Karaganda (Kazakhstan) - Un avion de la compagnie aérienne chinoise de Hong Kong, Cathay Pacific Airlines a été contraint de se dérouter et de se poser en urgence sur l'aéroport régional de Karaganda (Kazakhstan) suite à une panne du système de pressurisation de l'appareil.

L'avion, un Boeing 747-400, vol CX270, qui effectuait la liaison entre l'aéroport international Schiphol de Amsterdam (Pays-Bas) et l'aéroport international Chek Lap Kok de Hong Kong (Chine) avec 306 passagers et 20 membres d'équipage à bord, était en vol depuis plusieurs heures lorsque les pilotes ont été alertés d'un problème technique sur le système de pressurisation de l'appareil. Les masques ont été déployés alors que les pilotes se déroutaient vers l'aéroport régional de Karaganda où ils se sont posés près de deux heures plus tard.



L'avion s'est posé sans autre incident et il n'y a pas eu de blessés. Les passagers ont dû attendre plus de quatre heures que les autorités kazakhes leur accordent une exemption de visa pour pouvoir quitter l'appareil et rejoindre le terminal. Un autre appareil a été envoyé au Kazakhstan afin de récupérer les passagers en souffrance. Une enquête va être ouverte par les autorités de l'aviation civile de Hong Kong.

Un vol de la compagnie aérienne hongkongaise Cathay Pacific avec à son bord 306 passagers a effectué lundi soir un atterrissage d'urgence au Kazakhstan, en raison d'un problème de pressurisation, a indiqué la compagnie mardi.
Le Boeing 747-400, qui effectuait la liaison Amsterdam-Hong Kong, a été dérouté vers l'aéroport de Karaganda, au Kazakhstan, six heures après avoir décollé, a précisé Cathay dans un communiqué.
Un appel de détresse a été envoyé à l'aéroport à l'approche de l'appareil, et personne n'a été blessé parmi les 306 passagers et 20 membres d'équipage. Ils ont repris un autre avion pour Hong Kong mardi.

Source AFP

Eh oui, on peut être une compagnie qui évolue parmi les meilleures,
avoir été élue meilleure compagnie du Monde, d'Asie et d'Asie du Sud-Est en 2009, posséder un flotte d'avions de 10 ans de moyenne d'âge et connaître des soucis techniques.
Comme quoi tout arrive, même aux meilleurs...

Avec une descente rapide? On sait quelque chose?

Je ne sais pas s'il y a effectivement eu "descente rapide" ... l'équipage a déclaré l'urgence en tout cas, et déployé les masques à oxygène dans la cabine.

Immat. de l'avion : B-HOP

Suite à cet incident, mais aussi à d'autres incidents du même type rencontrés précédemment, la compagnie Cathay Pacific aurait décidé de faire remplacer une valve d'évacuation vieillisssante sur toute sa flotte de Boeing 747.

pour vous qui lisez l'anglais, voici un copié-collé du South China Morning Post d'aujourd'hui.

The Cathay Pacific (SEHK: 0293) plane forced to divert to Kazakhstan on Monday after losing cabin pressure made another emergency landing two months ago after a mid-air crisis involving a malfunctioning valve.

On September 11, the 21-year-old Boeing 747-400 - the oldest of its kind in the Cathay fleet - was forced to jettison fuel and return to London's Heathrow Airport an hour after taking off for Hong Kong when the cockpit crew realised a valve in the cabin pressurisation system had failed.

The valve was replaced and the plane took off again without incident. It remained in service before being forced early on Monday to declare an emergency and divert to Karaganda in Kazakhstan six hours into a flight from Amsterdam to Hong Kong.

Oxygen masks were deployed to 306 passengers plus the crew as the plane navigated mountainous terrain before a normal landing in Karaganda, to where a replacement plane was flown from Hong Kong to collect the passengers and crew early yesterday.

The cause of Monday's incident was a malfunction in another valve in the plane's cabin pressurisation system. Cathay Pacific last night said the two incidents involved different valves at opposite ends of the plane and were totally unrelated.

However, engineers are to carry out checks on valves in the cabin pressurisation system on board another of its 22-strong fleet of 747-400 planes to see if there are any problems that need further investigation.

Christopher Gibbs, engineering director for Cathay, said the 747-400 was put back into service "within hours" of the Heathrow incident but said the incident was still under investigation at the time of Monday's incident.

"Obviously we can't launch actions until we know what is going on, so what we will do is remove another couple of valves [from another 747-400]," he said.

"We will then send them to our overhaul shop, and based on the findings, we will then take appropriate action."

The valve that failed in the Heathrow incident in September was an outflow valve in the tail of the aircraft. It regulates cabin pressure and is used throughout the flight.

The valve that failed on Monday was a pressure relief valve - a back-up device in the forward fuselage to help prevent the aircraft becoming over-pressurised.

Gibbs said: "These are completely different valves. They are even in different locations on the aircraft. Everything is different about them. So it is a coincidence that one has failed and then a different component has failed.

"With the one that resulted in the diversion to Kazakhstan, I have a very experienced team and my guys can never recall a similar incident. What is odd is that this valve usually just sits there so [a failure] is extremely rare.

"The pressure relief valve [involved in Monday's emergency] doesn't fail commonly and it is also rare but not as rare as [a failure in] the outflow valve."

Comparing the two valves, he said: "One basically sits there and only comes in in the case of an overpressure situation and the other is constantly being used. They are completely different. There are a lot of valves on an aircraft. It is always the case that we follow up on these cases very vigorously as fast as we can. We are doing exactly that."

An airline engineer flew to Kazakhstan on the Cathay plane sent to bring the stranded passengers home early yesterday. The Boeing 747-400 will have its valve replaced with the help of a local engineering team and is expected to fly back to Hong Kong within days.

Asked if the plane would return to service or be investigated further when it arrived back in Hong Kong, Gibbs said: "Once it's had this valve replaced it is fully airworthy.

"We understand people might associate these two events but they are totally different valves at opposite ends of the aircraft serving different purposes. In the case of the second one (Monday's incident), none of my guys recall anything similar."

"We investigate these things as quickly and thoroughly as we can and then take appropriate action. And if we do take action it will be well above the manufacturer's requirements."

Despite the drama surrounding Monday's emergency landing, Gibbs said the plane was at no point in any danger.

"At all times we are 100 per cent safe," he said. "The reason is that there are two back-up systems. First there are the passenger oxygen masks. Secondly the planes do descend.

"The planes are designed to accommodate just this situation and they can."

La vanne qui est tombée en panne ( et qui s'est sans doute ouverte intempestivement ) est une des 2 " pressure relief valve " situées à l' avant gauche de l' avion .Elle ne sert qu'en cas de surpression de la cabine , de façon à protéger la structure cabine d'un gonflement excessif et potentiellement destructeur.


A ne pas confondre avec les " outflow valves " situées à l' arrière de l' avion et qui ne font qu'ajuster le débit de sortie de l'air cabine de façon à monter, maintenir , ou descendre l' altitude cabine.




Pressure relief valve : 2 ronds situés sous le dernier hublot avant porte 2 gauche









Outflow valves : 2 vannes situées sous le fuselage tout à l' arrière. On voit la vanne gauche sous la dernière porte passagers .

Désolé , c'est en anglais et plutôt long à traduire ... extrait du bulletin syndical de Cathay .

C'est le " vécu" d'un des copilotes lors de cet incident



The departure from Amsterdam had been relatively uneventful, with a minor technical issue requiring the for-ward cargo door locks to be visually inspected before departure. I was Relief Pilot for the sector and typically was woken around the half way mark approaching Airway Y1. I took the Right seat at approximately 17:45Z with the Second Officer in the Left seat.
The handover briefing was straightforward apart from deterio-ration in the weather in Almaty and Urumqi, two of our En-Route Alter-nates (ERAs). Almaty had a visi-bility of 350m with RVR‟s down to 1100m while Urumqi was below landing minima. I busied myself by entering the escape routes into ROUTE 2, which also helped me wake up and get my head around the overall situation.
I discussed the Escape routes with the S/O and we agreed on a plan. The weather at Almaty and Urumqi being as they were, we agreed that until waypoint REVKI we would turn around and head back to Karaganda initially, as it was CA-VOK, then look at other European options should the situation arise. For those not familiar with the Y1 airway, the area around REVKI has a grid MORA of 28,200 ft with an MRA within 5 miles of track to the west of REVKI of 17,900 ft whilst east of REVKI the MRA is 22,500 ft then 24,600 ft.


The salient points were typed into the FREE TEXT page of the centre CDU as follows (The wind was less than 50 Kts):
REVKI TO UAKK
MRA 179 FL197/6000M
MORA 282



We called the Galley to order drinks - I ordered a coffee straight up to get me started - and requested some soup noodles to be delivered later, after we‟d passed the highest ground of the Y1 route, when it wasn‟t so busy. A little pedantic maybe but I‟d always thought it was one place I didn‟t really want a meal tray on my lap.
Approaching Urumqi Airspace we climbed to FL371/11300M.
Not long after I‟d sat down the Second Officer swapped with the F/O and I performed the standard brief, fin-ishing by discussing the plan for the Y1 escape routes. Although it was the same brief as I‟d given the S/O, it was good to have it reinforced as I was still waking up! I made sure the F/O was happy with the plan then asked him to check the numbers in the FREE TEXT to ensure they were correct.

The Coffee arrived, however so did the noodles - half an hour before the requested time, but I politely ac-cepted - what are the chances really? I made a start whilst they were hot.


The estimate for REVKI was 18:20Z. At 18:18Z, just as I picked up the Enroute Diversion Guide to discuss the plan after REVKI, we got a “PACK 2” EICAS Advisory message.


I put the escape route chart down and quickly placed the noodles on top of the fruit tray sitting on the 1st ob-servers seat. We began the standard checklist protocol, but with the cabin altitude initially climbing in excess of 3000 fpm I called for the Oxygen Masks to be donned. As we continued with the QRH checklist, the cabin rate of climb slowed to less then 500 fpm and eventually reduced to less then 300 fpm. We promptly ascer-tained that the Outflow Valves were indicating closed.


Without knowing what the actual problem was, we were attempting to reset the PACK as per the QRH before the ""CABIN ALTITUDE warning was triggered. Despite our efforts, and just as we were about to reset PACK 2, the “CABIN ALTITUDE” Warning appeared on the EICAS along with the appropriate Master warnings. We immediately performed an emergency descent to 28,200ft and commenced a left procedure turn. This in-cluded dropping the Passenger Oxygen masks and declaring a "MAYDAY". I didn‟t wind up the speed as we only had 10,000 feet to descend with 28,200 rapidly approaching. Note: the Passenger oxygen masks were dropped at 18:24Z according to the CMC, approximately 6 minutes after the PACK 2 Advisory.


We didn‟t have time to contemplate why the two remaining packs couldn‟t handle the pressurization, although the Forward Cargo door did cross our minds at some stage, but at this point we had no other indications of what the problem actually was. With the highest terrain of the route beneath us we weren‟t in a position to do any serious problem solving. Prior to reaching FL282 the cabin altitude stabilised below 10,000ft.


We now had a full complement of flight deck crew up front as both the Captain and S/O had been woken by the surging pressure and the chime of the PA. With the pressure stabilised we continued with the PACK 2 QRH checklist. The Captain, kneeling in the noodles that had fallen on the floor when we commenced the turn, was now assisting the F/O with this task whilst I concentrated on flying the aircraft.


At some stage during the return to track the PACK RST switch was pushed as per the checklist, I believe this coincided with the cabin altitude climbing above 10000ft again. Hence we performed a further rapid descent down to 6000M as we intercepted the reciprocal track to Europe and west of REVKI. By the time the aircraft was at 6000M the cabin altitude had again stabilised below 10,000 ft.
Importantly, from my perspective, in a busy cockpit with poor lighting and the oxygen mask on with a bit of dust, scratches or fogging, the FREE TEXT page was a comforting backup. Although I had a pretty clear idea of the numbers, it was difficult to read the green MORA numbers printed on the Enroute Diversion Guide.


In amongst all this we had built a route back towards Europe and we advised ATC of our intention to divert to Karaganda. We were working steadily - but not overloaded - it was nice to have 4 crew up front. At some stage the Captain briefed the passengers and the ISM, and as terrain permitted we descended to FL5400m.



We performed a quick fuel calculation to see if Moscow was an option, but fuel was insufficient at our current altitude, let alone 10,000 ft. We advised IOC of our intentions and asked if they had a better plan. They agreed with our decision to divert to Karaganda.
With the Captain in the LH seat and myself still Pilot Flying, the Captain ran the CLEAR model to ascertain if there was anything else we needed to consider.


Once in Almaty Airspace the diversion was fairly straightforward with vectors to long final for the ILS Runway 23 at Karaganda. We ordered some updated weather and one of the crew organised a Landing Data advi-sory for Karaganda. ATC at Karaganda were very helpful, asking us what services we required on arrival. The weather was indeed CAVOK for our arrival with a runway friction coefficient of 70%. Easy vectors to the ILS, on a clear night, rolling to the end of Runway 23 for a 180-degree turn at the turning node.

A follow me car was waiting on the taxiway to guide us to the parking position with drifting snow covering a lot of the taxi-way lines.
As soon as we shut down stairs were at the door with an interpreter, Security and Customs & Immigration. Engineering support was also provided.


As with most diversions the hard work started here. I won‟t go into details but the crew were great. Having an S/O who spoke Dutch helped calm some of the passengers as they disembarked into the cold Karaganda evening. The Captain, F/O and the Cabin Crew who went with the passengers to the terminal did an out-standing job.

Karaganda turned out to be a better option then it may have first sounded. A passenger recovery flight from Hong Kong could be turned around by one crew. Although the passengers arrived in Hong Kong about 24 hours later than scheduled, I believe most of those with connecting flights were able to connect to the same flight number a day later than planned.
It was now that we had time to find out what the actual problem was. Although I believe it wouldn‟t have changed our actions, the Upper Pressure Relief Valve had failed open, which automatically shuts down Pack 2. This was the reason that two packs couldn‟t maintain the pressurisation at high altitudes.


The LOFT exercise that started when we tried to depart after the pressure relief valve was replaced was a scenario that even the nastiest of Simulator Instructors would have had trouble thinking up. This earned us a few more days in the very pleasant Hotel Cosmonaut before finally coming home via Paris on the freighter, which brought in a replacement engine due to our failed No.2 Engine Oil pump.


Preparation:

Usually when I get in the seat I go through a mental Cabin Altitude/Rapid Depressurisation procedure to help me wake up and get the head working.

I review the Weather and NOTAMS for the ERA‟s, and then build the Escape Routes in Route 2. For me, this is not just an accepted convention or recommended best practice; it helps to get my head around where I am when I‟ve usually just woken up. It builds your situation awareness whilst your head may still be a little fuzzy.

I always discuss the plan with the other crewmember. I‟ll often ask them “What do you reckon?” This is so I don‟t just talk them into what I think and to ensure they are in the loop. Often they have thought of a consid-eration I‟ve missed, or their eyes are better and they have read the charts more clearly.

Once agreed on a plan I put a summary of the big numbers into the Centre CDU FREE TEXT page. Unlike using the scratch pad, you can use another page, make inputs and come back to the FREE TEXT and the information is still there. Every route segment is different, but I usually put in the applicable segment and diversion airport, the Highest GRID MORA, the Highest MRA, and maybe the ATC Level in Feet and Metres. As mentioned earlier the green numbers of the Grid MORA‟s aren‟t that easy to read through the Oxygen mask, especially if it scratched or fogs up. The FREE TEXT page is much easier to read when the heat is on. I always ensure the other pilot confirms the details entered are correct.


Usually coming back from Europe 3eng Drift down isn‟t the main threat, but it certainly is when going to Europe, as you are still heavy.
I flight follow the NOTAMS - my brain is not big enough to remember all the salient NOTAMS for a ULH - as a new ERA comes into consideration I like to have a quick review.

Incident similaire en Oct 2008 sur un MD 83 :

Rapport en allemand , mais il y a des photos !