Ice Bridging

Several generations of pilots operating aeroplanes with pneumatic de-icing boots have been cautioned against the dangers of ice bridging. Pilots were -- and are -- advised against activation of the pneumatic de-icing boots before sufficient ice has built up on the leading edge -- generally between ¼ and 1 inch -- out of concern that the ice would form the shape of the inflated boot, resulting in the boot inflating and deflating under a shell of ice, making de-icing impossible.


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It used to be a big problem a little time ago. Now, not nearly as much. When a pilot used to activate the boot, ice would build up behind boot, on the actual metal of the leading edge of the wing.
 
Pilotforhire587 said:
Seen it on the MU2, and that is nasty, like Hey this an emergency if they don't let us change altitudes in the next couple minutes.
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Yeah, I saw it in the Mitsi more than anything else I've flown. The plane actually handles the ice it gets pretty well, but for whatever reason, it seems to be more susceptible to bridging than, say, a 99. I would hypothesize that it has something to do with the thinner, more high-performance nature of the wing on the Mitsi, but that would be uninformed speculation on my part.
 
KHanson said:
It used to be a big problem a little time ago. Now, not nearly as much. When a pilot used to activate the boot, ice would build up behind boot, on the actual metal of the leading edge of the wing.
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That's not bridging—that's just ice accretion on a non-protected area of an airplane. Which still happens too.
 
I think that a lot of times, pilots who arn't "used" to winter ops in booted airplanes mistake a "non aerodynamically clean" surface for bridging. I've seen a lot of pilots who haven't flown in winter conditions much, get worried about dirty boots after a cycle. So long as there is a physical change to the planform area of the leading edge, there isn't bridging.. no matter how "dirty" it may look still. The big issue, as most eveybody here seems to know, is when you blow the boots, and there is no longer a change to the size, shape, or form of the leading edge. At that point you have bridging.

Generally speaking, If you are packing on enough ice, fast enough to bridge, then you are prob. operating beyond the capabilities of you ice protection systems, and need to get out of the ice. I think that the FAA guidance as it is, is set to try to dissuade people from thinking if they "just wait" to blow the boots, that it won't be a problem. They would rather you activate the boots quickly, and frequently, thus giving you a better idea if your ice systems can keep up with the current conditions. Letting ice build up can lead to other aerodynamic issues, from premature airflow seperation, to control reversal. In static testing, consistent activation at the beggining of the enounter prevents ridging, and standing ice formations aft of the protected areas. In extreme examples, especially large super cooled drops, delaying the activation leades to a ridge of ice built up beyond the protected area. This ridge effectivly moves the center of pressure, and can cause control and airflow issues. While activating the boots immeadiatly does not prevent the accumulation of ice aft of the protected areas, it does recuce the the ridge at the boundry of the protected area, "somewhat" perserving the airflow.

I used to be of the mind, let it build. It gives a nice clean blow when the boots go... it feels satisfying... but it may be masking issues that you can't see well from the flight deck. Honestly, if running your boots at a normal scheduled interval isn't "cutting it" then all ride pride aside... it's time to be somwhere else.

Ice forms in areas with a smaller cross sectional area first, wing tips not roots, tail planes before wings, probes, pipes, small tubes, etc...

All that being said, yes "bridging happens" and it sucks when it does. I do wish the FAA didn't completly write it off as a non possible event, <b>And</b>, I'm not saying that anybody in this thread doesn't know what bridging is... more that, the faa writes it's AC's for the guy who has 100 hours, and just bought himself a barron. They don't want him thinking to himself, " well bob said if i wait untill i have an inch of ice... then it won't bridge" because he may well "wait" himself right into other problems.
 
When the regulators start prevaricating to make the dumb monkeys behind the yoke hit the right switch, we're all screwed. Not that I really disagree with your analysis.
 
In my experience and training ice true ice bridging is a thing of the past as boot technology has increased. We now have better shapes to the boots, stronger and faster inflation and deflation times compared to the boots our grandfathers used. It also helps to keep a good coate of boot dressing on the boots in the winter to help the ice release. The E110', King Airs, C310, 402, and 421's all handled the ice pretty well. I did see what I thought was ice bridging on the Bandit but it wasn't in retrospect as the SLD was causing ice to run back and freeze behind the boots. IMO boots are best in light ice to light to moderate ice. You get above that you better not hang around too long.

Thankfully I am in a hot wing now and love it.
 
Boris Badenov said:
When the regulators start prevaricating to make the dumb monkeys behind the yoke hit the right switch, we're all screwed. Not that I really disagree with your analysis.
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The reasoning behind the "lap child" rule (not assosiated with icing at all) alone squanders any faith i have in the FAA pushing rules/advisories strictly based on hard "data"... I'd love to see somebody try to hold a 30 lbs weight in a 10+g deceleration event.
 
TucknTruck it is a purely money and blood driven. They fear it will cut down on travel if you parents have to purchase a seat for an infant. Second, not enough children have died from getting shot around the cabin during turb or accidents. Promoting Aviaiton and Promoting Safety don't always go hand in hand and sometimes the FAA has a conflict of interest.
 
Bandit_Driver said:
TucknTruck it is a purely money and blood driven. They fear it will cut down on travel if you parents have to purchase a seat for an infant. Second, not enough children have died from getting shot around the cabin during turb or accidents. Promoting Aviaiton and Promoting Safety don't always go hand in hand and sometimes the FAA has a conflict of interest.
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I've always bought a seat. How can you charge extra for being large, but be forced to let people double occupy a seat? They have just as much impact. ( we always buy an extra seat for our kid)

Unfortunately, the FAA has integrity issues due to their conflicts, politics, and money mongering. Because of this, many (me) have an inherent distrust of most things that come from them now.

Example, hold over times, and permissible take of conditions keep getting tighter for us. We(121) guys haven't had a crash due to fluid failure in a long time. Does this mean that the fluid is not as good as they once thought, or, is Dow laying pressure on the FAA to increase ucar safewing IV fluid sales?

Is forcing me to use the composite airframe hot's because we have some small areas of aramid fiber enhancing safety?
 
Some of our plane's boots inflate pretty slow, and are susceptible to having ice on the inside, preventing them from inflating. I've yet to see them bridge, but I've seen them inflate fine on the ground, and then not in the air from the freezing water inside them.
 
z987k said:
Some of our plane's boots inflate pretty slow, and are susceptible to having ice on the inside, preventing them from inflating. I've yet to see them bridge, but I've seen them inflate fine on the ground, and then not in the air from the freezing water inside them.
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heh heh heh
 
I've seen bridging in "modern" airplanes. It exists...the icing has to be pretty bad for to happen. More common is when the ice doesn't come off the wing because there's not enough airflow to pull it off and you get a jagged, f-ed up leading edge that doesn't really help your performance at all. This is a common problem in the van.
 
Bandit_Driver said:
In my experience and training ice true ice bridging is a thing of the past as boot technology has increased. We now have better shapes to the boots, stronger and faster inflation and deflation times compared to the boots our grandfathers used. It also helps to keep a good coate of boot dressing on the boots in the winter to help the ice release. The E110', King Airs, C310, 402, and 421's all handled the ice pretty well. I did see what I thought was ice bridging on the Bandit but it wasn't in retrospect as the SLD was causing ice to run back and freeze behind the boots. IMO boots are best in light ice to light to moderate ice. You get above that you better not hang around too long.

Thankfully I am in a hot wing now and love it.
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Mmm... Hot wings!

To add on, if someone if flying around in severe icing, they need to look at the definition of "severe icing".
 
mshunter said:
Until that one time you either forget to fill it.

TKS works great, better In fact than boots until the fluid runs out. Then you are no different than any non ice certified airplane out there.
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i think if you run your tank dry in flight you probably didn't try hard enough to get out of the icing. not saying it can't and doesn't happen, but the pilot should have made a drastic change to the flight if they get in that situation.
 
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