A320 Airframe vibration
Hello Gentlemen
How many of you have faced airframe vibration issues on A320 family airplanes? Thanks for sharing in advance Ame |
Often, usually about five seconds after extending the landing lights.
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On a few airframes (2 or 3 out of the 30+ I can recall) starts about FL180 ends FL260 when above 280 kias. Seems to be common parameters. One company got info from Airbus saying there was not enough damping of a particular elevator servo. The company I'm with now no longer has the problem on that airframe (don't know what was done if anything).
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heard once about some SEC problem as well.
Once attributed to frayed/ damaged deicing boots on the stab, as well but dont go by me , i am just a pilot... |
Boots? On an A320? You really have lost the plot! :ugh:
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AME1117;
I experienced airframe vibration a number of times on older A320's. The vibrations were about 6 to 8Hz and could be felt on a larger cycle of about 1 minute - about 20 seconds of vibration, 40 seconds of calm, and repeated, sometimes quite strongly, in the cockpit and through the thrust lever quadrant. I kept records in my log book and got a particularly bad airplane one day - climbing through about 270, Mach 0.76 and increasing, when the vibrations began. I asked my F/O to go back to see if anyone felt it in the cabin. He was a very sharp guy and returned about ten minutes later and said to me, "you have to go to the back of the airplane and look out". I did. I watched, as both horizontal stabilizers began fluttering up and down describing an arc of about 1 ft or so. They were fluttering at about 6 to 8Hz for about 20 seconds gradually damping then beginning again after about 40 seconds. The pattern did not vary with Mach or altitude. It would gradually stop after some time in cruise. We'd been writing up airframe vibration for years. It was always dismissed as "gear doors", "flaps", "turbulence" etc. I grounded our aircraft at the next station. 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. That's one experience. Hope it helps solve what you're looking for. |
It happens on a few of our old A320's,and i find a gentle squeeze on the left rudder gets rid of the vibration.
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Many years ago the high frequency vibrations were attributed to some of the rubber seals between wing fillet/centre section and fuselage. More recently, vibration (moderate frequency) and felt through the floor in the cockpit, occurring between FL180-230 and speeds 280kts-310kts, can be attributed to excessive wearing on the TPFE (Teflon) bearings in the aileron hinges and even the hinges on the elevators and rudder.
Good luck. N.M. |
Originally Posted by PJ2
... We'd been writing up airframe vibration for years. It was always dismissed as "gear doors", "flaps", "turbulence" etc. ...
... Why our maintenance people or flight ops people had so much trouble finding out what it was, was a mystery. ... Worn elevator bushings are not the only cause of vibration. Our crews have a reporting sheet (out of the AMM) that we please them to fill out: http://img44.imageshack.us/img44/632...ngsheet.th.jpg The hydraulic actuation to 0.5 degrees nose-up should be already done on A320Fam. Ref.: EASA AD 2007-0136 LTA 2002-514 CN 2002-514 SB A320-27-1114 |
New experience
hi everyone,
A bit of new info on A320-200. a collegue of mine was flying back from JKT n he experience the same problem . A/c was CRZ bout FL300-370.There was severe vibration at the rear part of the aircart. Auto rudder trim is normally bout +- less than 1degree. b'coz of the vibration, auto pilot was not able to control rudder input. the trim just went to 8degrees indicated on rudder trim window of the centre pedestial. they had to fly the aircraft manually all the way back. b'coz of the rudder trim at 8degrees, AP could not be engaged. that's something new. :hmm: |
http://www.airbus.com/store/mm_repos...A320_ATA27.pdf
. Though I read about single system checks can sort many of these problems, find the surface that like different positions with different hyds on and Bobs your uncle, thought rudder was top of the list. |
Have occasionally had some vibrations, I feel the most important aspect of writing up the defect would be to use the Airbus form as previously posted by IFixPlanes, this form helps engineers pinpoint the problem and becomes part of the permanent aircraft history.
Cheers, D.L. |
Elevator vibrations-servo spherical bearing
by Sonia Bouchardie, Engineer Flight Control Systems, Customer Services, Airbus Industrie Folloowing reports of in-flight vibrations on the A320 Family, an intensive flight test campaign was launched by Airbus Industrie to determine the different sources of elevator vibrations. They are described in the Trouble Shooting Manual (TSM) Chapter 05-50-00, and each possible cause is associated with corresponding trouble shooting procedures. The TSM also provides a recording sheet to help operators establish the cause of vibration. The main source is the elevator system, which accounts for more than 70% of all vibrations. Further to the flight test campaign, it was revealed that the phenomenon was in fact a Limit Cycle Oscillation (LCO) which is a sustained vibration at a fixed frequency with limited amplitude and having no impact on flight safety. This article describes how to avoid elevator vibration through the incorporation of a modification on the spherical bearing of the elevator servo control and a new elevator Two solutions were developed to eliminate these two causes: reduce backlash and increase hinge moment. CONCLUSION The extensive work performed by the Airframe Vibration Task Force led to conclusions for eliminating airframe vibration which have since been proven in service. The effectiveness of these modifications has been clearly demonstrated through the positive feedback from the Operators. Therefore as a preventive measure, the incorporation of the Service Bulletins are highly recommended by Airbus Industrie. ( TO REDUCE BACKLASH Several cases of excessive play within the spherical bearings of the elevator servo control, due to premature wear of the Teflon liners, were discovered during inspections following reports of in flight airframe vibrations. This condition has now been eliminated thanks to higher performance NMB bearings, introduced on the elevator servo-controls through the LUCAS Service Bulletin 31075- 27-17 and Airbus Service Bulletin A320-27-1111. This modification incorporates an additive in the existing liner, and chromium and super finishing of the inner ball to reduce the wear rate and friction coefficient. Also the maximum acceptable value for backlash, measured at the elevator trailing edge has been reduced from 10mm to 7mm, as described in the AMM. TO INCREASE HINGE MOMENT The Airbus Service Bulletin A320-27-1114 describes the resetting of the elevator neutral position to 0.5 degree (aircraft) nose up. Accomplishment of this modification ensures that the elevators are aerodynamically loaded in an appropriate manner in order to eliminate vibration, even during flight in turbulent conditions. Those changes have no effect on aircraft performance and there is no change in the handling characteristics of the aircraft, nor is there any penalty in fuel consumption. This modification has been developed to fit easily into the maintenance program. To perform the revised elevator rigging, a new elevator rigging tool, developed by Airbus Industrie, enables the new neutral position to be determined. It is highly recommended that this new tool be used, as it allows more accurate rigging through a simplified procedure. Nevertheless, the elevators can also be set using the previous tool which was developed originally to set the elevators to a 0 degree position. Therefore the Aircraft Maintenance Manual (AMM) procedure now describes how to set the elevators to the 0.5 degree using the original tool orthe new tool. ADVANTAGES As a preventive measure, these modifications will: improve the fleet reliability due to the new elevator servo spherical bearings and revised elevator rigging, improve passenger and crew comfort by removing the causes of vibration, reduce maintenance costs." |
IFixPlanes;
Did you ever give the maintenance more hints than speed and affected area? Today it's obviously well known and well understood - I don't think it was back then. |
Is this related to the VS problems that I have been reading about lately?
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yup
yup same form.. and our planes are averaging 4-5 years old so its not only on the old A320s
if i remember correctly ours have a prob with the rudder too.. |
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