JasonC wrote:
Start once there is more than a trace subject to temp limits (-30C).
But please note that this advice applies to modern kit, such as Jason’s, but is not good for older boots such as you will find on most old MEPs. On these the advice is to wait for a substantial build up before cycling the boots.
While I haven’t as much legacy MEP time as Timothy, the risk of ‘bridging’ due to cycling the boots without a build up, and therefore creating a crust where the boots are ineffective, is Ernie Gann stuff from DC3 days. IME experience on legacy twins with boots from the 70’s onwards, there is no risk of bridging, and I believe this may even be stated in the relevant approved flight manual.
This is an ice bridge on an Aztec.
…or leaky, tired boots?
I don’t see a bridge there, unless that little piece of ice is it. It looks like a boot with little bits of ice stuck to it, which is normal.
That big piece had the boot inflating and deflating under it in the classic ice bridge way. The boots were operating properly and normally.
@what_next wrote:
I have flown a lot on Cessna 421s in all weather. I have operated the de-ice boots on this aircraft on very few occasions because obviously that wing does not tend to accumulate ice in the first place.
What kind of wings tend to accumulate ice in the first place ?
I think that the reason that C421s do not accumulate ice is that they are pressurised and fly most of the time at FL200 or above.
I have flown a lot on C404, the C421’s unpressurised brother, and I can assure you that the wing can accumulate a lot of ice.
Thanks Timothy
So that’s always about flying above and being able to get up there quickly
PetitCessnaVoyageur wrote:
So that’s always about flying above and being able to get up there quickly
Well, not “always”, but certainly “nearly always”. 
