@Timothy wrote:
difficult to persuade the responsible people in middle management at the CAA that the safety advantage of having a 3D approach to prevent CFIT when scud running hugely outweighs the miniscule risk of mid-air collision in IMC when using such an approach.
The safety cases in the above post and in Timothy’s various formal papers on the subject of Cloudbreak Procedures are surely incontestable, but the U.K. regulators still seem frozen like rabbits in car headlights.
What if the use of such approaches was restricted to aircraft squittering Mode S-ES and equipped with TAS or ADSB-in? Might that give the UK CAA bunnies a nudge in the right direction?
It could probably be done with a single paragraph in the ANO, and would constitute a significant “carrot” for the UK IFR-capable fleet to equip early with ADSB-out – the safety benefits of which would extend throughout Class G airspace.
Jacko wrote:
What if the use of such approaches was restricted to aircraft squittering Mode S-ES and equipped with TAS or ADSB-in?
Why would you want to continue to put at risk the lives of those not so equipped? The risk of mid-airs is small enough to be put to one side in the discussion.
I think we’re in danger of comparing apples & oranges here. There’re risks with both mid-airs and with scud running due to lack of capability – each has to be assessed and, where necessary, mitigated. We should not put aside any risk, even just for the nature of the discussion, as there are actually some interesting collision risks brought about by implementing IAPs.
Personally, I’ve been involved in a IAP proposal for an AFISO airfield and the process has been painful. Three iterations of the safety case have been bounced back with supplemental questions which indicate a perceived lack of appetite to engage. There are some tricky little bits in various CAPs that do not allow for IAP at uncontrolled airfields and for some reason these can be quoted as reasons “why not” rather than looked upon as things that require rewording, something which is in the gift of the CAA.
One other point – traditionally the lack of mid-airs has meant a similar lack of useful data. It is not bad practise when mitigating the risk of a mid-air to incorporate all the class A AIRPROX (ones which are basically assessed as a collision did not ultimately occur because of luck). Utilising an increased volume of data available allows you to identify trends, weakness and develop mitigations. Clearly any figure attached to such an assessment is ‘dumbed-down’ to reflect real numbers but at least you can generate a reasonable thought stream.
Why would you want to continue to put at risk the lives of those not so equipped? The risk of mid-airs is small enough to be put to one side in the discussion.
I don’t think the risk of a mid-air on an IAP is small because if you have one plane flying with GPS guidance at 100kt and one behind it is flying with GPS guidance at 150kt, the latter will likely go into the back of the former, somewhere between the IAF and the FAF. With 2D GPS guidance you lose the “big sky” concept totally. Especially with WAAS/EGNOS which is even more accurate (although a KLN94 is perfectly capable of guiding you into the back of another KLN94 user). So there must be some other form of separation and in the absence of approach control it could be e.g. mandatory TCAS, or self announcement.
Mandatory Mode C would be a good idea because most modern GA planes and nearly all commercial stuff have TCAS.
Mandatory Mode S would be fiercely resisted by the “civil liberties” crowd because it identifies the aircraft; also shows up on FR24. Personally I don’t buy that argument at all (because all the reasons I have seen are specious or dishonourable) but politics is the art of the possible 
Also Mode S does nothing for TCAS (except on some systems showing the N-reg tail number).
However with the massive attachment to Mode S and the current illegality of installing a fresh Mode C (other than to replace an exact same-model Mode C box) the above is not going to happen – a huge wasted opportunity.
Well Timothy, when you put it like that, I’m inclined to say that I wouldn’t. But I’m trying to look at it from my favourite regulator’s point of view – not an entirely comfortable position for me , but here goes:
1. Yes, the probability of mid-air collision in IMC in Class G, en-route or on an unpublished CP, is currently very low – it’s never happened, so let’s say zero – because (a) relatively few of us are doing it and (b) the few are all flying slightly different routes and procedures. But the consequences of a mid-air in IMC could be quite severe. So is it reasonable to consider mitigating the risk if we (a) do something which may encourage more pilots to fly CPs and en-route IMC in G and/or (b) promulgate/standardise some CPs?
2. You ask, “Why would you want to continue to put at risk the lives of those not so equipped?” and I might answer, selfishly, that if they’re too tight-fisted to spend a few hundred quid on a CAA/NATS portable ADSB-out gizmo, let alone a thousand quid on a proper ES transponder upgrade, then I’d rather condemn them to scud-running than have them flying somewhere in the soup with me.
Peter wrote:
So there must be some other form of separation and in the absence of approach control it could be e.g. mandatory TCAS, or self announcement.
Or both?
Is it true that ADSB, even the cheap uncertified variety, is more accurate than TAS or TCAS? Isn’t it also about two or three orders of magnitude cheaper? The only drawback is that not many of us have installed it, but that could change in a few months if the CAA were to say “no IFR in class G without ADSB-out, certified or portable”.
I’ve been playing with a SkyEcho (ADS-B in) and the accuracy is very good, certainly far better than the TAS we have installed on the G1000NXi Diamonds. Furthermore, the GPS element is almost always accurate to <10m (we accurately measured it whilst stationary on the ground and achieved a steady 1.72m in an EGNOS environment).
I don’t think anyone is suggesting that CAP1122 approaches should be approved in non-radio environments, are they? They will mostly be in AFISOland.
So we will hear each other self-announce and we will self-separate. It will be somewhat like approaches to non-towered airports in the US.
There aren’t loads of mid-airs there.
That is an often repeated misunderstanding, Timothy.
The USA always involves an approach controller.
It is like the Walney Island case in the UK, except that the FAA (not the airport) is paying the remotely-located controller’s salary.
In the UK, the cost of a remotely located approach controller would be billed to the airfield – which usually cannot afford it. Rumour has it that Biggin Hill is paying some 50k-100k a year to Thames Radar, which is ironic since Biggin has ATC (presumably the cost of the radar plus the bigger salary of a radar qualified ATCO would exceed what Biggin pays to Thames, plus the controller would still have to closely coordinate with Thames). It has been widely reported that the fully costed cost of an H24 radar desk at NATS is c. £1M/year and that will give you a taste of what a dedicated controller would be billed out at. Otherwise I am sure NATS (Gatwick, probably) would be delighted to allocate one to Shoreham, Goodwood, Dunsfold, Deanland, Headcorn, your farm strip, etc 
In effect, the privatised (and/or “user pays”) system in the UK prevents the deployment of many facilities in the UK which other countries have. How long those other countries will have them is a good question.
Well, there you have it. Some people hold that ATC is necessary for instrument approaches, even in low traffic environments.
So long as that lobby hold sway, and are unwilling to accept that it is an issue of proportionate risk, we will get very few LPVs to currently VFR airfields in the UK.
So people will scud run or do unpublished approaches, and a proportion will continue to die in the attempt.
At least the situation will be somewhat improved by v6.41 of the GTN software.
