A320 vibration

[The Nr Fairy]

Yesterday I flew from AMS to LHR as pax in an A320. I'd fallen asleep before we took off, but woke up as we were in the climb, and noticed an odd vibration. I was seated in 26A.

It was low-frequency and of reasonable amplitude - by that I mean I could feel my seat moving because of the vibration. The vibration disappeared as we started the descent.

I dithered about mentioning it to the cabin crew, but ended up not doing that. I'm curious as to what could have been the cause, and whether it's worth further digging. My wife mentioned that when she flew LHR - AMS some days before the A320 she was on suffered a similar vibration, but apparently with bigger amplitude - she said she could see the wall panels moving.

I'm not trying to point blame, nor dig up problems unneccesarily but I thought the vibration was so unusual it was worth trying to see if it's "normal" or not. I do fly with this airline and others frequently, and on A320s quite regularly, and have never experienced this before.

Any ideas ?

[woderick]

The A320 commonly suffers from Airframe Vibration, there is a troubleshooting pro forma in the trouble shooting manual to give to Pilots to complete and aid diagnosis. It is typically felt in the aft cabin, although the cause can be far removed. Typical, common, causes are play in one of the rudder PCAs (actuators), Play in one of the Elevator Actuators, and play in the nose undercarriage doors, particularly the aft ones. The list goes on, but to summarise, it’s not unusual – cue for a song!:O

[The Nr Fairy]

wodders :

Thanks for that. Was it worth reporting ? Unusual airframe vibration isn't the most beneficial to longevity especially with the lives of these aircraft.

[G-ALAN]

could it perhaps be something to do with the powerplants? I noticed the same thing flying from STN to Malta lastyear (Air Malta CFM engined) it was really quite noisy. Then a few months back I flew from LHR to GLA with bmi (V2500 engined) and it was smooth as silk, no vibration whatsoever.

[lomapaseo]

Unusual airframe vibration isn't the most beneficial to longevity especially with the lives of these aircraft.

It is no more harmful than the vibration of a drumhead which makes a lot more noise.

Everything mechanical vibrates some of the time at some frequency and amplitude. When you get a big enough surface vibrating at the right frequency it makes noise. Sometimes its only a hum or whine while in other situations it sounds like a rumble. Most of the time it is outside of both your hearing range and yout ability to feel.

[avioniker]

A more common cause of airframe vibration (which has been reported as aileron flutter, elevator flutter, and rudder flutter) is the wing to body fairings above the mid section of the wings. The rubber seals get distorted and start to allow air under the fairings and cause quite a loud and tactile vibration that has driven many technicians nuts. If you see a 320 with speed tape along the top seal of the fairing panel this is usually the reason.
I was skeptical until I saw a few chronic vibrators "fixed" with the speed tape.

[woderick]

Avioniker.
Yes the wing - body fairings have caused a few headaches, I just listed common causes that my company is coming across at the moment. It seems to vary across companies as to the current fix.

Nr Fairy.
I find that reporting something to Cabin Crew is not over effective, by all means if you see a large fluid leak, or a lump of airframe depart ship, but they are probably well aware of vibration, having been on the aircraft several times before ! believe me they are usually the source of the first complaints.

G-ALAN
Engine Vibration is usually detected by instrumentation long before it is felt by anybody, and is normally only one engine, normally at Take-off and Climb power settings, it usually settles in the cruise. This goes for both CFM & V2500. Vibration that is noticed by Pax is usually airframe.

[A320 SFO]

I experienced quite a pronounced vibration enroute from LCA - STN last week.

There had been entries in the Tech Log for similar reports. The aorcraft had all the Ailerons, Rudder and Elevator rigging re-examined, all found within tolerance, gear bays doors were examined for excess play...nothing

I found that reducing from .79 using IAS rather than Mach No, when the speed/mach was equal to appprox 0.765 the vibration ceased. After approx. 3 -4 min at 0.76 accelerated to ECON, no vibration thereafter.

2 days later crews reporting the same vib...strange

[G-ALAN]

woderick: The vibration seemed to change as the engine power changed. At cruising alt it was at its worst, all throught the climb there was little virbration and when we reached cruising alt and reduced to cruise power this was when it started. When we started the decent and reduced power the virbration ceased. I found this very perplexing.