing icing conditions. Definition see here. Icing conditions exist in flight at a TAT of 10°C (50°F) or below, and visible moisture in any form is encountered (such as clouds, rain, snow, sleet or ice crystals), except when the SAT is - 40°C (- 40°F) or below.

 

This is how Bombardier defines icing conditions in their operating manuals for the CRJ Series 100-1000.

 

Although the pitot and static probe heaters should be switched to ON after engine start. You dont want to have these blocked during flight as that would mess up things badly. Especially when you do not know how to handle these situations.

 

If you use the anti ice system -which depends of the respective aircraft you use- in jets airliner you will have your take off performance degraded. 

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Do engine and wing anti-ice always come on at the same time or are there conditions under which one would only use one or the other?

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On the ground. You would only have engine anti ice on if taxiing in icing conditions.

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in addition to Kevins post, if icing conditions exist AND deicing/anti icing is required the airplane should be in a clean configuration. Setting flaps for take off as well as a flight control check should be performend after deicing/anti icing is finished. While lining up for take off the wing anti ice system will be switched on.

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If it is cold, but the weather is clear, no precipitation and the runway is dry, then you don't need to use the engine anti ice on the ground or for take off.

Be careful with wing anti ice..... On the B777, you do not use wing anti ice on the ground or for take off, for example.

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Ok, now another question regarding anti-ice; if engine anti-ice will be used during landing, when are you meant to turn it off again? When you get into the gate, or just when you have vacated the runway?

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And also, I'm wondering if you should turn on Engine anti-ice during taxi to the deicing apron when you know that you will be deiced, or if you turn on EAI after the remote deicing?

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Ok, now another question regarding anti-ice; if engine anti-ice will be used during landing, when are you meant to turn it off again? When you get into the gate, or just when you have vacated the runway?

 

Depends on the weather situation. Normally you would turn it off when leaving the runway as it is not needed anymore. If you have bad icing conditions and you would run into fan icing for ex freezing fog or even worse freezing rain then you could leave it on till on the gate.

 

During taxi you dont want to have fan icing cause 1.) it could damage the core engine 2.) you might get fan vibrations -the vibes scares the hell out of your passengers :Smug:

 

When you head over for deicing you have to switch off all bleeds so consequently your EAI does not work and to keep the switching logic you turn it off before switching off packs and last the bleeds. Turning off all packs and bleeds will prevent deicing fluid getting into the bleed system. There it could get hot and develop a thick white bubblegum smelling smoke. You dont want to have that when performing a take off ;)

 

After deicing is finished all packs and bleeds set you can turn on EAI again.

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Ok thank you,

 

I might be wrong, but as far as I'm aware I didn't think the EAI on the 737 needed engine bleed air, and that only WAI needed bleed air. But I'm not 100% sure.

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Ok thank you,

 

I might be wrong, but as far as I'm aware I didn't think the EAI on the 737 needed engine bleed air, and that only WAI needed bleed air. But I'm not 100% sure.

 

 I can only speak for Embraer E190/195 and CRJ Series as i flew them both. They both need bleed air for engine ant ice. You should refer to the Operating Manual B12 chapter "Ice and Rain Protection"of the B737. 

 

Just found this "It uses 5th stage bleed air, augmented by 9th stage as required, from the associated engine."

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After landing, if the taxiways are wet or it is raining, snowing, etc....and cold obviously, then you keep the engine anti ice on all the way back to the gate.

If you deice/anti ice on a remote pad with engines running, you would taxi there with the engine anti ice on, and keep the switch on during the de/anti ice treatment.

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