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BigHitDH
22nd Jul 2003, 12:41
Hi,

I'm hoping one of the more experienced users here can answer a question that's been bothering me for some time.

In may of last year, I departed Narita International bound for Heathrow aboard a JAL 744. I've been on many 747 types before, including the 744, and this take-off roll seemed to take a long time. At least it seemed that way at the time. Anyway, upon rotation, just before V2, there was a very loud bang from behind and below me. I should mention at this point that I was in the last row of seats at the rear of the aircraft, in the left-hand window seat. The jolt was strong enough to make me jump an inch or so from my seat.

Of course, I presumed a tailstrike, seems logical I thought, long take-off roll and all. However, the flight continued normally, and no announcement was made. Some of the passengers I talked to also expressed concern about the bang, and we chatted about the probable causes, but we never really could figure it out.

One thing I did rule out in my own mind, was that we were just hitting the raised runway centre lights, it was much louder than the "thud thud thud" of that.

Any idea what might have caused this?

Thanks in advance!

747FOCAL
22nd Jul 2003, 14:47
It was prolly the gear hitting the extend binders after the plane became airborne. It also may have been a discontinuity between two pieces of concrete.

Or maybe the stew left one of the carts unstowed in the back and she banged into something really hard.:E

willoman
22nd Jul 2003, 15:12
Possibly incorrectly stowed freight in the rear hold shifting position on rotation.

BigHitDH
22nd Jul 2003, 15:16
It was prolly the gear hitting the extend binders after the plane became airborne. It also may have been a discontinuity between two pieces of concrete.

No, it felt like it was before the wheels left the ground, but a good suggestion.

Possibly incorrectly stowed freight in the rear hold shifting position on rotation.

I hadn't considered this. How does that affect the aircraft balance? Surely several thousand pounds of baggage/frieght shifting upon rotation massed up the CofG?

slingsby
22nd Jul 2003, 16:23
Unsecure cargo sounds probable, but sometimes you do get uneven runway surfaces. Undulating surfaces can catch you unwares, especially if you haven't flown into or out of a particular airport. Corfu is known for a big dip in the runway, crews are reminded of this (or were, they may have resurfaced it since i was there several years ago). When departing out to sea, there was a dip just about the rotation point of a B737 take off run, get it wrong on rotation and the runway comes back up to meet you within a few metres, and bang, the main gear hits the upward surface of the runway.
Sometimes certain bits of cargo move inside the containers, fall over, this can cause alarm if it's quite loud.
tailstrikes can cause pressurisation problems, so that theory could be discounted but not dismissed.
If you had posted it earlier, like a few weeks after, we could have asked the engineers here, as my company use the same company.

Notso Fantastic
22nd Jul 2003, 19:22
The fact you were in the last row means that it was no special undercarriage noise (as in oleo extension). I'm pretty certain tailstrikes are inaudible and unfelt unless they are violent. I have known many reports of them where nobody felt a thing. I would say it was certainly cargo shifting- maybe an insufficiently secured container sliding a few feet in the rear hold in front of you and 'booming' when it stopped, or bulk cargo items immediately below you moving or settling. Shouldn't have happened, but not really a hazard in a passenger aeroplane.

747FOCAL
22nd Jul 2003, 21:08
Flying out of Algiers in a 767 a few years ago there was something that I could feel rolling around beneath my feet for about half an hour after rotate. Didn't say anything(which was prolly bad) because I did not want to go back and go through that security again. Was a little scary though knowing it was doing that.
:zzz: