On one UK GA chat site I have just seen a post which is interesting:
Trust me. I’ve flown a few Boeings. They rarely pick up ice. In fact, on 747 classics, I only EVER used the wing anti-ice procedurally to ‘warm the leading edges’ just before selecting flaps 1 as they tend to stick with a little moisture in the tracks. On the -400, I never saw the wing anti-ice come on (automatically) anywhere but in the Lambourne hold.
Engine anti-ice is another matter and comes on more often, because it comes on at +10°C.
None of us know why, but Boeing airframes are inherently resistant to icing.
The poster claims to be a jet pilot!
My view is that the protection comes from ice protection systems, and from going fast. A TAS of 350kt+ gives you a delta T on the leading edges of 15C which pretty well prevents icing there. However the main protection comes from enroute flight at say -60C in which you can’t have supercooled water.
A UK pilot there appeared to have heavily iced up in an unprotected PA32 over France, on a VFR flight, and said that the IMC Rating is what saved him. So he was flying VFR in IMC. IAS dropped to 40kt, presumably because he wasn’t using pitot heat, or it may have been a deep stall. This sort of discussion is best avoided getting into (because one cannot even guess where to start) but it was the comment about Boeings which I was curious about.
I can only say that on the 777 I’ve seen wing anti ice come on automatically less than 3 times in 6 years, which doesn’t mean much because most of the flying is not in icing conditions.
On the 787 wing anti ice is electric and it is my feeling it is coming on automatically a bit more conservatively (as it takes longer to heat up !!not verified!!).
Apparently Boeings are not susceptible to tail ice so these surfaces do not have anti icing.
Snoopy wrote:
On the 787 wing anti ice is electric and it is my feeling it is coming on automatically a bit more conservatively (as it takes longer to heat up !!not verified!!).Apparently Boeings are not susceptible to tail ice so these surfaces do not have anti icing.
Even on my plane I almost never use wing anti-ice as it rarely forms on the wing. Engine anti-ice is mandatory at 10 or below in visible moisture.
In 700 hours on the HS125 I never saw ice, but, as Jason says, we had to use engine anti ice quite a lot.
From the OP I take it that we are Taking just airlines vs other planes, not Boeings specifically, are we?
She said Boeings specifically 
I can tell you that A320 can take a huuuge load of ice and you would not even feel it.
My highest score was (looking at the ice probe which is located between front windshields) about 15cm ice ball.
That was in the hold in freezing rain conditions. Low speed. Flaps up. Landing which happend 10 minutes later was completely normal.
Boeings and Buses are really not sensitive to icing. Thats why you have only 3 out of 5 leading edge slats heated and no deicing on the tail at all.
And the best weapon against ice is the speed. Speed up to 330kts IAS will give you about 20degC TAT increase. That means NO ice regardless of conditions.
However dont try that on small GA piston planes. Especially modern ones with efficient laminar profile.
OK, so it looks like the post I read about Boeings being specially immune is nonsense; big jets generally are pretty good.
Excess power and protecting the power source help a lot against icing.
Big jets are definitely another type of birds I witnessed few times Dash 8 turboprop picks the ice at same rate as my DA42 in the same conditions. I was commenting that with captain and he said that the boots were capable of handling a lot of ice but freezing rain would be a problem.
