It was a quiet flight yesterday evening between Hartford and Washington-Dulles, and the seat belt sign was off. I got up to use the restroom, to be shocked when I opened the door to find someone sitting there already. Hey now! But the real shocker came seconds after I returned to my seat: Just as I was starting to buckle up again, our plane was jolted with severe turbulence. And not just jolted — jolted hard. The left wing tilted skyward, with the Boeing 737 at an apparent 45-degree angle. The pilots corrected our angle shortly thereafter and took us to a different altitude with dispatch, but it was a rough moment, even for seasoned travelers.
I was glad not to have been standing in the lavatory at that time, as I had originally planned… Or, perhaps better, the passengers and cleaning crew who would have followed me into there should be glad I wasn’t standing in there…
Grabbing my headphones, I tuned in to channel 9 on the audio system (on United, I’m a sucker for listening to the cockpit communications when I’m not reading or working) to hear what was going on. The first officer came on a few seconds later to inform the tower that we had encountered severe wake turbulence.
The culprit? Sixteen nautical miles ahead, a Virgin Atlantic Airbus A340 was barreling down the Eastern Seaboard on its way to Washington-Dulles, just like us. It took about two minutes for us to cross the same airspace as the Airbus.
Two minutes, I thought? Sixteen nautical miles? Well in excess of the minimum 5 nm separation between planes in our size classes. How could we get so powerfully smacked by turbulence from a plane so far ahead of us?
For an answer, take a look at this 1-minute video, filmed by NASA in the 1970s to test the effects of wake turbulence. A widebody L-1011 passes through a smoke screen, which indicates the waves that follow an aircraft. Note how long it actually takes for the violent swirls to actually appear:
And here’s a 30-second clip of a four-engine military C-5A, creating a lovely vortex. It’s like a vertical hurricane cloud, really impressive in its force:
Seeing that swirl eventually appear, the violent bumps we felt last night make much more sense. Thankfully, it was just a brief shake-up, and, other than surprising a fellow passenger in the lavatory, the only blemish on an otherwise pleasant, on-time flight.
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September 8th, 2007 at 10:16 pm
Visualizing an airplane’s wake turbulence…
Visualizing an airplane’s wake turbulence Very cool videos of the unseen wind patterns left in a plane’s wake….
April 28th, 2008 at 11:42 am
[...] I might as well use the past tense in describing it myself. When things seem amiss (like a powerful jolt of turbulence) it’s nice to hear know what’s going on. My affection for channel 9 is probably [...]