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 positions.

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.

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