Crosswinds & Rudolphs

Yesterday I laughed when my new-to-fixed-wing-ops operator had a chance to cut his teeth as a small aircraft passenger and had a moment of sheer terror on takeoff. These last couple days the winds have been fairly strong and blowing pretty much across the one gravel runway where we are. Yesterday's flight was no exception. I pulled out onto the runway and started my takeoff roll with a 16 knot crosswind from the left. Just before I rotated and lifted off he lowered his head to look down at something on his display screen, when he looked up a second later, I had just gotten airborne and let the nose of the aircraft weather-vane into the wind, and was skimming the runway 10 ft off the ground while I accelerated in ground effect to my climb out speed. For the non-pilots, with a strong crosswind like that the result is the airplane tracking straight down the runway, but pointing sideways in a crab angle. My operator looked up out his side window to look straight down the runway with it scrolling beneath him. For that one second he thought we were about to crash and start cartwheeling down the runway. It was a bad sense of timing on his part to look up if he wasn't familiar with how the airplane reacts in a crosswind takeoff. I had to laugh at his moment of terror. I have to give him credit though, other than that short moment of terror he hasn't expressed any other moments of terror, and has just trusted me and let me do my thing.

**Disclaimer: These next paragraph's may be tedius and uninteresting to those not interested in the technical side of aviation, but I have more non-technical stories coming. Scroll down to the line of # signs to skip my technical babbling.

Personally I've been enjoying the crosswind landing practice. The winds have stayed pretty much around 15 kts at 90 degrees to the runway, so they haven't been strong enough to make the takeoff's hairy, but just strong enough to keep it a challenge and make me work for a smooth departure and arrival. Normally between takeoffs and landings, a good landing is more of a challenge, but I've found in strong crosswinds its actually reversed. I find crosswind takeoffs more difficult to accomplish smoothly than crosswind landings. On strong crosswind takeoffs good rudder pedal control is key. On the initial acceleration when most of the weight is on the wheels, I find the airplane has a tendency to be pushed by the wind to the downwind side of the runway. Proper aileron position on takeoff is to start turning into the wind and then slowly neutralize the ailerons as you accelerator. However since ailerons are an aerodynamic control, on the initial acceleration there's not enough airflow over them to affect directional control of the airplane. Therefore to counteract the wind pushing the airplane to the downwind side of the runway, you have to steer into the wind with the nosewheel (controlled by rudder pedals).

As you accelerate however, and aerodynamic control increases with the increased airflow, steering into the wind with the nosewheel/rudder begins to work against you, because the weight on the wheels lightens, which reduces the effectiveness of the nosewheel, and the effectiveness of the rudder increases with the increased airflow. Now with the rudder turning you into the wind you're now compounding the problems you start to have with weather-vaning, which is the effect of a crosswind exerting force on the tail and causing the nose to pivot TOWARDS the wind.

So as the airplane accelerates and you're fighting the crosswind trying to push you downwind, as you accelerate and airflow around the airplane starts to increase, the airplane starts to weather-vane which starts to pull you upwind, in the OTHER direction. This change can catch you by surprise if you're not ready for it. At the point where this change starts to happen, which can be very quickly, you have to REVERSE your rudder pedal input from steering the aircraft upwind, and start counteracting the weather-vaning effect by steering with the rudder DOWNWIND. Its at this moment the ailerons really start coming into play. This whole time you've been steering with the ailerons into the wind, which hasn't really had an effect until now, but now this causes the airplane to want to bank. This is a good thing, because without banking into the wind, your rudder control, which is counteracting the weather-vaning, would cause the airplane to drift back downwind and off the side of the runway.

So now that aerodynamic control is in effect, you have to counteract weather-vaning with rudder to the DOWNWIND side, but you have to counteract your rudder steer with aileron to the UPWIND side. This in effect puts the airplane into what we call a "slip", which is essentially flying sideways. We want the airplane to fly sideways at the exact opposite angle that the wind is trying to push the airplane sideways. In theory these two sideways effects cancel each other out and we end up tracking perfectly straight down the runway without the wheels skidding along the runway surface.

So in effect, when we're taking off, we start steering with our feet one way, and at a critical point reverse that steering in the opposite direction, and at the same time begin to balance that steering with aileron control with our hands. What actually ends up happening, while we're in our slip maneuver but still not fast enough yet to become airborne, is we end up going up on one wheel and rolling down the runway perfectly balancing on that single wheel, with the nose wheel and downwind main wheel lifted off the ground.

This "wheelie" is a side effect of a slip manuever, which is straight flight that is "banked" or leaning into the wind. We're only in this state for a few seconds, between the point the airplane is sufficiently aerodynamic to cause a bank, and the point where we're going fast enough to actually leave earth altogether. Despite the brief time, is quite fun to go rolling down the runway in this balancing act. Once we're airborne, we're free of the burden of making sure the wheels are tracking straight, and we can then neutralize all controls, at which point the airplane yaws sideways, weather-vaning, and we accelerate to climb out. Even though at this point the airplane appears to be flying sideways (and may be very scary looking for new-to-fixed-wing-ops operators), from an aerodynamic sense its actually flying straight (not in a slip), and thats a more efficient way for the airplane to fly, which is a good thing when we're trying to generate lots of lift and very little drag as we climb out.

My experience has been that even in very strong crosswinds the wheelie effect is an experience unique to high-wing airplanes that have narrow-stanced landing gear. Low wing airplanes like a Cherokee 6 or Twin Comanche that have a wider landing gear stance don't typically do this because the aerodynamic force required to lift the one wheel is much greater when the stance is wider, so usually they end up just rolling down the runway and then lifting off, without the whole "wheelie" phase. Its not nearly as dramatic, but sometimes it can be just as challenging to make a smooth and safe crosswind takeoff.

The same "wheelie" maneuver comes into play during a crosswind landing as well, for the very same reasons, although its much easier to hold it for longer periods during landing, because we're not in a mad dash to accelerate, but more in a slow, controlled deceleration back to earth. I remember one of my old instructors used to make his commercial students do a crosswind touch and go landing and takeoff, while only ever letting one wheel touch the ground. We had to land in the wheelie, and balance it there while we accelerated again to takeoff.

I remember way back in flight school, before I had even soloed, and before I fully mastered the muscle memory required for the right input at the right time, I had a few scary moments practicing takeoffs (even in light crosswinds fit for a student). I'd start to drift off to side of the runway because my control inputs weren't correct, at which point I would freeze, because I wasn't grasping what was happening. Thanks to my instructors who were always vigilant and quick to take over and provide instruction. Primary flight training is filled with exciting moments of terror, when you know things are going quickly wrong, but you're not quite skilled enough to recognize it and correct the problem, lol. Kudos to all the instructors out there who bail their students out like that and are still ready to get into the airplane again for the next lesson.

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Ok, so some stories now of a different nature. Today we started work on the survey block we were flying before my break. When I came back the clients were anxious to finish the other one first, so we flew that one, but now we're back to our original one. This second one is further inland... and HOLY CARIBOU BATMAN!! I've never seen so many caribou in my entire life. Apparently the migration has just finished, so they're all just chilling out. Up until today I can count the total number of caribou I've ever seen on 1 hand. After today the number is in the triple digits. Before it was the highlight of the flight if we saw one. But after 10 minutes into our flight today, we stopped counting, and didn't even bother to point them out anymore. They were all over the place. There were 2's and 3s all over the place, a number of small herds numbering between 8-15, and then we even flew over a herd that probably numbered between 30 and 40. It was quite the site, the sheer vastness of the open land with caribou spotting the landscape everywhere you could look.

Also, I've come to realize that there are differing opinions amongst the caribou over what should be considered imminent danger. It was pretty funny actually. Most of the caribou we flew over we hear us coming and kind of hustle out of the way. Others would half heartedly get up if they were laying down, you know "just in case" I guess. While others would run like it was the end of the world. I laughed out loud when I saw a small group of 5 that we flew over. Four of them were laying down on the tundra, and didn't even bother to get up when we flew over. The fifth in the herd was convinced we were death from above. He went running for dear life (pun not intended), just blasting right past the other 4. The rest didn't budge, but just watched him run past like he was an idiot. I could just imagine the dialogue:

Blitzen: "RUN FOR YOUR LIVES!! RUUUUN!!"

Comet: "Relax you idiot, they've been flying over us all day"

Blitzen, who now stops running: "Oh."

It was quite comical to see the different reactions. There was another one who panicked just a little too late, and got up to run, but he wasn't sure which direction to go because we were directly overhead. He just ended up deeking back and forth until I lost sight of him behind us.

It was also interesting to watch them run flat out on the tundra. The tundra surface, although generally flat, is incredibly rocky and uneven. Yet the caribou would goose step around all the stones and rocky ground and splash through the puddles like nothing. I consider myself fairly athletic, but if I tried to run flat out on that terrain, I'd end up tripping on a rock and smashing my teeth out or rolling my ankle in no time flat. It was quite impressive.

We also saw many young colts, some probably less than a month old. They stuck to their mother's heels like little ankle-biters as she hustled away from us. It was interesting to note that all of the young ones are a much darker colour than the grown caribou, which are kind of an off-white tan colour. My theory is that calves are born in the spring, when there is no snow and the land is brown, so they blend into the summer terrain. Grown caribou camouflage better in the snow with their lighter colour. Any expert's opinion welcome.

We should be finished up here soon, and then we have another very short job in Ontario again on our way to Northern Quebec.