SD,
If you're getting ice, regardless of your de-ice or anti icing capabilities, do something to get out of it if you can. Climb or descend. If you can't descend to warmer air, then climb to get altitiude to deal with your problem, or to climb out of the icing layer if you are able.
The airplane may be able to handle the present rate of icing. However, you may lose that deice capability. If you're in it at the time, what was once an annoyance or no big deal, may suddenly turn into a really big deal.
The loss of a blanket or boot, or the failure of a bleed valve may nor may not be noticable until the indications of aerodynamic difficulty become manifest. We're all so accustomed to relying on idiot lights and agreement/disagreement lights to tell us that everything is working. If we can't see it on the ammeter or the annunciator panel, it must be okay. However, this isn't always the case, and it's too late to figure that out when in the ice.
Icing can get bad fast. I had an experience in a Twin Commander once that put the fear of God and Ice into me in short order. It involved a rapid ice accumulation that put an inch of ice on in a minute, and caused an initial 50 knot speed loss. In less than a minute and a half we were through blue line and then slower, and descending, and unable to maintain MEA. We were in mountainous terrain in instrument conditions. Ice from the props sounded like a 12 gage being continuously fired behind our ears, and it did significant structural damage to the airplane.
The significant part of that experience was that the aircraft on the route ahead of us didn't get it, nor did the trailing aircraft. We flew through an area which was small geographically, that was pushing some warm, moist, saturated air upslope rapidly. It cooled rapidly, and it occured right where we were. The chief pilot for that operation was in the right seat, and I was flying. I had been present only a short time previously when he had declared to a class of new-hires that the Twin Commander can carry any amount of ice, and only lose 15 knots.
Be really careful when people tell you an airframe can carry a lot of ice, without trouble.
Some years ago I was eastbound in a large four engine airplane. We were picking up some ice, but it didn't seem to be a big deal; the usual 1/4" or trace that we would see in the winter in the clouds. In a short time period, it built such that large 6" horns were sticking off the leading edge and prop spinners, and we began to get a very pronounced aileron "snatch." I immediately descended and notified ATC, and onl 2,000 to 3,000 below the icing layer, we shed most of it.
Had we been unable to descend for whatever reason (we were fortunate enough to be over low, flat terrain), I would have elected to climb. Even if I was unable to get out of the ice, the altitude might buy time in the event of a problem. The point there is that if all the options aren't available, pick the best of what you have left and work with that.
Be cautious of systems failures or issues such as a blown boot, or blown cell. You can have a single cell in a multi cell boot or blanket that fails, and this can cause some ice bridging issues...even in nice, modern equipment.
The FAA has pushed more recently for continuous use of boots at the first sign of icing, and has even published a paper trying to tell us that "ice bridging" is more myth than reality. I disagree strongly, even with more modern boot systems that pulse at higher rates and frequencies, or that operate at higher pressures. Additionally, anybody who has ever popped a boot, only to have the boot pop or burst, comes to realise staying in ice and relying on deice capability is a fools errand.
Icing conditions exist that can take down the most capable of aircraft. Embedded cells or orographic lifting action, or any convective activity or mountain activity, can result in severe ice in very light or mild conditions. I'm sure that many of us have had our scares. We're coming into icing weather again here shortly. At the higher altitudes, it's a year-round issue. It's a good time to begin thinking seriously about ice once more.
Remember that de-ice and anti-ice equipment isn't really for flight into or through known icing conditions. It may be labled that way for certification, but really it's for getting out of ice.
Ice bad. Very bad. Except maybe in a slurpee. The coke ones, not the cherry ones, that leave you looking like you wore closet lipstick or something. Ice bad. Very bad. Snowcones good. Except in the winter when give bad headache and chills. Then ice very bad.
