Out of respect to the families who lost loved ones, I dont want to speculate and weather may have been the most significant contributing factor to this disaster, however a review of several airline pilot message boards and forums shows us that the pilots who fly the Airbus A330 are very concerned about the ADIRUs and specifically the lack of any software redundancy: Below is a sample of these comments.
Please understand these are on-line comments are between pilots and give a good insight to the cause or causes of this accident however the are not FACT and only speculation at this time:
In light of no other information, this really spooks me that its an ADIRU issue which brought this plane down. I agree. After the QF lucky break and others, I have feared there is a core problem with the Airbus software that is a catastrophic accident waiting to happen. You just have to wait, and it will happen.
The ASI works on airflow from ahead. The altimeter works on barometric pressure. The compass works on magnetic attraction, sometimes with added gyros. The turn and bank usually works on a simple pendulum arrangement .
Inertial navigation works on differential airflows from numerous directions its a true breakthrough in that it can precisely and continuously record and display an aeroplanes true flightpath and speed.
That is NOT "inertial" navigation as I know it. Inertial navigation does not use sensors or signals external to the unit itself. It computes its own position by measuring accelerations along three mutually orthogonal axes using accelerometers mounted on a gyro stabilized platform. The signal is integrated once to render a velocity output and a second time to yield a position signal. The integration process is pron to drift as any noise present in the signal is added along with the actual signal. The electrical drift along with the tendency for gyros that establish the reference plane to drift requires that the system be periodically tweaked using an external reference (GPS or celestial sightings) to minimize accumulating error. GtG
From 02:11 to 02:13, multiple faults regarding ADIRU (Air Data and Inertial Reference Unit) and ISIS (Integrated Standby Instruments System) were reported. Then on 02:13 the system reported failures of PRIM 1, the primary flight control computers that receive inputs from the ADIRU and SEC 1 (secondary flight control computers). The last message at 02:14 was a Cabin vertical speed advisory.
The points being made on here are that there have been three recent cases (all A330s) in which the ADIRUs have suddenly started transmitting rogue messages to the autopilot (usually that the aircraft is climbing or descending when its not). Throwing the aeroplane into sudden sharp descents or climbs.
Since that AD was issued, it has been reported that the OFF light did not illuminate in the cockpit after setting the IR and ADR pushbuttons to OFF. Investigation has determined that the ADIRU was indeed sometimes affected by another failure condition.
To prevent such a failure, the operational procedure has been updated to instruct the flight crew to de-energize the ADIRU if the OFF light is not illuminated after setting the IR and ADR pushbuttons to OFF. Consequently, AD 2008-0225-E, which superseded AD 2008-0203-E, required accomplishment of the updated AFM operational procedure.
Since this second AD was issued, a new in service event has been reported highlighting that, in some failure cases, even though the OFF light illuminates in the cockpit after setting the IR and ADR pushbuttons to OFF, the IR could keep providing erroneous data to other systems.
In order to address all identified failure cases, de-energizing the affected ADIRU must be done by setting the IR mode rotary selector to OFF. Consequently, this AD, which supersedes AD 2008-0225-E, requires accomplishment of the updated AFM operational procedure.
So three Emergency Airworthiness Directives in the space of a few months and no sort of permanent solution yet.
Regards,
GtG
INERTIAL NAVIGATION DOES NOT WORK ON AIRFLOWS. IT WORKS ON ACCELERATIONS! ACCELERATIONS ARE INTEGRATED (CALCULUS) TO PRODUCE VELOCITIES, AND VELOCITIES ARE INTEGRATED PRODUCE POSITIONS. IT WORKS JUST THE SAME IN SUBMERGED SUBMARINES, AIRCRAFT AND SPACECRAFT!
Thanks for the post.
It appears almost certainly to me that ADIRU failure is the cause (GIGO). The Air Data and Inertial Reference Unit merges input data: airspeed data from the pitots, directional info from the DGs, and yaw, pitch and bank data from other gyros etc. There are 3 ADIRUs for redundancy.
Here's the crux: the units are failure-prone. There have been three Emergency ADs issued on the ADIRU in the last few months. This is very startling in view of the importance of the component in a flight critical system. I am surprised the fleet wasn't grounded until the ADs were addressed - emergency ADs are very serious.
The other surprising thing to me is that apparently the FCS does not automatically isolate a bad ADIRU so it can't confuse the other channels -- it is up to the pilot to turn off a bad unit manually!