Monday, February 25, 2013

Icing Considerations Begin On The Ground

Flying a plane during actual or potential icing conditions, involves not only inflight weather, but what happens on the ground before take-off. Most of my flying career, the majority up north, I tended to worry most about encountering ice enroute, not usually too concerned about the first part of the trip, ie: the take-off.

By now, we should all understand the negative effects that icing has on aerodynamic lift and drag. Basically the accumulation of ice on the wings, fuselage and control surfaces, may seriously degrade performance to the point of inadvertent stall. OK, so what’s new? Mainly, that to get the plane through a safe take-off and departure, you must keep dangerous accumulations of ice from forming on your plane. If your plane is parked outside during a period of icing potential it must be checked thoroughly for any ice accumulation. Some of the articles I just read, state that a thin coating of ice only .08mm thick can cause problems. (Fellow pilots, that’s not much!)  I know I have flown with some tiny amounts of ice on the wings without bad effect. However, the plane was light and not flown near stall. Also, the type of wing design has a bearing on the negative effect of ice, e.g. the thick less inefficient airfoils are somewhat less sensitive to icing.

I just reviewed some of the latest thoughts and practice on dealing with ground accumulation of ice.* I believe the studies are aimed at the large commercial types (Airliners). The interesting things I learned were: the amount of liquid in the precipitation is key, as is the type of deicing material applied. This article gets technical, but here goes. The more liquid in the precip the more icing potential it offers and the more the pilot will have to deal with. So for example, freezing rain is more of a problem than a fairly dry snow.

Once you have decided to deice the bird, you will have to decide on what to apply or have applied. This will vary depending on whether you are at JFK or the local FBO. The topic of deicing fluids is beyond discussion here, but worth reviewing if icing is in your future. The other aspect to consider is Holdover Time, (the length of time the particular de-icing substance will prevent ice accumulation). That means you have only so many minutes after the de-icing substance is applied to safely take-off. Once airborne, your inflight de-icing systems must take over. The reason this is so important is that there have been quite a few accidents on take-off due to unappreciated ice on the wings etc. One particular case comes to mind. On Jan 13,1982, an Air Florida 727 crashed into the Potomac, after being deiced 45 minutes before take-off. That was too long (exceeding the holding time for that deice substance) with the resultant crash due to the wings losing lift, etc.

I do remember one Sunday years ago at KEQY (Monroe, NC). It was late and no one was at the FBO. My wife to be had driven me to the airport, but hadn’t intended to be a lineperson, but rather only to give me goodbye hug and kiss and head back home. Instead when we reached N340JC, a Cessna 340 (a plane I really miss), we found the wings and all else covered with a pretty thick film of ice. Well. As I indicated no help was to be found from the FBO, so we were it. I would have waited for Monday, except that I had a job to perform the next day and had to get back to eastern, NC. So we started banging on the ice covered surfaces with our gloved hands, knocking off as much ice as we could. Finally after about an hour, I deemed it clear enough to take-off. I know it wouldn’t have passed today’s standards for ice removal, but as no more was coming down, off I went. I didn’t experience any adverse effects from what was still on the plane. But, as I mentioned above, we were light. Not at gross or even near it.

So, if flying when icing is a possibility, keep in mind that de-icing considerations begin on the ramp. Your safe take-off and departure depend on a thorough inspection of the airframe and application of de-icing materials when needed. Then start your stopwatch and don’t exceed the Holding Time of the particular de-icing material applied.

*www.RAL Aircraft Ground De-icing
  www.Skybrary Aero./  Aircraft Ground/Anti-icing