Aircraft-Induced Turbulence

I just saw the movie “Pushing Tin,” which was OK. It featured an odd ritual of standing on the runway below a landing 747. The turbulence and wind of the landing plane was (in the movie) so intense that the characters performing this crazy stunt were lifted up bodily and thrown accross the runway, oddly enough, to their great delight.

Is this remotely realistic? Sure, there’s got to be a stiff breeze from many tons of metal hurtling through the air just overhead, but would it be powerful enough to knock you down, let alone pick you up and throw you?

Has anyone out there tried this?

I haven’t seen the movie and I don’t know if it’s factual that you can actually get blown around like that, but…

It’s not just a big wind from the plane rushing by that they’re depicting. Airplane wings create vortices as a byproduct of the lift they generate. These are essentially horizontal whirlwinds that are shed from the wingtips and remain in the airplane’s track for quite a while. They can be very powerful and very persistent, and the bigger the plane the bigger the vortices.

There are FAA regulations dealing with how close one plane can follow another that are based on the likelihood of the vortices from the front aircraft interfering with the control of the following plane. It’s a real problem with a 747 followed by a Piper Cub, for example. Pilots of small aircraft report handling difficulties even at distances of a mile or more.

From the Asleep at the Wheel CD, Bob Wills Rides Again:
“It must be hard to lose your wife.”
“Sometimes it’s damn near impossible!”

The vortices from a large jet are powerful enough to flip smaller airplanes on their back.

A friend of my dad’s was flying a Cessna 172 when she was cleared to land in front of a 747. The tower asked her to expedite her landing because there was a 747 behind her. She told the tower, “Tell him to be aware of my wake!”

Wingtip vortices can be very dangerous. My dad was caught in one and was flipped over. The “heavy” was quite a distance away. I was flying a small helicopter over downtown L.A. one morning. It was dead-calm. We ran into a slight burble and decided the only source was a jet thousands of feet above us.

Excerpted/paraphrased from the Airman’s Information Manual (Para 7-3):
Vortices are generated from the moment an aircraft leaves the groud and continue until it lands. The vortices from larger (transport category) aircraft sink at a rate of several hundred feet per minute, slowing their descent and diminishing in strength with time and distance. A vertical seperation between the “heavy” and a light aircraft of 1,000 feet may be considered safe.

When vortices of larger aircraft sink to within 100-200 feet of the ground, they move laterally outward at a rate of 2-3 knots. Surface winds alter their courses. A light, quartering tailwind requires max. caution. This is because this wind would keep a vortex over the runway for a longer period of time.

So! Did the movie portray a probable event? I don’t know. I haven’t seen it. But there is a lot of downwash from the wings, blast from the turbines, and powerful vortices generated by the wings.

“I must leave this planet, if only for an hour.” – Antoine de St. Exupéry

Are you a turtle?

The only thing improbable about it was that they were standing over the end of the runway. The vortices start at the wingtips and move downwards and to the outside of the airplane. Unless there is a strong crosswind, the vortices won’t be over the runway.