A little bit of everything

The weather and flying conditions that each of the four seasons typically offer can be summed up with relative ease, at least in the western prairies. Summer will hold generally good weather with more time spent dodging thunderstorms than doing low approaches, Fall brings with it low ceilings and fog mixed in with whatever nice days summer has given up, Winter yields generally smooth conditions, with stronger winds aloft that can make for longer flight times when heading in a north-westerly direction, and finally Spring has the ability to give the worst and best of all the seasons combined. Some of the worst flying weather I have come across to date has largely been in the Spring months, and I have learned to be extra wary when the flat stratus cloud of winter give way to the rounded cumulus clouds of spring.

Driving into work last week for a flight destined for Rainbow Lake, a flash lit up the early morning sky. An upper cold front was forecast to pass through the Edmonton area prior to departure, so thunderstorms were a possibility, albeit a remote one given that it was mid March.

Looking at the radar after arriving at work, a north-south line of thunderstorms were clearly visible at the leading edge of the eastbound cold front. After doing the walkaround inspection on the 1900, I opened the hangar door to find light rain falling outside. With the temperature slightly below 0, I was concerned that the upon pulling the plane outside, once the aircraft's skin cooled down to the freezing mark, the rain would freeze, which could make de-icing difficult. I pulled one of the king airs that were parked in front of the 1900 outside and waited a few minutes to see if the rain would freeze on its wings. Shortly after pulling the second plane out of the hangar, the rain let up. I pulled the 1900 outside for the waiting fuel truck, hoping that that rain would continue to hold off and that the ramp would not freeze prior to us departing.

With all of our passengers checked in, we boarded with puddles of water still sitting on the ramp. As we begin our taxi out for departure, the sky has an ominous darkness to it, even in the mid morning light. Lining up on the runway, I tilt the radar to see what weather we will have to contend with immediately after departure. The radar shows nothing in front of our nose, although there are showers showing to the east of our departure path. Climbing through 1000 feet above the ground, Edmonton Centre gives us a turn to a north easterly heading to separate us from inbound traffic. I roll into a turn to the right and as I do, the weather radar begins to paint a return ten miles ahead on our assigned heading. At our current speed of 180 knots, we will reach the rain the the weather radar is showing in just over three minutes if Edmonton centre keeps us on this heading. The radar return sitting in front of us today is green, which indicates light precipitation. During the summer months we would usually not give too much thought to a green radar return, as at its worst, could mean flying through a shower or two, and light to medium turbulence on the way. It is the red and yellow radar returns that will grab our attention and usually require a deviation. However, this morning, with the temperature outside showing -5, any rain that we fly through would freeze onto the plane and even though the shower looked to be only 4 or 5 miles across on radar, we could pick up a significant amount of ice traversing the 5 miles to the clear air on the other side.
We ask for a deviation left of track for weather, and with the traffic that centre was keeping us separated from now behind us, we are cleared direct to Rainbow Lake which keeps us clear of the returns showing up on radar. Soon enough all of the convective weather is well behind us and we turn our attention to the weather in Rainbow Lake.

While it was rain and potential thunderstorms that we had to deal with on the departure out of the city, it will be snow that we will face on the arrival into Rainbow Lake. Getting an idea of the weather in Rainbow Lake can involve a bit of educated guessing, as there is no weather reporting station at the field, although there is weather reporting out of Fort Nelson about 50 miles to the west and High Level, 55 miles to the east. What makes the job of figuring out the weather in Rainbow Lake interesting is that even while you may know the weather on either side of Rainbow Lake, the weather in between does not always match the weather on either side. There have been many days where I have flown into Rainbow Lake with both Fort Nelson and High Level reporting clear, only to find an overcast layer sitting over the airport. I have learned to plan for the instrument approach every time I fly into Rainbow Lake to avoid surprises at the last minute. Abeam Peace River heading North, we pick up the new weather for Fort Nelson and High Level, and both are reporting between 1 1/2 - 2 miles visibility and a 1000 foot ceiling in snow. Although it is not the best weather, it should be more than enough to get into Rainbow on the NDB approach. 70 miles out from the airport, we contact the radio operator on the ground for the winds and altimeter setting, as well as the runway condition. The woman on the other end of the radio reports ten knot winds out of the north west and that the runway is in the process of being cleared. Shortly afterward one of the maintenance vehicles that were working on the runway reported the runway as slippery to the radio operator and is then passed on to us. The thing about a runway which is being reported as "slippery" is that it is a pretty subjective description. At better equipped airports, a vehicle calibrated to measure the friction of the runway will drive down the runway and report what is referred to as a crfi, or the canadian runway friction index. A bare and dry runway should have a friction index of 1. On the other end of the spectrum, a runway completely covered with ice will yield a friction index of anywhere from .07 to .22, depending on the conditions. I have landed on runways where the friction index was being reported at .25, which would put it somewhere slightly better than an ice covered runway. While it would seem that landing under such conditions defies logic and common sense, in reality landing on a slippery runway should be no different than landing on a bare and dry one. One of the main things to consider when landing with less then perfect runway conditions is wind, especially crosswind. For each friction index value, there is a corresponding maximum crosswind that can be safely handled. If the friction index is reported at .3, anything over a 10 knot crosswind could push you off the runway on landing.

20 miles back from the runway we break out of the cloud bases with the airport just slightly to the left of our nose. Turning final for runway 27, it is obvious that the runway has been cleared, although it looks as though there is still a layer of hard packed snow on the runway. The winds are still out of the north west, as I am having to point the nose of the plane slightly to the right of the runway in order to continue tracking to the runway. Over the runway's threshold I bring the power levers to idle with the intent touching down prior to the 1000' runway markings. Under conditions such as these, I will aim to touchdown at the desired spot on the runway and sometimes forgo a passenger pleasing smooth touchdown, in favor of a more controlled solid landing. Although most passengers like landings where they cannot feel the airplane touching down on the runway, the technique required to accomplish landings like these can often use up a few hundred feet of runway that may come in handy later on in the landing when you are trying to get the plane stopped. With the main wheels on the runway and the nosewheel close to touching down, I move the power levers into reverse. Typically once the plane has slowed through 60 knots, reverse is no longer used as it can blow debris forward, only to be sucked up into the engine intake. At 65 knots I begin to bring the engines out of reverse and test the brakes to determine how slippery the runway actually is. With the brakes depressed, the plane shows only a small decrease in speed, it would seem that the maintenance crew were right about the runway. I move the power levers back into reverse once again to slow us to a speed that will allow us to taxi off the runway. Once slowed to a taxi speed, the captain takes control and continues the taxi back to the taxiway and to the ramp. Often the most challenging part of landing on a slippery runway is not the landing itself, but rather taxiing off the runway and to the ramp. On landing, we have both aerodynamics and inertia working in our favor. Inertia will keep the plane moving in the direction that it is already going, and at speeds greater than 50 to 60 knots, the rudder is quite effective in keeping the plane pointed in the direction you want it to go. Once down to a taxi speed, especially when trying to turn onto a taxiway, inertia is now working against you, and any aerodynamic help that was there disappeared once we slowed below 50 knots. Getting the plane to do what you want it to now means using the thrust generated from the engines to help steer, and moving at a snails pace to keep things on the rails.
Once off the runway, we find that sitting on the ramp, the plane wants to creep forward even with the engines running at idle. We feather the propellers to keep the plane in place while we complete the shutdown checklist. With the engines shut down, I open the cabin door, and make a mental note to watch my step from the stairs to the ramp. I have seen a few pilots pull off flawless landings in icy conditions only to slip and fall stepping out of the plane. I step outside and manage to keep myself upright. The ramp is slick, although only in patches. I unload the the passenger bags and help our passengers brings their things to the terminal building. We will wait here for a few hours for our outbound passengers to arrive and then deal with whatever conditions the return leg has in store for us. Fortunately for the next few hours the biggest decision we will have to make is what to have for breakfast.