CX A340 YVR-HKG Flies 10 Hours with cracked windscreen

[cathaychap]

Reported by South China Morning Post, 20 June.

Pilots thought it was safe to fly after noticing the crack 2 hours out of YVR. Diverted to SEL. Pax offloaded and put on CX777 back to HKG.

Kinda interesting, I thought. Never had a cracked windscreen - and 10 hours is something else.

[gilderoy lockhart]

What does the MEL say? Lots of layers in a windscreen!

[F4F]

As aircraft was airborne, MEL irrelevant...

Open questions:
What does the abnormal or emergency checklist say?
What layer, outer/middle/inner was it?
Did they change flight level?

live 2 fly 2 live

[Spanner Turner]

From a Boeing Manual, my highlighting;

(2) Flight adequacy of the windshield shall be determined by visual
inspection of the transparent components (elements) and weather
seals and by an operation check of the electrical anti-icing system.

(3) Removal of a windshield is only required for obvious reasons such
as:
(a) Heat inoperable for reasons internal to the windshield.
(b) Structural glass ply contains cracks, chips, or shatters.
(c) Cracking or shattering of outer glass ply. Refer Dispatch
Deviation Guide for dispatch.
(d) Cracking of vinyl ply if vision is seriously impaired.
(e) Delamination of any plies if vision is unacceptably impaired.
(f) Objectionable pressure leaks.
(g) Vision seriously obscured for any reason.
NOTE: Removal for structural reasons is not expected.
If structural deterioration does occur, the obvious
removal reasons above will have occured well before the
assembly has become structurally unsafe.

point (c) above refers you to the DDG. The Boeings I work on allow for the removal of the outer 'Glass' layer. If it's cracked or 'spider-webbed' one of us engineers gets up there and chisels off the complete layer of glass which restores the visual quality of the windscreen and then you can fly home to replace the windscreen. This glass outer layer is not structural in any way and is utilised as it's very hard and resistant to abrasion from flying at 900kph and from the windscreen wipers dragging crap to and fro across the windscreen. Imagine a plastic windscreen on your car, it would look terrible after not too long. Bare in mind that some windows also utilise glass in the primary structure (although most use plastic/vynyl) but there are generally up to 4-5 layers so a crack in one doesn't affect the strength of the complete assembly.

In addition, below is from the inspection procedure for windows;

(3) Cracks:
(a) A crack is a fissure that has a visible width or depth.
(b) Cracks can start from a scrath or a crazing mark (Fig. 601).
(c) Cracks can be single or dual (Fig. 601).
(d) Cracks in glass will usually occur 90 degrees to the surface of
the pane.
(e) Cracks in stretched acrylic plastic will occur at
a 45 degree angle to the surface of the ply and can become
in - plane cracking.
(f) The cracks in an outer vinyl ply (the ply between the middle
structural ply and the outer ply) are caused by incorrect heat
application.
(g) The cracks in the vinyl usually occur in the window corners and
are within the edges of the release tape.
NOTE: Vinyl cracks are not a problem structurally.
NOTE: Only replace the windshield if your vision is limited.

[Phil1980's]

If he flew 10hours then why didnt he just carry on to hong kong? why fly 8 hours and decide to divert?

[SuperRanger]

Our B777 Non-Normal Checklist says:

If forward window arcing, shattered, or cracked:

FORWARD WINDOW HEAT
SWITCH (Affected window) . . . . . . . . . . . . . . . . . . . . . .OFF
[Removes electrical power to prevent arcing.]

Do not accomplish the following checklist:
WINDOW HEAT FWD

If damaged window deforms, or air leak is observed:

Plan to land at the nearest suitable airport.

If airplane altitude above 10,000 feet:

Descend to lowest safe altitude or 10,000 feet,
whichever is higher.
[Minimizes forces on the window. Outward cabin pressure
differential counters inward dynamic air load on the window.]

Sustained flight below 10,000 feet is not recommended
due to greater risk of bird strike.

[Old Fella]

CX Cracked Windshield

Of course the SCMP account would have to be regarded as an authoritative report, I don't think!! Why don't you ask CX what the real nature of the event was? All this speculation based on a newspaper report is a waste of effort.

[Thunderbug]

Airbus (A320) drill

COCKPIT WINDSHIELD/WINDOW CRACKED
In case of a one ply failure, whichever one it may be, the windshield is still able to sustain the maximum differential pressure. However, because the pilot is unable to accurately determine how many plies have failed, the differential pressure must be reduced to 5 PSI by applying the following procedure :

MAX FL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230

The maximum flight level is restricted to FL230 to obtain DELTAP 5 PSI, without resulting in an excessive cabin altitude and corresponding EXCESS CAB ALT warning.
The following procedure, allows maintaining DELTAP 5 PSI in manual cabin pressure mode.
– CAB PRESS MODE SEL . . . . . . . . . . ...... . . . . . . . .. . . . . . . . . . . MAN
– MAN V/S CTL . . . . . . . . . . . . . .. . . . . ..... . . . . . . . . . . . . . .AS RQRD
Set the cabin altitude, according to the table below :
DELTAP = 5 PSI
FL 100 - CABIN 0
FL 150 - CABIN 3000
FL 200 - CABIN 6000
FL 230 - CABIN 8000

•When starting the final descent :
– CAB PRESS MODE SEL. . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . .AUTO

[parabellum]

"If damaged window deforms, or air leak is observed:"

And this is the decider, if it is an outer window and all else is normal just switch the window heat off, (electrical) and the air supplied window demisting on.

[spannersatKL]

Dont think you can switch the window heat off on an A340!! Oh and the CBs are down below!!!!

Some time ago with the same aircraft type I was involved in observing an in flight return for a cracked windscreen.......lots of arcing and smoke on the outsde as it came on the bay!!!! Not recommended.....

[zone]

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

[CEJM]

A330/A340 QRH Drill.

-MAX FL......................230
-CAB PRESS MODE SEL...MAN
-MAN V/S CTL..............AS RQRD (Delta P 5 PSI or lower)

When starting final descent:
-CAB PRESS MODE SEL...AUTO

[Caudillo]

F4F - as the aircraft was airborne, the mel is inapplicable, but not irrelevant. Could still contain information that would be useful.

[Dream Land]

Well let's see, the MEL is for dispatch, you planning to dispatch with a cracked windshield?

[BOAC]

Dreamer - what Caudillo is saying is that good airmanship says you look at the MEL if time permits. You do, don't you?

[CONF iture]

Originally Posted by spannersatKL

Dont think you can switch the window heat off on an A340!! Oh and the CBs are down below!!!!
Some time ago with the same aircraft type I was involved in observing an in flight return for a cracked windscreen.......lots of arcing and smoke on the outsde as it came on the bay!!!! Not recommended.....

Actually, they are not called CB but Computer Reset Button, there is one per side, and are located on the over head panel.

Regarding the Airbus procedure, if the problem is limited to a cracked windshield, there won't be any associated ECAM Message, pilots will go straight to the Quick Reference Handbook, then they can find more information in their FCOM 3, and it doesn't hurt if they open the MEL especially if they have 10 more hours to go.

The limitation is on the differential pressure, but there is no restriction to proceed to destination ... if fuel permits !

[BYALPHAINDIA]

True the MEL is irrelevant once Airborne.

[GlueBall]

Yawn.

This thread is a wind up.

[wings1011]

dispatch with cracked window

That is perfectly leagle depending of what is mentioned in the MEL and ofcourse depending of the magnitude of the crack etc, that will be determined by the engineers or in some cases with photon taken and sent to manufactor of the aircraft and they could potentionally make a release to service or release for ferry flight to homebase etc all depending of the situation. But ofcourse at most cases the release to service will be without windowheating and that could be the same as ground the aircraft depending of the weathercondition during flight since no known ice condition is allowed.
And in most cases also the max allowed spd of the aircraft will be affected. This procedure have been used many times to be able to get an aircraft back to homebase for window replacement if it is difficult to perform the repair at the outstation.
But at this specific event it happened in FLT and then it depends of what conditions are related to that aircraft and how serious of a crack the commander thinks it is and decides from there and what kind of weather is expecting during FLT and at destination.

Regards

1011

[Storminnorm]

I'm cracking up!

The old adage used to be "Outer pane! Outta trouble!"
250 kts restriction below 10k feet.
I once took a DC 8 outer MIDDLE pane down to NBO.
Got all the way down there and found that it was
the Capt's outer that was cracked.
Nice steady flight back after a night stop and a few
Tuskers!