737 NG de-ice / anti-ice, packs off?

[EightsOnPylons]

dear forum,

I have heard that the packs need to be off when deicing a B737? My understanding was that it was enough if all three bleed air switches were turned off, since the packs will not function without bleed air? is that correct or not?

thanks,
eightsonpylons

[Voodoo 3]

You keep the packs on while de-icing and turn all three bleeds off. Two engine and one APU. Simple reason is to stop any of the fluid entering the air conditioning and creating a nasty smell. Once finished keep the bleeds off for a minute or so to ensure all the fluid clears from the engine etc.

[EightsOnPylons]

Ok,yes thanks for your reply. That makes sense. Is there any more reason for turning the bleeds off except creating a smell in the cabin? does it matter to the engine if you blast it with deicing liquid while running or is turned off? not that there is any reason to blast it straight into the engine.. but just if it happened to happen.. does it prohibit a takeoff, maintenance action?

thanks

[Voodoo 3]

There is no real problem if you get fluid in the engines. Generally though de-icing is done before you start. However some airports have taxiway de-icing rigs which you taxy to. You hold while the rigs passes over and de-ices the aircraft (with engines running). These are there because sometimes the holdover times available by de-icing on stand will not give you enough time to pushback and taxy to the runway and therefore you will have to turn around and return to stand. As you de-ice through the rig, turn the bleeds off etc but really there is absolutely no problem with the fluid getting in to the engines.

[EightsOnPylons]

thank you for your replies voodoo, I saw a picture of fluid beeing drawn into engine of a 727

http://www.airliners.net/open.file/789611/L/

/eightsonpylons