• Feature: Let It Snow

    By Tony Vallillo

    That song begins..."When the weather outside is frightful, the fire is so delightful..." Although I have no fireplace in my office these days, it is nonetheless comfy and delightful as I watch on the Weather Channel web site as the Blizzard of '15, aka Winter Storm Juno, lashes New England with just about every manifestation of Arctic nastiness that Mother Nature, perhaps angered by someone rash enough to substitute margarine for butter, can whip up! New York apparently escaped the worst of the snow, but from Connecticut to Maine it piled up in near record amounts, propelled by winds that in some areas reached gale force. Naturally, the weather snarled all forms of transportation, particularly air travel, over a wide area. I well remember days like this in winters past; for in the course of my career I have encountered a number of winter storms such as Juno, and just looking at the video of planes being de-iced and flights being cancelled en-masse brings back many memories of my own struggles with Old Man Winter.

    Snow, and its handmaiden ice, wreak havoc on airplanes in a number of ways. Snow or ice adhering to an airplane, particularly the wings, can completely alter the shape and streamlining, reducing lift and increasing drag - often exponentially. The weight of snow or ice on an airplane also degrades its performance. The engines are affected, sometimes starved of air as intakes are choked off by accumulating snow or ice, occasionally to the point of failure. Runways can be piled high with snow to the point that they completely disappear, even the lights! Even when plowed, enough snow remains (and usually more is falling) to create significant additional drag during the takeoff roll, just when you don't want it. And, God forbid, if you need to abort the takeoff, the snow becomes slippery and the brakes are less effective even with anti-skid. Visibilities can be reduced to nil in really heavy snow. All in all, snow and ice bring nothing good to aviation.

    The military and the airlines have learned over the years to deal with winter weather, at least to some extent. Indeed, we can now fly in conditions that would have been impossible in years gone by. But extreme caution is still the watchword, and there will usually come a time when the towel gets thrown in and flight operations cease. But not all operations, since some things like snow clearance keep on going even after the decision is made to stop flying.

    A pilot has several areas of concern when flight is contemplated in the midst of snow and ice. The first concern is the weather itself - the visibilities, winds, and temperatures. Visibility, of course, is a factor all of the time, and it really makes no difference whether the 600RVR is due to fog or snow. Snow tends to be a bit more distracting, since it is composed of millions of individual elements that each reflects whatever light there is. Snow also creates a vortex effect when you move through it a high speed, not unlike going very fast through a tunnel that is lined with tiny reflectors. In my experience this creates more visual sensation, and thus distraction, than mere fog, which is why we often make the takeoff with the landing lights off.

    The second consideration is the airport, specifically the taxiways and runways. There are strict limits on the depth of snow, slush or ice allowed on runways and taxiways for flight operations, but this is always a moving target since snow is usually falling heavily during the worst part of a storm. Airports publish frequent snowtams about field conditions, and the larger airports have a duty officer on the field in a car or truck constantly keeping track of the conditions and the progress of snow removal. Finally, the pilot must concern him or herself with the condition of the airplane itself. It must be free of contamination by snow or ice, and certain systems like anti-skid brakes must be operational, as well as reverse thrust.

    Several reminiscences may serve to illustrate these points, and give you a glimpse into the processes that drive risk reduction in winter operations. I shall work backward on that list I just gave you, starting with the condition of the airplane. It was long ago permissible to accept a certain amount of contamination on an airplane, particularly on the wings of propeller driven airliners, on the theory that the prop blast would clear the snow from the wings very early in the takeoff roll. This approach was discredited in the middle 1950's when a DC-6 attempted to take off from runway 04 at LGA with snow on the wings, in anticipation of it being "removed" by the airflow and propwash. Things did not go according to plan, and the airplane rolled sharply left shortly after lifting off, crashing on Rikers Island after the Captain was, miraculously, able to roll the wings level just prior to touching down.


    De-icing of airplanes had been around even then, but it was left pretty much up to the Captain whether or not to utilize it, and when. Things had still not been completely codified in 1982 when Air Florida flight 90 attempted a takeoff in a snowstorm at DCA and crashed into the Potomac. In the aftermath of that tragedy, new and much more specific rules were promulgated, and eventually new methods of de-icing and anti-icing airplanes were introduced. The newest type of deicing fluids, type IV, was introduced when I was a chief pilot at JFK, and I brought a beaker full of it to a pilot meeting that winter. The stuff had the consistency of Karo syrup, which served to keep it on the airplane much longer, even with snow or rain falling on it. It somehow chemically "grabbed onto" the water molecules and then, around 50 knots or so on the takeoff roll, gave up its hold on the wing and slid off, taking the snow, slush or ice with it. It had a great ability to absorb water, and thus the concept of "holdover time" was introduced - the time that could elapse in rain or snow while this fluid still had the capacity to absorb more.

    We are sitting in the cockpit awaiting engine start on one of "those" days. Not a day like Juno, for nowadays the airlines cancel all flights well in advance of an event like that, but rather a garden variety snow storm, say 4-6 inches in the New York area. The FB has done the walk around, in conditions of stinging snow and sleet that I remember well from my flight engineer days, and has reported, to no one's surprise, that a goodly amount of the white stuff has made its home on the wings and tail of the ship. At one time I would have called ramp control and ordered up a deicing crew, but nowadays the drill is to schedule everyone for deicing, since the need for it is both obvious and regulatory. At the appropriate time we start engines, turning on the engine anti-ice after each engine is started, followed by pushback, which is sometimes a delicate affair in the slippery conditions that exist on the ramp on days like this.

    1. tsbco1a's Avatar
      tsbco1a -
      Loved your article.
    1. dbauder's Avatar
      dbauder -
      Great article, as always! I'll share two stories...I once got snowed in at Greenville South Carolina on what was to be a short layover. As you can imagine, a foot of snow shuts everything down in that part of the country and we were stuck there for two nights. Day three opens with blue skies. 'Our' plane is inbound from DFW and we're in the hotel van heading towards the airport. Big traffic jam, big problem. We get to see 'our' MD80 approach for landing from our static location on the interstate. An hour later, we see it take off again without us. Dispatch reassigned the inbound crew and we couldn't contact the airline as cellphones were a thing of the future.
      Another time, I overnighted in Norfolk. There had been some snow overnight and our plane had a maintenance issue that required me to personally check to see just how clear the runway was. I was driven out in an airport vehicle and we drove the length of the runway to do some braking checks. I felt like Burt Lancaster in the movie 'Airport'!
    1. vflight2's Avatar
      vflight2 -
      Many thanks for a great article, it surely did get my heart athumpin'!
    1. flyboy416's Avatar
      flyboy416 -
      Tony has penned another very interesting article which, as always, gives some of us "lesser mortals" the opportunity to "be there" on the flight deck with him. Many thanks. Looking forward to the next one with anticipation!
    1. avallillo's Avatar
      avallillo -
      Burt Lancaster!? I know that feeling too. I spent many the hour riding around JFK in snow and ice storms with the Port Authority duty officer, who was known informally as the "99" after his radio call sign. Their job in winter was to monitor field conditions and the progress of plowing, and report that information to the tower, where it would be broadcast to the flights.

      One morning I got a call from my boss over at LGA (the regional chief pilot) to the effect that JFK operations was not getting what they felt was the latest reporting on field conditions. So I called the 99 and got picked up on our ramp a few minutes later for a look-see. This was a morning in early 1994, a season in which we had weekly ice storms, and by now the runways and taxiways were coated with around one inch of clear ice. The Port had no equipment that could remove something like that, since the runways are all grooved, and the ice was in the grooves as well, pretty much making it impossible to scrape it up - it was too firmly attached to the pavement.

      Ice can be quite a problem, especially near zero degrees C, because watery ice is the most slippery thing you can imagine, and that is what appeared to be the case that morning. At that time, JFK had one of those SAAB friction measuring vehicles, but the Port did not use it, and thus no calibrated measurements of runway condition were available. I decided to to an uncalibrated experiment of my own devising - I had the 99 drive down 04L at around 80mph and then hit the brakes. Weeeeeeeee! What a ride! We spun around about 720 degrees in our uncontrollable excursion and it took half the length of the runway to stop. Of course, this runway is over 10,000 feet long and 150 feet wide so there was no danger to us, but right then and there I decided that none of our flights was going to use that runway until they completed sanding it, which was just beginning.

      Meanwhile, only moments after our wild ride, a 747 of another airline was vectored for an approach to 04L. Had it been one of ours I would have directed a go-around but I had no authority over another airline's airplanes, so we relayed our information to the tower and moved well off to one side to observe!

      The Captain took the 1 wire, of course, and used every bit of reverse thrust he had, right down to taxi speed, but managed to turn off with around 1500 feet of runway to spare. The 99 and I let out a small sigh of relief - apparently Boeing anti-skid systems are better than those on a Buick!

      About 10 minutes later they had completed sanding the runway, and we took another 80mph ride. This time, we managed to stop straight ahead, in around 1000 feet. The sand really did make a big difference, at least until the reverse thrust from several landing airplanes managed to blow most of it off the runway; then it was back to square one!

      Safety is always a minute by minute affair in winter storms. But the airport people work really hard to keep things safe, and in conditions far more uncomfortable than my nice warm cockpit. My hat has been off to them ever since!
    1. jbob101's Avatar
      jbob101 -
      Great review Tony, reading this article made me fell like I was in a snowstorm, delayed, and feeling all of its effects! Now I want to go out and do some winter flying :-).
    1. capt hgb's Avatar
      capt hgb -
      Thanks for a great story.
      Safety first rules!
    1. FSXF0zzer's Avatar
      FSXF0zzer -
      A great story, you should write a book! Or am I the only one who doesn't know you wrote one already?
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