This can also be found here on our Avidyne Live site.
So far my posts have been very high level, so I want to dive
in a bit deeper on a topic that highlights the advantage of the R9
architecture. First, let me provide some definitions that will make it
easier to talk through the example. Admittedly, this is a very
Avidyne-centric view of how the technology has progressed, but then again this
is an Avidyne blog!
Definitions:
Gen 1: this refers to the first generation of
architecture that led to the Avidyne Entegra PFD and MFD that integrates with 3rd-party
navigation / communication systems and autopilot systems. In 2003 these
systems provided a level of flight instrument integration that was only found
on the highest end jet-class avionics systems. The systems were
integrated using point-to-point interfaces that either restricted the flow of
data or created a high level of engineering overhead to control or monitor
these other systems. Also, the PFD and MFD were built on different
hardware and software systems that narrowed the features available on each
component.
Gen 2: this refers to the architecture that was brought to
market with the G1000 in 2005. It provided a higher level of integration
with the navigation / communication systems, and it also allowed for shared
functionality between the PFD and MFD components. A digital autopilot was
later added to the G1000 and provided a higher level of integration than found
on Gen 1 systems. This integration did provide an increase in system
functionality but was still predominantly based on a point-to-point, federated
architecture.
Gen 3: this refers to the architecture in the Entegra R9
system. Every component of the R9 system is connected to a passive, peer-to
-peer databus that is based on the byteflight
communication protocol. Byteflight was developed by BMW to manage safety-critical
systems that needed deterministic protocols with fault-tolerant behavior.
With every component of the R9 system on the databus, we have the
infrastructure to monitor or control every component of the system. The
R9 software is architected using the ARINC 653
protocol that separates the various functions like PFD, MFD, and FMS into
separate partitions. This allows each function to run independently and
avoids the situation where an MFD or FMS software failure could take down the
PFD functionality. This type of architecture has been adopted by
Honeywell and Rockwell Collins on their latest avionics platforms.
Analysis of an LCD Failure
The failure of an LCD (Liquid Crystal Display) is one of the most common failure
modes experienced in Gen 1 and Gen 2 avionics. Here is how a pilot would
have to react to an LCD failure of the left box (the primary flight display).
Gen 1: A failure of the LCD on the PFD would result in a
loss of the primary flight instruments with no choice but to use the backup
instruments for attitude, airspeed and altitude indications. The
GPS/Nav/Com 1&2 systems, MFD with engine, map, Wx and traffic and the
Autopilot would still be operational.
Gen 2: A failure of the LCD on the PFD would require the
pilot to press the red button to put the system into
“reversionary mode”. In this configuration, the MFD goes into a
specific configuration that shows critical flight information, engine data and
a small map with Wx and traffic displays. This is a large improvement
over a Gen 1 system, where the pilot would then have to fly off of the backup
instruments. While this is an improvement, a significant amount of the
system’s flexibility and functionality is lost in ”reversionary mode” and the
user interface is different than the normal mode of operation.
Gen 3: In the Entegra R9 system a failure of either the left
or right LCD results in only small changes to the information that can be
accessed throughout the entire system with no change in the user interface.
The left box will not be able to display anything, but all of the components
remain operational and available because they are on the byteflight
databus. The right box has the ability
to show the flight-critical, PFD data and provide full access to all of the
other screens that a user is accustomed to using during normal operation.
We believe this has the obvious advantage of increased functionality but also the
advantage of user familiarity in a failure situation.
The Entegra R9 system was
designed around the lessons learned from previous generations of avionics. The loss of an LCD screen is the most common
failure mode and we wanted this to have minimal impact on the pilot during a
potentially stressful time. This is just one tangible example of how this
third-generation architecture improves the safety, simplicity and utility of
flying general aviation aircraft.
Patrick Herguth
COO, Avidyne Corp
Posted
19 Oct 2009 9:03
by
Patrick Herguth