747-400 Heavy Vibration - should I report it?
 

Guys and Gals, can you help...

I am a Heli and fixed wing pilot with about 800hrs combined (hopefully to qualify that I am not a total prat)

I flew BA017 on the 12th November LHR-Singapore (21.15, Seat 33c) and as we rotated from 27R there was the most awful vibration through the airframe. Not your usual wheels still turning, but a very harsh shuddering which I guess lasted for about 4-5 seconds. My fellow passengers all thought it was very serious, so I thought it should be reported. I was quite worried.

I contacted the local cabin crew as soon as the seatbelt lights were out and they also said they had felt nothing like it. I suggested very seriously that they report it to the flight crew - which they did.

The CSR came back about 15 minutes later and was very dissmissive about the noise and said that the captain said that it was either the wheels still spinning, or wake turbulence from the previously departing aircraft and not to worry.

I asked if he or the pilot felt the vibration, however they said they did not as they were at the front of the aircraft.

I suggested again, that had this been my aircraft, it would be noted in the tech log and I would have taken (as PIC) it very seriously, especially as it was reported by some cabin staff and a qualified pilot.

Again, the CSR went off, but never came back to me.

Should this be escalated? Your thoughts would be interesting?

Regards, Jon P

It seems to be very common on 747s. In a short period of time I've flown LHR-LAX-LHR on BA's 744 (as a pax) and there was HEAVY vibration thru the rotation until gear was retracted, both ways. Lufthansa's 744 on FRA-SIN was awful too, but it was worse when leaving SIN, we had to (according to announcement) offload some cargo, to not be overweight. Vibration and rattle, never experienced anything like it. Few bins flew open and some pax were disturbed.

The most alarming possibility is pre-stall buffet.......... which presumably would have operated the stick shaker (which would NOT cause the vibration!) , which would be recorded on the FDR / FLIDRAS (?)

Rotate at too low a speed and you're either going to scrape the tail as it struggles to get airborne or if it does, by definition, your going to be right on the limits of the available lift. Wrong numbers punched into the FMC and/or incorrect weights have resulted in accidents before.

I don't know, I wasn't there etc etc......

A4

When the fmc puts the v numbers for take-off do you normally just say lets go a few knots over to make it safe?

There is also a possibility that the vibration you felt was merely the wheels spinning as they are retracted into the wheelwells.

If the tyres are unevenly worn, as most are (being retreads) then the wheels will be out of balance (like on a car) and a vibration will be felt throughout the plane.

We often feel it on the B738, and I do recall feeling it on the B744, but those are from the nosewheel.

Hope that explanation puts your mind at ease.

Yep... few years back we were flying out of LAX for Auckland late at night. Just on rotation the most horrendous vibration was felt for about 20 seconds. I whispered to my wife that we'd probably dump fuel for a while before going back.... but to my suprise the flight continued as normal. I haven't experienced it elsewhere and wondered if it was just a rough surface at the end of that particular runway.

Sounds to me like main wheel vibration, after wheels leave the ground they will shake the landing gear.

When gear selected to up, the main wheel brakes are applied to stop wheels spinning, this is very nice.

With 18 wheels, they will at times balance each others vibs and the totel effect will be less, but at times they will act together due to the random effect, when they act together, vibs will be high.

I don't like those vibs when I travel, so I book seats on the upper deck or between doors 1 and 2.

Have a nice flight......

going LHR-YYZ on BA 744s have often experienced fairly loud vibration on rotate.

From what you describe, it would have to be more than one mainwheel not snubbing. It might have been all four on a bogie.

Sometimes spoiler(s) will 'float' a bit , but they won't cause vibes.

Did you snag it in the book?

phillip2004uk, NO

Typical Vr for a busy SIN would be 170-174 kts, the first time I flew the 747 I remember thinking the shaking, rattling and general vibration was quite alarming,at least untill the gear came up, got used to it now, and don't worry about it any longer:ok:

I've felt this on a heavy 74 out of Singapore before. Was worried at the time (I was about 14). Now that I fly the 767, we get it a fair amount of the time, especially when heavy. As you rotate the nose, it gear extends on the oleo with a thump and you often get vibration. It is like hitting something as soon as you rotate in sound and feel. 767 nose wheels are known to go out of shape and vibrate - I imagine 747 wheels are the same. With a heavy aircraft, it will be travelling faster at rotate and the oleo will have more travel due to higher compression when loaded on the ground.

If the CSD reported it to the Captain I wouldn't worry. If it was anything like the pre stall buffet mentioned above (extremely unlikely) it will be picked up almost straight away and dealt with by BA's safety management systems - which are excellent.

Flat spotted nose wheel(s) will be unbalanced and they are not snubbed (rotation stopped) like the mains. They will keep turning until they rub up against their respective spring loaded pads up in the ceiling of the wheel bay. Vibes will be transmitted up thru the leg or strut into the aircraft structure.
Nothing to worry about, relax and enjoy the ride.

Any HEAVY vibration should be reported to maintenance for inspection. It sure does ruin your whole day when that 34ply, 225mph speed rated, 44,000lbs capacity tire comes crashing through your roof!:E

Cabin Crew will be a good monitor for vibs at any and all stages of flight or T/O or LDNG.

Enjoy the vibs...

Whilst I have no 1st hand reports of vibration incidents (other than when I was PIC and the AC was a bit smaller than a jumbo and handled none too deftly in the beginning stages.... :)) ...


My cousin and his wife on return from the Philippines on an A340 also noticed what they described as a terrible vibration from 'under the plane' right after takeoff.

They were very concerned, spoke to an FA who replied,
'sometimes it does that - it's OK' ...............many miles later, at their flight's end, my cousin asked the captain what was that scary feeling ?' The Cap did not notice, but promised to 'have it checked out' - maybe they were blown off - or not.................

An EAL A&P told me long ago that the LDG Gear wheel/tire balance is often the cause of such worrisome but non-issue vibration reports.

Had it last night as a PAX on a 734 from Turin to LGW. Definately the wheels spinning, stopped instantly when PIC gave a "tap" to brakes before raising the gear.

Have experienced this once, on rotation on a VS 744 departing LHR-SFO....some pax were quite alarmed.

The creaks and twangs (I believe from the body gear steering) on the 747 when taxying often cause concern/questions aswell.

I flew ca. 150 times on BA 747s when I worked for them.

I've heard exactly the same vibration 6 or 7 times - it was always G-BNLH for some reason - and I think Skyvan and others have got the explanation.

Just to be very clear, is the vibration on rotate, or 8-10 seconds after rotate?

If it is on rotate, it cant be the gear. You got to remember there are a few wheels to retract on a 747, it takes a little while!!

If the vibration occurs after the rotation and airbourne, it is more than likely the gear has been retracted and wheels are still spinning giving the gyroscopic effect in the undercarriage bay.

It's good that you brought it to the attention of the crew - good CRM!!

Never any harm in mentioning noises with which you not familiar. Pax are sometimes better placed and perhaps more objective in their observations; remember Kegworth?