"Neil Gould" wrote in message
et...
Yesterday, I attended a 4-hour seminar on the G1000 presented by Charlie
Masters (Cessna/FITS & Sporty's @ Clermont County). The focus was on
providing an overview of transitioning from steam gauges to glass panels
as implemented in new Cessna single-engine aircraft. Charlie did a great
job, and has good general knowledge of the system. Overall, I am quite
impressed with the thought behind this unit, and think it will be the way
of things to come.

Of course, in addition to the general information, I was curious about the
possible causes for NW_Pilot's experience during the ferrying of a 172,
and asked a couple of questions that might have provided some insights. I
believe that I have some clues, but I'm still at a loss to explain some of
what he went through.

There are many things to understand about the G1000 installation, perhaps
foremost is that this is not a single box that is located in the panel.
There are more than a half dozen modules (not including the sensors), some
located in the tail of the plane, some located behind the panel. These
have specific functions, for example the Attitude/Heading Reference System
(AHRS) provides attitude and directional information to the virtual AI &
HSI separately from the Integrated Avionics (GIA) that provides GPS/NAV &
Comm functions. Other modules include the Engine/Airframe (GEA) unit, Data
Link (GDL), and audio panel. The modules are on separate breakers in the
panel.

The significance of this kind of modularity is that the failure of any of
these modules will not cause an overall system failure. I also asked
Charlie about the connections between these modules and the monitor. There
is a single multi-conductor cable connection to the back of the monitor
panels. The entire system is fed power from a connection to the master
switch (there is also a backup battery that can operate the unit
separately from master power). So, the total failure is unlikely to have
been caused by sensors, monitors or modules, as all of those would have to
not only fail simultaneously, but would have to reinstate themselves to
"come up" after a reboot, which is highly unlikely. Even a problem with
the multi-conductor cable would only affect one of the two monitor panels.

All of this confirms my original suspicion that for the entire system to
periodically spontaneously reboot, the cause is likely to be an
intermittent power connection. In such a case, all of the modules would go
down, and the process would emulate the POH procedure for intentionally
rebooting the system.

Neil


Neil,
You could be correct. A bad power connection or poorly regulated power
could cause big problems. But the G1000 has an internal battery pack that is
supposed to provide graceful transition with bad power inputs. Accordingly,
I would not rule out a latent software problem. After reading NW_Pilot's
postings, I was thinking that the original fuel quantity display problems
might have caused some sort of over or under-range internal calculation
error. Since my day job involves integrating hardware and software in large
million-line control systems, this is one of the first things that came to
mind. It is exceedingly difficult to test hardware and software in complex
systems at the possible extremes to guarantee proper operation.

I sure hope that Garmin reads these types of newsgroup postings and
investigates. Invalid or over inputs on one or more sensors should not have
radical effects on unrelated operational modes of the G1000. But it
certainly looked like it was happening to NW_Pilot.

Regards,
John Severyn