737NG Door heaters
 

Is the purpose of the 737 door heaters to prevent ice build up externally?
Cheers

737 door heaters?
I know of no door heaters, pax doors or cargo doors.

Enlighten me! :ouch:

The 737 Ng has additional heating to prevent cold zones around the main entry doors.(electric heaters) for the confort of your cabin crews.

Always room for enlightment aint there not?:E

The B737NG has door area heaters on all 4 cabin (pax/service) doors, as well as all over wing emergency exit hatches. The heaters are electrically powered thru the cab/util switch in the flight deck and the aircon system provides the motive flow of air across the heaters which is directed at the door areas to be warmed. The system is powered when the aircraft is in the air and the cab/utility switch is on.

Framer,

The heaters are for pax/crew comfort only. They have nothing to do with external icing.

Thanks folks, appreciated.

Are such heaters common to jet transports? Had a thought that it was to prevent ice formation preventing operation of doors/emergency exits during evacuation. Had a quick look in FAR 25 but couldn't find reference.

Advisory Circular (AC) No. 500-003 - Transport Canada

That was my thought to Brian.
I can't find an official reference either.

Arrr...that's probably why I haven't heard of this system, we don't have a cab/utility switch!
think military version.....

Well, even on commercial variants the usage of the cab/util switch is vastly different. On some of ours they have to stay on at all times, otherwise there wouldn't be any lighting available in the cabin. Somewhat weird setup to be honest.

To be honest, there is nothing in our documentation about the door heaters, which doesn't mean they're not there of course. Sadly i do not have access to our maintenance documentation.

Unfortunately there is very little technical content in Boeing FCOMs today. They have been deliberately dumbed down.

Door heaters
 

Could it be that it is an option? Also never heard of this system before...

Hi-dee-hooooo :}

Heater Supplier and part numbers
 

Hartzell Aerospace - Products - Air and Surface Heaters
www.hartzellaerospace.com/EF_PMA_List_web.xls
http://www.hartzellaerospace.com/pdf/air_duct.pdf

It seems B777 and 757 have also.

As others have said, the purpose of the door heaters on the NG is solely for supplemental heating.

The heaters on the pax/service doors are inline heaters while the overwing exits use electric blankets. They are not operated by the cabin/utility switch. They are energized when the plane is in the air mode and one of the pack flow control and shutoff valves is open.

I'm pretty sure its a standard feature on all NG's.

Ours are on the cab/util switch.

Yeelep,

I did not say they are operated by the cab/util switch. I said they are powered through the cab/util switch.

A couple of the other systems powered through the cab/util switch are:

Overwing escape hatch flight lock solenoids.
Potable water compressor.
IFE.
BSI cabin lighting.

There are more but those are off the top of my head.