Why do you use engine anti-ice ?
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hey hey vnav i,ll give you all the answers you need to all the questions i will email them to you. In answer to this question though. I believe it is two-fold
1.) To prevent large supercooled droplets forming on the engine intakes i.e formong clear ice which can disrupt airflow into the intakes. Hence icing conditions exist at TAT +10.
2.) and I think more importantly the heat created at the intakes warms the moist intake air so it does not cause icing on the fan blades which can obviously lead to disrupted airflow, compressor stalling, and vibration. I hope others can clarify these points somewhat.
1.) To prevent large supercooled droplets forming on the engine intakes i.e formong clear ice which can disrupt airflow into the intakes. Hence icing conditions exist at TAT +10.
2.) and I think more importantly the heat created at the intakes warms the moist intake air so it does not cause icing on the fan blades which can obviously lead to disrupted airflow, compressor stalling, and vibration. I hope others can clarify these points somewhat.
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On the 757 RB211s and 767 CF-6s, only the cowl ring is anti-iced. The 211's have a small rubber tip (US technical nomenclature "dohicky", UK technical nomenclature "thingy") that supposidy sheds ice.
Other times A/I should be used is when encountering volcanic ash and in severe turb - A/I increases the stall margin of the engine.
[ 09 August 2001: Message edited by: Roadtrip ]
Other times A/I should be used is when encountering volcanic ash and in severe turb - A/I increases the stall margin of the engine.
[ 09 August 2001: Message edited by: Roadtrip ]
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Roadtrip:- That little rubber "Thingy" is called the "Bullet"! As ice builds up on it, it becomes unbalanced. The rubber flexes and the ice vibrates.This causes the ice to be shed through the engine. 
Eff Oh.
Eff Oh.
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Because the engine cowl (the part that is anti-iced) is much like any other forward facing surface on the aircraft and heated by the ram effect. Therefore -2c oat can be +12C on the leading edge of the cowl - hence ice will not form.
So you don't ice-up your engine parameter sensors and end up spudding your 737 into a frozen river because you didn't have correct EPR readings, amongst other things. (Like the Air Florida 737 on Jan 13th 1982.)
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We are more concerned about disturbed airflow, meaning more nasty vibration, decreased power, surges and stalls. We stick it on below +10 TAT when there's visible moisture or standing water. Although some people get extremely hung up about the difference between 10 and 11 degrees...
[ 16 August 2001: Message edited by: Checkboard ]
[ 16 August 2001: Message edited by: Checkboard ]
vnavspeed,
For detailed treatment of that accident, "Air Disaster" Vol 2, Macarthur Job, pp 83-95, ISBN 1-875671-19-6 (still in print) makes fascinating (and disturbing) reading.
For detailed treatment of that accident, "Air Disaster" Vol 2, Macarthur Job, pp 83-95, ISBN 1-875671-19-6 (still in print) makes fascinating (and disturbing) reading.
still learning....
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Why do I use engine anti-ice?
To prevent icing of the nose cowl, guide vanes, etc., and to keep chunks from breaking lose and getting ingested.
A few other abnormal situtions may be helped by opening the bleeds as well, like hung starts, unscheduled surge bleed openings, etc. But those are "desperation" measures. Is that what you're looking for?
To prevent icing of the nose cowl, guide vanes, etc., and to keep chunks from breaking lose and getting ingested.
A few other abnormal situtions may be helped by opening the bleeds as well, like hung starts, unscheduled surge bleed openings, etc. But those are "desperation" measures. Is that what you're looking for?
You know what I think?I think the reason you need engine antice on on take-off is that you do not want ice in your engines. It's solid.
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Just beware of that bloodey TAT gage guys! Make sure its reading what it should read. Ive had erroneous TAT indicating +17 at FL290 at M.75! ALWAYS keep an eye on the underside of your windscreen wiper as a backup, and a reasonable knowledge of expected TAT at various levels at your usual flying speeds. If in doubt throw open the valves and be done with it. Most modern engines can handle engine thermal anti-icing up to a very high ambient temp (+38C in 737 CFMs) so its not like youll burn anything.
