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Plavt
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Again........ :?

Postby Plavt » Sat, 21 Mar 2009 8:30 pm


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sierra2469alpha
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Postby sierra2469alpha » Sat, 21 Mar 2009 8:44 pm

Love the way each new service mistakes the A/C type! Not to mention that in the real world it's called a "tail strike". Over-rotation on the Chairbus (they float better than they fly - remember the river??) is more common even though the "computer" is supposed to stop it from happening (any Charibus drivers here? Maybe it's out of Alpha?) . On a Boeing, well, the 73 that I am endorsed on, you can do it, but we don't have that many computers making sure we do it "a la proper" :)

Nice of them to dump the fuel in Port Phillip Bay, but I won't hold the crew respnsible for that - I'll give it to the sleepy ATC at YMML at 0300 Local time.

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Postby Strong Eagle » Sat, 21 Mar 2009 10:58 pm

So, I've heard that one reason the A340-500 only has business or premium economy in the back is CG problems. Even Thai economy on the A340-500 offers humongous seat pitch... 41 inches as I recall.

Having heard that the A340-500 tends to be tail heavy I'd like to know if a) this is true; and b) if this could have been a factor in banging the tail on the ground.

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Postby Plavt » Sat, 21 Mar 2009 11:50 pm

As far as I know the A340 is 'fly-by-wire' (as mentioned by Sierraalpha2469) and is supposedly stall-proof so taking it as a fact that the plane is 'tail-heavy' it shouldn't have made any difference. However, as is the usual case we will have to wait and see what the subsequent inquiry produces. Hope singaporegrrl and queenie-me haven't had a hard time if they happened to be on the that particular plane.

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Postby sierra2469alpha » Sun, 22 Mar 2009 9:37 am

SE - I doubt that given the J class/premium Y is a factor, if anything you're only talking (in theory) 83kg per pax, say 100kg per seat. If anything, less seats would theoretically move the CoG forward. I'll check with a couple of people and get it straight from the horses mouth regarding your other two questions.

2 pics for y'all

Image

Image

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Update #1

Postby sierra2469alpha » Sun, 22 Mar 2009 12:32 pm

Some information from an Airbus A340 - 500 FCOM may assist in providing some sober second thoughts and perhaps a pause before contributing some of the inexperienced, uninformed and wilder notions we are seeing.

The following is in no way intended as speculation but only as information. OK

Tailstrikes on any transport category aircraft have a fairly narrow range of causes. In tailstrike incidents and takeoff accidents, the following have occurred:

- incorrect rotation technique, (early, fast, two-stage)
- incorrect takeoff data calculation, (wrong weights, wrong runway)
- incorrect takeoff data entry, (correct calculation, wrong FMGC entry)
- wrong runway used for takeoff, (taxiway used in some cases)
- incorrect weight and balance numbers, (includes incorrect stabilizer setting)
- incorrect stabilizer setting by the crew (correctly calculated, wrong setting)
- cargo shift, (extremely rare today, but it has happened in the past)
- strong tailwinds/windshear (rare)

Operational Bulletins (not cautionary in nature but expanding upon operations), for the Airbus 340-500 state that, with respect to the A340-300, the flight control laws have been adapted to take into account the longer fuselage length and that the tail clearance is monitored and if marginal, the rotation rate is reduced until lift-off. The information also states, (and this ought to be obvious to anyone), the airplane has a large inertia and the rotation takes time to build up. For rotation, one "sets" the sidestick about 2/3rds back and waits - one does not pull further.

For information, the aircraft does not have a tailskid, but nor do most transports including the B747. The DC8-61 and 63 series did and the B720 had a ventral fin which may have acted as a bit of protection but that aircraft had a very short fuselage compared to the 707.

The Airbus A340-500 rotation technique requires some care. Even though the technique is (or certainly should be) well known/understood by those trained on the airplane, there is specific guidance in the FCOM regarding the maneuver, there remains an aspect to rotation of the Airbus A340-500 that can be a bit of a surprise if one is not prepared for it or knowledgeable about it.

I stress here that this information is for those new on the airplane. This is a non-issue for someone who has been flying the -500 for more than a couple of legs. The FCOM has very specific cautions on rotation technique:


AT VR SPEED
PNF..."ROTATE"
PNF observes the speed and completes the call by VR. When V1 and VR are the same, the calls must be completed by VR.

At VR , the PF initiates the rotation with a positive sidestick input and maintains the positive sidestick input to achieve a continuous rotation rate of about 3°/sec towards a pitch attitude of 12½°

[A343] /15° [A345, A330]. Changes to the sidestick position should not be made until airborne. After lift off, follow SRS pitch command bar. In the event of no FD after liftoff select 12½° [A343] /15° [A345, A330] pitch with all engines (maintain minimum V2 plus 10 kt) or 12½° in the event of an engine failure (maintain minimum V2).


As the rotation maneuver is flown in Direct Law with full authority, pitch control is very sensitive to sidestick inputs. Altering sidestick backpressure can produce pilot induced oscillations and/or may produce a two-stage rotation which significantly increases the chance of tail strike.


Minimize lateral inputs on ground and during the rotation, to avoid spoiler extension. In strong crosswind conditions, small lateral stick inputs may be used, if necessary, to maintain wings level.


If some lateral control has been applied on the ground, the Sidestick should be centralised during rotation so that the aircraft becomes airborne with a zero roll rate demand.


Info
Airbus Training advises that once the rotation has begun, increasing side stick back pressure will increase chance of a tail strike.


CAUTION

In the unlikely event that a tail strike should occur, flight at altitude requiring a pressurized cabin must be avoided and a return to the nearest suitable airport should be performed for damage assessment.

[source: PJ2 at pp]

The upshot is the flight control law on take-off is 'DIRECT LAW' and pitch transitions to 'NORMAL LAW' 10 seconds after liftoff. (Roll transitions from direct to normal 5 secs. after lift-off). It has a pitch limiter indication on the PFD, an orange "V" indication the approaching angle of pitch that would incur a tail strike if over rotated beyond the bottom point of the "V".

But there is no flight control lawpreventing the tail from striking the ground. There is a very small tail skid, but more of a tell tale sign if touched or scrapped.

[thanks jetjock330 at pp]

Further info on the incident itself. [multiple sources] Having flown out of YMML RWY 16/34 is huge. Weather was fine at the time (I checked). Departed on RW16 and removed the LOC antenna during rotation. Track marks found at the end of RWY16 (!) - begs the question exactly how low were they.

[source: hempy at pp - thanks!]
[EDIT: New info: [source: pp ] Hempy. I was at MEL at 1300LT today. Your photo of R/W34 depicts strobes 350M south of the threshold. This is incorrect. This is the R/W 16 LLZ antenna array (Orange in colour). It appears to me from the damage to the antenna array it may have been caused by vortices. There were 10 officials inspecting the antenna array area at 1300Lt today.]

If anyone wants me to scan the Jepp chart for YMML let me know.

Image


Received vectors for a fuel jettison.

Received a report of smoke in the cabin and elected (very reasonably) to return immediately to YMML for an OWL. My guess is the smell of smoke from the tailstrike - lots of blackened skin in the photos but not neccessarily a cause for cabin hysterics. When the girls ring up and say "THERE'S SMOKE IN THE CABIN!!!!" the reality, the wording and the image in the capt's head could easily be three very different things.

Abandoned the jettison plan and set up for return.

Landed on RW34. No need for vectors around the field from PFB to land on RW16 since there's no longer a LOC signal on RW16. It was an overweight landing which sereverly damaged the undercarriage.

Stop on the RWY for an inspection by RFFS followed by "normal" taxi, or possibly a tow, to the bay to disembark the punters via the bridge.

Crew were deadheded back to DXB on the next flight which was almost immeditaely rescheduled. At this stage CASA are saying they have not spoken with the 4 tech crew.

Latest (unconfirmed) FMC figures:
Gnd Dist 6420nm
Ramp Fuel 137t
Trip Fuel 126t
ETOW 363t
ELWT 237t
EZFW 227t

So, they were at MTOW of 363t, apparently.

As Plavt knows I never, ever, speculate on incidents or accidents. However, I will say this is an extremely serious incident. Can you imagine the affects of 137t (less taxi fuel) of JET A going up with 4 of Chairbuses most powerful engines probably at max FLEX or TOGA, going in? Or, conversely, given the OWL and gear possibly collapsing. As ex tech crew, I need new undies after just thinking abou this.

Hope this info is useful. Took me a while to compile it from the various sources.

Cheers, P

[/i]


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