Rockies Soaring Safari

A Solo Soaring Safari over the Rockies:

3,000 NM  in a Stemme S10 Chrysalis

Self-Launching Sailplane

by Marc Arnold

It isn’t possible to capture the beauty and splendor of soaring the entire length of the American Rockies in a high performance sailplane.  You have to experience it yourself.  I can only hope to describe a unique kind of soaring adventure available to pilots of self-launching sailplanes.

In the summer of 1994, I toured the Rockies in Stemme S10, N5021, for two weeks.  Starting in Aspen, Colorado, my route zig-zagged the Rockies as far north as Kalispell, Montana and as far south as Phoenix, Arizona.  The trip covered just over 3,000 nautical miles of America’s most beautiful terrain.

The first 20 years of my flying experience was powered flight, mostly 3,000 hours of single pilot IFR while conducting business in my Cessna 421 throughout the U.S.  Over the years, I earned an ATP and attended Flight Safety recurrent training sessions semiannually to stay current.  Although I enjoyed the mobility of flying and the aesthetics of flight, my flying was strictly for business purposes.  Then, three years ago, my horizon expanded with the addition of a glider rating.  Within a year I bought the first Stemme S10 in the U.S. and since that time, my logbook shows thousands of miles of cross country soaring.

The Stemme S10 Chrysalis is a high performance two place side-by-side self launching sailplane with a glide ratio of 50 to 1.  Equipped with a 93hp four stroke aircraft engine, it can taxi at any municipal airport on its conventional landing gear, self-launch without any ground support and cruise at 120kts more than 900 nautical miles.  Where can you soar in a Stemme S10 sailplane?  Anywhere!  This is a brief account of highlights from the Northern leg of my Summer, 1994 adventure soaring among the Rockies.

7/14/94  Aspen, CO

I stowed my luggage in the baggage compartment and strapped additional gear into the right seat.  Aspen ground control cleared me to taxi to the active runway behind a Gulfstream IV.  The only similarity was our wingspan.  In spite of a 12,500 foot density altitude, the Stemme’s ground roll was less than 1,500 feet and it climbed away from the runway nicely.  Throttling back to 3,000 RPM, I proceeded down the valley, wandering about the valley exploring the air, looking for the first lift of the morning.  Would the first thermals happen on the east facing slopes due to the rising sun? Or would the light wind blowing up the valley provide ridge lift on north facing slopes?  In soaring there is only one thing that can be said with certainty about lift:  Lift is where you find it!

Only 15 minutes after takeoff, the first thermal kicked off a couple miles south of Glenwood Springs airport.  Banking and pulling up sharply to take full advantage of the thermal, I turned off the motor and retracted the propeller:  Throttle – idle, magneto – off, propeller – brake to stop rotation, propeller positioning control – pull to position prop, nose cone handle – pull to close.  The total elapsed time to transition from powered to soaring flight: 5 seconds.

I “centered” the thermal using the beeping of the electronic HUDIS/light variometer to confirm my seat-of-the-pants feel of the rising air, a process of minutely moving the circle’s center to maximize the rate of climb.  A few minutes of circling in lift, and my altitude was 14,000 feet.  Instead of looking up at the valley walls, my view now encompassed the valley below and an extensive mountain range in all directions beyond.  I looked to the northwest in the direction of my planned destination, Kemmerer, Wyoming 230 nautical miles away.

An Airmet was active for smoke along the direct line, so I headed northeast along Highway 70.  I pushed the nose down and left the thermal at 100 kts looking for more lift.  Altitude is distance.  Altitude is time.  As I glided down the valley, I was loosing both.  After continuing down the valley for another 10 minutes, the sides of the valley began to loom upward.  The head up display indicated enough energy to glide all the way to Eagle.  Nevertheless, I prepared to start motor:  Switches-on, fuel pump-on, fuel selectors-on.  Propeller deployment and engine start is now less than 4 seconds away.

Just as I reached to extend the nose cone, and only 5 NM from Eagle airport, a thermal bumped.  Rather than a symmetrical bump, the left wing rose more so I banked steeply to the left and happily found the welcome lift.   At first, the lift was weak — only two knots (about 200 feet per minute) and narrow.  As my altitude climbed, however, the strength and diameter of the thermal grew as well.  At 10,000 feet it was up to 3 knots; at 14,000 feet, 4 knots; and at 17,000 feet, 5 knots.  Such is the fascination of soaring.  Each thermal is unique and learning how best to find and utilize lift is the lifelong ambition of cross country soaring pilots.  At 17,500, the lift was stronger than ever, but without clearance from ATC to enter Class A airspace, I took up a heading and flew on course, mindful to avoid climbing further.

Heading to the north, there was considerably more lift than I could use.  To avoid climbing, I pushed the nose further down and converted the lift to speed.  The airspeed nibbled at the placarded Vne for much of the time.  High altitude, high speed flight in a straight line normally offers an opportunity to enjoy the scenery.   In this case, however, the visibility was marred by smoke from a forest fire to the west.  I diverted somewhat to the east, but it did little good.  The smell of smoke grew as the forward visibility fell to a few miles.  I considered my options: Higher, lower, left, right, or return.

Flight Service was unavailable in my location, but a helpful TWA crew above me was willing to come up on 123.3 to relay their view from FL370:  Tops of the smoke were above FL240 (the certified limit of my oxygen system).  Smoke was considerably thicker to the west.  Strong lift to the east had kicked off a squall line with towering CU’s to FL350.  We compared our relative positions.  Continuing another ten miles north, they estimated, would take me out of the smoke.   The ground was still visible below, but the horizon became less and less clear.  Forward visibility was difficult to judge.  The electric attitude gyro was on, just in case it deteriorated suddenly.  Just as predicted, only a few minutes later the boundary of the smoke ended, revealing an area of fair weather cumulus clouds with bases above 20,000 feet, indication of ideal soaring conditions.

For the next 45 minutes, the flight alternated between high speed dash in areas of sink and slow thermalling flight to regain altitude.  Equipped with 76 feet of full span flaperons, the S10 is ideally suited to both flight regimes.  With flaps at 10° positive, the wing is optimized to achieve a minimum sink rate of 110 fpm.  When flaps are set to minus 10°, the sink rate at high speed is minimized.  Speed is crucial since it allows the pilot to make good progress towards the destination, spend the least amount of time in sink, and cover the most distance in search of lift.  Based on the rate of lift expected in the next thermal, a calculation can be done to yield the optimum speed-to-fly.  The greater the sink rate, the faster you fly.  The relationship used to be indicated by a moveable ring on the face of the airspeed indicator.  Thanks to advances in avionics, this calculation is now done in real-time by a flight computer.  After entering the plane’s weight, abundance of bugs on the wings, and MacCready number, the head up display indicates the speed to fly and up/down command arrows directing you to the ever changing optimal target airspeed.  Even with the help of modern flight computers and GPS, one’s ability to go from A to B in a sailplane is still a challenging and rewarding experience which depends on reading subtle meteorological clues to find lift.  No instrument exists today which allows the pilot to “see” lift before entering it.

Proceeding further north, the air became still.  For power pilots accustomed to bumping along at lower altitudes, utterly smooth air is a welcome change.  For a sailplane pilot, silky smooth air at lower altitude signals the lack of convection and its corresponding lift.  Had there been CU’s to one side of the course, it would have been easy to divert.  The blue sky in all directions, though, gave no clue of where the lift might be.  So from 16,500 feet, I entered a long glide in the direction of rolling hills in the distance where the chances of lift would be greater.  For more than 50 NM, there was nothing but serene quiet at 80 Kias as the descent continued unabated at 200 fpm.  If there was no lift, I would restart the motor and power the remaining few miles to Kemmerer.

This time, the theory and practice coincided.  There was weak lift over the hills which was enough to get into a mass of cooler air over the desert southwest of Rowlings, Wyoming.  The desert terrain produced a solid 3 kts of lift to 16,000 ft.  Proceeding west above 16,000 feet, the outside air temperature was a cool 20°F.  Nevertheless, the greenhouse effect kept the cockpit warm.  Convective activity to the south was generating build-ups and the sun was casting long shadows on the staggeringly picturesque scene below.

The oxygen supply was down to 300 PSI and in need of replenishment.  Unable to reach Kemmerer unicom, landing at Rock Springs immediately below seemed more prudent.  AWOS was reporting wind from the southwest at 23kts, gusting to 45kts!  The reason wasn’t hard to find:  An old cumulus was giving up its moisture in a large shaft of virga.  With the luxury of excess altitude, I explored the air beneath the virga and found the narrow core descending at more than 2,300 fpm.  Is it any wonder such phenomena can produce microburst phenomena at the surface?

An uneventful landing ended my first flight.  Although only 225 NM from Aspen, my route took me nearly 300 NM over six flight hours for an average speed over the ground of just over 50 kts.  Not bad when you consider the engine operated enroute for less than 10 minutes and fuel burn was less than a gallon.

7/15/94  Rock Springs, WY

The morning weather forecast was favorable:  Good VFR with scattered to broken mid-level clouds with isolated thunderstorms in the afternoon.  My VFR flight plan was soon filed to Bozeman, Montana, 266 NM to the northwest.  The briefer was surprised to hear my estimated time enroute of seven hours and 14 hours of fuel on board.  Since my speed and route of flight would depend my skill in finding and using lift, I padded the ETE considerably.  Once underway, regular position reports along the way would give accurate information of my route and progress.

I arrived at Rock Springs airport at 9 am.  Fifteen minutes later the wings were unfolded, the refilled oxygen tank reinstalled, luggage loaded, drinking water and snacks replenished, and preflight complete.  Winds were light and variable, temperature 48°, clear, and unlimited visibility.

Moments later the engine purred along at cruise while the desert floor slipped beneath the perfectly smooth carbon fiber wing 1500 feet below.  The sun’s morning rays beat through the canopy and heated my right leg.  Certainly the dry terrain below was absorbing the same infrared energy and radiating it back to the air.  Nothing to do but enjoy the scenery until the trigger temperature is reached.  Then bubbles of warmer air start to rise and make themselves felt.  In the meantime, the flight proceeded in the absolutely smooth morning air.

Twenty minutes into the flight and half way to Big Piney the first bumps reached up to meet the Stemme.  Cautiously at first, I thermaled in the weak lift with the engine at idle.  Once centered, the lift was stronger and the engine was no longer needed.  Up and up I went.  The view from 14,000 feet over Big Piney encompassed a broad landscape.  Wisps of cumulus clouds to the west marked columns of warm rising air cooling below its dew point.  The lift, which began weak grew to 400 fpm and continued to strengthen.  All the indicators were positive, so I optimistically headed off to the mountains north.

Mountainous terrain is welcomed by a soaring pilot in search of lift.  Valleys heat unevenly as the sun hits different sides of canyons throughout the day.  Gentle breezes over complex topography dislodge heated bubbles of air to kick off thermals.  Stronger wind flows up the face of inclined terrain generating ridge lift.  And the smooth flow of wave lift can be found high over mountains where air resembles the laminar flow of water over a boulder in a stream.

The sport of cross country soaring instills a valuable discipline of thinking about alternatives.  In spite of all the positive indicators, I was sinking through 10,000 foot MSL as I approached the 9,000 foot high terrain ahead.   If lift was not found, I would fall back on Plan B: Gliding back to Big Piney.  At 50:1, the Stemme can glide more than 7.5 NM per 1,000 feet in still air.  Given my proximity to Big Piney, there was still enough altitude to make it back.  And, of course, starting the Stemme’s Limbach engine was the third alternative.  Fortunately, Plan A worked.

A band of violent lift flexed the wings upward as my flight path passed just 300 feet above and south of the vertical face of a 1000 foot high cliff.  The shaft of lift coming off the face was narrow.  Each circle was marked by violent transitions between light and very strong lift.  The HUDIS computer indicated an average lift of 7.8 knots (780 feet per minute), but the instantaneous readouts varied from 3 to over 15 knots.  Passing in and out of the strongest lift was like riding a bucking bronco.  Before long, the digital head up display read 16,000 feet and Jackson Valley spread out before me.

The cliff proved to be a good omen.  The strong lift over the hills bordering the east side of the valley were perfect for “dolphin flight”.  By pulling up to go slow in the areas of lift and pushing the nose down to go fast in areas of sink, high speed can be accomplished in a straight line.  Based on the strength and prevalence of lift in the area, I entered a high MacCready number into the glide computer.  Thirty miles zipped by in half as many minutes as I followed the aggressive nose down commands displayed by the glide computer.

Straight dolphin flight offers a good opportunity to take care of housekeeping chores.  First, I contacted Jackson Hole to provide a position report and check on the weather along the route.  Next came a timely use of the urinal.  Then a snack of food followed by a deep draught of water.  Rehydrated and refreshed, it felt like the start of a new flight.

The cumulus clouds gave way to blue sky and smooth air over Yellowstone National Park.  With lift or signs of lift for twenty miles ahead, I turned the MacCready number to zero and followed the slower speed commands to optimize the glide for distance (at the expense of speed).  It was now more important to conserve my altitude and arrive at the next area of lift with the most altitude possible.

For many pilots, much of the joy offered by flying stems from the opportunity to exercise their judgment in varying circumstances.  For the VFR pilot, accurate flight planning and execution offers its rewards.  For the IFR pilot, a sense of accomplishment  comes from shooting a precision approach to minimums in actual conditions.  For a sailplane pilot, each mile of a two hundred mile flight is a triumph!

Barring mechanical failure or unforecast weather deterioration, the pilot of a powered plane progresses from Point A to B with little call on his judgment.  Cross country soaring, on the other hand, is a continuous challenge to the pilot’s judgment:  Is that wisp of a cloud 5 miles straight ahead likely to develop into lift by the time I get there, or should I divert to the cloud off course to the right which clearly marks lift now, but which is past its prime and may only have sink by the time I get there? Should I take the time to pick my way around the perimeter of the blue “hole” ahead where there isn’t likely to be lift, or do I have enough altitude to go straight across and find lift on the other side?

How the soaring pilot answers the myriad judgment questions determines the outcome of the flight.  To put this in perspective, a world class sailplane pilot racing during a typical four hour flight makes a decision critical to his success every ten seconds.

Now approaching Yellowstone Lake, I was now confronted by a typical judgment question.  The minor bumps on the south side of the lake showed little evidence of lift and my altitude was down to 2,000 AGL.  There wouldn’t be any lift over the cool surface of the lake ahead, yet an area of promising CU’s lay on the far side of the lake.   Is it wiser to use the altitude to glide across the lake, or use the altitude to search for lift on this side of the lake, then cross with ample reserve?  I decided to exploit what lift could be found on this side before crossing the water.

Turning into the first thermal, it soon became apparent that it only offered enough lift to achieve zero sink.  I searched for and found another, then another.  But finding and centering each weak thermal cost altitude.  After ten minutes, I’d lost 1,000 feet and was now trying to work a weak thermal over an open meadow.  This is the pattern that leads to an “outlanding” in an unpowered sailplane.  As altitude is lost, the search area is further constrained more and more by the necessity to stay in the proximity of a suitable landing site.  A few more minutes, and the outcome became clear.  I was boxed in and wouldn’t be soaring away from this field today.

Rather than just start the engine and fly away, I went through the process of setting up for an outlanding.  This practice keeps me current in off-field landing technique and ensures a viable alternative in the unlikely event the engine fails to start. A close observation of the field revealed no hazards such as boulders or fences or power lines.  The surface of the lake revealed the wind direction and velocity.  Set up on final and ready to go through with the landing, I deployed the propeller and started the engine in five seconds.

Only six minutes of climbing under power northwest and I was back in a solid 4 KT thermal climbing in sight of Old Faithful.  Back up to 12,000 feet, I turned northeast and dashed into the mountains of Yellowstone.  Flying around the summit of a peak, I traded waves with a Park Ranger staffing a lookout station.  There was good lift over the peak so he had the pleasure of watching me circle many times as I gained a thousand feet and set off to the next peak.

For the remaining 30 NM to Bozeman, the lift was widespread.  The eagles were up in numbers and they marked the better thermals for me.  I hopped from one gaggle of eagles to the next, marveling at their superior skill in finding the strongest core of the thermal.  Sharing thermals with eagles is surely the best way to view Yellowstone National Park, a vantage point rarely seen.

Five and a half hours after leaving Rock Springs, I was cleared to land at Bozeman, Montana after an arriving Challenger.   We both taxied to Sunbird aviation where a sociable Bar-B-Q was in progress.  Newly found soaring friends graciously opened their home to me where I spent the night.

7/16/94  Bozeman, MT

After ridge soaring with my new friends in the morning, my bags were packed once again and I was aloft once again in a northwesterly direction, this time to my northernmost destination, Kalispell, Montana.  I shut the motor down about 10 minutes into the flight, just east of Three Forks.  The early morning thermals were very weak and it was difficult to hold my altitude.  Once again, my search area had narrowed to a small area within gliding distance to an open field.  It looked like a repeat of my experience the previous day and I began to think an engine restart would be necessary.

It was south facing ridge line with green pastures forming a patchwork quilt below.  My shadow passed a farmer pulling a hay wagon.  He pulled his tractor over to the side of the road and waved.  Only a few hundred feet away it was easy to see him and I waved back.  He climbed up onto the hay, took out what seemed to be a lunch, and sat watching me circle low over the field.  Evidently, he was interested in my search for lift.   My broad looping circles took me over each of the objects which might “trigger” a thermal — a small shed, the bare rock at the summit of a small hill, the paved road — Anything which might radiate more heat than the surrounding terrain.

Visualize the triggering of thermals by imagining droplets of water hanging from the ceiling of a damp basement.  If you reach up and touch one droplet, not only does it run down your finger, but many nearby droplets run to the point of your finger and follow the first droplet.  Now turn that image upside-down and picture a layer of air a few hundred feet thick heated by warm ground.  The warmer air is ready to break loose and rise in many places, but it takes one particular spot to trigger the start.  Experienced glider pilots in search of a low “save” pass over potential trigger points.  Once the bubble breaks loose, other warm air flows in and up the same path, just like the droplets of water down your arm.

Then, I felt a significant bump and focused my full attention on centering this little thermal.  It would be my last chance before starting the motor.  Where did this particular thermal come from? I couldn’t be sure which of the likely candidates was responsible.  Nonetheless, I doggedly stayed with it and found it grew stronger as my altitude increased.  Having attached myself to this bubble of air, we drifted together along the ridge line.  Constantly turning, the bank angle of 30° and airspeed of 45 Kias remained nearly constant.  Each revolution, however, wasn’t symmetrical.  Small adjustments of bank angle during each rotation moved the center of the circle small but critical amounts.  These minute adjustments exploit the thermal and extract the most kinetic energy possessed by the bubble of air.  At 12,000 feet, I made one last turn and saw the farmer’s tiny vehicle where he’d pulled over.  It’s nice having an audience.

Negative 10° flaps and 110 kts across the next valley.  Cumulus clouds were forming ahead over higher terrain.  There was strong lift under the clouds.  Climbing at 1,000 fpm, it only took a few turns before I approached cloud base, then headed on course.

The strong lift of my previous thermals and the nearby large runways at Helena International gave me confidence.  I passed several good thermals and continued abeam the airport getting lower over the mountains south of airport.  My thinking was that the northerly winds would flow against the hills and kick up thermals, but I was wrong.  There was only sink.

Only ten minutes earlier I optimistically passed useable lift.  Now I was scratching for any lift I could find, no matter how weak.  Ultimately, I started the motor and headed north in search of lift.  After four minutes, I pulled up and centered a very weak thermal at less than 1,000 feet.  Once established in a climb, I shut down the motor.

At only 60 fpm, it was hard work–a balance of intense concentration to stay centered in the thermal, yet relaxed enough to avoid over controlling.  It’s a very Zen process of “relaxed concentration”.  Fluidity is key in manipulating the controls.  It’s similar to many sports when trying harder leads to worse results–your actions become jerky and forced.  When you become more skilled, the movement is automatic.  In tennis, for example, the racket meets the ball at just the right spot, your feet move you to the right location without direction imparted by you–it all just flows!  The soaring became effortless as I forgot about the bank angle, airspeed, flap settings, speed-to-fly calculations, rate of climb and G-force leaving only the air around the plane.  It’s like staring at a high-contrast picture and suddenly seeing the negative space around the object.  Without any conscious effort, my body, my mind and the ship flowed into the lift, meeting it at just the right speed and bank and configuration.  I was truly soaring.

When I first entered learned to soar, it was more a mechanical set of actions–Pull up, check the airspeed, bank into the turn, check the variometer, think about which side of the thermal was strongest, lessen the bank to move the center, tighten the bank to stay closer to the center, etc.  Now, without effort, the rate of climb in this thermal had grown from its initial value of 0.6kt (60 fpm) to a solid 9 kt (900 fpm) and my altitude was now over 13,000 feet.  And in the process of climbing from a few hundred feet to thousands, my field of view expanded as well.  With the help of one more thermal over Lincoln airport I headed off into the mountains leading to the Swan Valley.

Jagged peaks rose on the  right, each topped by a roiling cumulus cloud revealing strong updrafts caused by the sun’s heat throughout the day.  This resulted in a “cloud street”, a band of lift topped by a row clouds. Using this street I speed along the tops of the peaks on the east side of the valley.  Emerald colored high lakes passed under my wings.  Each lake a windswept surface of water surrounded by near vertical walls of rock. Verdant tree farms stretched on the left.   Thousands of feet above the ridge line, altitude was not an issue–the strong uplift made dolphin flight easy.  Diving in the sink, pulling high G’s in the lift, it was a dance with kinetic energy.  The nearby scenery was breathtaking.  Swan Lake passed by on the left.  Then, all too soon, I rejoined the world of conscious aviation.  Radio chatter replaced quiet serenity in my Plexiglas chrysalis.  A moderate crosswind combined and narrow runway kept my attention high during the landing at Kalispell, MT, only a few miles from Canada.

7/17/94  Kalispell, MT

I flew under power about ten minutes to the north end of Swan valley.  The previous day I flew northbound in this valley at high altitude, above the peaks on the east side in late afternoon thermals.  Today, however, the morning sun was still too low in the eastern sky to heat the west-facing slopes.  Fortunately, the wind was blowing strongly from the west creating strong ridge lift.  This allowed me to fly below the peaks and in the valley, instead of above it.  On the northbound leg the previous day, the conditions took me above the valley at an altitude of 17,000 feet.  The valley and its tree farms could be seen as a whole.  Now my view comprised individual trees less than 100 feet away.  A pause to “S” turn in front of the slope instantly causes my altitude to zooms up and I can look down on the peaks, though most of the 60 miles was spent looking up at the peaks and at the trees off my left wing.  Soaring a ridge is the provides ultimate challenge in opportunistic decision making.  When the topography of the slope ten seconds ahead is likely to force the perpendicular wind upward, you keep the nose down and push for speed.  When a gap in the ridge opens up ahead, you judge whether you have enough energy to cross, or whether it is necessary to slow for a period to gain altitude and store energy.  The violent turbulence, high G pull-up’s in lift, zero G push over’s in sink and close proximity to terrain make ridge soaring the most dynamic flight regime I know.  It is exhilarating!

All too soon, the valley came to an end, and I converted my 140 kts of kinetic energy to altitude over the broad open valley ahead.  The rush of pounding along at high speed close to the trees and rocks gave way to the serene quiet once again of a well-sealed world class sailplane in smooth air.  Cumulus clouds moving in from the west are obvious indicators of lift.  The first provided 4 kts, as did the second and third.  It was a normal progression of circling in thermals followed by brief dashed through sink to the next.  Then I saw an unusual cloud formation ahead.  The thin wisp of condensation seemed to be the start of a standing lenticular cloud.  I diverted to investigate.  Suddenly the air became silky smooth–all motion stopped.  The wave was condensing on the leading edge of the cloud and evaporating on the trailing edge.  Slowly “S” turning into the wind, the wave carried me vertically up the face of the “lennie”.  I surfed the rising, growing cloud.  It was silent and perfectly smooth.  It was a magic carpet lifting me straight up.  With the permission of ATC (and mode C transponder), I rode this vertical elevator up to 24,000 feet.  Then I left the wave and headed south having experienced the most amazing flight in more than 20 years of flying.

A long glide to Three Forks, Montana and Bozeman was in easy gliding range.  Still exhilarated from the earlier flight, I went to the nearby ridge instead.  Joining up with a Ventus A 15m sailplane, we chased each other back and forth along the 25 MI long ridge.  Cavorting in the severe turbulence brought all the loose items up to the top of the canopy.  Heavy G’s bent the wing tips up more than 5 feet.  And always the Ventus above or below or swooping alongside.  The pilot was practicing for the National Championship the following week.

My perfect day of flying adventure ended as the sun set. Once again on the ramp at Sunbird Aviation, a number of local soaring pilots came out to see the Stemme.  They were well acquainted with the local ridge and nearby soaring, but few had ventured across Yellowstone to the south or the Swan Valley to the north.  They were able to appreciate the freedom provided by the Stemme’s Limbach motor standing by.

7/18/94  Bozeman, MT

After three hours of ridge soaring with a number of the local pilots, the CU’s began to pop.  With baggage packed, I headed southwest.  Passing Livingston, Montana, the lift was weak.  I scratched along a wide valley to the south, just barely holding my altitude.  The terrain was rising as I flew south.  Then, over a plateau in the center of the valley a thermal bumped.  With a lot of work, I extracted a few hundred feet.  Then jumping to the east side of the valley, I discovered very strong lift of more than 1,000 fpm on the south face of Sheep Mountain.  Whammo: 14,000 feet.  Then east down the Yellowstone River valley, high speed down the valley, swooping past hundreds of tourists at a scenic overlook, through Sylvan Pass, followed by a good thermal to 17,000 feet.  I stayed high and fast over Wind River mountain range, then enjoyed a long calm glide towards Rock Springs, Wyoming.  This flight in particular demonstrated the different kind of challenge presented by cross country soaring.  There is no steady state as in the cruising phase of powered flight.  Instead it is a kind of three dimensional sailing in which you are constantly in one of two states: Loosing or gaining altitude.  And no matter what, you are always employing all your knowledge of meteorology and flying to find more lift.

With daylight fading, I landed at Saratoga, Wyoming and spent the night at a delightful resort with outdoor natural hot springs.

7/19/94  Saratoga, WY

Ten minutes under power, then the motor was off once again to soar east to Medicine Bow Peak.  Circling low over a landable meadow, I prepared to restart the motor, but a small bump grew.  Soon I was at cloud base and turned south.  Unfortunately, lower cloud bases and rain showers to the south made the prospect of continued soaring unlikely.  I flew on, expecting to finish the flight under power when a fascinating phenomenon occurred.

A mass of cooler moist air was flowing upslope from the east forming lower stratus layers to my left.  Drier unstable air was being heated by the afternoon sun permitting convective cumulus with bases at 2500 to 3000 feet AGL to the right. As I flew along the confluence of these two air masses, I found a zone of weak lift along my southbound course — about 80 fpm.  With fog and haze on the left and low cloud bases to the right, I was able to ride along slowly without losing altitude from Medicine Bow to South Bald Mountain, a distance of 60nm at 70 knots.  Nothing the soaring books I’ve read described this condition other than the general proviso:  Lift is where you find it.

Eventually the ceiling deteriorated and continued VFR was not possible over the higher elevations.  A recent weather report confirmed good visibility beneath a 1,000 foot ceiling at Boulder and Jeffco, so I glided down the Poudre River Valley under the solid status overcast then flew under power the rest of the way to Boulder.

A friend at Boulder’s Cloudbase Soaring center wanted a ride, so we took off under the stratus layer.  The short, ten minute introduction flight turned into an hour long soaring flight when I discovered the second unusual source of lift in the same day.   My attention was first drawn by an unusual circular dome in the status above and to the left.  Sure enough, the first lift of the day was there.  There was weak but usable lift as bubbles of warm air punched up against the thinning status layer above.  After exploiting the first one, we were able to go directly to these “negative CU’s” of clear, warm air rising into the uniform stratus layer above. We could have stayed up the rest of the day — Truly amazing given the prevalence of stratus which generally marks the impossibility of lift.  Yet another fascinating day of learning and exploration in the Stemme!

7/20/94  Boulder, CO

I spent the morning flying with Bruce Miller, a glider pilot who flies instrumented gliders in thunderstorms for the National Center for Atmospheric Research.  Then I was soaring again along the Flatirons southbound to Denver’s Centennial airport to meet a friend.  Flying in and around high density traffic posed no difficulty.  By entering downwind at 110 kts, the whole pattern can be flown with the engine off while the speed slowly decays.  Even 360’s on short final can be accomplished without the motor if necessary for spacing.  Normally, I land with the motor off, then start it as I’m rolling off the runway to taxi to parking.  I launched after lunch and soared to Colorado Springs for the night.  The ramp was so full, I had to fold the wings to fit between a Lear and a Challenger.  Several of the local people were aware of the Air Force Academy’s decision to purchase Stemme S10’s.  After some interesting hanger flying, this short flying day came to an end.

7/21/94  Colorado Springs, CO

Lift off was at 10 am.  I took off and immediately headed west towards Pike’s Peak.  Finding morning lift on the east side, I turned off the motor and retracted prop at 1,000 feet AGL and  thermaled up to 14,000 before realizing that I’d forgotten to retract the gear!  The electric gear switch has three positions: Down, Off, and Up.  Distracted by a missed transponder code assignment, I inadvertently moved the selector from Down to Off, the middle position.  Although embarrassing, it certainly wasn’t as bad as forgetting to extend the gear, a situation I’ve not yet experienced.

Soaring around the summit of Pike’s Peak, hundreds of tourists photographed the Stemme as I flew round and round.  Then west to thermals over Tincup Pass.  Soaring over a hiker at the top of Mt. Shavano, I used the huge updraft flowing into the base of a building thunderstorm to hitch a ride to 17,500 feet at over 1,500 fpm.  As I fully enjoyed the mixture of terrain and weather phenomena at that moment, it occurred to me that only a few abnormal flights in over twenty years of flying power became vivid, permanent memories.  All the rest were “uneventful” and soon forgotten.  Almost by definition, every cross country soaring flight, on the other hand, has been memorable.  Each leg is a challenge with no chance to become complacent, even for a minute.  Perhaps this is the greatest appeal of soaring.  Leaving the big lift, I soared west to Gunnison, then Montrose to visit with friends.  Thunderstorms were forecast over night, so I folded the wings and put the S10 in a hanger for the night.

7/25/94  Montrose, CO

The next morning, I took off and found lift a few miles east of the airport.  Climbing at several hundred feet per minute, the temperature dropped quickly.  At 17,000 feet the outside temperature was down to 0°F.  Leaving the lift, I flew through virga south of Crested Butte and emerged with a thin coating of ice on the plane, spoiling its laminar flow.  A few thousand feet lower and it disappeared.   I thermaled over Crested Butte, then explored the Elk Mountains south and west of Aspen.  Then I soared for two hours with a friend already soaring around Aspen in his sailplane and then, all too soon, ended the Northern half of my Rockies tour with a landing back at Aspen.

In ten days, my travels took me 1,552 NM, not counting the numerous excursions off course in pursuit of lift and entertainment.  While enroute, the average amount of time under power was just 12 minutes per day which lead to a fuel consumption of just under four gallons of gas.  After a week hiatus, I resumed my travels and over another ten days, traveled south along the Rockies and San de Cristo ranges, then to Tucson and Phoenix before returning to Aspen.  Total enroute fuel consumption for both legs was eight gallons in 63 flight hours aloft, covering more than 3,000 memorable miles.  What a way to go!

Marc Arnold