golftango
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Slight Side-to-side Rolling During Flight

Fri Mar 24, 2006 3:54 am

In two instances I've noticed the ac rolling right to left.

Once on a SAT to DFW flight aboard a DL 732. During the entire flight the ac rolled back and fourth. No one else seemed to notice, but it was pretty evident while looking out the window.

Again, last year aboard an AA MD80 while on finals to BOS from MSY. The ac started to incrementally roll right in three or four small motions, then the same back to the left, repeat. I became a little nervous during that flight.

So, what is the culprit? Autopilot?

[Edited 2006-03-23 19:56:41]
 
jamesbuk
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RE: Slight Side-to-side Rolling During Flight

Fri Mar 24, 2006 4:02 am

Probably the auto pilot making corrections due to wind or just the wind itself, maybe it was the aircraft making a slight turn at a waypoint.

Rgds --James--
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ramerinianair
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RE: Slight Side-to-side Rolling During Flight

Fri Mar 24, 2006 4:03 am

I have noticed this on the A320.
It was very pronounced on the TO and Landing. When the Pilot was flying, the rudder application was not solid. It felt like the pilot was pushing down and letting go rapidly and the rear of the A/C was "wobbeling" back and forth.
I think it was only when the pilots was controlling the A/C. I think Airbus calibrates the rudders so that the sensitivity changes with the airspeed. Maybe when gaining or loosing altitude, the rudder deflection changes when holding the same pressure.
SR
W N = my Worst Nightmare!!!!!
 
KAUSpilot
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RE: Slight Side-to-side Rolling During Flight

Fri Mar 24, 2006 4:04 am

In the aircraft I fly it is quite common as well. During cruise the airplane will often bank back and forth continuously, no more than 5 degrees to either side.

The culprits are the autopilot and the FMS, more specifically the way they interface with one another. When you have the autopilot tracking the FMS course, sometimes it gets the message that it needs to bank to maintain course when in reality it should just be holding the wings level.

If I recall correctly, the DL 732 you rode on likely doesn't have an FMS, in that case, it was probably the autopilot attempting to hold a course based off a land based navigation signal....sometimes these signals aren't precisely accurate, especially at high altitudes, therefore the autopilot will initiate a bank anytime the course signal fluctuates.
 
flyinghippo
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RE: Slight Side-to-side Rolling During Flight

Fri Mar 24, 2006 4:09 am

Flying STL-LGA on AA MD-80 last Thursday, we had to circle around LGA a few times due to high traffic caused by high wind conditions which actually closed LGA for a while.

While we're in the holding pattern, the strong wind shook the MD-80 pretty good, I was sitting near the rear part of the plane and I could feel the big yaw movements, as well as the roll and pitch constantly changing.

It's nothing to be scared of, it's either the pilot or the auto-pilot constantly adjusting the plane to keep it on it's flight path and glide scope.

The good thing is that as we approached the runway, we were still very bumpy (I did get a bit nervous by then), but the wind calmed down right as the pilot flared for the landing. A great job by the AA pilot!.
 
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ManuCH
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RE: Slight Side-to-side Rolling During Flight

Fri Mar 24, 2006 5:25 am

I always notice this on my flights on A320s and A330s. It's a slight back-and forth rolling (no more than 2-3 degrees, full cycle takes about 10 seconds), even in smooth air. Looks like the FMS/autopilot are compensating slightly all the time.
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golftango
Posts: 211
Joined: Mon Feb 20, 2006 1:12 pm

RE: Slight Side-to-side Rolling During Flight

Fri Mar 24, 2006 5:53 am

Thanks for all the input! FYI, that DL 732 flight seemed to roll more than 5 degrees each time. I wish I got the tail number.
 
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HAWK21M
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RE: Slight Side-to-side Rolling During Flight

Sat Apr 01, 2006 12:16 am

Was the Yaw Damper working.
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regds
MEL
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LGAtoIND
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Joined: Sun Jan 23, 2005 5:32 am

RE: Slight Side-to-side Rolling During Flight

Sat Apr 01, 2006 1:46 am

If the pilot turns the yoke, the aircraft will roll. If the pilot moves the rudder pedals, the aircraft will yaw. Both of these motions are common on commercial flights, especially when landing in a crosswind.
 
L1329II
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Joined: Fri Feb 17, 2006 11:52 am

RE: Slight Side-to-side Rolling During Flight

Sat Apr 01, 2006 1:16 pm

Quoting Golftango (Thread starter):
Once on a SAT to DFW flight aboard a DL 732. During the entire flight the ac rolled back and fourth. No one else seemed to notice, but it was pretty evident while looking out the window

If its constant its almost always an autopilot issue.
"By the way, is there anyone on board who knows how to fly a plane?"
 
RubyMtn738
Posts: 40
Joined: Tue Jan 03, 2006 10:10 am

RE: Slight Side-to-side Rolling During Flight

Sat Apr 01, 2006 2:00 pm

Funny you should bring this up, I just finished flying with SkyKing Airlines on N977UA a B737-200 and I encountered the same experience. I asked the captain about it and he indicated it was an issue with the autopilot. Spent 3.5 hours rolling like we were in a boat.

Ruby
 
OPNLguy
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RE: Slight Side-to-side Rolling During Flight

Sat Apr 01, 2006 2:26 pm

Quoting HAWK21M (Reply 7):
Was the Yaw Damper working?

First thing I wondered...

http://en.wikipedia.org/wiki/Dutch_roll

The yaw damper works to mitigate this, but sometimes they go inop and get deferred...
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.

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