Emir, Can you specify the page number in the G1000 manual where the procedure of turning off the GPS is detailed? Many thanks
It’s in G1000 configuration. Press and hold “Enter” before turning on G1000 and hold it for 3 seconds (or so) and the release it. G1000 will turn on in configuration mode and then you can browse through different pages and configure the system. However, I don’t recommend doing this except if you really know what you’re doing and have appropriate manual.
Interesting and rather scary that the AHRS depends on GPS in that way. Unfortunately it is a certification requirement that “AHRS” is supplemented by either airdata or GPS, while the old mechanical AI has no such requirement 
Why this is, nobody seems to know.
We have done this before here here here etc.
Historically Aspen used airdata so if the pitot tube froze you lost the whole instrument – a big X. Garmin were not vulnerable to this particular one because they used GPS data (as you have found). But I think Aspen now use GPS too – here presumably because they got a bad name for this.
I can’t think of a solution except an uncertified one which uses triple FOG AHRS and basically simulates a GPS NMEA data stream. Costs a few k though Here and this was one product which now appears gone. They also did a CNS-5000 which was just right. Now you have e.g. this. I was once looking at this, for driving a tablet satnav app and then obviously there is no legality issue. Of course if you are flying in places with GPS jamming then you are there for good reasons and legality is hardly relevant
The remaining problem is that the G1000 will be useless as an attitude presentation, if GPS is being spoofed. So you need a backup attitude instrument; one can use a tablet for displaying that data too (I am not talking about using the internal solid state gyros – those are of little use).
…And then, again I would get (at least) a stable AHRS
Yes, no problem, I’ll try to explain.
I fly G1000 with Cessna NAV III configuration. Many times I fly in areas with prolonged GPS blockade. Several times (in addition to the DR situation), it happened that the AHRS disappeared and started self reset (but no red X on the AHRS).
In normal situation you should still get a degraded AHRS, because Magnetic heading and barometric altitude are still present. My assumption is that if during that time a GPS position was spoofed and, let’s say for example, providing a GPS position that was seen to be traveling west when magnetic heading information says it’s traveling east. Then, because the AHRS doesn’t know which information is the correct one, it starts to reset.
The possible solution I was thinking about is temporarily disconnecting the GPS through the G1000 settings, before the GPS starts to spoof.
Emir,
Can you specify the page number in the G1000 manual where the procedure of turning off the GPS is detailed? Many thanks
COM1 and COM2 are separate CBs. And to answer properly OP’s question – IIRC GPS can be turned off within system configuration like any other device.
GPS1/NAV1 and GPS2/NAV2 CBs will turn off both GPS and NAV.
This is also a thing to be worried about:
gallois wrote:
The G1000 on the DA42 has 2 GPS and each has it’s own circuit breaker.
The G1000 (don’t know about the G1000 NXi) has two integrated avionics units each including COM, NAV/ILS and GPS. They each have a COM and NAV circuit breaker. If you pull the NAV circuit breakers you’ll lose all radio navigation. Also, if you disable the GPS the AHRS will be more sensitive to failures.
