Peter wrote:
Not a Lear; sorry. A $60M GulfstreamSo you are doing it with DME/DME corrections.
INS not good enough for this?
You got it! ;-)
The “INS” aka IRS→IRU will, as mentioned, maintain high precision for some time after de-selecting the GPSs (keyword “de-selecting” as opposed to getting “spoofed” BEFORE de-selecting them and thus updating the “INS” position with false position data (from the spoofed GPSs)).
Yes, DME/DME, VOR/DME will be used to update the “INS” and maintain a lower level (eventually) of RNP capability (sufficient for the eg. Newcastle International Terminal Arrival (according to the charts details “dme/dme”).
Airborne_Again wrote:
INS alone. Of course an INS which is constantly being updated by DME/DME and/or GPS could be accurate enough for a while after the update stops.
Yes, in the case of the EGNT STAR the GPSs are removed from the equation (IRU position data input) before the initiation of the STAR.
Not sure if it has any interest, but attached are some photos of my latest spoofing experience North of Turkey last week. You can see the GPS 1 is completely without data flicking on/off with a spoofed “far off” from the correct FMS (IRU) position. GPS 2 is a similar status.
Further, the first signs of spoofing in this cockpit (and likely other similar Honeywell equipped cockpits) is the blue CAS msg. ATC ADS-B Transmitter Fail.. Quick action to de-select the GPSs and the 3 “hybrid” IRUs will assure/maintain correct IRU/FMS position data (having isolated the GPSs and “hybrid” position data).
Recovering the GPS position data, say 30-90 minutes later has proven to not always be as simple as one would think. In fact, on multiple occasions now, my GPS 1 has never recovered until after a full power down on the ground.
Nice 
Thanks for posting these.
Of course an INS which is constantly being updated by DME/DME and/or GPS could be accurate enough for a while after the update stops.
Well, INS by itself is completely useless; it needs an update to get it started. About all an inertial nav system can do without that is finding true north, which I believe most can do within some minutes.
Airliner grade INS is a few NM out after crossing the Atlantic (w/o GPS) which is about 2500nm, and I personally saw that in a 747 cockpit pre-9/11, so should be just fine for flying an IAP, having got a fix some minutes before. But somebody decided otherwise…
Peter wrote:
Well, INS by itself is completely useless; it needs an update to get it started. About all an inertial nav system can do without that is finding true north, which I believe most can do within some minutes.
Well, in the current climate (of GPS jamming and worse spoofing), of course the IRU (“INS”) is updated on the ground (in Honeywell case of G650 by GPSs) and continuously until de-selecting reference units (GPS, “hybrid”, dme/dme, vor/dme). The “INSs” are very useful, as you describe yourself, for as long their position data is not invalidated by GPS spoofing input data, hence why we de-select them in know spoofing area.
As soon as you reach, from a, oceanic crossing, land fall and ground based navigation stations, the “INSs” will be updated and shortly after archive an EPU level sufficient (or not) to meet RNP for the type of Enroute and Terminal planned.
