GNSS Substitution
Thread Starter
Joined: Jan 2008
Posts: 162
Likes: 8
From: Scotland
GNSS Substitution
Recently an examiner were banned from performing a PBN approach into Dundee, due to the NDB being U/S.
While CAP 1926 bans the use of GNSS replacement from the FAF, it's clear that if you can load the overlay you are allowed to substitute any terrestrial beacon with GNSS for the initial approach and missed approach. Except as said for the final approach.
CAP 1926 is also very specific in stating the following: Operators/pilots may apply RNAV Substitution as an Alternative Means of Compliance where Charts indicate that a published route or instrument approach procedure segment is not available without a particular conventional radio navigation aid e.g., NDB(L).
Yet Dundee are saying the approach plate requires the NDB for the missed approach, therefore if the NDB is U/S no approaches are allowed.
Surely if the NDB is U/S Dundee should notam it, announce it on the ATIS, then let the operator decide if they can commence the approach?
It's not just Dundee, have heard Loganair have been prevented from flying an approach for the same reason and had to divert. Surely it's not the airport that decides if an approach can be performed, but the operator? What's next are they going to ask our qualifications?
While CAP 1926 bans the use of GNSS replacement from the FAF, it's clear that if you can load the overlay you are allowed to substitute any terrestrial beacon with GNSS for the initial approach and missed approach. Except as said for the final approach.
CAP 1926 is also very specific in stating the following: Operators/pilots may apply RNAV Substitution as an Alternative Means of Compliance where Charts indicate that a published route or instrument approach procedure segment is not available without a particular conventional radio navigation aid e.g., NDB(L).
Yet Dundee are saying the approach plate requires the NDB for the missed approach, therefore if the NDB is U/S no approaches are allowed.
Surely if the NDB is U/S Dundee should notam it, announce it on the ATIS, then let the operator decide if they can commence the approach?
It's not just Dundee, have heard Loganair have been prevented from flying an approach for the same reason and had to divert. Surely it's not the airport that decides if an approach can be performed, but the operator? What's next are they going to ask our qualifications?
Joined: Aug 2001
Posts: 696
Likes: 10
From: Shropshire
Hi Edgington
I believe the original reason for change over to 'traditional' navigation for the missed approach segment in the UK, was that some RNAV equipment of the time would occasionally turn in the wrong direction even though coded correctly. This is the reason you will see more recent RNP approaches being designed with a couple of waypoints in the missed approach to ensure a turn in the correct direction. I assume that this has been taken into account by the CAA prior to publishing CAP 1926.
Cheers
TeeS
I believe the original reason for change over to 'traditional' navigation for the missed approach segment in the UK, was that some RNAV equipment of the time would occasionally turn in the wrong direction even though coded correctly. This is the reason you will see more recent RNP approaches being designed with a couple of waypoints in the missed approach to ensure a turn in the correct direction. I assume that this has been taken into account by the CAA prior to publishing CAP 1926.
Cheers
TeeS
