QF 72 Diverted to Learmonth

[Rhys Xanthis]

Originally Posted by damien b

I would imagine that Airbus would be involved in this investigation very closely.

They are receiving updates and helping out with the investigation. An Airbus representative has been sent to Australia to assist.

[Philip Argy]

Originally Posted by damien b

Agree with Nigel on the Physics and g forces being felt by the passengers. They would have hit the ceiling on the pitch down movement, whilst when the aircraft pitched up - depending on the g loading they may have been pushed back into their seats for a brief moment.

I need to articulate my analysis in a little more detail to see if it makes a difference to yours and Nigel's responses. Imagine that you were in a lift that suddenly accelerated downwards rapidly. You'd hit your head on the ceiling of the lift. If it then reversed direction just as suddenly, you'd be slammed into the floor.

Now think of the a/c as pivoting around the fulcrum of the wings like a see saw, so that in a sudden climb the displacement of the rear of the aircraft is like the suddenly descending lift - the inertia of the unrestrained mass of people and service carts will tend to make them rise in relation to the descending portion of the fuselage at that point.

The physics is complex but my thinking is that the aircraft was not climbing under power - this was an uncommanded climb during stable cruise, so the kind of acceleration forces that push you back in your seat on take off would not have been present when the sudden elevator displacement was initiated.

It may need a bit of a crash test dummy experient to see which forces take precedence. If the aircraft had no forward movement component, you would get the see saw analogy. My suspicion is that in level cruise the sudden movement had the same effect. I agree that under horizontal acceleration the physics would be different, as they would be if my see saw were on a platform that was undergoing additional acceleration forces. Then you need to study all the vectors to see how they work out.

With CAT, the sudden downward displacement of the fuselage is what makes unrestrained people contact the cabin ceiling - I'm positing the same effect in the aft of the cabin from a sudden pitch up during stable cruise.

In the second movement sequence recorded on the FDR the 8.4 degree pitch down and descent to my mind would have more likely created almost zero G for everyone on the a/c and that would not have resulted in the injuries being so concentrated in the aft section of the cabin.

Would love to get more views so let's hear what others think.

[Edward Terry]

Take for example the abrupt transition to the downward attitude, which was responsible for the zero-g forces passengers experienced. Assuming the aircraft's power setting was constant, the tangential accleration is negligible compared to its centripetal acceleration. This one acts towards the centre of the circle whose radius is given by the arc traced out by the aircraft as it changes attitude. The appropriate formula for centripetal acceleration is F = mv²/r, so the sharper the attitude change, the tighter the radius of the circle and hence the greater the force. By this logic, these forces would push people up-down but not forwards-backwards.

[Nigel C]

Phillip,
I understand what you're trying to say, however I don't see it as practically feasible.
If the aircraft pitched as sharply and as violently as you're suggesting to create the effect you're describing, then surely that would put the aircraft into a high speed stall. With the existing airspeed plus the thrust being generated during cruise at that time plus a sudden nose-high attitude, surely the aircraft would have gained more than 200ft on the initial climb.

I notice Brenden sent you the chuck movie I mentioned via email. You can clearly see the way the aircraft is going by the scenery below.

Does that help you understand the G loadings a little better?

[Philip Argy]

Yes - I saw Brenden's graphic movie and cetainly understand the alternative scenario. The only aspect of the incident that doesn't gel with what you are putting to me is the fact that the serious injuries and cabin ceiling penetration were apparently confined to the aft section of the rear cabin rather than randomly across all parts of the cabin.

If you could help me understand what would cause that focal point on your theory that would assist me. Maybe it's just the natural place for the majority of unrestrained people to congregate waiting for the toilet etc and my assumption that it reflects the forces at work is wrong.

[Nigel C]

Perhaps you've answered your own question?

Maybe it's just the natural place for the majority of unrestrained people to congregate waiting for the toilet etc

I don't know the layout of the A330's, but perhaps the loos are at the back.

[damien b]

Originally Posted by Philip Argy

Yes - I saw Brenden's graphic movie and cetainly understand the alternative scenario. The only aspect of the incident that doesn't gel with what you are putting to me is the fact that the serious injuries and cabin ceiling penetration were apparently confined to the aft section of the rear cabin rather than randomly across all parts of the cabin.

If you could help me understand what would cause that focal point on your theory that would assist me. Maybe it's just the natural place for the majority of unrestrained people to congregate waiting for the toilet etc and my assumption that it reflects the forces at work is wrong.

Along with the last bit mentioned, the injuries would have been confined to the back as the g forces (negative) would have been the greatest at that point. As the aircraft has transitioned from the climb to a dive the forward pax would have experianced something i am guessing to be around normal g forces whilst the pax at the rear would have experianced negative g's as the tail stopped moving up and followed the nose of the aircraft.

8.4 degrees nose down is not significant by itself. I think its the manner that the elevators have moved abrubtly from one directon to another that has induced the neagtive g forces onto the pax, particularly at the rear of the aircraft.

Happy to be corrected.

[Philip Argy]

This eyewitness account from The Australian throws a bit more light on the situation:

RETURNING home after visiting his fiancee in Singapore, Tim Ellett found flight QF72 from Changi to Perth began like the 12 other trips he had taken before.
The Airbus A330-300 jet that carried Mr Ellett and the 302 other passengers is one of the most technologically advanced planes in the world. It is also reputed to be one of the safest.
But three hours after takeoff, the jet plunged 650ft, injuring 50 passengers, some seriously. And it has now emerged that the calamity has striking similarities with two previous incidents, including an emergency involving a Singapore Airlines flight in 1996.
In these cases, questions were raised about the design of the A330's cockpit, including whether it could lead to both pilots, instead of just one, inadvertently overcorrecting the plane, resulting in the plane's computers recording a double input.
Settling in for the four-hour flight, Mr Ellett, 22, watched a movie and kept track of the trip via the flight path map on his television screen. The woman passenger next to him slept.
When the plane was only about an hour away from Perth, the journey turned into an extraordinary experience.

The jet was soaring over the Indian Ocean, 110 nautical miles north of Carnarvon on Western Australia's north coast, when it suddenly and inexplicably climbed 200ft.
This slight rise from the jet's 37,000ft altitude went unnoticed by many of the passengers and crew, but aviation experts believe moves would have been under way in the cockpit to discover why the aircraft had risen.
The plane returned to cruise normally, but about a minute later, passengers were suddenly hurled up to the cabin ceiling as the plane plunged 650ft in 20seconds. As bruised and battered passengers, many crying and screaming, clambered back to their seats, the jet levelled out and returned to cruising at 37,000ft. But 70 seconds later, the jet dropped another 400ft for 16seconds, creating havoc.

The plane then made an emergency landing at Learmonth airport, near Exmouth.

It appears that the initial climb to FL372 and the return to FL370 went almost unnoticed by pax. So that debunks my theory about that inital sequence causing pax to be injured.

It then appears that the main injuries were caused by the second movement sequence, being the 8.4 degree pitch down and 650 ft descent and return to FL370, followed by the third movement sequence of another pitch down, descent to FL366, and return to FL370. That would support Nick and Damien's theory.

I think the aggregated pilot input issue was the subject of an episode of Air Crash Investigation but I thought I read somewhere that Airbus had changed the software to give priority to the left hand joy stick if both joysticks were in active use. Does anyone here know more about that?

[Bill S]

Originally Posted by Philip Argy

I think the aggregated pilot input issue was the subject of an episode of Air Crash Investigation but I thought I read somewhere that Airbus had changed the software to give priority to the left hand joy stick if both joysticks were in active use. Does anyone here know more about that?

No, they average/total the two stick positions, eg, if you literally push one stick all the way forwards and the other all the way back nothing will happen to the flight path of the plane - But you do get an aural & visual warning that you have dual control inputs.
One pilot can take full control by pushing & holding the red button down on their stick and about 1.5 seconds later that stick is the only one controlling the plane. An aural advisory "prority left/right" comes up when that happens.
There's ways to regain dual control but I can't remember the details sorry.

Apparently the reason the sticks aren't mechanically connected is because Airbus was worried that if one pilot fell unconcious on their stick the other pilot would not be able to control the plane adequately. However I still think this is perhaps one of the most daft things I've ever seen on a plane.

[Philip Argy]

Does it mean that A330 aircrew would be more likely convert to A380 than B744 aircrew presumably due to the ease of type upgrading?

I'm not a pilot but I know there are strong views held by Boeing afficianados about the "unconventional" sidestick system that Airbus uses.