flyingnanook
Posts: 817
Joined: Thu Jan 15, 2004 4:41 pm

Severe Turbulence In ANC On Monday

Tue Dec 11, 2007 7:12 am

Hi all,

Earlier today (Monday) around 2:30PM, I was on approach to ANC in a DL 752, when we suddenly encountered severe turbulence. It was crazy. Thankfully, no one was hurt, because we were warned of moderate turbulence in the area and everybody was buckled up for landing. But no one was expecting the turbulence to be severe. The pilot said after the flight that at 7000 ft, we had suddenly encountered an 80kt tailwind and had subsequently dropped at least 500 ft. There were also at least 2 or 3 more sudden drops. Everything in the cabin had flown up to the ceiling and was deposited far away from its original place. I got smacked in the head by a book that had come from 3 rows behind me. My small carry on, which was stored under the middle seat, since it was empty, had somehow freed itself from under the seat and flew forward a few rows and ended up on the other side of the aisle. During one of the smaller drops before the huge one, the lap baby in front of me was temporarily airborne. Thankfully, that shocked the parents into keeping a better grip on her. All in all it was quite a scary situation, and I'm still somewhat unsettled.

So now I have a couple questions. How often does severe turbulence occur, especially outside of thunderstorms/wake turbulence? Also, what happens in the cockpit during such turbulence? I understand that you're supposed to maintain attitude, and not worry so much about altitude, but what is there to do when the plane drops like that?

Also, just in case anyone thinks I was exaggerating about the severity, here's the PIREP from my flight.
ANC UUA /OV ANC180005 /TM 2330 /FL070 /TP B757 /TB SVR
Semper ubi sub ubi.
 
AA737-823
Posts: 4898
Joined: Wed Mar 01, 2000 11:10 am

RE: Severe Turbulence In ANC On Monday

Tue Dec 11, 2007 10:12 am

Yeah, ANC gets crazy sometimes. I have never experienced anything nearly as severe as what you went through today, but we do have a reputation.
Some of my friends have feared for their lives on approach to Uncle Ted International.

Most of our turbulence is not caused by storms, as we don't get those much, but by air currents over the mountains.

And that is about all I know on this subject! I'll let someone who flys 'em explain, rather than me, someone who just fixes 'em.
 
dispatchguy
Posts: 606
Joined: Sun Jan 29, 2006 6:08 am

RE: Severe Turbulence In ANC On Monday

Tue Dec 11, 2007 3:12 pm



Quoting FlyingNanook (Thread starter):
So now I have a couple questions. How often does severe turbulence occur, especially outside of thunderstorms/wake turbulence? Also, what happens in the cockpit during such turbulence? I understand that you're supposed to maintain attitude, and not worry so much about altitude, but what is there to do when the plane drops like that?

It occurs somewhat infrequently, that being said, however, there are some places in the world that are famous for their turbulence. ABQ is one, ANC is one, any of the ski airports in the West US are all places for low altitude mountain wave turbulence.

I was jumpseating a UA B757 TPAORD a few years back and we were skimming the cloud tops at FL390 and we got slammed. I was in the B757 high chair, we were 10 degs nose up attitude, with a 1000fpm instantaneous descent. The F/Os water bottle flew up and fell backwards, and I am trying to get it with my feet, without letting loose any of my 5-point harness. We got a TCAS FAIL EICAS message, and a very faint burning smell in the flight deck. Probably something in the E&E bay came loose - possibly the TCAS.

Since we were only about 5 mins prior to top of descent, we continued on to ORD, but it was a singular hard SLAM. Once we recovered, gave the airplane a quick controllability and systems check, reported it to IND Center, the rest of the time at 390 was smooooth.

When you know turbulence is out there on a day, it pays to be a vigilant dispatcher  Smile

Oh, for reporting the turbulence as severe, the aircraft is grounded until a severe turbulence inspection can be completed by maintenance. That applies to any airplane, and any 121 airline.
Nobody screws you better than an airline job!
 
zrs70
Posts: 3313
Joined: Sun Dec 10, 2000 4:08 am

RE: Severe Turbulence In ANC On Monday

Tue Dec 11, 2007 3:47 pm

And in another thread, people were saying that they look forward to turbulence.
17 year airliners.net vet! 2000-2016
 
spacecadet
Posts: 2792
Joined: Thu Sep 20, 2001 3:36 am

RE: Severe Turbulence In ANC On Monday

Tue Dec 11, 2007 6:36 pm

Quoting FlyingNanook (Thread starter):
Also, what happens in the cockpit during such turbulence?

Disconnect the AP unless it has a "turbulence" mode (or whatever it's actually called). AP in severe turbulence will sometimes make things worse by continuously trying to react to the changing conditions, and end up over-correcting. Some AP's have a mode where they will react more slowly to account for turbulence. But I wonder how often pilots actually use that; I'd guess most pilots would rather put the plane in their own hands in that situation.

Quoting FlyingNanook (Thread starter):
I understand that you're supposed to maintain attitude, and not worry so much about altitude, but what is there to do when the plane drops like that?

Make sure everything's tied down and hold on!

I know one thing pilots are trained to do is as little as possible. That's why the AP gets disconnected, so the engines aren't constantly spooling up and down and the nose isn't pitching up and down with altitude deviations. The pilot's job is to keep the aircraft under control in that situation, which means no abrupt control inputs. Airliners are inherently stable, so unless the bank angles get really crazy, the plane will return to level flight on its own during most turbulence.

IIRC pilots are supposed to report severe turbulence to control, and they'd obviously also report any major altitude deviations so ATC could clear the airspace. Other than that, there's not much you can do other than turn around, request a different altitude or just ride it out.

[Edited 2007-12-11 10:38:59]
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