737 3/400 Wing De-ice

[lost soul]

As far as I am aware MOST 737 EFIS operators have followed the Boeing recommendation to always select Wing De-ice whenever Engine Anti-ice is selected on whilst on the ground. ((I think BA and (old)GO differ on this). I have just recently come across some 737's that do NOT automatically drop the Wing De-ice switches at lift off. I thought that all 737's had been modified to do this so would be interested to hear any comments from other 737 Classic drivers!

[lost soul]

What? No comments?? Hasn't anyone got anything to say on the subject??

[lost soul]

Thanks ASFKAP ,
No my company bought these aircraft from Lufthansa (1987 733's) and we have found quite a few oddities as time has gone on! Apparently there is NO wiring or microswitches on these two aircraft to achieve the usual "drop off" on lift-off. We have been instructed to manually select OFF prior to commencement of the takeoff roll!

[dolly737]

All the 737-classics I know close the valve if either engine thrust is above t/o-warning setting or thermal switch is activated in either distribution duct - leaving the switch on. It's just the switch that trips to OFF at liftoff.

happy landings

[jorgvaz]

HI,

There two kinds of Wing Anti Ice systems installed in classics 737's.
One that positioning the WTAI switch ON opens both control valves if thrust on both engines es below the setting for take off warning activation and the temperature inside ducts is less than the thermal switch activation temperature. On ground with WTAI ON , the switch remain in this position regardless of control valve position, when the air/ground sensor goes to the air mode, the switch automatically trips OFF. In flight this logic is desabled.

The other system, based on the air/ground sensor prevents the wing anti-ice control valves from openning on the ground excpt during ground test. As a procedure i.e. low altitude ice conditions exist or are anticipated, the switch is placed in ON on the ground, the vavles are closed, but the system is armed for flight.
During liftoff air/ground sensor enables the WTAI system and both valves open. A thrust penalty is taken du to WTAI bleed air extraction.