Caution: Ice may be falling!

[Simon Says]

Any theories on this.........

After having aquired large sums of ice on my wings I blow the boots. This in turns gives me a good break and large chunks of ice break off. Does anyone think that these large chunks of ice actually make it to the ground. Could this have possibly killed somebody. Or even cause property damage.

I know when I turn our prop heaters on that sometimes we hear large chunks of ice sling off the prop and hit the fuselage. We hear it all the way upfront with headsets on.

 

[ILLINI]

I'm pretty sure the ice that brakes off usually either sublimates or melts before it gets to the surface. At least that is what i've been told. However, I wonder if the ice has enough time for this to occur at lower altitudes? Anyone else know for sure? I have heard of "blue ice" from the lavatory in aircraft making it to the ground on rare ocasions.

 

[AWACoff]

Anytime you blow the boots close to the ground with lots of ice on them, you will cause some "hail" damage. The Lakes crew room always had those stories floating around in Denver.

 

[avbug]

Ice does make it to the ground, but if you've ever flown next to or behind another airplane when it's exercising the boots, you'll note that there are very rarely any "large chunks." It's usually in a thin layer that shatters and blows back in very small pieces.

You can't make a comparison between this and the prop. Thin, sharp airfoils accumulate ice faster than thick, blunt airfoils. The props are some of the first surfaces to collect ice. When you engage boots, heat, alcohol, whatever, the ice is slung outward on the long axis of the prop. It's accelerated directly into the side of the aircraft (I've had structural damage and holes from ice being removed from prop blades). This means all the ice on the blade is going one place, and it's being put there with a lot of force (the force being dependent on prop RPM and the weight of the ice).

When ice leaves your wing, it shatters and blows aft in a series of small pieces. The pieces slow down, generally, before accelerating to "terminal velocity", which is typically l far less than the airspeed at which they exited the airplane. Airfoil icing is seldom an issue to those on the ground, but the "blue ice" which you mentioned earlier certainly is. That's rare, but any such large frozen buildup (sometimes reaching the size of a basketball, or bigger) can do a lot of damage.