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What Is "window Heat"?  
User currently offlineFastFlyer From United States of America, joined Aug 2003, 8 posts, RR: 0
Posted (12 years 8 months 4 weeks 20 hours ago) and read 12106 times:

Hello. Im wondering what exactly the "window heat" switches do on the overhead panel Boeing planes like the 737. Is it like a defroster?

8 replies: All unread, jump to last
User currently offlineDalmd88 From United States of America, joined Jul 2000, 2888 posts, RR: 14
Reply 1, posted (12 years 8 months 4 weeks 19 hours ago) and read 12076 times:

The cockpit windows have heating elements in the glass. Turning them on prevents ice from forming on the glass.

User currently offlineLstc From Canada, joined Jun 2003, 320 posts, RR: 0
Reply 2, posted (12 years 8 months 4 weeks 17 hours ago) and read 12044 times:

On several aircraft as well as the role of keeping ice of the window, window heat makes the window pliable for resistance to bird strikes.

Many aircraft have airspeed restrictions when window heat is unavailable.

[Edited 2003-09-02 01:19:29]

User currently offlineCx flyboy From Hong Kong, joined Dec 1999, 6811 posts, RR: 55
Reply 3, posted (12 years 8 months 4 weeks 14 hours ago) and read 12009 times:

Yes, cold windows become very brittle whereas warm windows have a degree of elasticity in them that makes them withstand birdstrikes better. On the 777 we always have them on and the system automatically turns them on at the beginning of a flight and off at the end. On older aircraft you have to manually turn them on or off.

User currently offlineBroke From United States of America, joined Apr 2002, 1325 posts, RR: 3
Reply 4, posted (12 years 8 months 4 weeks 5 hours ago) and read 11942 times:

One of the most common problems with windshield heat is thermal shocking. Most manual systems had a two position switch; the first position turned the heat on at a low level to gradually warm the windshield up; the second position would bring the windshield up to it normal operating temperature. A lot of people (crews and mechanics) would turn the windshield heat to the high position and, in turn, reduce the windshield's life.
Later windshield heat controllers would ramp up the windshield temperature gradually and thus improved, greatly, the windshield's reliability.
If you look in one corner of the windshield, you will see the electrical grid that is the electrical connection from the power source to the windshield, usually there are two such grids, so if one goes out (which they do), the second grid provides a backup and allows use of the windshield for a longer period.
The windshield has a conductive layer between the glass and acrylic plies that heats the unit.

User currently offlineFredT From United Kingdom, joined Feb 2002, 2185 posts, RR: 26
Reply 5, posted (12 years 8 months 3 weeks 1 day 7 hours ago) and read 11785 times:

On a sidenote: if the heating is left on on the ground, with no cooling air flow, you'll likely end up with a peculiar looking windshield...  Smile


I thought I was doing good trying to avoid those airport hotels... and look at me now.
User currently offlineGordonsmall From UK - Scotland, joined Jun 2001, 2236 posts, RR: 20
Reply 6, posted (12 years 8 months 3 weeks 1 day 6 hours ago) and read 11779 times:

A stupid question I know but - Is the window warm to the touch when window heat is on? How hot does it get?


Statistically, people who have had the most birthdays tend to live the longest.
User currently offlineAvioniker From United States of America, joined Dec 2001, 1109 posts, RR: 10
Reply 7, posted (12 years 8 months 3 weeks 1 day 4 hours ago) and read 11766 times:

Yes the window is warm to the touch. A normal temperature is 110deg F.
The systems have thermostats which keep the window from overheating so unless there's a malfunction (not uncommon) there's no danger to the window on the ground.

One may educate the ignorance from the unknowing but stupid is forever. Boswell; ca: 1533
User currently offlineL-188 From United States of America, joined Jul 1999, 30408 posts, RR: 57
Reply 8, posted (12 years 8 months 3 weeks 1 day 3 hours ago) and read 11751 times:

We have/had at the A/P school I used to go to a windscreen out of a 747 that had a runaway thermostat.

Yes very particular.

At least I now know what the bee sees.

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