Wake Turbulence - "Pushing Tin" style


Well-Known Member
Wake Turbulence - \"Pushing Tin\" style

This is an article from the October Salt Lake City Department of Airports General Aviation newsletter. It reminded me of the scene in Pushing Tin. The first couple paragraphs are what I found to be entertaining, the rest if FYI about wake turbulence.

A Hidden Peril In a Heavy's Wake

A few years ago, an experienced pilot was loitering with a couple of his local bush pilot friends by a hangar at the international airport of Guatemala City when a Boeing 747 taxied into position at the far end of the main runway. His companions signaled him to follow them and they sprinted across the taxiway to a patch of weeds and hunkered down just outside the runway lights to wait. The big jet rolled toward them, stately and slow at first, and then picked up speed. It began to rotate a little distance away and was just beginning to lighten on its gear as its wing tip passed by some 20 or 30 feet above their heads.

For a moment, he thought that was what the group had come there for... a thunderous close-up of that titan in mid-career. Then something like a huge boxing glove hit them and they went rolling head over heels in the dirt. When they picked themselves up, gasping and laughing, he knew what the inside of a 747's wing-tip vortex was really like... and it certainly was not a place to go flying.

Wake turbulence isn't necessarily a significant hazard, any more than the low rate of accidents due to encountering a sheer rock cliff at cruising speed implies that it is safe to do so. The low rate of vortex accidents is due to controllers' and pilots' awareness of the danger, and to the precautions taken by both to avoid wake encounters.

Wake turbulence is an inevitable by-product of lift. An airplane passing by is bound to leave some disturbance behind it; the energy dissipated in creating that disturbance is what we know as drag. The good Lord bound flight and wake turbulence together and until a frictionless neutrally buoyant airplance is developed, a man is not likely to put them asunder.

The eerie persistence of the vortex after the airplane is long gone is due to the low viscosity, or internal friction of air; like a top on a smooth surface, the considerable mass of air spinning in the vortex takes a long time to slow down. And a light crosswind can cause an invisible vortex to remain over the runway for a relatively significant period of time after the heavy lifts off.

The heavier the aircraft... the worse the vortices. Few pilots are able to adequately control their aircraft near the ground if they fly into a heavy's vortices.

Time and distance are the only available safegaurds against vortex encounters. Controllers usually provide several miles spacing between small and large aircraft and time delays of up to three minutes between departures if lighter aircraft are departing from intersections. Pilots have the right to waive delays imposed by controllers by specifically stating that they would like to "waive the 3 minute wake-turbulence interval." To do so may be reckless; however, you may be the best judge of your airplane's loading and takeoff performance. By the same token, you have the right to refuse a takeoff or landing clearance that you consider unsafe.

Wake-turbulence encounters are so infrequent that pilots who have never experienced one may not take them seriously. We all tend to suppose that dangers we have not personally experienced are probably exaggerated. Nothing could be more unwise. "Caution, wake turbulence, departing such-and-such" is no mere formality inteded to indemnify controllers; it is advice meant to be acted upon. If you think of wake vortices not as insubstantial phantoms but as vast threthers and combines capable of chopping you into little pieces, then you will accord them the respect that they really deserve.


respect my authorit-I!!


Ahh! This is how I change this!
Re: Wake Turbulence - \"Pushing Tin\" style

I think that is a very good article. On a side note, the 757 leaves a particlary nasty wake. Doug, have you had any wake turbulence storys to share?


Well-Known Member
Re: Wake Turbulence - \"Pushing Tin\" style

For any of you that are from or living in the Columbus, OH area, a great place to feel a little wake turbulence is the golf course across the street on the East side. I had wake swirl my hair more than a few times there. Just make sure winds are such that the big guys are using 28 (preferably as much down the runway as possible so it doesnt move the wake on the way down).


New Member
Re: Wake Turbulence - \"Pushing Tin\" style

One particularly cloudy day at John Wayne a 737 took off, followed by a 757. The 737 disappeared into the clouds, nice and smooth. The 757 swirled and mixed up those clouds pretty nicely as it was disappearing into the soup.


Resident Knucklehead
Re: Wake Turbulence - \"Pushing Tin\" style

A while ago I worked for an alarm company doing onsite investigations... There was alot of down time and I would sometimes find myself close to O'Hare airport, so I would watch planes from there (if you know where to go, you can get REAL close to the approach ends of some of the runways). Anyway, the most prominant thing I noticed was when MD-80 series or 757 aircraft would go over, you could actually HEAR the vortices. Very cool sound!



New Member
Re: Wake Turbulence - \"Pushing Tin\" style

I was rocked by wake turbulence a couple of times in the J41. It's like moderate to severe turbulence that only lasts for a few seconds (if you are lucky). We passed through it quickly, but it wasn't very pleasant.


New Member
Re: Wake Turbulence - \"Pushing Tin\" style

I have been in my Ops car about 1500 feet from the runway end when a global express landed. Just about the time of touch town I felt the wake hit me, not much more then a shake(a bit like a small earthquake), with the nice sound that it makes. But that cant be anywhere close to a 747. I think it would be something fun to do. That is if you survive.