turbo prop de-icing
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turbo prop de-icing
Flying a seneca round essex for my IR, I could look at the wing to determine whether ice was forming on my leading edge and blow the boots if necessary.
How do you know when to do the same thing on a turbo prop atr, dash 8 and the like?
How do you know when to do the same thing on a turbo prop atr, dash 8 and the like?
Last edited by wobblyprop; 7th Oct 2004 at 09:04.
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The ATR has an icing probe on the wing which vibrates, when icing starts, the frequency change is detected triggering a warning in the cockpit. For additional visual cues, there is an icing probe on the Captains' side. And if not heeded, the slamming of the ice against the fuselage will get your attention
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BN2. Is my memory correct? When the Islander was first designed/prototype built, I think I recall reading that the CAA were horrified by the wing, hundreds of proud rivet heads etc and so very un-aerodynamic from a drag point of view. B & N were tasked by the CAA to re-skin the wing with balsa wood to achieve a more laminar flow so the CAA could show them the difference a smooth wing would make. Just 1 - 2 kts as I recall.
The extra production costs could never offset an extra 1-2 kts. The warty wing remained as designed by B & N.
The extra production costs could never offset an extra 1-2 kts. The warty wing remained as designed by B & N.
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In a King Air, you watch for ice build-up on the wings. The manual says to cycle the boots when 1/2" builds up. You also need to turn on the prop deice (electric) at the first sign of any ice. The best places to look for the initital traces of ice are on the sharper, smaller parts of the airframe like the w/s wiper arms (again, in a King Air) the OAT probe or the point on the prop spinner.
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On the Caravan we use the Mark 1 eyeball technique....I find looking at the tyres gives the first and best indication, and then its pretty much the same as the Kingair...1/4 - 1/2 inch of accretion..then on with the old blow-ups. The prop we just leave on in visible moisture below 4C with the inertial sep open.
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Our DHC8-100/300: When visible moisture and below 5degC - ice protection full, and ignition "manual" if "auto" not installed. Takes care of itself, pretty much.
Might wanna keep an eye on the ice detector vanes just below the windshield though...
Might wanna keep an eye on the ice detector vanes just below the windshield though...
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Reference waiting for ice to build up prior to operating the wing boots, Fairchild amended their AFM to boots on at first sign of ice. Embraer recommends on E120 to go to level 3 de-icing on the ice warning, and have modified the cycle on the de-ice boots to heavy, ie 1 min cycles.
The possible risk to waiting for the ice to build up is that ice will form over the boot above its inflation height and there fore can't be removed.
Where I fly, the conditions are not as harsh as Europe or USA, and the MSA's are quite low, but icing can be a problem in monsoonal conditions. I normally climb or descend to get out of ice, as while you can keep all the de-iced bits clean, the extra weight of the ice you are carrying on the airframe reduces performance and increases fuel burn
The possible risk to waiting for the ice to build up is that ice will form over the boot above its inflation height and there fore can't be removed.
Where I fly, the conditions are not as harsh as Europe or USA, and the MSA's are quite low, but icing can be a problem in monsoonal conditions. I normally climb or descend to get out of ice, as while you can keep all the de-iced bits clean, the extra weight of the ice you are carrying on the airframe reduces performance and increases fuel burn
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There is also a subtle difference between FAA and JAA (UK) flight manuals. The FAA would have you switch the boots on as soon as icing condtions exist, the UK version fudges the issue by the expression 'as required'. I think think most pilots in UK subscibe to the 'let it build up and then break it off ' technique.
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Dog One says
This is now an obsolete theory.
From the FAA
"Previously, pilots delayed deploying the boots in order to avoid ice bridging. Ice bridging, ice formations above the furthest extension of the boots, occurred in older generation boots which were not powerful enough to completely shed ice. The commonly held belief was that premature use of even modern-day deicing boots, would cause ice formation beyond the system's capability to shed.
Research since the mid 1990s found that modern deicing boots do an effective job in both shedding ice and preventing ice bridging completely."
And from the Canadians (who know a thing or two about ice)
"Several generations of pilots operating aeroplanes with pneumatic de-icing boots have been cautioned against the dangers of ice bridging. Pilots were -- and are -- advised against activation of the pneumatic de-icing boots before sufficient ice has built up on the leading edge -- generally between ¼ and 1 inch -- out of concern that the ice would form the shape of the inflated boot, resulting in the boot inflating and deflating under a shell of ice, making de-icing impossible. Despite the widespread belief in this phenomenon within the pilot community and its coverage in numerous technical publications, its existence cannot be substantiated, either technically or anecdotally".
The possible risk to waiting for the ice to build up is that ice will form over the boot above its inflation height and there fore can't be removed.
From the FAA
"Previously, pilots delayed deploying the boots in order to avoid ice bridging. Ice bridging, ice formations above the furthest extension of the boots, occurred in older generation boots which were not powerful enough to completely shed ice. The commonly held belief was that premature use of even modern-day deicing boots, would cause ice formation beyond the system's capability to shed.
Research since the mid 1990s found that modern deicing boots do an effective job in both shedding ice and preventing ice bridging completely."
And from the Canadians (who know a thing or two about ice)
"Several generations of pilots operating aeroplanes with pneumatic de-icing boots have been cautioned against the dangers of ice bridging. Pilots were -- and are -- advised against activation of the pneumatic de-icing boots before sufficient ice has built up on the leading edge -- generally between ¼ and 1 inch -- out of concern that the ice would form the shape of the inflated boot, resulting in the boot inflating and deflating under a shell of ice, making de-icing impossible. Despite the widespread belief in this phenomenon within the pilot community and its coverage in numerous technical publications, its existence cannot be substantiated, either technically or anecdotally".
Last edited by Engine overtemp; 14th Oct 2004 at 21:31.
