QF670 ADl\MEL Depressurisation descent

[Bandit]

Reports in this morning that QF670 a Boeing 734 ADL to MEL had to do a rapid controlled 26,000ft descent due to depressurisation. Oxygen masks auto deployed. 99 pax onboard. Aircraft landed safely at YMML. All reported safe.

See article in SMH ]

[Gurdy]

Yea, News.com.au are reporting it as Qantas jet plunged 20000 feet .. sensationalism at its best.

[alan2]

Poor old Qantas, nobody hurt by the sound of things.  They still have my confidence . We'll get the real story later on no doubt .

[John Dow]

Breaking News from a typical Murdoch rag:

  A Qantas 767 plane with nearly a thousand terrified passengers tumbled out of control as the pilot wrestled with the aircraft systems which threatened to bring down the plane and result in Australia'a worst ever aviation crash.  Bill Morsley, a businessman from a media organisation and a self-confessed expert on aviation matters told our junior aviation reporter, Chenelle, that he was terrified for his life as the oxygen masks tumbled from panels in the ceiling and the front of the aircraft pointed down at a terrifying angle.  "I know when an aircraft is in danger" said Mr Morsley, "and this was definitely a time when I and the other passengers were fearing for our lives".  Other passengers reported that the aircraft was in danger of tumbling uncontrollably out of the sky and the wings were shaking, particularly out near the wingtips.  "It was obvious to us in the back of the plane that the pilot was having real trouble keeping the plane under control" said Gwendolyn Smyythe, a pensioner from Hervey Bay.

A spokesperson for Qantas confirmed that a depressurisation event had occurred on the aircraft which plunged 26,000 feet in a matter of minutes.  Engineers, some with identity tags obscured, were seen to enter the aircraft after the last of the sobbing terrified passengers escaped through the emergency airbridge linking the stricken aircraft to the passenger terminal, where it's possible to buy Chanel perfume and other duty free goods at the GoinAway Duty Free store at prices up to 60% off retail.

In scenes reminiscent of the JFK assassination cover-up and unanswered questions about the 9/11 attack. a spokesperson from the Australian Civil Aviation Safety Authority was less than keen to answer our reporter's probing questions on the cause of this near catastrophe and skulked behind a typically bland bureaucratic response to our question: "When is the catastrophic state of Australian aviation going to be fixed once and for all so that the flying public can feel confident and safe in the knowledge that tragic and avoidable events such as we have witnessed today will not continue to stalk the travelling public?"  Her inadequate response was evasive as usual:  "The results of the engineers report will be made available however we believe that a compressor bleed valve may have failed leading to a gradual loss of pressure in the cabin".  Well, for this reporter that's hardly a suitable response, pick up a copy of this newspaper for the rest of the week to see what our independent and probing investigation reveals.

[Gurdy]

LOL ... I wondered who the news.com.au reporter was!!

[Martin Henare]

I know many of you are going to play it down and say that the media are overstating the seriousness with over sensationalized statements. While that part is true consider these pieces of information next time you are sitting at 36'000ft.

At 36'000ft your time of useful consciousness is 30 to 60 seconds, thats just not for you the passenger that is also for the Pilots and cabin crew. What this means is if the pilot does not react swiftly enough he could initially start to be affected by Hypoxia which will affect his decisions and will ultimately fall unconscious. And thats just the pilots.

At 40'000ft which many airliners fly at now your time of useful consciousness is 15 - 20 seconds. Feeling a little more less sensational now?

The type of depresurisation will have an impact on the reaction and performance of the crew. Slow and gradual depressurisations are more dangerous than fast rapid ones because they creep up on the crew and if they are not watching their Cabin Altitude indication they will already be at 10'000ft cabin altitude before they even realize anything is wrong. Cockpit warnings do not trigger until Cabin Alt is 10'000ft. Hypoxia will start to affect people above this altitude. The Passenger masks automatically drop at 15'000ft.

Hypoxia is one of the most deadly things a flight crew can encounter in their flying career and many many many pilots have misjudged the importance of understanding the danger and the physiological effects it can have before you even know anything is wrong.

There have been a number of well known Depressurisation events in recent times.

The Payne Stewart accident is well know where a rapid depressurisation killed all on board and the aircraft flew across the US until it ran out of fuel and crashed into a field.

Then there was the the now infamous Helios Accident.

During overnight maintenance and engineer was working on the cabin pressure system and left the Outflow Valve selector panel in Manual mode. The Outflow Valve works like a plug and controls the pressurisation by opening and closing during flight. It is normally kept in Auto menaing the Cabin Pressure system automatically controls the valve from take off to landing with no action required by the crew.

The Flight crew carried out their preflight checks but missed the switch being in the Manual Position (this panel is just above the FO's head beflow the Airconditioning systems controls which they do interact with in flight.)

The took off and when passing 10'000ft they got a warning horn (which Boeing also use as a Take Off warning horn, but in flight it ONLY sounds if the cabin altitude reaches 10'000ft) The crew became confused and started looking for configuration of flaps, brakes and trim (for takeoff warning issues... err guys you have already taken off) Critically they did not stop the climb and level off. As the aicraft continued past 15'000ft they got two warning lights at once one was an equipment cooling failure (due to low cooling airflow because of the unpressurised state) and the second critcally was that the Passenger Masks had deployed. But now it was too late and the outcome was set in stone as the crew began to suffer Hypoxia and their judgement failed and ultimately the fell unconscious simply because they never put their oxygen masks on.

The Aircraft kept flying on the autopilot to its destination when it then put itself into a holding pattern until it ran out of fuel and crashed into a hillside. On flight reportedly made it into the cockpit but he did not know what to do even tough he had some flying experience and he would have also been suffering badly from hypoxia too.

Everyone was killed and autopsies showed some people were infact still alive when it crashed but they would have suffered major brain damage due to the loss of oxygen.

Because the Crew (I say this because the crew are responsible for configuring the aircraft systems before flight regardless of what anyone else has done previously) left the Out Flow Valve switch in manual it never closed as in this mode the pilots must use another switch to close the valve after takeoff it then manage the cabin pressure. Being left open meant the Airconditioning Packs pumping air into the airframe was simply just leaking out the OFV so the cabin altitude stayed equalised with the outside ambient altitude.

Plunge, Controlled descent, great piloting skills call it what you may, but never never never underestimate how dangerous depressurisation and hypoxia is. If you see the mask don't hesitate for one second get it on and get it on fast!

Finally from personal experience i can assure you the Pilots and Cabin crew will have been shaken up badly by this event, I have personally seen the effects once the adrenaline has worn off after landing.