achimha wrote:
The battery driven mechanical AI has no such failure mode.
To be fair, nor does a battery driven glass device that is designed robustly as described in the Goodrich/L3 case.
achimha wrote:
MD302 in the TBM 930, probably Garmin G5 next year and then you have the same software/logic running everywhere.
The G5 was specifically developed to have no software (and I think no sensors) in common with the other Garmin EFIS products precisely to avoid a problem caused by a software/system fault happening simultaneously with the G5 and some other Garmin kit.
Peter wrote:
or a defective GPS antenna which radiates on 1.575GHz and wipes out the others
How can a receiver antenna radiate anything? Do you mean that the electronics inside an active antenna get messed up and somehow magically rewire themselves to start radiating stuff?
JasonC wrote:
To be fair, nor does a battery driven glass device that is designed robustly as described in the Goodrich/L3 case.
We’re going a bit in circles but the L3 documentation explicitly says that the instrument’s performance is degraded in case of an iced up pitot. So I disagree, there is a significant difference between a battery powered mechanical AI and a battery powered standby solid-state AI, at least the ones we have discussed so far.
achimha wrote:
We’re going a bit in circles but the L3 documentation explicitly says that the instrument’s performance is degraded in case of an iced up pitot. So I disagree, there is a significant difference between a battery powered mechanical AI and a battery powered standby solid-state AI, at least the ones we have discussed so fa
Not in an aircraft that has a battery that can power the pitot. I think this is an overreaction to a theoretical problem.
How can a receiver antenna radiate anything? Do you mean that the electronics inside an active antenna get messed up and somehow magically rewire themselves to start radiating stuff?
Yes; exactly that. I think Garmin had a bad batch of these antennae, a few years ago. I don’t know the mechanism but presumably the antenna contains a tuned circuit which ends up in the amplifier feedback loop, or something like that.
Not in an aircraft that has a battery that can power the pitot.
It would need to be a big battery. My 28V pitot heater draws 5A which is a quarter of the whole aircraft. The battery is 15Ah so shedding the pitot heater until the approach procedure would be quite a good idea, but obviously you can’t do that with this type of cockpit. So a single alternator aircraft combined with these instruments is extra risky.
It is theoretical, until it happens 
Speaking about Air France 447: everyone here should read the book ‘Understanding Air France 447’ by Bill Palmer. It shows the limitations of men and machines if they don’t understand each other and don’t fall back to basic instrument flying if needed at the worst possible time.
could you please tell me if the MD302 will continue to display attitude indication if the pitot pressure source fails in flight?
Yes it will continue to display. The Pitot/Static system only effects the AS and Altimeter.
Wil Guy
Mid-Continent Instruments and Avionics
Peter wrote:
It would need to be a big battery. My 28V pitot heater draws 5A which is a quarter of the whole aircraft. The battery is 15Ah so shedding the pitot heater until the approach procedure would be quite a good idea, but obviously you can’t do that with this type of cockpit. So a single alternator aircraft combined with these instruments is extra risky.
I am talking about what I fly and a single pitot heat remains powered on EMER power.
loco wrote:
Yes it will continue to display. The Pitot/Static system only effects the AS and Altimeter.Wil Guy
Mid-Continent Instruments and Avionics
That’s not what the manual says. You should post a follow-up question and ask how the erection mechanism works and how it will react to an iced up pitot as the manual specifically says that this will impact the AI.
JasonC wrote:
Not in an aircraft that has a battery that can power the pitot. I think this is an overreaction to a theoretical problem.
I wouldn’t consider it to be just theoretical. If the electrical system is out (something melted, etc., perfectly possible), the AI’s backup battery will surely not power the pitot heat. If the electrical system could not fail, the backup AI would not come with a battery of its own, would it?
I hope you agree that should the electrical system in a Piper M600 fail in icing conditions, the only AI backup (Aspen EFD) would crap out within a minute or two.
