Soaring is staying aloft flying a glider using only rising air currents, called lift.
The three main sources of lift are thermals, wave, and ridge lift. In the early 1920s, soaring pilots found they could stay aloft using updrafts caused by the wind blowing against the side of a hill. Soon they discovered thermals in the valleys adjacent to the hills. In the 1930s, mountain waves were discovered that allowed pilots to make the first high altitude-flights. Minden is popular because of the quality of all these techniques. Other sites may be famous for one or two, but Minden has all three.
Thermals are often the most common type of lift for soaring. This rising mass of air may be triggered by “hot spots” in an open area heated by the sun. The warm air rises, often with enough vertical speed to carry up a glider. Sometimes the thermal can create a visible dust devil as the warm air rises. Cumulus clouds often form at the top of the thermals and mark their locations. Our Carson Valley is particularly prone to thermal activity due to the areas of cooler green crops next to the barren desert areas. The desert areas get hotter, and the temperature difference causes rising air, or a thermal. Thermals here can be several hundred feet across. The trick is to locate the center of the thermal and circle the glider around that point.
The upper parts of the mountains and ridges heat up earlier in the day where the slope of the ground is more directly oriented towards the sun. These mountain ridges on the east side of the Sierras exist over most of the range creating nearly continuous lift, allowing pilots to remain airborne for long distances.
To utilize thermal lift, a glider is towed, (or motors on its own if a motorglider), to an altitude of 2,000-3,000 feet above our valley. There, after sensing a thermal, the pilot releases from the tow, centers the glider in the thermal, and climbs by circling, to a higher altitude. Pilot can often fly to the top of the Pine Nut Range, find more lift there, and follow the ridges for hundreds of miles either north or south.
Thermal soaring in the Sierra and Minden is enhanced by the extreme contrasts between desert and mountainous terrain. Thermals are generated from both the heat of the valley floors and the granite and barren mountain tops which allows pilots to fly from mountain top to mountain top.
Mountain Wave occurs when the prevailing winds from the west are deflected by the gradual slope of the Sierras with the air continuing to rise past the abrupt drop on the eastern side; much like water pouring over a rock in a stream. The flowing air bounces off denser air underneath and rises, producing a series of rising and falling waves downstream of the ridge. The westerly wind needs to flow approximately at 90 degrees to the rising terrain. The wind should increase with altitude for optimum wave conditions and the stronger the better. The north-south range of the Sierra lying across the path of the prevailing westerly wind is an ideal wave generator.
Waves are very smooth, but below the wave there is often a rotating turbulent layer, called rotor. Rotor normally exists below the height of the mountain range. Soaring pilots are towed or motor through the rotor to reach the higher, smooth wave. They can release early in the rotor and work the lift there to get through it into the wave, or they can tow higher until the air is smooth.
Once in the Mountain Wave, pilots fly into the wind, and the most exhilarating feeling is experienced. It feels like you are going up in an elevator with the western slope of the Sierra and the central valley stretching out before you. Pilots here often reach altitudes of 20,000-30,000 feet. The band of smooth air usually exists between the airport and the crest of the Carson Range. Standing wave can exist along the entire length, north and south, and downwind, reaching hundreds of miles east of the Sierra crest. Whether the lift band is narrow or wide, the descending sections of the wave contain very strong sink; the downwind moving air will be as strong as the smooth lifting air followed by undulating ripples for hundreds of miles, that gradually lose strength.
These waves are called standing waves because they appear to stay in the same position in the sky as the air flows through them. The visible clouds are an indicator of the moisture in the air at that particular altitude. As the deflected wind over the mountain rises, cools, and reaches the appropriate temperature, the moisture condenses and forms a visible wave cloud. As the air descends in the wave, it warms up, the moisture evaporates, and the cloud disappears. Wave may be invisible if there is no moisture in the air. Sometimes following the primary wave cloud, secondary and even tertiary clouds can be visible. These clouds are called lenticular clouds because of their lens shape.
Ridge lift is caused by the surface winds blowing uphill along the fairly steep side of a mountain or ridge. When the wind encounters the surface it is deflected upward allowing aircraft to remain aloft slightly upwind of the crest of the mountain or ridge. If there is an east wind in our Carson Valley, ridge soaring is possible in the updrafts adjacent to the eastward facing slope of the Carson Range on the west side of the valley.
Ridge soaring can be treacherous since the air on the downwind side of the ridge may be sinking and one can get caught below the peak of the ridge and not be able to penetrate against the flow and get back over the top of the mountain. The strength of the flow tends to push the aircraft over the top and thus into the sinking air. Gliders must fly parallel to the ridge and be careful to remain in the rising air.
The Soaring Society of America and the Federation Aeronautique Internationale sponsor several programs of accolades for soaring accomplishments. Although Minden has all three soaring techniques, wave soaring here is most famous due to the ease of flying to a higher altitude from a lower starting altitude. Large altitude gain is one objective and is easier to accomplish here. The other practical problem here is the need to achieve the absolute altitude or gain without violating National Controlled Airspace rules. Minden has an international advantage compared to other sites because of fewer controlled airspace constraints.
Minden and soaring are synonymous. Minden is world famous, and from the early days glider pilots traveled from the Bay Area to experience the superb thermals and mountain wave in the Carson Valley. The word got out around the world and pilots who experienced the conditions would say, “We’re coming back and telling all our friends.”
Linda Mae Hivert is past president of the Sports Aviation Foundation. For more information visit www.sportsaviationfoundation.org