Flying IFR at FL180 over mountainous terrain and solid overcast, the roads if any don’t help much.
I am visiting Zilina University (or is it Bratislava University at Zilina, I am not sure) shortly, where they have a research project into GPS loss. I’ll try to report back.
I don’t have too much experience but once briefly lost AHRS at Sheremetyevo. A friend flying a brand new CJ3+ lost both AHRS, AP, YD at FL400 in Russia two months ago. In both cases it was not just DR, but losing everything except the small standby.
loco wrote:
a brand new CJ3+ lost both AHRSHow is GPS involved? nothing inertial/gyro + magnetometer in these?
Arne wrote:
How is GPS involved? nothing inertial/gyro + magnetometer in these?
The ones using MEMS need airspeed or GPS to provide some stability to the “solution” as the MEMS drift too much.
Maybe a ring laser gyro option need to be introduced by Cessna or Garmin
Arne wrote:
How is GPS involved? nothing inertial/gyro + magnetometer in these?
The cheapest ones like in my phone will rely on “GPS derived attitude” (from position & speed) to calibrate a weak solid state gyro base line configuration while static and also give frequent updates while in movement, so with a continuous GPS signal, you can go from a junk that precess 200degs/h to 2degs/h, the latter will do a good job for flying 
But I am surprised a CJ3+ will have an AHRS with cheap 3 axis mechanics against GPS fixes only?
A good one will have good 3 axis mechanics then GPS fixes, magnetic fixes or even stellar fixes (R2-D2 in SR71 )
This Cessna is G3000 equipped and after reporting the event to Textron, reply was that this is expected behaviour. Nothing wrong with the plane. Must be a ‚phone gyro’ in the G3000 then :)
Just wondering after reading abiut an accident (report not published yet) :
I know for a fact that one can loose GPS if fly low over a road. Truck drivers (and maybe some criminals) use a lot of GPS jammers to block trackers.
What would happen if this occurs during an RNAV final approach with a GNS box ? Does the CDI show flags ? The approach path is parallel to a motorway.
If you have an integrity indicator, it would be active, also you would get a message on the GPS and the CDI would show a flag.
AFAIK, truck drivers use GPS jammers to get past the working time limitations.
It would be interesting if GPS on an aircraft could be jammed from 1000ft below, given that panel mounted avionics use rooftop antennae. Tablet/phone GPS is a lot more vulnerable.
