anti-ice on at 10c
Some normal Op's procedures a various Air Carriers call for A/I anytime visable moisture is encountered or expected at 10c and below.
The idea is to have the A/I on when you need it, I. E. - the phrase "expected". Obviously on modern transports, the A/I acts fairly quickly. However, you want it on to prevent Ice ingestion and not to de-ice. sO, ANTICIPATE the need for A/I.
On the DC-6 we would "fire up the heaters" at least a 1000' before penetrating anticapted Icing conditions.
The phrase "Anti-Ice" vs "DeIce" regulates how we use it.