OCA on Gloucester RNAV plate
 

On the Gloucester RNAV (GNSS) 09 plate here:

http://www.ead.eurocontrol.int/eadba...2013-05-30.pdf

there are two Procedure LNAV OCAs given, one 'At 3.2% MAP' and one 'At 2.5% MAP'. The latter is higher.

What do these mean? (Neither relates to the 'recommended profile' of 5.24%)

Missed approach gradient of climb - better perf gets you a lower minima.

Ah, thanks. Makes sense.

There's a sort-of hill-thingy to the right of Gloucester.

Indeed. The one that made the NDB approach sporting. Rather looking forward to trying an RNAV one instead.

Tim , I’ve used the GPS for an LPV RNAV approach ( LFAT ) ...... clearly it’s the way forward.

Trouble is the CAA have made the ATC requirements and paperwork costs of setting up an RNAV app in the UK so outrageously expensive you will never see many here.
Considering the safety case and lack of infrastructure required by an airfield the cost should be minimal. All the required kit already in place, satellites up there and Avionics in the aircraft.
GPS overlay approaches on present NDB and VOR procedures could be published immediately and at minimal cost as was done in USA decades ago.
Small non ATC US airfield I visited had a GPS/LPV approach in place at each end of their runway in about 3 months at a cost of less than $20000.
And didn’t charge the usual UK £20/40 a go to use it.

What’s the RT procedure for this outside controlled airspace? Do I just call with an estimate for the IAF and ask for a level? And what happens if they need to delay me - will they hold me at the IAF (no published hold) or the published hold at GST? (If the latter then I would need then to proceed to one of the arms of the T afterwards, presumably.)

PS cessnapete they do publish RT procedures in CAP413 for AFISOs for RNAV approaches.

Cessnapete
 

Overlay and GPS substitution for DME have issues in Europe because some ground based radio aids that are closely located have the same ident. This could result in the wrong radio aid being substituted in the GPS and a plausible approach being carried out. In North America radio aids with identical idents have to be geographically separated by 500nm producing a gross error of a wrong substituted nav aid totaly implausible.

An example of this can be found at LCLK, the LCA VOR is at the eastern end of the airfield and the LCA NDB is about 4NM west of the airfield , selection of the wrong LCA in the GPS database could result in a plausible approach being made on the wrong location.

Only when Europe adopts the same identical IDENT policy as North America will overlay and DME substitution become viable.

This however does not prohibit using the GPS data and more user friendly presentation to fly any approach provided you also have the conventional aids selected in the aircraft and displayed as the master.

That’s interesting. Why is it that so many procedures require conventional aids for the missed approach? (Eg GST for Gloucester.)

So that you're not completely stuffed if your GPS kit fails?

Plenty of approaches where the NDB is the only aid, though.

I heard a claim it's because setting up a new hold (eg at one of the RNAV IAFs) would require an ACP (airspace change proposal) to be done, but not sure on the truth of that.

I guess also for airfields having all traffic using the same holding fix regardless of what approach they're wanting to do might make procedural separation easier etc?

Your source was correct: CAP725 - Introduction - para 6iv is the reference. Whereas many of the triggers for an ACP contain the caveat "within controlled airspace", the one referring to holding patterns does not. Therefore, by clear inference, changes (as described in the CAP) to holding patterns in Class G airspace are subject to an ACP. Consequently, airports try to retain their existing holding patterns, based on terrestrial navaids, to minimise expense and avoid stirring up the NIMBYs.

https://publicapps.caa.co.uk/docs/33...16%20amend.pdf