It’s late in the year, late in the day, and you’re descending from high above clouds. Though bathed in light, you’ve been shuddering cold for what seems like ever. Below, the near total undercast is sculpted by wind into a fleecy of sea mounds and swales, sleek undulations flowing all around, chrome to black. Highest cloud tops are around 9000 MSL, their bases most of a mile lower, summits glowing while depths fade into menacing voids. One of them will become your portal back to the underworld. You must study whatever’s visible through those deeps so you’ll know where best to return.

They’re wave troughs that have lain downwind of mountains since before dawn, stationary all day more or less, each gradually migrating and changing shape as hours pass. Sometimes they drift away when new ones form upwind, requiring periodic windward penetrations just to stay near home. And now they’re all healing shut the way ice fishing holes do when no one tends ’em.

Diving toward a narrowing aperture in wave sink with spoilers fully extended, you’re burning off 3,000 feet a minute. At this rate you’ll be on the ground well before dark. Kudos for being smart enough to get down in time.

Then down near cloud base you spy a V of ducks, flapping frantically as always, nosed into the wind and using wave lift as a boost. Thrilled at this opportunity, you close spoilers and try to sneak in from behind and above, fly slow as possible to hold position and quietly sink into their V.

But ducks are savvy to tricks like this. Individual birds on both sides ahead turn their heads to glance, apprehensive. A pulse transmits from the leader back along both echelons and all flap even harder, with no break in formation. Then as on a signal the two diagonal lines separate, executing wide circles away from each other in exact parade fashion. Shrewd strategy to evade potential threat, a lone pursuer able to follow only half the group.

One circle in a thermal takes between twenty and thirty seconds, but circles in wave flown with very flat bank can take more than a minute. By the time both lines have arced back around to their original formation you’ve fallen below, but gaze up in admiration at their smooth rejoin. Real pros. Then, still climbing away, they turn neatly south for an evening leg on their seasonal migration, low sun strobing beneath their wings. You imagine going with them and wonder where they’ll be tonight!

Now for the first time since joining the ducks you look down instead of up, and… Uh Oh!

During that long roundel the ducks gained more than a thousand feet of altitude, and even as you fell below you were rising with them. Now the wave gap has filled in.

While sea-swell tops still gleam in the sun, low areas have sunk into deep shadow, and neither are clearly visible in the harsh contrast of horizontal light. Unsure, you climb a bit higher to look for a hole still open elsewhere, but similar gaps nearby have closed too. And with every second the lowering sun is more blinding. You’re trapped above a solid deck of undercast below which dusk will very soon surrender to full darkness…

OK, resume the rapid descent spiral as before, toward that darkening hollow where the wave gap had been. Position over the ground may have drifted miles in the wind by now, over local hills toward featureless forest extending who knows how far east. Air whistling through the cockpit from wide open spoilers and speed intensifies anxiety’s shivers, reminding you you were already freezing an hour ago. Least of your worries.

Down close the prospect is ominous. You’re in a gray bowl with no way out but further down, into the soup. Surrounding cloud’s wooly textures defy perception of depth and distance, yet their flow through this wave trough indicates the wind’s direction. In order to stay near home, you square up and head into that wind toward the descending side of the bowl.

It’s standard doctrine that inside a cloud without specialized instruments your aircraft will inevitably adopt some uncontrolled attitude and gain excessive speed.  Lacking a horizon for reference, information from your inner ear will be dizzying and nauseating – maybe worse than useless. Leveling the wings would allow you to level and slow up, but the chances of doing so without visual reference are miniscule, and anything else will make the situation worse.

The only way to limit enormous risk in a blind descent is the procedure called ‘benign spiral’. In it, you level the glider before entering cloud, open spoilers fully and then hold stick and rudder dead neutral while waiting, praying that the aircraft will list into a flattish bank and circle steadily down in approximately one place. It’s not a bit scary – except when you do it for real. Now there’s no choice. Time to act.

Tock, TICK