Martin wrote:
I doubt the CAA would endorse such a practice.
Of course but it is likely that some sort of fix substitution will be in place before long.
Nothing actually prevents you from flying to the NDB as a waypoint in the GPS database.
This is how NDB/VOR approaches have been flown by GA for as many years as GPS has been around.
NDB bearings and VOR radials have been intercepted using the GPS in the OBS mode, etc.
Also anyone who doesn’t have the AFMS for their GPS (to make flying approaches legal) has to overtly fly the NDB/DME approach trajectory, to “look legal”. That’s what I used to do before I sorted this out.
All that the NDB in the published IAP means is that you have to carry an ADF.
There appears to be zero enforcement of this anyway. Look at all the SR22s with no ADF and no DME. No known prosecutions – not even in Germany.
Sure, but that doesn’t make it less silly to design an RNAV approach that way…
No one has yet been able to tell me how they are going to find the missed approach holding point if their GPS fails for some reason.
I can’t understand why those of you who own aircraft are so reluctant to carry an ADF box, they are light, reliable, don’t take much panel space and some of them even have Superflag output to make them safer for your EFIS systems.
Although the approach is restricted to Approved Operators Only and is also PPR, is it likely to appear in the next database update and be available/visible on our Garmin GPS boxes?
This would at least allow the possibility in the future for the airport to relax these constraints and apply the same basis as for their ILS.
One wonders if these restrictions have been driven by the airport or the regulator. Extreme caution seems to be the watchword.
As for outages of navigation systems, I’ve visited several airports in the past year where the ILS has been out of service or glideslope unavailable. Our local airport NBD has finally been switched off after many years of intermittent operation. Temporary failures can also be due to vehicles in the wrong place, lightning strikes or even the controller switching on the wrong runway. GPS certainly isn’t infallible and can be jammed by military if they want to, and equipment can fail (see Peter’s recent screenshots for a good example), but there has been not even one second of recorded outage of the basic GPS constellation over the past 10 years. Detailed stats are reported by the US DoD which maintains the system.
I’d argue that authorities should be seeking to implement an RNAV approach to every instrument runway in the country at least as a backup for when ground based aids are out of service, and should aim to match the Cat 1 minima wherever possible. The argument that GPS is unreliable etc. doesn’t fit with the real world situation where ground based aids fail and there is no precision/high quality alternative to continue IFR operation. For example at Kirkwall, if the ILS was out of service, everybody would have to revert back to the VOR non-precision which is implicitly higher risk, unless you had PPRed and were on their “approved operator list”. Again, in reality, this would be flown as a GPS overlay without an indicated glideslope.
Why is the UK regulator taking such an extreme and radically different view of RNAV approaches from the rest of the world? Do they really know something that nobody else does, despite lacking almost any practical experience on the topic? This enforces lower grade/higher risk approaches which in practice are flown by GPS anyway.
No one has yet been able to tell me how they are going to find the missed approach holding point if their GPS fails for some reason
A valid point, and I would say Use your other GPS 
GPS is so necessary for flying anywhere nontrivial that having just one is daft. The second one can be a handheld. I am sure your local pilot shop will be delighted to sell you one. They sell hardly any these days.
Or use the GPS app on a tablet or a phone. Are there any free apps which show basics like navaids?
Peter wrote:
All that the NDB in the published IAP means is that you have to carry an ADF.
Having to carry it is bad enough. And at least my logic dictates that you’re supposed to use it, at least for crosschecks. I wouldn’t expect to successfully argue otherwise in a court (putting aside how would they prove it).
DavidC wrote:
I’d argue that authorities should be seeking to implement an RNAV approach to every instrument runway in the country
IIRC ICAO recommends that. But that’s all they can do.
There is no GA regulation stipulating equipment to be used. Only carriage of it is required.
The MAP at Kirkwall for the ILS and VOR approaches uses the VOR only…not the NDB….so (Kirkwall at least) it seems even sillier to require the NDB for the RNAV MAP….
Btw, Kirkwall has one of the greatest selections of approaches I know of: DME Arcs, NDB and VOR only, NDBDME, VORDME and ILS…at both ends….and now RNAV with LPV….brilliant!
Peter wrote:
There is no GA regulation stipulating equipment to be used. Only carriage of it is required.
I just don’t think I would be able to say that with a straight face. And I seriously wouldn’t expect a judge to agree (not on the continent). Otherwise, why bother requiring carriage/ not allowing substitution? And I would expect the prosecution to have a line of expert witnesses disagreeing with me. Not that I think it’s even remotely likely I would be prosecuted, I just wouldn’t expect to get away with it if they could prove it.
How would you use DME or ADF while flying on vectors or navigating using GPS? That’s why they’re just carriage requirements. And you could use this logic to argue, that you can fly an approach even when a required aid is inoperative. By the way, that equipment must be operational (at least according to NCO). I vaguely recall someone arguing that it could be a dead box, as long as you’re “carrying” it.
