UK VOR removal, and how to navigate with just VORs (no DME used)

... although I think the non WAAS 430/530 units used for IFR will start to disappear quite quickly now that 8.33 has become a requirement for everyone

All non WAAS 430/530 units that I have flown with in the last 10 years were 8.33 capable. It can be set up somewhere in the AUX menu. 8.33 has been with us for a long time, at least at levels that can be reached by pressurized airplanes.

Meanwhile EASA plod on with their IR based on 1950s technology. Nobody has though to modify the training to match changing requirements. The CAA launched its Future Airspace Strategy a couple of years ago with a target date of 2020; this is what is driving the removal of conventional nav aids so, much like the closing of power stations with no alternatives, soon there will be nowhere to train for the traditional IR. Dismantle Britain continues.

All non WAAS 430/530 units that I have flown with in the last 10 years were 8.33 capable. It can be set up somewhere in the AUX menu. 8.33 has been with us for a long time, at least at levels that can be reached by pressurized airplanes.

Thanks, somehow I equated 8.33 with the W upgrade. Having said that, now that more and more (soon most?) instrument capable runways have an RNAV approach (including many without an ILS), I think quite a few people will upgrade just to get the advisory glideslope.

Meanwhile EASA plod on with their IR based on 1950s technology. Nobody has though to modify the training to match changing requirements.

I don't think that's entirely fair on EASA/the CAA - the requirements are more or less that you have to train to fly any of the approaches you might find on your test. Sadly there are still lots and lots of NDB/DME approaches (practically every airport has one) and as an NDB is still required equipment (more or less) you can't just mark it as inop on your test and thus drop the need to train for it, and this takes up most of the IR training time.

Ideally all FTO planes would be capable of flying RNAV approaches, then everyone would have to train for them (and like Jason and I, choose them over the alternatives). Then we could get rid of all the NDB approaches and move on...

the requirements are more or less that you have to train to fly any of the approaches you might find on your test.

But the proposals indicate a very major change in a small time scale and so far nobody is thinking how the change over will occur. Waiting for the aids to disappear is not the time to start thinking about it! No training is being considered for approaches that are in the proposal!

The fibre-optic gyro is only one part of an INS. The other one - the accelerometers - are at least as expensive as the gyros.

It's all in one box. The FOG is the gyro/accelerometer.

Ideally all FTO planes would be capable of flying RNAV approaches

I am reliably informed that UK FTOs routinely get around GPS approaches being in the IR test, by having a GPS which is INOP or which has an out of date database, which prevents it being used in the test.

Then we could get rid of all the NDB approaches

There are many NDB approaches in southern Europe though... removing them in the UK would not really solve anything - unless one is trying to train pilots to never go anywhere. I realise most people fly them with a GPS but if the navaid is removed, it won't be in the GPS database and then it will have to be entered as a user waypoint, which adds a failure mode (especially if your plane is shared with other people).

Out of interest, will you be installing the Sandel horizon as well (SA4550)?

I had to google on that one!

Gosh - it looks amazing especially if it replaces the KI256. Will look later.

I spoke to Sandel a couple of years ago (they contacted me after they read about my SN3500 installation) and they weren't going to do anything like this due to certification problems

There are two forms of advisory vertical guidance generally available. Baro-VNAV or SBAS wih GPS. WAAS is the US SBAS, you have EGNOS. Baro-VNAV is provided on the high end FMS systems. It requires a position source, typically a GNSS without SBAS for the lateral guidance and it uses a computer with the barometric altitude information to calculate and construct the glidepath. The Baro-VNAV glidepath is affected by temperature, so there are temperature limits for using them on approaches. Since MSL follows the curvature of the earth, the glidepath is a curve and not a straight line in space. The Garmin G1000 has a VNV function that provides an advisory glidepath, but not on the final approach segment, so isn't usable for approaches. The SBAS GPSS systems also provide for both official vertical guidance (LPV or LNAV/VNAV) and advisory vertical guidance (LNAV). In order for these units to provide vertical guidance, they must be in the SBAS service volume and meet HPL/VPL requirements for integrity at the time of the approach. We call these SBAS GNSS systems WAAS, for example the GNS530W, GNS480, GTN750, and the G1000W. For the vast majority of NPA procedures, these units provide an advisory vertical guidance that in every respect, both to the pilot and the autopilot look like an ILS. The WAAS GPS annunciates the approach as LNAV+V, where the +V is to indicate that the vertical guidance is advisory. Here in the US, the advisory vertical guidance may only be used to descend to the MDA and not below it. This is because the +V is the invention of the manufacturer and is not an official part of the approach. No provisions are made by the procedure designer to assure that the +V will clear obstacles or terrain and in fact they don't even know it the manufacturer provides the +V. I know of several approaches that if you follow the vertical guidance below the MDA, you will crash. One in particular will penetrate a ridge line more than 100 feet below the summit. That is not to say that on a specific procedure, it would work, but there are no guarantees.

If the procedure is clear of obstacles, as is the case with official vertical guidance on a LPV, the path to the threshold will be clear. Unlike the Baro-VNAV, the SBAS generated glidepath is a straight line in space, although when viewed by an observer from the ground, the curvature of the earth makes it appear to curve in the opposite upward direction. However, the Baro-VNAV generated GS and the GNSS SBAS generated glideslope are close enough to each other that the LNAV/VNAV minimums are approved to be used by either type of system, however the GNSS SBAS system is unaffected by the temperature limits as its GS is relatively fixed in space.

The manufacturer is required to assure that the +V will clear all step down fixes inside the FAF, but special care must be taken by the pilot when using the +V to obey all the minimum altitudes. This isn't an issue for the Baro-VNAV units as the MSL (QNH) altitude will stay in sync with the +V as temperature varies. However, the GBAS units, the minimum altitudes will move up and down with temperature which means that on a hot day, the +V will be below the minimums, not because the +V GS moved, but because the altimeter indicates lower than actual altitude. This issue is mostly a legal point when beyond the FAF, but will show up as a discrepancy in altitude when following the +V from further out. In other words, the radar return will show an aircraft below the minimum and could earn a pilot deviation being filed here in the US. If the pilot doesn't use the altimeter indication as the primary requirement, but follows the +V on a check ride, they can be busted and fail the check ride.

One last point, in the US, if the approach has a DA/DH and the approach must be missed, the aircraft is permitted to descend below it due to the momentum of the aircraft as long as the pilot has initiated the missed approach. The area is inspected for obstacles that could be encountered in the "sink thru" portion of the missed approach procedure and it is assumed that the obstacle clear path starts from a lower altitude. In the case of a NPA, there is zero tolerance for sink thru and the pilot is expected to continue the procedure at the MDA or higher, all the way to the MAP. Since the design of the NPA assumes that the miss will occur at the MAP (usually located at the threshold), no provisions for turns prior to this point are checked for. In summary, although the +V may look in every respect as if one is flying an ILS, there are important aspects that are different. Local knowledge of the procedure and the obstacle/terrain is useful before one blindly follows the +V to the threshold.

When would the GNS430W offer a +V approach? I have never seen vertical guidance other than for ILS and LPV.

This is because the +V is the invention of the manufacturer and is not an official part of the approach. No provisions are made by the procedure designer to assure that the +V will clear obstacles or terrain and in fact they don't even know it the manufacturer provides the +V. I know of several approaches that if you follow the vertical guidance below the MDA, you will crash. One in particular will penetrate a ridge line more than 100 feet below the summit. That is not to say that on a specific procedure, it would work, but there are no guarantees.

ISTM that the key thing here is that with ILS or LPV you can (not legally but safely) descend below the decision height so long as the trajectory is maintained, but with +V you cannot because obstacle clearance is not assured below the MDA.

This issue is mostly a legal point when beyond the FAF, but will show up as a discrepancy in altitude when following the +V from further out. In other words, the radar return will show an aircraft below the minimum and could earn a pilot deviation being filed here in the US.

Would the temperature effect be visible on the Mode C return, which has a +/- 200ft tolerance anyway?

If the pilot doesn't use the altimeter indication as the primary requirement, but follows the +V on a check ride, they can be busted and fail the check ride.

That makes sense; in that respect it is no different to flying a NP IAP by taking the ground speed at the FAF, looking up the corresponding ROD on the plate, and setting that as the -VS on the AP. You then have to watch out for each SDF to make sure you don't bust it.

Baro-VNAV is provided on the high end FMS systems. It requires a position source, typically a GNSS without SBAS for the lateral guidance and it uses a computer with the barometric altitude information to calculate and construct the glidepath. The Baro-VNAV glidepath is affected by temperature, so there are temperature limits for using them on approaches. Since MSL follows the curvature of the earth, the glidepath is a curve and not a straight line in space

Do you think that is what What Next had in his jet? Bear in mind he didn't have WAAS/EGNOS.

One does wonder if the use of the FMS was predicated on RAIM being continuously available

Garmin has to code the approach procedure to provide the LNAV+V. Here in the US, most of the GPS or RNAV(GPS) procedures that have LNAV as the only service and are straight in have the +V coded by Garmin. That is probably 95+% of the LNAV only procedures, I would guess it is provided on some 2,000 to 2,500 approaches. Outside of the US, I don't know their policy for coding them. Do you have a few examples of approaches, I have the GTN and GNS530W simulators with the recent world wide database and I could load them and see if they show a +V. I need the full ICAO ID of the airport. Regardless if it is coded or not, it will show up in the simulator and it will work the same in the aircraft.