Pitot Heat / Anti-Ice

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Pitot Heat / Anti-Ice

Post by sanins192 » 15 Dec 2007, 19:43

I have never always fully understood when to turn each of these on. At the moment, I always have pitot heat on, and I only ever turn anti-ice on when I fly at really high altitudes.

Can anyone elaborate when I need to turn these on / off?
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COA413
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Post by COA413 » 15 Dec 2007, 20:02

Well, not sure about the exact procedure for Pilot Heat, but I turn on my Anti-Ice when the outside temperature is nearing 0 C. I usually turn it on somewhere between 2-4 C. I then turn it off again between 2-4, when I am on decent. I usually keep my Pilot Heat on at all times, as I don't know the correct procedure.

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Post by bapilot25 » 15 Dec 2007, 20:05

When I was watching a video of United 777 from World Air Routes, the captain said that they only use Window Heat, he really didnt explain the full procedure, but will research.
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Post by sanins192 » 15 Dec 2007, 20:10

Is the pitot tube the instrument that measures airspeed? What is window heat then?
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Post by DeanClay » 15 Dec 2007, 20:12

I think pitot heat heats the sensors on thw wing when the temp is under 0C. If it is not applied, the sensors stop working, and your airspeed reads as zero, completely messing up our autopilot etc
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Post by sanins192 » 15 Dec 2007, 20:13

Oh OK, so the same rules apply as they do to anti-ice.
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Post by Northwestdc9 » 15 Dec 2007, 20:14

The Pitot-Static system powers the airspeed indicator, should it ice over you'll get false airspeeds and if it goes un-noticed can cause a crash as happened to an Air Peru 757 a few years back when it's pitot tube was covered with tape after being painted.
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Post by CaseyD » 15 Dec 2007, 20:22

The Pitot-Static system also powers the Altimeter and VSI.
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Post by Northwestdc9 » 15 Dec 2007, 20:26

CaseyD wrote:The Pitot-Static system also powers the Altimeter and VSI.
Kind of... The altimeter and VSI get their readings via the Static Port. See: http://upload.wikimedia.org/wikipedia/e ... system.JPG
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Post by Dennis » 15 Dec 2007, 22:36

HA...I fly with both of those off. I turn them on only at ground levels when there are freezing conditions on the ground. :roll:
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Post by sanins192 » 15 Dec 2007, 22:40

I suppose freezing ground temperatures are nothing compared with the air temperature at FL420.
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Post by Dennis » 15 Dec 2007, 22:41

It's just that I too haven't understood their functions.
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Post by CaseyD » 16 Dec 2007, 00:04

Kind of... The altimeter and VSI get their readings via the Static Port.


Exactly, hence part of the pitot-static system. :lol:
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Post by detpilot » 16 Dec 2007, 01:24

Pitot heat should be on at all times near 0C, Anti-ice only for when you are in visible moisture (clouds), and between about +5 C and -10C.

Below about -10C, it's too cold for icing (remember icing is water that hits the wing and freezes, there is no water below -10C).

Pitot heat stops the pitot tube from being blocked by ice, the pitot tube is the instrument that measures ram air flow, and determines airspeed. (ie, the harder the air goes in the hole, the faster we're going)
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Post by Dennis » 16 Dec 2007, 01:28

So let's say I'm flying on a clear day at FL360, no clouds. Does that mean that pilot heat must be on during the cruise and during the descent and climb, turn on the anti-ice ?
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Post by detpilot » 16 Dec 2007, 01:40

If there are no clouds, you never need the anti-ice. That's only used if you are in clouds, and the temp is between about 5 and -10 C. Technically, pitot heat is only really needed during that time as well, but since it has such a small electrical draw, most airlines just have the pilots leave it on all the time.

More often than not, you'll never need the anti-ice though.
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Post by CaseyD » 16 Dec 2007, 02:03

Like Brandon said, no clouds no problem. Only way you'd need anti-ice below -10 would be if you decided to fly through a CB cloud, and that would just be a stupid idea... :lol:
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Post by RatherBFlyin » 16 Dec 2007, 03:11

Most airlines have their pilots turn the pitot heat on when pulling onto the runway to takeoff and turn it off when pulling off of the runway after landing. As Brandon said, the power drain is so small it's not worth having to remember to turn it on during the flight, just turn it on and leave it on until you land. Just remember to turn it off, though. A pitot tube left on can heat up enough to give you a serious burn if there is no airflow to cool it (which is why you never wrap your hand around it during pre-flight to make sure it is working).

Other anti-ice (generally wing leading edges, engine inlets, tail leading edges, and prop blades, but not necessarily all of those on every aircraft) is, as Brandon mentioned, only necessary when flying in or near visible moisture (clouds, rain, etc) when the temperature is between +5 and -10 degrees celsius. I personally turn it on whenever I am in clouds and the temperature is between +10 and -15.

Window heat (generally only for the two window panes directly in front of the captain and first officer) is typically turned on during the initial cockpit acceptance check before the first flight of the day and left on until after the last flight of the day.

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Post by sanins192 » 16 Dec 2007, 16:08

Thanks for your help guys.

So basically the pitot heat should be treated similarly to the strobe lights, and the anti-ice when flying through water vapour which could potentially be at freezing point.

Can the anti-ice be used when starting the plane for the first time in cold conditions like in Alaska?
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Post by CaseyD » 16 Dec 2007, 16:19

It can, however if you're rediculously iced before starting, you'll probably want to go to a de-icing bay and get taken care of there. :wink:
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