If I'm not mistaken, the 777 has an automatic icing detection and activation system on it. Been a few years since I flew it at my airline as FO, but it was essentially a no brainer system and whenever the system detected icing, it atuomatically turned the anti ice system on for the engines. No real input needed by the flight crew. Can someone confirm?
Well that's the way the system was originally designed to work in flight, but in reality it didn't always work properly. As a result Boeing came out with a Bulletin some time ago stating that the engine anti-ice should always be selected ON in icing conditions. The contents of that bulletin are now in the Limitations section of the FCOM, ie "the engine anti-ice must be ON during all ground and flight operations when icing conditions exist or are anticipated, except when the temperature is below -40C OAT".
Does TAT probe icing ring any bells for anyone?