On August 14, 2005, 121 people died in the crash of Helios Airways Flight 522 after the aircrew became hypoxic due to the air pressurization system being incorrectly set to manual.
On April 1, 2011 a glider flight from Boulder, CO ended in a fatal accident after the pilot had spent 14 minutes above 22,000 feet. From there the sailplane spiraled to the ground. The accident report found hypoxia of the pilot to be the most likely cause.
These accidents were on my mind when I attended yesterday’s Hypoxia Simulation Training session, provided by AirCare Facts at Independence Aviation in Centennial, CO.
After an hour of classroom training covering the causes as well as the potential signs and symptoms of Hypoxia, I had the opportunity to participate in a simulation of low pressure conditions at up to 28,000 feet. This was accomplished by breathing through a mask feeding reduced levels of oxygen into the respiratory system.
Hypoxia is an insidious killer because it is often very difficult to recognize any symptoms before it is too late. The potential symptoms even include feelings of wellbeing and euphoria, which may make it even less likely that a pilot would take corrective action before passing out (and eventually dying – either due to oxygen deprivation or due to the plane crashing in uncontrolled flight).
The only good news is that the symptoms of hypoxia tend to be specific to each individual and relatively constant over time. Hence, it is possible for everyone to experience and “get to know” their early indications that something may be amiss. Recognizing these indications early is likely one’s best (and maybe only) chance to take the necessary actions.
At the earliest onset of hypoxia symptoms at altitude it is vitally important to act immediately (while still being “usefully conscious”). Normally this means beginning a rapid descent to lower altitudes where the air pressure is higher and normal oxygen saturation levels are restored relatively quickly (normally within a few minutes).
I took the following video during my own training session so that I would be able to see my own reaction and be able to remember my specific symptoms.
I can recommend to any pilot to participate in such a simulation. Knowing your individual symptoms may one day safe your life.
I recently demonstrated that soaring is an objectively dangerous pastime. On a per-activity-hour basis it is approx. 35 times as dangerous as driving, 70 times as dangerous as bicycling, and still about 3 times as dangerous as riding motorcycles.
One contributing factor has to do with the high number of fatalities during soaring competitions. (This article shows that during global soaring contests, the number of fatalities per number of flights has been more than 10 times higher than during flights outside of competitions.) Even though there is no (relevant) price money on the line, contests tend to tempt pilots into lowering or suspending their normal safety standards. To have a chance of winning or placing well, pilots are often inclined to take higher risks than they normally would accept – consciously or subconsciously. E.g., they will fly closer to terrain than they would on a normal cross-country day; they will fly in bigger gaggles, thermal closer to stalling speed, get closer to Vne – even in turbulent air, attempt safes lower to the ground, scrape across ridges or mountain passes, fly low over unlandable terrain, calculate their final glides with a narrower margin, etc.
It’s the same behavior I observe (and – to be honest – participate in myself) during races on the Condor competition soaring simulator. Fortunately it’s a simulator so if you crash you still get to live another day. But I’ve found that the dynamics in human behavior are very similar to real life competitions. No one wants (or expects) to crash but at the same time, most everyone flies in ways that they would consider irresponsible outside a contest environment. Sure, taking great risks won’t guarantee a good placement, but a good placement almost inevitably means that the pilot assumed a high degree of risk.
Here’s an example: yesterday I flew a Condor race set in the foothills of the French Alps as part of a competition called Regatta Cup. It was a short 188 km Club-Class task along and across several low mountain ridges. Thermals were moderate but a steady 12-14 kt wind from west-north-west made for optimal ridge flying conditions along the steep slopes of the area. As the name Regatta Cup implies, the race was to start at a set time for everyone with all 26 gliders trying to cross the start line below 1,800m simultaneously and as close to Vne as possible. From there they would all fly along the same course, round eight tightly-spaced turn points, then dash for the finish line.
The start was set away from any of the ridges so big gaggles formed underneath one of the few cumuli west of the Romans Saint Pau airfield. Cloud base was around 2,200 meters so everyone circled up to the base of the clouds and tried to stay there in order to maximize the potential energy when the start gate would open. 26 gliders were sharing two thermals, all flying within an altitude band of approx. 50 meters. I was not surprised when I witnessed two pairs of gliders colliding with one another. In fact, I had several close calls myself – and all of that before the race even got underway.
Trying to stay aware of everyone around me I began to dive about 20 seconds before the start of the race. Burning excess energy using the spoilers and watching the altimeter, the speedometer, the GPS, and the traffic around me all at the same time, I managed to cross the start line about 5 seconds after it opened, 20 meters below the ceiling, flying just below Vne with a ground speed of 272 kph. I considered this a very good start even though about half of the competitors were already ahead of me and the other half only seconds (or fractions thereof) behind. And, luckily, I was still alive.
With the wind at the tail and flying at a “conservative” air speed of 160-170 kph the altitude at the start was just sufficient to get the unballasted LS4 to TP1. I was in the bottom third of the pack but the leaders were less than a minute ahead. From there the ridge race began. The strongest lift tends to be near the top of the ridges and not more than one or two wingspans away from the terrain. That means everyone will attempt to fly in that narrow zone between winning and dying, and with so many gliders packed into the same tight spot at the same time, surviving is not much more than a game of Russian roulette.
Added to this is the complexity of different climb rates based on the angle of the ridge line with respect to the wind. You look ahead trying to anticipate where the best climbs are likely to be. Just before you get there you pull up sharply in order to fly two or three seconds longer through the best climb zone, then you push the nose down again, even more so if you anticipate an area of sink. Everyone else tries to do the same thing: flying as close to the ridge as possible, pulling up right before the best climbs, pushing down right before any anticipated sink. In doing so the speed of the glider might vary anywhere between minimum sink speed and three times as fast. Each time the altitude fluctuates by 200-300 meters as speed gets converted into height, or height gets converted into speed. Pulling up or pushing down too early or too late, or incorrectly judging the strength of the lift, costs precious seconds that add up and ultimately decide about your placement. Flying like this is more than risky enough if you are the only one around but doing so in the midst of a pack of more than 20 gliders is simply an enormous gamble.
After several close calls between TP1 and TP4 and being about two minutes behind the leaders at this time, I decided not to follow the gaggle in front of me on the direct route to TP 5 but to take a slightly longer route along the higher and steeper ridges further to the east, hoping not only for better climb rates along this route but for some stress relieve as well.
Soon I discovered that I faced another challenge: there was a mountain pass in front of me. I didn’t want to waste any time turning so I hugged the mountainside and flew at minimum sink speed hoping that the lift would be strong enough to carry me over the pass before I got there. I was aware that this was a hugely risky maneuver: if a wind gust would force the glider to stall I would not have enough altitude to recover before hitting the ground. And if a thermal would break off on the valley side and turn the glider towards the slope, I could easily get pushed into the trees. “There is no way I would fly like this in real life,” I thought.
The gamble paid off and I made it across the pass and dove for TP 5. As I got there I noticed that I had caught up with the pack. I could still see several gliders ahead of me but they seemed a few hundred meters lower. With a valley to cross ahead, they would likely have to stop to climb somewhere while I could cruise along the top of the ridge at a much higher speed. I dove across the valley at over 250kph and still reached the ridge on the other side at a good altitude. Again, I hugged the higher ridge to the east while the handful of gliders ahead of me were lower and further west.
There was another valley to cross between TP 6 and TP7. Again I put the nose down only to realize shortly thereafter that I would arrive too low on the other side. I dialed the speed back to 140kph – my slowest cruising speed of the entire race – to conserve what altitude I had left. As I headed straight towards TP 7 the trees on the slope ahead of me were getting closer and closer. Would I be able to get to the turn cylinder before the trees would get me? I wasn’t sure but just as I was forced to initiate a turn right over the tree tops the GPS confirmed that I had rounded the TP. If I had only been 20 meters lower I would have had to turn away from the slope and find a spot to climb.
Having turned TP7 I could now hug the ridge again and fly toward TP8, the final turn point. I could only see one glider ahead of me. My final glide calculator indicated that I would arrive a few hundred meters too low but I was confident that I could easily make that up by hugging the ridge between TP 8 and the finish line. So I decided to dive, flying a direct route towards TP8. I kept watching the other glider to my right and though that I might have a chance to beat him. I reached the next ridge closer to the valley with only 5 kilometers to go to TP8 and 20 kilometers to the finish when … I suddenly died.
Another glider that I had not noticed must have been slightly above or below me. I had not seen him at all and I must believe that he had not seen me either. It was quite a shock and a revelation. Obviously, had this been in real life I would not be here to write about this experience. Instead, my wife and children would stand by my graveside and wonder, with tears in their eyes, how this could have happened.
Yes, I know, Condor is just a game. I must and do believe that I would not have taken many of the risks described, if I had been in a real glider. Also, some of the race settings described here are not realistic. For starters, contest directors are unlikely to plan a task that is as dangerous as this one.
However, there are many things that are not so different from real life. The pressure of the competition, the desire to win, the fear of embarrassment. Also the fact that taking high risks does have the potential of giving you an advantage in the race: circling in gaggles under the cloud base to conserve energy for the start, flying close to ridges without adequate safety margin, hugging the tree tops, scraping over mountain passes, circling at minimum speed close to the ground, flying low over unlandable terrain, aggressively calculating the final glide – all these are risks that have killed many real life pilots. I believe that this is especially true in race settings when usual risk-mitigation strategies get too often ignored or even willfully suspended.
BTW – in case you’re wondering: I did analyze my flight track and those of the eventual race winners. I believe that I would have come second or third in that race – it would have been my best result against some of the world’s best Condor pilots. You can see the race results here. However, it was definitely not worth dying for.
The best soaring routes almost always correspond in one way or another to the terrain below, no matter what lift you use.
E.g., you would expect thermal lift over terrain that is most exposed to the sun (e.g. slopes that are most directly warmed by the sun based on the time of day); you would expect convergence lift where terrain features redirect the wind such that air masses collide with one another and are forced upwards; and you would expect ridge lift along long and steep slopes that are more or less perpendicular to the direction of the wind. (It’s no surprise that pilots love to fly along the top of ridge lines where thermal, ridge, and convergence lift often come together.)
It’s no different with wave lift. Wave lift forms when the wind pushes (relatively stable) air downward along the lee slope of a mountain, thereby warming it at the dry adiabatic lapse rate (such that it becomes warmer than the surrounding air near the ground). It will then rise again because it became lighter than the surrounding air mass, thereby starting a wave motion that oscillates on the back side of the mountain. (You can find more details about wave lift here.)
Wave lift will form only if the wind is relatively strong. In most locations, such strong winds usually come from the same direction. In Boulder that is from the west – especially in the wintertime when the jet stream blows at our latitudes. What makes Boulder a particularly great wave location is the fact that a tall, nearby, mountain range – the Colorado Front Range – is conveniently laid out in north-south direction (hence the prevailing wind has to cross it at a perpendicular angle) and the Boulder airport is just to the east in the lee of the mountains.
With all that said, it should be no surprise to see that wave flights from Boulder tend to follow the same routes: parallel to the mountains on the lee side. In fact, the following chart depicts 40 wave flights from Boulder from 2010 and 2017 that were longer than 2 hours in duration and extended above 17,000 feet.
If you study the flight logs a bit, you quickly notice that the traces tend to be parallel to the curving ridge line. The distance of each trace to the mountains depends on two things: (1) the wave length on the particular day (it can be longer or shorter depending on the strength of the wind and the stability profile of the air); and (2) in which wave bar the pilot was flying (e.g. the primary, secondary, or tertiary wave). The primary wave is the one closest to the mountains; it usually (though not always) provides the strongest and highest lift. As the name implies, the secondary is the second wave bar behind the mountains, the tertiary the third, and so forth.
Take a look at the red trace that extends furthest to the west – it is the only one in this set that crosses the Continental Divide. This flight was flown by Al Ossorio on Dec 29, 2010 in the club’s DG505 and reached more than 27,000 feet within the designated wave window (Arapaho Peaks Soaring Area). However, note that the high point was not over the Continental Divide; it was several miles further east, just where the red trace blends with all the other traces – the typical location of the primary wave.
Also quite interesting are the two greenish traces that extend furthest to the north. Both were flown much more recently by Bob Faris on two subsequent days in December 2017 (Dec 1 and and Dec 2) in his DG800. Both flights reached altitudes of just under 18,000 feet. During the more yellowish of the two, Bob got above 17,000 feet only on the outbound leg (following a fairly straight line parallel to the mountains). He then lost the wave near the Wyoming border and had to fly the return leg at much lower altitudes between 9,000 and 12,000 feet mostly in thermal lift (a very warm day in December!). During the more greenish of the two traces, Bob stayed in wave above 16,000 feet almost the entire time and actually flew back and forth along the mountains three times, covering 617 kilometers at the remarkable average speed of 174 kph (108 mph).