My Skills Getting Tested – Challenging Start of the OLC Season

Beautiful view of the Continental Divide near Ward. The Peak to Peak Highway is directly under the wing.

This past weekend marked the start of the 2018 OLC season for the Northern Hemisphere.  For those who don’t know, OLC stands for Online Contest and is an informal worldwide soaring competition. Pilots anywhere can upload their flight tracks to a website hosted by a group of soaring aficionados in Germany. The tracks are automatically analyzed and classified according to the rules of various leagues.

My club, the Soaring Society of Boulder (SSB), is very active in the “OLC Speed League”.  The Speed League runs on 19 consecutive weekends starting on the third weekend in April.  Club rankings are determined based on the three fastest flights per club on any particular weekend during a 2 1/2 hour soaring window.  You can read the full rules here.  In 2017, SSB pilots won first place in the US Gold League and came in eight place worldwide (out of 1,162 participating soaring clubs).

Participating in this friendly competition seems to be a good way to track the progression of my own skill level over time when measured relative to the skills of much more experienced pilots.  At the same time, I am acutely aware of the potential risks that participating in any kind of soaring competition could entail.  I have written before about the risks of soaring, especially in a competitive setting, and ultimately it is up to the pilot to stay disciplined and put his or her safety firmly ahead of any competitive ambitions. This is the only way to stay safe.

Both Topmeteo and Skysight predicted weak to moderate thermals up to about 10-11k feet.  A snowstorm had just dumped a few inches over the foothills the day before and – unsurprisingly – the forecast looked best for thermals over the plains that were sure to be free of snow cover.

A strong inversion lay over Boulder as I drove to the airport and the air was still on the ground. Speculating that conditions would likely improve later in the day I delayed my launch until 1 pm and watched other pilots take to the skies before me.  The fact that most seemed to be able to stay up was encouraging.

Just before 1 PM I took off into the glider box just south of the airfield thinking that I would try to stay over the plains as the forecast suggested.  However, as the tow plane climbed through 6000, 7000, and 8000 feet the air did not stir one bit.  That’s when I got on the radio and asked the tow pilot to take me over the foothills where I saw that some white wisps had already started to form.

View from the foothills towards the east. You can clearly see the thick inversion layer above the plains.

I kept my hand on the release ready to let go when I would notice a tangible updraft but the air remained still for a long time.  We had climbed to almost 11,000 feet above Big Horn Mountain when I decided it was time to set myself free even though we had still not crossed a single patch of rising air.

I pointed the nose straight towards a tiny cloud that was forming above Gold Lake.   Just as I hoped, I found the air stirring just enough to slowly gain some altitude back.  I could also see a convergence line with a much higher cloud base several miles further west but getting there seemed very difficult or even impossible to me given the lack of usable landing spots over the foothills.  With no other reliable options for lift in sight I decided to hold my ground for a while and wait for conditions to further improve.

After flying holding circles for almost 45 minutes a few additional small clouds had popped up here and there and I decided it was now or never if I wanted to get some cruising miles in.

The OLC rules require that the start of any flight has to be within 15 kilometers of the take-off airport.  Gold Lake is 20 km away from Boulder and I could not remember whether I had released from tow before or after leaving the 15 km radius around the Boulder airport.  So I decided to first head back and fly through the start cylinder near Lee Hill.

From there I returned to the area of lift near Gold Lake.  Now I had to decide whether to go north or south.  I remember flying several circles unable to decide.  There was a promising looking cloud with a slightly higher base about 6 to 8 miles to the south but it was uncomfortably far away.  If it did not work when I got there I would have no option but to bail towards the airport.  There were a few smaller clouds to the north.  Although they looked less compelling and had somewhat lower cloud bases they seemed to offer a more promising path forward overall.   My indecision with respect to my course direction clearly was not a good tactical move: I had already crossed the start line, the clock was already ticking, and I was just staying in place…

I have found once again that the best thermals are often near bodies of water. The temperature contrast between the cool air above the lake and the much warmer air above the surrounding forest and grassland can serve as trigger. The additional humidity that gets sucked into the thermal from the surface of the lake enhances the thermal.

If took me almost 15 minutes to make up my mind but eventually I decided to take the route to the north.  Once made, the decision felt liberating for now I had a direction and a plan I was going to pursue.  Why could I not decide quicker?

As I headed north towards the Twin Sisters I spotted some newly forming wisps that were about 2,000 feet higher than the cloud I had just left behind.  It seemed like a long shot but I wanted to give it a try.  I thought that if I could gain another 2,000 feet I might be able to get under the convergence line.

However, as I crossed the area below these wisps there was nothing but sink. There went my hope for reaching the convergence.  Fortunately I had already worked out a plan B and a plan C.  Plan B was sufficient.  A small cloud above some rocky outcroppings north of Cabin Creek allowed me to get back to cloud base at 10,800 feet and to continue my track to the north.

I headed toward another small cloud just across US36 between Lyons and Estes Park.  My Oudie indicated that my altitude was now barely enough to make it back to Boulder.  The cloud worked again and provided the strongest lift of the day with an average of almost 4kt.

This allowed me to keep going a little further north until I reached a point between Estes Park and the north side of Carter Lake where my Oudie indicated an arrival altitude above Boulder just below pattern altitude.  Considering the generally weak conditions it felt the right time to turn and head back south.

I followed a similar route on my return leg tracing along the most promising little clouds.  I made sure to maintain a reasonably comfortable altitude above the undulating terrain, rarely dropping below 1,500 feet AGL and never below 1,000 feet AGL.  I also always kept an escape path towards the plains and generally was within glide range of the Boulder airport (albeit sometimes with little margin).

View of the Convergence line along the Continental Divide. My glider in the foreground is to the east of the convergence line. The yellow arrows point at the relatively low hanging curtain clouds that separate the two air masses along the convergence. The cloud base east of the convergence was around 11,000 feet. The dotted red lines mark the much higher cloud bases to the west of the convergence line. Cloud bases there were around 14,000 feet and thermals there were likely considerably stronger.

Little by little, cloud by cloud, I made it to the town of Nederland, 30 miles from my turnaround point.  It was already 4PM MDT and the clouds began to dissolve around me.  So I decided that it was a good time to for a scenic cruise back to Boulder.I took advantage of the Discus’ 42:1 glide ratio and detoured via Gross Reservoir to Eldorado Canyon.  From there I followed the ridge line of the Flatirons  where I provided some entertainment for the hikers atop of Bear Peak.  The easterly flow was unfortunately insufficient to maintain altitude when soaring along the ridge.  (The windward side of the Flatirons was already in the sun shadow so I suspect any lift from the wind might have been negated by cool air descending the face of the mountains.)

Overall, this was a challenging but satisfying start to the 2018 OLC season.  Looking at the score board of the OLC Speed League, my flight was just fast enough to qualify to be scored for the Speed League as the third of the three Boulder flights that count this weekend.   (The Boulder pilot who flew the greatest distance yesterday did not fly through the start cylinder and consequently his flight doesn’t count for the speed league.)

A link to my flight track is here.

Lessons Learnt

  • Safety First, Always.  Not a new lesson but worth keeping in mind, especially when flying with a competitive streak.  There is nothing to be gained in soaring competitions; however, many lives have been lost when competitors didn’t always put safety first.  Only fools risk life and limb for no gain.  So don’t be one.
  • Always Keep a (Safe) Escape Path.  The terrain over the foothills is tricky.  Your computer may tell you that you are within glide range of the airport but it might not account for terrain that’s in the way.  Be especially careful south of Nederland where there is higher terrain to clear to the east if you want (or need) to get back to the plains.
  • You Cannot Fly In the Foothills, You Have to Fly Above Them.  When flying in the Alps you often fly very close to terrain and most of the time the steep valleys provide escape routes into wider valleys with land-out options.  There are no land-out options in the foothills and the canyons don’t provide safe escape routes into the plain.
  • 1,500 Foot Ground Clearance Above the Foothills Feels Ok.  1,000 Foot Feels Low.  That’s for a high performance ship such as the Discus.  For lower performance ships, maintain more ground clearance.  If the thermals don’t support it, get out of there while you can.
  • Don’t (Blindly) Trust the Weather Forecast. Again.  Both Topmeteo and Skysight had predicted the best thermals over the plains.  In reality the plains – where the inversion was very persistent – provided only very weak lift up to 8,500 to 9,000 foot while the better lift was clearly over the foothills and mountains. (Much of the snow over the foothills was gone by early afternoon and the south facing rocks heated up nicely.)  Skysight missed the convergence line along the divide.  (Topmeteo does not predict convergence.)  I will keep reading the forecast but always consider that reality is likely to be different.
  • Good lift can often be found next to lakes.  Today the first lift I found was next to Gold Lake.  Two of my other thermals were next to lakes too.  Most textbooks tell you to stay away from lakes but my (limited) empirical evidence suggests that the best thermals are often next to bodies of water.  There’s also a great German soaring textbook called Meteorologie für Segelflieger by Henry Blum (Meteorology for Soaring Pilots) that convincingly argues that humidity enhances thermals and the best ones are often found next to lakes, rivers, or next to moist forests, mainly because moist air is lighter than dry air.
  • Indecision Costs a Lot of Time.  If I want to improve my performance for the speed league, I need to get better at making decisions based on the information available at the time instead of flying holding circles until I have made up my mind.

Surprise: Fastest Flight of the Day

Wednesday, April 4.  I didn’t try but my two-plus-hour-easy-cruising soaring flight ended up being the fastest flight in a glider on that day.  Fastest as in: highest average speed. Worldwide. That came as a big surprise to me because I hadn’t even thought about it.  I had just been flying along – as it turns out at an average speed of almost 152 kilometers per hour (82 kts).  Equally surprising is the fact that the 325 kilometer flight was also the 10th longest flight that day. Here are the stats from the Online Contest:

List of soaring flights on April 4, 2018 sorted by average speed in kilometers per hour.
List of the longest soaring flights on April 4 sorted by flight distance in kilometers.

So how did that happen?  The answer is easy: strong winds from the west, increasing with altitude, blowing across the Front Range of the Colorado Rocky Mountains. In other words: mountain wave.

Looking at the sky in the morning it wasn’t all that obvious that a strong wave day was afoot.  Here’s a short time lapse of the sunrise from our home in the foothills looking east.  The wind seems to be coming more from the left, i.e. from the north.  The fuzzy edge of the cloud does not look like a lenticularis and you have to look very carefully to spot any indications of rotor activity.

The forecast from Skysight on the other hand looked very confident:

Forecast of vertical velocity at 13,000 feet for 13:00 MST (Skysight). The dark orange band indicates wave lift of approx. 5 m/s (10 kts) over the Colorado foothills along the lee side of the Rocky Mountains. Winds are westerly with a slight northerly component. 

Around noon, however, the wind on the ground was blowing firmly from the east.  The sky was overcast due to a layer of high clouds and seemed deceptively calm.  The only real indication of wave aloft came from pilots flying into Jefferson County Airport a few miles south of Boulder, who reported moderate to severe turbulence a few thousand feet above ground:  just because you can’t see any rotors doesn’t mean that there aren’t any.

Just before 1pm I was ready to launch.  The air became turbulent at about 1,000 feet above ground and when I hit the first strong climb at 1,600 AGL I released without hesitation. That turned out to be a mistake. After climbing in very choppy lift to 2,300 AGL I bumped up against a strong wind shear layer that I was unable to get through.  After a few attempts in different locations I returned to the airport and decided to take another tow.

This time I asked the tow pilot to take me above the wind shear layer and over the foothills.  After a very bumpy ride on tow where I involuntarily practiced several slack line maneuvers I released at 10,400 MSL directly in rotor lift. I had no difficulty to climb to 12,500 MSL where I first encountered laminar airflow and the climb rate improved. Within a few minutes I had ascended above 16,000 feet and from there everything became very easy.

The lift was strong and consistent, the wave bar wide and forgiving.  The wind was blowing at about 40 kts but the Discus flies fast and so I could easily cope with the necessary crab angle and make rapid progress relative to the ground.  As the air got thinner and thinner the difference between Indicated Airspeed and True Air Speed (and therefore ground speed) increased.  The lift was so strong that I had to trim all the way forward and fly at 100-110 kt IAS to avoid climbing above 18,000 feet.  At several occasions the lift was so strong I even had to open the spoilers to stay below Class A airspace.

View of the Front Range from 17,500 feet MSL. The cap cloud above the mountains was poorly defined. You can see the Föhn Gap at the top of the picture with a thin cirrus layer high above.

The clouds were only moderately useful to gauge the location of the wave.  There was a fuzzy cap cloud along the front range with a Föhn gap between it and the next layer of clouds to the east.  However, a high cirrus shield often obscured the position of any lenticular clouds.  For most of my flight I navigated by looking at the position of the mountain ranges relative to the direction of the wind, which blew from northwesterly directions.

Cockpit view. The town of Estes Park is directly in front of the nose and about 10 miles ahead. Note the fuzzy cap cloud indicating air streaming down the mountains on the left. There is one very clearly defined lenticular cloud far in the distance to the right of the picture (the brightest cloud in this shot). The high cirrus shield on top obscured the location of other lenticular clouds.

The position of the primary wave was a few miles further west than Skysight had predicted, and the northerly component of the wind was a bit more pronounced, but other than that the forecast turned out to be pretty accurate.

Unlike prior wave flights, I had no difficulty passing Longs Peak and continuing beyond Estes Park to the north.  To the south I crossed I-70 until I had a great view of South Park behind Mount Evans to my right.  I briefly considered an attempt to fly past Mount Evans but decided to err on the side of caution not knowing where I would land in South Park if things didn’t work as well as I thought they might. (I later learned that Bob Faris, another Boulder pilot flying that day, ventured into the South Park area.  He reported that the wave turned violent around Mount Evans and that conditions were much more difficult further south.  He dropped below the laminar layer and worked rotor lift and thermals all the way to Fairplay and back.  Otherwise his average speed would have been much faster than mine.  His flight track is here.)

Nice view of Mount Meeker and Longs Peak partially shrouded by the cap cloud.

So I kept cruising back and forth along the Front Range.  There was very little effort involved and not much decision making.  I enjoyed the scenery and was happy that my transponder was broadcasting my location and altitude so that air traffic control could make sure that no jets would suddenly emerge out of the cap cloud and into my flight path. After about two hours I felt quite cold and decided to return to the airport.  There is no doubt that I could have kept yo-yoing along the mountains for several more hours. It was one of my easiest wave flights to date.

The return from laminar airflow into the rotor zone brought me back to the harsher realities of wave flying. I encountered severe turbulence as high as 16,000 feet in the secondary wave and cautiously descended with open dive brakes at a save speed of around 70 kts through some of the most violent wind shear turbulence I had so far experienced. Fortunately I had remembered my lessons from earlier flights and tightened my straps and removed all loose items before starting the descent.

As I got close to the airfield I was surprised that the wind on the ground was still blowing hard from the east.  I checked three times to make sure that my mind wasn’t playing tricks on me.  There was no turbulence in the pattern and the landing was smooth and easy.

Here’s a link to my flight track.

Post flight: the level of moisture increased later in the day and the position of the wave became much more visible.  Here’s a short time lapse of the wave at sunset:

Lessons Learned:

  • Wave may be hard to see even if there are clouds in the sky. For most of my flight, the moisture level was too low at the height of most of the wave activity so no clouds formed except for the fuzzy cap cloud over the Front Range and the high cirrus shield above (that probably had little to do with the wave itself.)
  • Being fast can be really easy if the conditions are right. I made no attempt to fly fast.  My high average speed was simply a function of flying straight in consistently strong lift, even requiring high speeds to avoid climbing above 18,000 feet into Class A airspace, coupled with flying at high altitudes where true air speed is 36% higher than indicated airspeed.  So my cruising speed of 100 kts IAS was really 136 kts TAS at 18,000 feet.  My average ground speed was “only” 82 kts.  A big factor explaining that difference is the crab angle necessary to compensate for the wind drift when flying along a wave bar (when the wind must logically always come from the side).
  • Ground speed varies dramatically in strong wind conditions depending on your heading relative to the wind.  This is rather obvious and not a “new” lesson.  But the stats make it very clear: my flight trace shows that my maximum ground speed was more than 160 kts (considerably faster than the maximum airspeed of the glider) even though I never flew above 110 kts IAS, while my minimum ground speed was below 20 kts (much slower than the minimum air speed of the plane).
  • Remember that flutter, and therefore Vne, is a function of TAS, not IAS.  Don’t trust the red line on the airspeed indicator to determine how fast you can fly safely at altitude.  Fortunately the Discus is built to go fast, even high. According to the flight manual,  Vne is 135 kts all the way to 13,000 feet and only then begins to drop off.  At 16,400 feet it is still 131 kts and at 19,600 feet it is 124 kts.