(GPS) VOR Approach Rwy XX

[galleypower]

Hello. I am trying to find out a bit more about approaches labeled on Jeppesen Approach Charts like in the title.

I know that RNAV (GPS) Rwy XX Approaches can be flown with or without GPS and no backup conventional navigation (no overlay) is necessary as long as the aircraft is RNAV equipped.

But what when the approach is named e.g. (GPS) VOR 05 ?
Can I fly with GPS only or is it mandatory to have the VOR displayed as a backup and x-reference? The approach btw happens to be in Geneva / LSGG and the minimum is not an MDA, but a DA with lower WX minimums compared to a conventional VOR approach.

Does anyone have more info on this? References? Explanations?

Cheers

[Ibis]

http://www.caa.co.uk/docs/33/CAP773.pdf

Overlay Approaches
An overlay approach is one that allows pilots to use GPS equipment to fly existing non-precision instrument approach procedures. However, many of these overlays do not accurately reflect the correct approach procedure and may even represent a different speed category of aircraft. The normal equipment for that approach must always be used as the primary reference - not the GPS - otherwise any disparity between the displays and the potential for mistakes are just as likely to diminish the safety margins on approach as enhance them.
For example: VOR and NDB approaches to beacons actually on the destination aerodrome usually provide a final approach path or track which is not aligned with the main runway centre-line. Even on a direct approach to a particular runway, pilots should not necessarily expect to be on the extended centreline of the runway.
The terrestrial approach procedure may include DME ranges from the threshold, missed approach point or other reference, such as the beacon. The GPS may give distance guidance to a different point, such as the Aerodrome Reference Point. Pilots should be aware of any differences in the distance information given to step-down fixes and/or the MAP, as this has the potential for catastrophic error.

[Capn Bloggs]

The terrestrial approach procedure may include DME ranges from the threshold, missed approach point or other reference, such as the beacon. The GPS may give distance guidance to a different point, such as the Aerodrome Reference Point. Pilots should be aware of any differences in the distance information given to step-down fixes and/or the MAP, as this has the potential for catastrophic error.

In Australia, GPS-flown VOR or NDB approaches MUST be extracted from the GPS database. The database approach will therefore have the correct references for distances. It would never be approved for IFR use otherwise.

[411A]

In Australia, GPS-flown VOR or NDB approaches MUST be extracted from the GPS database. The database approach will therefore have the correct references for distances. It would never be approved for IFR use otherwise.

USA, likewise.
You can't just make it up as you go along (although some folks try to do this with portable GPS units):yuk:...'tain't legal.

[ahramin]

Same in Canada, where you can fly an approach with (GNSS) in the name without any reference to the underlying navaid.

[Henry VIII]

as long as the aircraft is RNAV equipped.And the airline has been certified by the respective CAA to perform such a kind of approach.
Otherwise GPS is an extra toy on the flightdeck only.

[galleypower]

Hi all,
Thanks for your answers and hints and tips.

I still have an issue with the naming of approaches.

Example:
RNAV (GPS) Rwy XX
No backup conventional navigation is required as long as RNAV equipped and approved.

GPS Rwy XX
Pure GPS approach. No backup navigation (VOR/NDB) required.

VOR or NDB Rwy XX
Can be flown conventional or with FMS overlay procedure

(GPS) VOR Rwy XX
Can this procedure be flown like a pure GPS approach or like a conventional approach? Is an overlay required?

Cheers

[Bruce Waddington]

galleypower,

The Canadian AIM states when referencing GPS Overlay Approaches;

"Unless required by the aircraft flight manual (AFM) or AFM Supplement, it is not necessary to monitor the underlying navigation aid, and it is even permissible to fly a GPS overlay approach when the underlying navigation aid is temporarily out of service. Nevertheless, good airmanship dictates that all available sources of information be monitored. "

The AIM also states that GPS overlay approaches are identified by including (GPS) or (GNSS) in the approach name i.e. (GPS) or (GNSS) NDB RWY 04.

Therefore, the answer to your question is yes and yes. You can fly this as a GPS overlay approach or a conventional approach or for that matter as a stand alone GPS approach based on the statement above.

best regards,

Bruce Waddington

[Pontius's Copilot]

Galleypower, you don't say whether you are a commercial or private operator, or where you are based (UK/Europe, US or elsewhere).

If you are employed in UK/Europe then your airline will probably be working to JAR-OPS or EU-OPS regs, in which case -
- If it says GPS (or GNSS, same thing but more correct) on the chart then you must be receiving valid GPS/GNSS data.
- If you are flying an overlay procedure and lose the GNSS, you may revert to the conventional 'reference aid' and continue, if you lose the reference aid (VOR or NDB) you must execute a missed approach.
- If it names a VOR or NDB aid then it is an overlay procedure and the RNAV system may only be used if the underlying 'reference aid' is available and agrees with the RNAV.
- An RNAV (GNSS) Approach is what ICAO (Doc 9613, the PBN Manual) calls a 'RNP APCH', and requires multi-sensor (ie, GNSS and DME at least) RNAV kit with a specific standard of 'on-board monitoring and alerting' (their phrase).
- For a GNSS (Only) Approach you need two independent GNSS receivers for starters, and, I believe, space-based augmentation system (SBAS).
Your '(GPS) VOR RwXX' I've not seen before. The principle in Europe at least is 'If it says GPS you must have GPS', if it says VOR (or NDB) you must have VOR (NDB).

We're talking about RNAV or FMS based approaches here, and an approach designed for VOR or NDB but coded for the FMS (ie, an overlay) may only be flown using the FMS if the underlying reference aid is available and confirming the FMS accuracy.