Brand new Etihad A340-600 damaged in Toulouse; several wounded

[ATC Watcher]

I was just shown a photograph of the aircraft taken from an helicopter after the accident, and the braking marks on the concrete are clearly visible, but curiously only on one side ( left) and it is a very straight (double) mark.

[Tediek]

you never know what has happened, but i guess when things really go belly up, people panic, do weird things, maybe breaking with one foot as it's different due to the dual function etc. etc. Do weren't pilots I guess, so the routine fails there.

[bsieker]

Originally Posted by old,not bold

I always thought that the fuselage structure is supposed to withstand quite severe unexpected and unusual forces. And this one didn't.

Among other things, an airframe also has to be lightweight. This is not only achieved by using lightweight, strong materials, such as aluminium, composite materials, and, in highly stressed places, even titanium alloys.

It is also achieved by designing it for a very precisely defined type of loads and forces, so it is in fact made to withstand only expected forces. It is the designers' and engineers' job to think of all the forces to which the structure could reasonably be expected to be exposed. Scaling a concrete wall is most likely not on their list.

The design must clearly state what types of loads and at what magnitude are expected, and how these maximum loads were derived, and must be demonstrated to break no earlier (in the case of the wings, at least) than at 150% of that load. For the wing this means, an actual production model must be bent until it breaks. This Youtube-Video shows what it looks like.

The certification authorities must agree with the calculations for the maximum design load and certify that the structure has met the test for the aircraft to receive airworthiness.


Bernd

[CONF iture]

Originally Posted by ATC Watcher

I was just shown a photograph of the aircraft taken from an helicopter after the accident, and the braking marks on the concrete are clearly visible, but curiously only on one side ( left) and it is a very straight (double) mark.

Any chance to see that picture ... ?
Please !

[ATC Watcher]

I have an electronic copy now but do not know how to paste a photo to a reply here.
If someone can help, or give me an e-mail address in PM and I'll send it.
ATCW.

[aerotransport.org]

http://www.myaviation.net/search/pho...767&size=large

[carholme]

This helicopter photo clearly shows the arrow in the centre of the pan, indicating that the a/c did not wind up at the red line position as described in post # 108. Looks like it travelled almost directly across the pan.

carholme

[forget]

Correct carholme The blue arrow is the first useable reference point we've seen here. These will show actual positions.

[bsieker]

Originally Posted by forget

Correct carholme The blue arrow is the first useable reference point we've seen here. These will show actual positions.

Incorrect.

Originally Posted by carholme

This helicopter photo clearly shows the arrow in the centre of the pan, indicating that the a/c did not wind up at the red line position as described in post # 108. Looks like it travelled almost directly across the pan.

I have inferred the correct position as early as post #118. Markings on the wall were perfectly usable references to the position. My post seems to have been largely ignored, except by CONF iture, maybe because I did not draw a big colored bar to indicate the aircraft position. I left that exercise to the readers.

The skid marks seem to be consistent with the ones seen in post #250, where they have been compressed by an long telephoto lens. On both photos they seem to end under the wing between the innermost and the second pylon.

Judging the offset from the engine scratch marks they appear to have come from the center gear.


Bernd

[BillS]

"they appear to have come from the center gear."

the two lines appear to converge - indicating gear turning?

[somepitch]

looks like the skid marks are from the nose gear, which as BillS pointed out would have been turning according to the position of the rudder...

[Good memories]

Maybe the ground /air sensor

I remember the accident in Madras with one of the first 320's delivered to Indian Airlines. I believe the towback truck sheered the wiring on the nose strut of the ground/air sensor. The acft. ended up with its nose in the terminal .

I think there could be a clue. Maybe the Alpha floor protection sensed a in flight condition with zero IAS and commanded the engines to GA thrust. I never flew an Airbus , but I'am sure many of you pilots out there know the logics of this machine. Q. Do the brakes get signals from the ground/air sensor. Could it be they had a T/O warning as the flaps were up and somebody tripped the ground/air cb to silence the warning. I realise there are a lot of maybe's and if's , but it could be a good starting point.

I like to hear your comments on this.


Good Flying!



John

[MD11Engineer]

This might indeed be a possibility. I have no experience with the A340 but on the MD-11, if during an engine run the AOA vanes stand in a high alpha position and due to some reason (e.g. the upper torque link being disconnected and hanging down, thus putting the NLG air/ground switch into "flight" position) the air ground system gets put into air mode, the stall protection system will activate, extend all leading edge devices and autothrottle will push all throttles to full power.

Jan

[bsieker]

Originally Posted by Good memories

I think there could be a clue. Maybe the Alpha floor protection sensed a in flight condition with zero IAS and commanded the engines to GA thrust. I never flew an Airbus , but I'am sure many of you pilots out there know the logics of this machine.

An involuntary activation of Alpha Floor protection is exceedingly unlikely. It is inhibited before take-off, and below 100ft RA during approach, and is triggered by angle-of-attack (as a function of IAS and high-lift device configuration).

Q. Do the brakes get signals from the ground/air sensor.

Yes, they do. Normal braking is only available (among other things) if the main landing gear is in ground condition. In the air, alternate braking is active.

Either way, brake pedal deflection will give braking action, and antiskid is available with both normal and alternate braking, unless explicitly turned off by releasing brake pedals, flipping the "A/SKID & N/W-STRG" switch, and pressing the brake pedals again, or because of a number of fault conditions.

(FCOM 1.32.30, P5, SEQ 100, REV 14,
FCOM 3.02.32, P13, SEQ 001, REV 24)


Bernd

[Good memories]

Hi Bernd,

Thanks for your quick reply. If somebody pulled the ground/air senser CB in the cockpit, could that trigger the event that happened.

John

[Good memories]

Hi Bernd,

Obviously you are well informed in to the logics of this acft. Suppose the crew makes the power check but the acft. is not in the T/O configuration. The Parking brakes are set >The acft is not in the T/O configuration> the T/O warning sounds, >somebody in the cockpit wants to silence the warning and pulls the ground/air CB. Q? Do the parking brakes remain set or not.

John

[hetfield]

If somebody pulled the ground/air senser CB in the cockpit

I'm not Bernd, but on Airbus it isn't that simple......

[Jetjock330]

Only 2 C/B's in an Airbus cockpit, one under each pilots chair, for electrical protection of movement of the each pilots chair. The overhead panel are just COMPUTER RESETS, although they resemble C/B's, as we would all know them to look like.
The C/B's are in the avionics bay, protected by a big dog from the engineering company, hence the reason I never get near them.

[bsieker]

Good memories,

I'm merely an academic, and this may be more authoritatively answered by pilots or engineers, but here's what I can see:

- The Parking brake is not part of the ECAM Takeoff-Memo, neither is it in the Before-Takeoff or Takeoff standard procedures. It is, however, in the Taxi procedure, as is calling-up (if not already displayed) and checking the ECAM T.O Memo.

(I do not have appropriate documents on engine test runs, so cannot comment on the procedures at all.)

- T.O Config test button will not trigger the warning for parking brake set, setting take-off power will. The engine test here apparently was nowhere near full or reduced take-off power, so it would not have been triggered. (FCOM 1.31.15, P5, SEQ 001, REV 08)

- I cannot see any condition other than simultaneous blue hydraulic and hydraulic accumulator failure that would disengage the parking brake when it is set to "ON".

- As Jetjock330 mentioned, there are no circuit breakers in the cockpit proper, so only any of the number of engineers on board could have pulled one. Would be rather silly, but humans are known to act like that sometimes, so only official publications will tell.


Bernd

[CONF iture]

That picture is a dynamite Thanks !

So let me go for this:

Yellow: 340 position when it strikes
Green: Final position
Tailstrike 1 due to the nose climbing the wall
Tailstrike 2 when left engines reach the wall

Originally Posted by BillS

they appear to have come from the center gear."
the two lines appear to converge - indicating gear turning?

Originally Posted by somepitch

looks like the skid marks are from the nose gear, which as BillS pointed out would have been turning according to the position of the rudder...

No other choice than to agree with you guys!
And NO BRAKING ACTION AT ALL !