YRP:
Let's be serious here. Accidents are not investigated by the court of public opinion. Does anyone here know whether the ACARs messages are transmitted reliably, or lossy? What is the transmit order, same as events, or based on priorities? How does the timestamping work? Specifically what messages does Air France enable/disable? What about messages that have _not_ been reported (eg excess cabin altitude)? Would there have been one, or is there no message for that event?
Precisely.
BOAC:
Thanks - you're right.
AJ:
Here's a description of the ADIRS:
The Air Data and Inertial Reference System (ADIRS) supplies temperature, anemometric barometric and inertial parameters to the EFIS system(PFD and ND) and to other user systems (FMGC, FADEC, PRIM, SEC, FWC, SFCC, ATC, GPWS, CMC, CPC).
The system is comprised of:
– three identical ADIRU's (Air Data and Inertial Reference Units). Each ADIRU is divided in two parts, either of which can work separately in case of failure in the other :
• the ADR (Air Data Reference) part which supplies barometric altitude, speed, Mach, angle of attack, temperature and overspeed warnings.
• the IR (Inertial Reference) part which supplies attitude, flight path vector, track, heading, accelerations, angular rates, ground speed, vertical speed and aircraft position.
The ADIRU gives the true heading instead of magnetic heading :
– above 82° North
– above 73° North between 90° and 120° West (magnetic polar region)
- above 60° South
– one ADIRS control panel located on the overhead panel for modes selection (NAV, ATT, OFF) and failure indications.
– 2 GPS receivers, which are connected to the IR part of the ADIRU's for GP/IR hybrid position calculation.
– four types of sensors :
• pitot probes (3)
• static pressure probes (STAT) (6)
• angle of attack sensors (AOA) (3)
• total air temperature probes (TAT) (2)
These sensors are electrically heated to prevent from icing up.
– eight ADMs (Air Data Modules) which convert pneumatic data from pitot and static probes into numerical data for the ADIRUs.
– a switching capability for selecting ADR3 or IR3 for instrument displays in case of ADIRU 1 or 2 failure.
– a MAG / TRUE pushbutton switch, used during polar navigation.
– AC BUS provides to normal electrical supply. DC BUS provides a back up possibility through an inverter.
Hope this helps!