I just noticed one of my youtube videos has over 20,000 views. I put it together a while ago using windows movie editor and a flash ripper. The soundtrack is Breaking Benjamin, Blow me Away. The tube is at Teahupoo and is one of the biggest ever ridden. The human glider is in Verbier, Switzerland and is Loïc Jean-Albert cruising 15 ft above the snow. The train surfer is unidentified and is in Germany surfing a bullet train at 330Km/h. The skater is Bob Burnquist in his own back yard on a $250,000 ramp of his own making. The climber jumping off the cliff is the late great climbing legend, Dan Osman.

One of the comment threads on youtube wonders if there’s an air cushion that helps Jean-Albert stay so close to the ground with such accuracy. The phenomenon is called Ground Effect and pilots are taught to add a little extra downward pressure to counteract it when landing. It’s also very dangerous on takeoff because your plane can become airborne before you reach takeoff velicity and as soon as you climb away from the ground you stall and crash.

Ground Effect is caused when a wing’s height above the ground is less than it’s span. It’s caused by a reduction in induced drag. Wing-tip vortices are reduced and there’s also a reduction in upwash and downwash. That means that when you’re experiencing ground-effect, the amount of thrust required to produce lift is reduced.

If Jean-Albert is in fact experiencing ground-effect, then the amount of altitude he has to trade for speed is reduced. But I doubt it. When a wing is at a height equal to it’s span, the decline in induced drag is only 1.4%. When it’s at a height equal to one fourth of it’s span, the loss of induced drag is about 24%. So if Jean-Albert is 6ft tall, he would have to be 6ft from the ground to begin experiencing ground-effect and 2ft from the ground to get any real benefit from it.

At that altitude, he’s probably going to get smacked by a mogul on his way down.