767 ER Engine Anti Ice

[None]

My company just came out with a memo that they want us to operate both the engine and wing anti- ice in the "auto" position on the jets that have the 3 position selector switch (all but a handful of our ERs). They want us to do so even in icing conditions (normally we select "on"). They say Boeing recommends it, but I highly doubt that. I also don't by his (the guy that wrote the memo) explanation that operating the system like this prevents run-back icing on the wing. To the contrary, I believe preventing ice formation in the first place (by having the selector "on" in icing conditions) is the best practice. Perhaps I need to be better educated on the system or on the latest information about inflight icing. Any ideas?

[Thunderbug]

None

My understanding as a RR 767-300ER driver is that the Eng anti-ice is on at all time where there is visible moisture below +10 OAT, except when climbing and cruising when SAT <-40. This heats the cowl intake, turns on the ignitors and prevents the ice from building up, then breaking off to disapear down the intake removing fan blades. Run back not really an issue here.

For wings, it was described to me that it should be operated a bit like pneumatic anti-ice boots. When ice is detected (using the high tech wiper arm) switch on the anti-ice for 1 minute. Then off for 1 minute, repeat until you leave icing condition or at 500' on approach 'cos you need the power for the go-around. Because it is only the leading edge (and then only outboard of the engines), run back is an issue. Operating it using cycles is supposed to dislodge the ice build up without run back occuring.

We do not have the "auto" function on our models, so not sure wether the auto function uses continuous heat or cycle method.

apologies if this is teaching you to suck eggs....hope it helps.
<img src="cool.gif" border="0">

[vmo]

Auto only for us, with eng. a/i to on for take-off in vis. moisture and less than 10 degr. celc. and when taken into account with take-off performance. Works more than fine. Little vibrators do their work well.