One subject that I have grappled with over the years is the disparity between mountain flying being “dangerous” versus a pleasant flight on a sunny day. The reality is, actual mountain flying can be either, or a grade of both. It is not accurate to unilaterally state that it is nothing but dangerous; yet, a cavalier attitude has gotten many in trouble. I started, in my ignorance, subscribing to the danger model, then flirted with the idea that it’s not that big of an idea at all, and now have settled into a new thought paradigm.
It took a recent experience crossing a shallow glaciated saddle at 10,000 feet for the concept to crystallize. Nothing bad happened on the crossing, though at my most vulnerable moment, it suddenly occurred to me that I had not factored one input related to wind. If I was proven to be incorrect in my initial assumption, I would suddenly find myself in a wind shear situation, 300 feet above a glacier, with an engine capable of putting out 70 horsepower at that altitude. The chance of descending onto the shallow glacier (or coming terrifyingly close), would have been unacceptably high.
The good news is that I was correct about the wind, there was no wind shear, and the crossing of the saddle and two glaciers was pleasant and uneventful. What did occur to me in the cockpit was how, if I was at 800’ AGL at the saddle instead of 300’ AGL, the thought wouldn’t have crossed my mind at all. I asked myself why that was the case, and it led to an answer which I think balances conflicting concepts of mountain flying terror and nonchalance.
Every aircraft, day, pilot, and mountain range combined produces a combination of factors where, based on each unique situation, there is a boundary between a safe flight configuration and an unsafe one in each geographic locale. That, I think, is relatively black and white. The result is that certain flight paths can be entirely uneventful, whereas others are extremely risky.
The reality is mixed with many variables. Note how I mentioned that I wouldn’t have given the saddle any thought at 800’ AGL, yet 300’ gave me waves of angst. That tells me that the boundary between safe and unsafe was somewhere in between. Yet, that boundary would be different if winds weren’t the same, if I was loaded with a passenger, if I had more horsepower, if I was flying a spam can, if there was a cloud layer…the list of variable inputs to the equation seems endless, though the boundary of safe versus unsafe flight in the mountains is not.
If there was a visual of how this plays out, I would imagine a landscape mountain scene with red shaded areas demonstrating danger. Box valleys where turning radius is too wide, strongly turbulent areas in the lee of ridges, formation of orographic clouds, low altitudes in valleys where terrain ascends faster than aircraft rate of climb…these would all be shaded red reflecting their danger. Areas that had plenty of altitude, wide enough valleys, and a lack of deleterious winds, well, those are wonderful places to fly and enjoy oneself in the mountains.
To revert back to the technical nature of my sudden concern, there is a 5-minute video of the crossing and below I will walk through some images, explaining what I knew and didn’t know, and where I was when I figured it out.
While I wanted to turn right over the Col de Charmotane, I wasn’t high enough. Snuggling with the glacier made it clear that winds were coming down the glacier, which made sense as wind reports were out of the south.
I went back to the left option, which took me to Haut Glacier d’Arolla. Winds were not evident here. It is interesting how fast terrain below seems to come up toward the airplane, and what seems like adequate room suddenly feels like it isn’t. Since there are no trees or buildings and the scene is clearly majestic, one can wrongly assume that things are bigger than they seem.
Back to the saddle that I would like to get over. The issue with high pressure days is that pressure differences build up on both sides of the Alps. With daytime heating, even in winter, winds begin to pick up, though they are not prevailing in the whole region as one would expect. Instead, they blow through valleys, passes, and openings various ranges, often blowing in a variety of directions. Therefore, I can presume, but not be certain, what the wind is doing. I knew it was coming off this glacier and heading down below me. My presumption was that it was blowing down the glacier in the middle left, and up the glacier on the right, both meeting and descending below.
By the time I got to the saddle, I had a sudden thought that I might have it wrong. What if the glacier to my left, which was blowing down into the valley I came, turned and was blowing forward in this image? I’d have some unpleasant wind shear. I also couldn’t tell how high above the glacier I was, as the snow was one giant soft pillow.
Looking to the left of the saddle, where I was now wondering if the winds were heading out behind me, or if they would bend to the right. It turns out my original theory was correct, and other than getting knocked a bit by wind, it was uneventful.