chasbondy

I was flying today IAH-SAN, and about 2 hours into the flight the plane took 2 pretty decent jolts. I opened the shade thinking we got wacked by lightning, but the pilot came on and explained we had flown through some jet wake turbulence of another aircraft. Of course he didnt answer the question I'm sure everyone else on the plane had. I had never heard that reason used before . Is it common??

COFreqFlyer

It may not be specifically indicated, but wake turbulence is a fairly common thing to experience, especially now that we have RVSM (reduced vertical separation minimums) above FL250, if I recall correctly. No big deal.

Disclaimer: While I'm not a commercial/ATPL pilot, the FAA has indicated that I am an authorized pilot in command of small single-engine aircraft. I do have to deal with wake turbulence around airports especially.

TWA Fan 1

It's obviously far more avoidable than a weather phenomenon, which cannot be predicted with complete accuracy.

At least with wake turbulence, planes can keep the required distance from each other.

But this also means you got pretty darn close to another a/c...

It does happen, of course. That's (at least indirectly) what happened tragically to AA 587 JFK-SDQ. This A300 was flying too close to a JAL 747 ahead.

When the pilots became aware of this, they apparently attempted to respond to the wake turbulence with aggressive rudder inputs. The NTSB concluded these rudder inputs were too violent and caused the vertical stabilizer, or tail, to shear off.

It was later revealed that the pilots were following AA's Advanced Aircraft Maneuvering Training Program procedures, so I'm not sure it could exactly be considered pilot error.

This accident came two months after 9/11 and everyone freaked out, of course. With 260 fatalities on board and 5 on the ground in the Queens neighborhood of Belle Harbor, it was the second deadliest U.S. aviation accident up to that point in time.

mpw81

If United keeps Channel 9 and you listen to it youll find that just about every take off you are behind, in, or in front of a widebody, you will hear "caution wake turbulence from a 767/777/747/etc." to the plane behind the widebody. Same on landing.

Finny side story, a few years back my father and I were in a single engine aircraft (Piper Cherokee) leaving BOS. ATC was annoyed they had to fit us in to the departure sequence while they were tryinig to get a bunch of big planes out, so after we take off we hear them clear the commercial jet behind us and followed it with "caution wake turbulence Piper Cherokee." He was obviously joking.

dayone

Pilots of narrow-body aircraft are typically warned of wake turbulence by ATC when their takeoff follows a departing wide-body jet.

TWA Fan 1

Right, but to experience the types of jolts I'm imagining were described at cruising altitude, not at take off, the other plane must have been very close...I would imagine that's more of an issue than the type of wake turbulence you could experience at altitude.

sbm12

I was actually in the air bound for JFK from FCO when this happened. We had no idea why we were 2 hours late nor why we circled Iceland for those two hours until we landed and I called my sister to tell her I was home. She was freaking out and it took a solid 2 minutes before she could explain why.

It is definitely more commonly referenced on take off/landing but I don't think that hitting it in flight really means that the OP's plane was necessarily "too close" to the passing plane. If that plane was flying across the OP's plane's route and they crossed the turbulence 30 seconds after the other plane left it then the other plane was already 4+ miles away.

Or maybe the pilot was lying and really they hit some speed bumps in the sky that they didn't slow down for like they should have.

And let's not forget that flying through wake turbulence caused the flame out of the engines in Top Gun that resulted in Anthony Edwards's failed ejection.

TWA Fan 1

First of all, that's an amazing story about 2001, and, yes, those were indeed harrowing times (my office was two blocks from the WTC and inside the red zone).

The wingtip vortices that create wake turbulence could indeed be felt at the distances you describe, but at altitude and at cruising speed, they represent virtually no danger.

Still, at over 500 mph, that is pretty close. You know, as you write, that it takes about 30 seconds to fly 4 miles at that speed...not a huge margin for error...

That's why I think the proximity, while not deeply dangerous, is more of an issue than the wake turbulence itself.

Oh, and regarding Top Gun, absolutely, but we should ask Jerry Bruckheimer how much he based himself on aeronautics...

chasbondy

Also, when I got home, I heard there was an earthquake in the CA desert, and thats about where we were in the air when the jolts took place. Do earthquakes cause air turbulence????? (I did not look the magnitude)

TWA Fan 1

Imagine the amplitude that would require to send a shock wave 5-6 miles up in the air...

pptp

Usually, when you feel a couple of sharp jolts with a little rolling motion, it's wake turbulence.

The vortices come off of the wing tips as horizontal 'tornadoes' that spread out behind the AC in a v-shape. They survive for quite a distance behind the A/C and can be moved around by the prevailing winds. So, wake turbulence in calm air would extend behind an AC in a spreading v-shape. But with winds, they can be blown horizontally and/or vertically while still keeping their vortex. When another plane happens across one of these horizontal tornadoes, you get the bumps described.



That's why there is separation between planes taking off. One problem is that, with just the right cross-wind, that v-shape can be distorted just right so it's blown straight in line with the runway. Pretty rare though since conditions have to be perfect.

chollie

We hit wake turbulence on a very small commuter plane between LAX and PSP. The FA was walking down the aisle when we got the jolt and she actually bounced up and hit her head on the 'ceiling' with a quite audible thump. None of us knew what had happened, but she went on to explain that we had hit the 'wake' of a much larger 747.

transportbiz

Wasn't there a period of time when they'd found out the 757 actually put out a unique wake signature, one that was particularly violent when encountered by a smaller plane.

Syzygies

Yes, 757 was the worst, and winglets help. Wake turbulence has been implicated as the first thing to go wrong, leading to a few crashes (after more went wrong).

Wikipedia: Wake turbulence
Ask the pilot: Wake turbulence

I was in rather dramatic wake turbulence, landing in SFO in the early 90s. As in, we appeared to nearly roll over. My body learned an involuntary response to turbulence, and after the return flight it took me a couple of years to get back to flying.

usa18dca

There are actually three kinds of turbulence, one we know as wake turbulence which is common on takeoff/landings sometimes due to what PPTP explained, the other is cobblestone turbulence which is what feels like when one drives on a brick paved road this is due to clouds and weather patterns.

The other turbulence is related to thunderstorm and is due to microbursts of air that moves the airplane around. I'd go into length as a flight safety analyst but it's 11PM and I had a long day on US.