CX A340 YVR-HKG Flies 10 Hours with cracked windscreen

[NigelOnDraft]

Wild guess, seems handled as per the QRH The Diversion to SEL required due to the low Cruise Alt, and gave nearly 10 hours for CX to get a 777 to SEL to meet the pax...

NoD

[Dysag]

A windup?

We're on post 20 and everyone is talking as if the pilots were left on their own. Surely CX ops/engineering at HKG were in a position to advise. Were they not asked?

[overstress]

We got to post 11 above before someone posted a relevant QRH...

Armchair quarterbacks R us?

[411A]

Continued flight perfectly reasonable if IAW QRH and manufacturers/company policy.

And yes, some windshields are tougher than others.
L1011 for example.
Cracks develop enroute...no restrictions whatsoever.
No lower flight level.
No lower speed.
Nada. Zip. None.

TriStar, built to a slightly higher standard.

[glhcarl]

The heat makes the windshield flexible and able to withstand bird strikes. When its un heated a birdstrike might shatter it.

How many degress does it take to make glass flexable?

[lomapaseo]

Quote:
The heat makes the windshield flexible and able to withstand bird strikes. When its un heated a birdstrike might shatter it.

How many degress does it take to make glass flexable?

Define flexible

[plain-plane]

Just a brief comment on the use of MEL airborne

On my type/company it would be considered very prudent to consult the MEL and DDPG en-route. That is where you will find information on down grating of, P-RNAV, MNPS, RSVM, CAT II/III.
But who needs to know that anyway…

I.E.: What will an INOP windshield wiper do to you?… or in a similar case to above… is it any good on a window that has crap’ed out on you?
Can you or can’t you then consider it operational…?
On the B73/NG: no wiper means no CAT II/III…

[411A]

If we look back in time, to the piston/large turboprop era, we find that many aircraft had NESA installed, as pilots windshields.
This was a propriatory brand of glass/plexiglas 'sandwich', and needed to be heated to some degree, for bird protection.
The B707 used a different brand (not NESA) however, heat was still necessary.
TriStar.
No heat necessary, except for anti-icing.
However, do not make the mistake of leaving the heat off for takeoff, and then find out two hours into the cruise that...opps, we forgot...and switch the heat on.
The outside layer of tempered glass will crack, big time, at cold temperatures aloft.

[glhcarl]

Define flexible

I don't have any idea.

Glass melts somewhere between 1400 and 1600 degrees C. So say it gets a little felxable around 1000 degrees C. At that temperature the actrylic an vinyl portions of the windshield would have melted.

The bottom line is that I don't really think windshields are heated to make the glass overlays flexable.

[arcniz]

Heating may well add some flexibility to the high-surface area interfaces at the boundaries from glass to plexi and back. Most of the change of behavior would be in the plastic layers and the bonding adhesives between plastic and glass. The overall rigidity of the glass would not be much affected, but the ability of the composite assembly to accept impact shock waves and dissipate them safely to successive layers and to the frame structure would be heightened.

Heating on the way up and down would also help relieve the inter-layer thermal stresses in the windshield panels. Fractures often result as release of the combined energy of impact plus stored internal stress.

Do not know this for certain, but it seems consistent with the behavior of the materials in the typical window sandwich.

[Swedish Steve]

L1011 for example.
Cracks develop enroute...no restrictions whatsoever

And on the Tristar windscreen change is easy. being prepared after a reported cracked windscreen in DXB, we replaced the windscreen on the 60min transit at BAH without a delay!, and the seal is rubber so no curing time involved.
The bolts are on the outside and are all the same length, all you need is a platform to stand on, and the crew can get on with their work in the flight deck.

To change a B737 screen is about 10 hours work, then dry the sealant, and wonder what the little bracket is for you have in your pocket.

[BlunderBus]

duh

if they flew happily across the pacific..why then divert at all? surely the same 'logic' would dictate they continue to hk?

[Thunderbug]

Blunderbus


Maybe flying at FL230 rather than FL390 made for a slight difference in fuel endurance....?


T'bug

[HotDog]

Have you ever tried to land without windscreen heat after descent from cruise? You better have a big cloth to wipe the condensation to be able to see where you are going,

[spannersatKL]

CONF iture
True....but they control the power to the processor in the associated computer...hence you can reboot a failed/stuck processor in a box.....The actual Circuit Breakers that control the real power to the affected system are below the flight deck......and its real power that powers the windshield heat and believe me when you see smoke and sparks coming from the top of the window its this one I would like to pull.....(along with Kylie Minogue!!).......

[Springer1]

Airbus seems to have an inordinate amount of windshield shattering. I have had two in one year on the A320 and know of 11 others in the same time period. Never experienced it on the DC-10 nor the B-727.

[CONF iture]

spannersatKL,
It's ok with me if you're more comfortable to go and pull that CB, I remember a few years back some guys were still used to go and feed the dog once in a while airborne ...
but the "reset button....................PULL" is part of of the Airbus COCKPIT WINDSHIELD ARCING checklist.

Nevertheless I don't disagree on the KM case.

[overstress]

Springer1:

Airbus seems to have an inordinate amount of windshield shattering. I have had two in one year on the A320 and know of 11 others in the same time period.

You may have been unlucky, I had none in 8 years on the type.