engfireleft
Quote:
If you are flying an NDB or VOR approach then you must have the radio tuned and displayed as your primary reference.
As I said, that is NOT true. One, with FAA approval, can do so with the proper equipment. There is no requirement on a Global or Challenger (ProLine 4 or 21) to tune, display or monitor the underlaying navaid. Obviously, you must have and use a current database, have the crew training, and have the correct annunciations. There is no RNP associated with the underlying approach, so no need for a specified RNP. We just need to have APPR annunciation, indicating proper RAIM calculations and, at least, 1 nm scaling.
With 2,000 hours in these types, I understand what navigation sources are being used or not. It is a matter of regulatory approval. Here is the relevant part of AC 90-94
Quote:
Phase III. Phase III began April 28, 1994, when the first instrument approach procedures were published to include “or GPS” in the title of the published approach procedure. Neither the aircraft traditional avionics nor the underlying ground station navaid(s) need be installed, operational, or monitored to fly the nonprecision approaches at the destination airport. For GPS systems that do not use RAIM for integrity, the ground-based navaid(s) and the airborne avionics that provide the equivalent integrity must be installed and operating during the approach. For any required alternate airport, the traditional ground-based and airborne navigational equipment that defines the instrument approach procedure and route to the alternate must be installed and operational.
It is OBE, but does apply for systems approved under it.
GF
If you don't have the VOR tuned you are not flying a VOR approach. If you don't have the ILS tuned you are not flying an ILS approach. If you are flying an approach using the FMS as primary guidance you are flying an RNAV approach. Your quote from the AC even says so (read the bolded sentence, if you did it back then you are flying a GPS approach, not VOR). If for instance the title of the approach was "VOR RWY 25" you could not do the approach if the VOR was not functioning. Why not? Because it didn't say "or GPS" in the title.
But even that is out of date because they are not called GPS approaches anymore although some plates may still have that in the title. According to the ICAO PBN manual they aren't even called RNAV approaches anymore, but almost all of the plates still say RNAV (in Canada overlays have (GNSS) in the title). It takes a while for naming nomenclature to make its way through the system.
Another thing I'm detecting here is too much reliance on aircraft FCOM's and FCTM's to tell the crew what they can and cannot do. If the aircraft says it will do something that doesn't mean you can from a regulatory standpoint, and vice versa. If the aircraft FMS displays a specific RNP during certain phases of flight, that doesn't mean that's the RNP that is actually required. You will notice that virtually all aircraft have the ability to input different RNP values by the crew.
One example of what I mean is GPS equipped Airbus. The RNP will automatically decrement down to 0.3 nm, but only if the approach selected from the database is titled "GPS". It won't if the approach is titled "RNAV" even though you still need 0.3. So the pilot has to select it manually.
PBN is a rapidly evolving discipline and it is impossible for a single country to keep everything up to date which is why you still have "GPS" approaches around even though they aren't officially called that anymore. When you bring different countries into the mix it is a hundred times worse than herding cats.