Winter Comes To Virginia
October 31st, 2009We are headed north, climbing underneath a solid overcast. The southern Virginia landscape of hills and valleys is sliding smoothly by below us while the FO and I discuss the news of the day. Lately, the news has been the same. Service reductions, quality of life cuts, mergers and the threat of furlough and shut down, with the economy less than stellar, the industry is a mess. The trick of course is not getting distracted, as was highlighted by the unlucky Northwest crew who missed Minneapolis last week. Our focus shifts from the latest rumor to the task at hand as we climb into the cloud bases and the plane starts bouncing.
Somewhere ahead of us a King Air advices ATC that he is picking up moderate rime ice and needs another altitude right away. Center drops him down to 20,000 feet and asks the King Air driver to keep him advised. Ice can be serious business and there is no reason to mess around. We have a hot air heated wing and engine inlets as well as electrically heated windshield and probes and despite all that I still keep a close eye on ice buildup on the airframe. With that in mind I glance over at the total air temp gauge which displays the outside air temperature from a probe just below the FO’s side window: +4 degrees, prime icing conditions.
We climb another 1000 feet to 24,000 and the temperature drops to +1 degree. Within seconds a white crust of ice is starts to form on the nut that attaches the windshield wiper blade to the arm. It always starts there, just like static electricity, and then spreads to bigger surfaces as the icing increases. I look up at the overhead panel and see my FO is on the ball and has already turned on the wing and cowl anti ice switches. I go back to staring at the wipers as the ice buildup continues to grow and spread. The arm of the wiper blade now looks like somebody has spread a layer of frosting along it. Looking back I can see the last few feet of the wing and it looks silver and clear of ice. The winglets, which are unheated, are carry a thin load of ice now which means the tail which is also unheated probably has some ice buildup as well.
I’m still not overly concerned. If we need to we can easily descend back into clear, warmer air below us or climb a few thousand feet hirer. Although ice can form at any temperature between about +10 and -40 it normally is found only a small portion of that range, around zero degrees. Climbing will lower the temperature and hopefully get us out of the ice. I take a quick look at our flight computer and realize that we only have about 100 miles to go and climbing isn’t going to be too beneficial. Despite the almost inch of ice covering most of the wipers now the windshield is remaining clear and what I can see of the wings are clear as well. Our anti ice system is keeping up fine and as long as things don’t get worse we are ok to stay where we are.
Minutes later ATC descends us back down to 15,000 feet. Passing through 22,000 we exit the cloud bases and the temperature starts climbing again and the ice starts to shrink as it melts. As the integrity of the structure starts to break down, pieces fly off into the slip stream and zip by the window. By the time we get to 15,000 the ice is gone and the FO reaches up to turn off the anti ice switches. It’s good to know the system is working because it could be a long winter.