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Full Duplex (AFDX) switched ethernet avionics network16.
A380 operators will be able to choose to add a third server attached to the network through a
secure router. The operator can then host its own applications and modify them at will as long
as configuration control is maintained. Applications such as weight and balance, troubleshooting
guides and wiring diagrams could be hosted.
15 From the Embraer 170/175 Aircraft Maintenance Manual.
16 Aviation Today, Virtual Data Acquisition, January 2004.
8
Boeing 787
Figure 9: Boeing 787 ‘Dreamliner’
The B787 will have a networked avionics
architecture and will be fitted with two
enhanced airborne flight recorders (EAFR’s).
Each EAFR will combine the functions of a
CVR and FDR giving system redundancy. A
separate flight data acquisition unit (FDAU)
will not be needed as a ‘virtual FDAU’ will be
distributed among other software and
hardware including the EAFR itself. This will
reduce the total weight as a separate line
replaceable unit for the FDAU will not be
needed.
3.2 Onboard avionics
Modern commercial airliners contain many avionics systems that record data in non-volatile
memory. Although not crash-protected, these sources of data can be very useful for accident or
incident investigations, particularly when FDR or QAR data is not available. The EGPWS17
computer is an example of a source of valuable data stored by onboard avionics equipment18.
3.3 ATC datalink message recording
Datalink messages such as CPDLC19 transmissions are required to be recorded. Originally the
ICAO requirement was only going to require recording of messages that affected the trajectory
of the aircraft but in practice it would have been difficult to separate these messages from other
messages. It is simpler to record all messages, however, this is not as straightforward as it
appears as enough information needs to be recorded so that investigators can know:
• the contents of a received message
• its priority
• the number of messages in the uplink/downlink queues
• the contents of a message generated by the crew
• the time each downlink message was generated
• the time any message was available for display to the crew
• the time any message was actually displayed to the crew.
While these datalink messages could be recorded on the FDR or CVR, in practice they will be
recorded on the CVR and retained for the duration of the CVR (typically 2 hours).
17 EGPWS: Enhanced Ground Proximity Warning System.
18 Refer to this case study for more information on EGPWS data:
http://www.asasi.org/papers/2005/Use%20of%20EGPWS.pdf
19 CPDLC: Controller-Pilot Data Link Communications.
9
Figure 10: Extract from ICAO Annex 6 Figure 11: Example presentation of a datalink
message on a cockpit MCDU20
3.4 ADS-B data
Mode S21 transponders are carried by large airliners. There are two types of Mode S –
elementary surveillance and enhanced surveillance. Enhanced Mode S has a datalink capability
that can be used in providing an air traffic management function. ADS-B22 is such a function
and uses Mode S as the datalink technology.
ADS-B data transmitted from a suitably equipped aircraft includes:
• time/date stamp
• flight number
• Mode S ID (unique 24 bit address for a particular aircraft)
• latitude and longitude
• actual pressure altitude
• selected altitude or flight level
• groundspeed
• track angle
• vertical rate
The update rate is approximately once per second. Mode S receivers that can decode ADS-B
data are commercially available. An example is the SBS-1 base station manufactured by
Kinetic Avionic Products Ltd of the UK. Figure 12 shows the receiver unit and aerial and
Figure 13 shows the pseudo-radar display produced by the base station software.
20 MCDU: Multi-function Control and Display Unit.
21 Mode S is a secondary surveillance radar (SSR) technique that allows selective interrogation of an aircraft using its
unique 24 bit address. This removes the risk of confusion due to overlapping signals.
22 ADS-B: Automatic Dependent Surveillance – Broadcast.
10
Figure 12: SBS-1 Receiver and antenna
Figure 13: Display of ADS-B tracks near Canberra
4. DATA RECOVERY
4.1 Wireless transmission of QAR data
The recording media for QAR’s has evolved as follows:
o magnetic tape cartridges
o magneto-optical disks
o solid-state (eg. PCMCIA23 cards or CF24 memory).
Traditionally the recording cartridge/disk needed to be removed from each aircraft on a regular
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