On the seventh of October 2008,
a Qantas plane flying from Singapore to Perth
declared a MAYDAY to air traffic control.
When it made an emergency landing
at a small airport on the West Australian coast,
it had onboard
more than a hundred injured passengers and crew.
They had broken bones, lacerations and spinal injuries,
while compartment doors had been ripped from hinges
and passengers' belongings were strewn throughout the cabin.
Less than an hour earlier,
passengers with and without their seatbelts on
had impacted the cabin ceiling
when the plane had twice dropped several hundred feet
without warning.
“A sudden loss of height,
the plane being thrown around in the air
and the screams of those around you.”
For Qantas -
which boasted an unparalleled flight safety record -
this was completely out of the ordinary.
The media was quick to blame the accident
on clear-air turbulence,
but what really happened to the plane
was something far more disturbing.
QF72 was an Airbus A330 plane
that was just one hour and a half from its destination
when all hell broke loose.
The flight’s captain, Kevin Sullivan,
was a former US Navy fighter pilot -
at the time of the accident he had
over 13 thousand flying hours in his logbook.
When I returned to the flight deck,
I knew that we were flying at 37 000 feet.
The body angle was 2 degrees above the horizon.
The flight control computers, however,
thought we were flying at 50 degrees body angle
and overspeeding at the same time.
Now we know that’s pretty impossible.
It says that’s where we’re flying -
we’re flying like this -
“I must protect the airplane”.
So it pitched the nose down.
It went from plus 2 to minus 8.4
in less than a second.
Look what the tail’s doing.
If you’re back there,
you’re going to feel the force.
What Captain Sullivan was coming up against
was a change in how airplanes have been made
in the last thirty years.
Traditional jumbo jets -
such as the Boeing 747 -
are controlled by the pilot
through mechanical connections to the hydraulic systems
which move the flight control surfaces -
that is, the rudder,
the elevator and the ailerons.
But the Airbus A330
is what’s known as a fly-by-wire system,
where there is no such manual control.
Instead, the pilot’s controls make requests of a computer,
which sends electronic signals
in order to move the flight controls.
Fly-by-wire planes are lighter and more fuel-efficient.
They’re also capable of executing
faster and more precise movements than humans,
and they reduce the chance of pilot error
by preventing the plane from exceeding certain limits,
known as the flight envelope.
It is the flight computer’s protection modes
that prevent the aircraft from exceeding the flight envelope -
and when they became active,
they blocked Captain Sullivan’s attempts
to stop the computer’s command.
It’s like 2001: A Space Odyssey.
“HAL, open the pod bay doors.”
“I’m sorry Dave, I can’t let you do that.”
I’m saying, “Don’t push the airplane down”.
I’m pulling back on the stick.
The computers are saying, “I’m sorry Kev,
I’m not going to let you do that”.
But the fact is that fly-by-wire planes
have actually made air travel much safer.
In the past decade,
the number of commercial passenger flights has surged,
while the number of fatalities in plane accidents has fallen.
But in the case of flight QF72,
the manufacturer’s design prevented the pilot
from overriding the computer’s control.
In the A330 course,
you’re taught you must interact:
you can interact with the plane.
It’s great and when it works, it’s great.
But when it doesn’t work,
you’re in the dark.
An investigation by the Australian Transport Safety Bureau
found that one air data computer
was sending incorrect body-angle and speed information
to the three primary flight control computers -
which reacted to the data
by forcing the plane to pitch down.
The flight maintenance log revealed
that 10 simultaneous faults
had occurred during the accident -
and most of these had been hidden from the pilots.
The hierarchy of this particular airplane
is that the computer is number one
and the pilot is number two.
If they, for example, decide that
you’re overspeeding and stalling
and they’re going to protect you -
there’s no right to veto that.
But for Captain Sullivan,
there is a bigger question left to be answered
and it’s not just about the computers onboard flight QF72.
As we start to trust computers with delivering our goods
and even driving our cars -
just what level of control
should we keep for ourselves?
I’ve never even -
in all the extreme flying I did in the military -
did I ever say to myself:
“Hey, you’re in trouble”.
Those are very profound words for a pilot
to admit to himself, as I did,
and saying, “Yeah, I’m in a knifefight with this airplane
and only one person is going to win
or one computer is going to win”.