NW_Pilot's Trans-Atlantic Flight -- All the scary details...

A few years ago, I remember reading an excellent book on general design of
modern avionics. In particular, one thing that I believe is different between
Garmin's baby and what they have in B-s and A-s is redundancy. The whole thing
there is doubled, and some critical components are tripled. And then there's
a whole body of software that takes care of voting-elimination among inputs.
By design, the event of the computer reboot (i.e. all three redundant computers
reboot) is perhaps as likely as the event of all four engines quitting at the
same time. What surprises me is that Garmin got FAA approval for such a system,
whereas it doesn't even come close to what "normal" glass cockpit is supposed
to be like in terms of robustness of system design. I understand it's all done
in the name of affordability, but this is clearly a dangerous game to play.

If you think about it, just to be able to claim any kind of "robustness",
you should be reasonably sure that there's no single failure that will take
the whole system out, right? And there we go: excessive fuel venting took
airspeed indicator out completely, and CO indication out completely. And this
is aside from any software bugs; this is the way G1000 is supposed to work
by design!

So, I guess my point is: you can't just take a steam-gauge-type airplane,
replace all the individual *independent* instrument systems with one
electronic box, and claim you've got an equally reliable plane. No way. By
tying everything together and establishing inter-system dependencies that
never existed before, you increase your likelihood of a catastrophic failure
by orders of magnitude. If you want to use an all-in-one instrument system,
you need to redesign the airplane and fit it with redundant systems to
compensate for that loss of overall reliability.

That's the book, btw:
http://www.amazon.com/Avionics-Handb...e=UTF8&s=books


Andrey


Larry Dighera wrote:
On Mon, 02 Oct 2006 10:18:13 GMT, Matt Whiting
wrote in :

... , it isn't a good idea to have all of your
eggs in one basket, especially when that basket is made of software! :-)

It would seem that Airbus has successfully grappled with this issue.
Perhaps Cessna and Garmin should get a clue from them.

"Andrey Serbinenko" wrote in message
...
A few years ago, I remember reading an excellent book on general design of
modern avionics. In particular, one thing that I believe is different
between
Garmin's baby and what they have in B-s and A-s is redundancy. The whole
thing
there is doubled, and some critical components are tripled. And then
there's
a whole body of software that takes care of voting-elimination among
inputs.
By design, the event of the computer reboot (i.e. all three redundant
computers
reboot) is perhaps as likely as the event of all four engines quitting at
the
same time. What surprises me is that Garmin got FAA approval for such a
system,
whereas it doesn't even come close to what "normal" glass cockpit is
supposed
to be like in terms of robustness of system design. I understand it's all
done
in the name of affordability, but this is clearly a dangerous game to
play.

If you think about it, just to be able to claim any kind of "robustness",
you should be reasonably sure that there's no single failure that will
take
the whole system out, right? And there we go: excessive fuel venting took
airspeed indicator out completely, and CO indication out completely. And
this
is aside from any software bugs; this is the way G1000 is supposed to work
by design!

So, I guess my point is: you can't just take a steam-gauge-type airplane,
replace all the individual *independent* instrument systems with one
electronic box, and claim you've got an equally reliable plane. No way. By
tying everything together and establishing inter-system dependencies that
never existed before, you increase your likelihood of a catastrophic
failure
by orders of magnitude. If you want to use an all-in-one instrument
system,
you need to redesign the airplane and fit it with redundant systems to
compensate for that loss of overall reliability.

The G1000 system If you buy one or intend to fly one in the Soup be current
and really proficient on you partial panel skill because in the event of a
G1000 failure or even partial failure you will be left with and Compass,
Altimeter, Attitude Indicator, and Airspeed Indicator and a bunch of useless
knobs and buttons or questionable reading from a partial failure. It's
almost an IFR pilots worst nightmare yea a Vacuum and Electrical System
Failure as when the G1000 goes radios, navigation, & transponder go along
with it!

I don't think it would cost Cessna much $$$ to put some manual back up
instruments in the panel even if they are the small ones they already charge
to much for a skyhawk why not add 3k or 4k if even that much to the price
and add some redundancy to the system!

NW_Pilot writes:

The G1000 system If you buy one or intend to fly one in the Soup be current
and really proficient on you partial panel skill because in the event of a
G1000 failure or even partial failure you will be left with and Compass,
Altimeter, Attitude Indicator, and Airspeed Indicator and a bunch of useless
knobs and buttons or questionable reading from a partial failure.

Better still, just skip the G1000 in the first place.

I don't think it would cost Cessna much $$$ to put some manual back up
instruments in the panel even if they are the small ones they already charge
to much for a skyhawk why not add 3k or 4k if even that much to the price
and add some redundancy to the system!

Is a G1000 standard equipment, or can you opt for reliable avionics
instead?

--
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On 02 Oct 2006 19:26:50 GMT, Andrey Serbinenko
wrote in
:

So, I guess my point is: you can't just take a steam-gauge-type airplane,
replace all the individual *independent* instrument systems with one
electronic box, and claim you've got an equally reliable plane. No way.

Obviously you are not a member of the Cessna marketing team. :-)

Thanks for the link to the book. If I knew the appropriate
individuals at Garmin and Cessna to send it to, I would.

Andrey Serbinenko writes:

What surprises me is that Garmin got FAA approval for such a system,
whereas it doesn't even come close to what "normal" glass cockpit is supposed
to be like in terms of robustness of system design.

My guess is that the FAA doesn't know how to certify glass cockpits.
There are no procedures in place to certify software, or for some
reason they are not applied to toys like the G1000.

I understand it's all done in the name of affordability, but this
is clearly a dangerous game to play.

Is a G1000 cheaper than a set of normal instruments in the cockpit?

So, I guess my point is: you can't just take a steam-gauge-type airplane,
replace all the individual *independent* instrument systems with one
electronic box, and claim you've got an equally reliable plane. No way. By
tying everything together and establishing inter-system dependencies that
never existed before, you increase your likelihood of a catastrophic failure
by orders of magnitude. If you want to use an all-in-one instrument system,
you need to redesign the airplane and fit it with redundant systems to
compensate for that loss of overall reliability.

Absolutely.

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"Mxsmanic" wrote in message
news


Is a G1000 cheaper than a set of normal instruments in the cockpit?

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Ahh!!! Go to look here! http://skyhawksp.cessna.com/pricelist.chtml This
bird had every thing NAV III + some but the A/C! Them airbag seat belts are
not very comfortable either!

congrats on a successful flight NW... half of me is really jealous and
the other half thinks it'd be too scared to try that even if given the
chance. loved the story though...

i was curious about cessna's explanation of the airspeed problems - you
said "the loss of the airspeed indicator was caused by fuel vapors
entering the pitot tube". how did it get in there? the wing vent is
well behind the pitot, right? i see the picture with fuel on the
nosewheel, did that come ouf of one of the drains under the fuselage?
did you lose both the G1000 and steam gauge indications or did one keep
working (accurately?)

thanks,

todd.