A320 Vibration

[bossa]

Hi,

One aircraft in the A320 fleet that I fly is experiencing some vibration during climb between FL180 and FL300. This is felt on the whole aircraft but more so in the aft galley and a little also in the cockpit.
All engine parameters are normal, no ECAM advisories, and it reduces by slowing down (275 IAS). It is more intense when the gross weight is heavy (greater than 70T)
Maintenance has been advised several times, the trouble shooting sheet has also been filled out many times but they canīt seem to fix the problem permanently. The aircraft has gone to the hangar and no lose joints were found.
From what iīve heard many A320 suffer from this problem.
Has anyone come across this problem? Was it fixed and what was the source of the problem?

[bio161]

Hi bossa,

check this one:

http://www.pprune.org/archive/index.php/t-385214.html

I had the same problems during climb in my airline, no matter which weight. The problem was ending in cruise and it was starting again during approach with flaps configuration, mainly between conf 2 and 3.
When the a/c went under check D they changed the servojack of the elevator. It was nothing of serious and Airbus itself describes airframe vibration as "comfort concern only".

Have a nice evening,
bio161

[IFixPlanes]

That are not much information to fix that problem.
- did you see any flight control oscillation on ECAM ?
- can the vibration be stopped by flight control inputs ?
- is the vibration in conjunction with audible noise ?
- is the vibration lateral or vertical ?

With your already given data and my above given questions answered, your maintenance should find the cause of the vibration.
(All that is part of the "Vibration Reporting Sheet" AMM 05-50-00-810-801)

[Beeline]

The FIM sheet uses a point system to pin point troubleshooting according to flight phase, config etc the more info engineering gets the better.

Quite common fix is to change the rudder to PCA eye end fittings or Elevator hinge bearings.

[grounded27]

Yes if it is most severe fwd and aft, i would be thinking along the lines of a dampening issue.

[exeng]

Once had experienced this on an old 320 in BA (an ex Caledonion) during the climb. Quite shook me up to be honest and I reduced the airspeed until the vibration disappeared. I spoke to a couple of ground Engineers on arrival who explained that such vibration was 'normal' on these aircraft.

I've never experienced such a phenomenon on any other aircraft in 34 years of flying and I don't wish to experience it again.


Regards
Exeng

[bossa]

Earlier this year I did a flight to Cape Verde and on the return, it was the first time I experienced the vibration. Let me tell you that having your airplane vibrating worse than a farm tractor, in Africa, over the ocean at 4 in the morning, with 165 holiday goers is not the most comfortable place to be.

IFixPlanes: As I stated in the original post, that "Vibration Reporting Sheet" was filled in many times. When the airplane went to the hangar, they found problems with the THS. Now 6 months later the problem started again and the "Vibration Reporting Sheet" was again filled in many times (by myself and colleagues I talk to). ALL Ecam parameters are normal. And it only happens in climb between approx. FL180 and FL300

[tom775257]

If you (very) gently squeeze in a little rudder does the vibration stop?

[Microburst2002]

I used to fly one with a similar vibration (noticeable but not intense) and it ceased if you pushed the rudder a little bit.

But no one ever found the cause. It was a very old msn.

[bio161]

I don't remember where and when but my mind reminds me of a publication in which airbus was saying that was going to programme the autotrim of the airbus to give a slight nose down input so that the elevator, the part of the tail where the 90% of the vibrations come from, was always under a constant load and it would not vibrate. At least this is what comes in my mind..

[Eric Janson]

I've had similar vibration problems inflight with a number of older A320's.

It was bad enough to spill drinks in the aft galley.

Vibration could be eliminated by disconnecting the A/P and setting rudder trim to zero. When A/P was on the rudder would trim and vibration would return.

Source was the rudder actuators which wear with age allowing a small amount of play causing the vibration.

Even after the rudder was identified as the source of the problem the Engineering department still wanted vibration reporting forms filled out

Took several months to fix.

[ampclamp]

Hi eric , that is a poor maintenance response.Vibration to that degree with a positively identified source should have been dealt with much much quicker.Scary stuff.

[forget]

Extensive thread from last year.

http://www.pprune.org/archive/index.php/t-385214.html

From PJ2.

I learned later that it was a known issue by Airbus and that another large US carrier had had experience and it was even written up in Airbus' larger "industry issues" publications they used to distribute. Why our maintenance people or flight ops people had so much trouble finding out what it was, was a mystery. The fix was as stated here - replace worn elevator bushings, and, using a special tool, bias the elevators "down" by half a degree (if I recall). The fleet problem disappeared overnight.

[rit]

I had the same problem with some of A320 in my airline. They are very new aircraft (appx. 3 years) So I can say it s not only for old aircraft.

[Springer1]

"I don't remember where and when but my mind reminds me of a publication in which airbus was saying that was going to programme the autotrim of the airbus to give a slight nose down input so that the elevator, the part of the tail where the 90% of the vibrations come from, was always under a constant load and it would not vibrate. At least this is what comes in my mind.. "


bio161 you are correct. My company which has a very large Airbus fleet, did an intensive investigation with Airbus and this was the corrective action. Little vibration problems since.

[Lotetu]

You can try to switch off one FAC at a time.

[grounded27]

Heard manual rudder input helped, sounds like a design flaw, wonder if the wing is sending dirty air over the tail at certain air speeds/air density? Any load on the tail (be it rudder) may help to load and stabilize. Bearings on the elevator with current spec's should not be an issue..

[Beeline]

Friction keeps me in a job thankfully.

Bearings in both the Rudder and Elevators still wear regardless of actions taken by Airbus.

Selecting a bit of rudder trim takes up the null slack in the eye end bearing/ actuator connections to the main fittings of the rudder, if of course it is not another cause.

Control surfaces in non-fly-by wire aircraft have all hydraulic PCAs powered at the same time. We are therefore able to react one actuator slightly against another at null by a slight tweak when rigging the surface . This takes up the backlash preventing flutter and/ or vibration.

Airbus does not have this luxury with active and damping actuators, only one is in control at one time, hence tweaking the elevator actuators slightly down reacts against the air-load; in essence the other actuator as above, taking up the backlash.

With this in mind the bearings do tend to wear quicker on the Airbus, why is anybodies guess?

[Vspec]

I agree with Beeline

Change the rudder to PCA eye end fittings or Elevator hinge bearings.

But A/C has to be planned in for an input......................................

[Wind Shear Ahead]

Our tech dept says is just a bearing issue if it solves with a touch of manual rudder input. Got plenty of those in our fleet. Donīt know if is just a matter of more bearings or more grease but heard was kind of endemic with the type.