flybymike wrote:
Has there ever been a mid air collision between CAT and GA as a result of infringement of CAS?
Cerritos, Los Angeles area, 1986. AOPA Article. This was in the old style FAA airspace system that was subsequently revised circa 1991, including Mode C mandatory areas, along with the introduction of TCAS on airliners. Those changes made airspace infringement less likely to cause a collision.
Ah yes thanks. I recall that one now.
Incidentally, the total number of people killed by the 1986 Cerritos accident was a little less than the average number of road deaths in the US every day since. Not many relatively speaking but regardless the changes in airspace design were apparently effective. I can’t recall any more recent US CAT/GA collisions despite for example the continuation of phenomenally high air traffic density in the same area where that collision occurred.
Thanks for this one Silvaire, do I infer correctly from that that the DC9 was flying along the boundary of the controlled airspace as cleared by the controller?
I’m guessing there’s nothing from the UK recently (or ever?)
Off_Field wrote:
do I infer correctly from that that the DC9 was flying along the boundary of the controlled airspace as cleared by the controller?
I see this in the AOPA article: “Flight 498 and the Piper Archer collided over Cerritos at about 6,650 feet. The Archer had inadvertently penetrated the 6,000-foot floor of the TCA without a clearance”. A TCA was the old FAA type of controlled airspace, similar to what is now Class B.
It is obviously not impossible but it would be amazingly bad luck, and probably with some holes in the cheese lining up on the ATC end too.
If you look at FR24 you see that the usual height of jets at the boundary of a CTR/CTA (controlled airspace which goes all the way to surface) is a few thousand feet higher than the vast majority of GA flies at, especially when near CAS.
The jet traffic is entitled to be a lot closer to the edge (I believe 500ft is the minimum vertically; no idea of the lateral amount) but in reality they almost never are, due to steep climbs and descents. Most of the complicated shapes in the UK are to contain sids/stars etc which are rarely actually flown. I posted some tracks further back which I recorded myself when on a flight.
And if a non TXP aircraft enters a CTR/CTA, ATC will immediately act on the primary return because he is obviously infringing.
Obviously it is possible but equally obviously there are very sound reasons why it has practically never happened. If GA was routinely flying around, non TXP, at say 6000-8000ft, right up to the edges of CTR/CTAs, i.e. dramatically busting CAS all over the place by say 5000ft vertically, then the situation would be very different, but for a number of reasons people don’t do that.
Losses of separation are a different discussion because the UK adds 5000ft/5nm to any infringer’s Mode C readout, to create a huge artificial volume around him, and this makes a “loss of sep” easy to do, but it isn’t one actually.
I think in Europe commercial jets may always be in Class A in their descent from cruising altitude, but in my US area and many others they descend from 18,000 ft in Class E, and particularly as they get down to non-oxygen altitudes they need to be looking out the window, listening for radar based traffic advisories and I assume monitoring TCAS as a last resort. That segment is not “their” airspace or ATC’s. Conversely, VFR traffic needs to be looking for jets after climbing through roughly 8,000 ft, as I do departing the area on almost any long flight. The system seems to work fine as there haven’t been significant jetliner midairs in that phase of their flights. I think the FAA approach of not fixing things that aren’t broken has worked.
In local flying as a student pilot in the US I was cautioned to fly no closer than 500 ft vertically away from Class B, mainly to avoid busting airspace since I was most often not talking to Approach, but I think 300 ft vertically is more typical for people familiar with flying and the area. In relation to avoiding collisions versus airspace busts, other traffic (CAT and GA) flies right up to and across the edge between Class E and Class B so although you may get advisories (and separation if you’re on one side of the line) you’re not avoiding traffic by maintaining distance from the airspace boundary.
If you look at FR24 you see that the usual height of jets at the boundary of a CTR/CTA (controlled airspace which goes all the way to surface)
Not sure exactly what you mean by the “boundary” here, but A CTA would be a shelf above ground level.
And if a non TXP aircraft enters a CTR/CTA, ATC will immediately act on the primary return because he is obviously infringing.
No mode C readout under a shelf would normally be “deemed” to be outside CAS.
Malibuflyer wrote:
Airspace infringements are never “momentary lapses” or “distraction”. They are – as all other serious incidents – always the result of a series of several mistakes a pilot makes – almost always starting with inappropriate flight planning or tactics.
I beg to differ. This is what happened to me once.
A flight abroad. Of course I knew the rules, but I hade no experience of ATC practise in the area. I was on a Y flight plan. Of course I got a complete rerouting so that I approached my destination from the south rather than from the north as planned. Thus my clearance limit was completely different than the IFR/VFR transition point in my flight plan.
I tried in good time to negotiate an IFR descent towards a suitable transition point but although controlled airspace extended down to 4500 ft with the MSA being much lower ATC was not cooperative and didn’t seem to at all consider what should happen after I reached the inconveniently placed clearance limit at my cruising level of FL100. Eventually I realised that no descent would be forthcoming so I canceled IFR at FL100 (fortunately the WX was SKC) and had to make a very steep descent (1000 fpm or more) to reach the first approach VRP at the prescribed altitude of 1000 ft. On the way down after leaving controlled airspace I believe I briefly clipped a “vertical corner” of another controlled airspace sector (although I’m not sure) due to my descent starting much later than I wanted and I didn’t manage to descend quickly enough. Things were happening very fast. I was in radar contact with FIS the whole way down and they made no comment. The VFR descent clearance I got towards the VRP may have been valid for the other controlled airspace sector.
Anyway — if I did infringe on the way down, would it really have been caused by “several mistakes” starting with “poor flight planning”?
That‘s why I wrote „almost“ ;-)
Yes, in rare cases things like that happen – and though both of us theoretically know that accepting an IFR cancellation w/o knowing exactly how to legally get to the destination in VFR we also know that sometimes things happen fast (makeing accepting the cancellation still a mistake but who never does mistakes).
More importantly: I‘ve never heard (and you are obviously also not such a case) where a pilot in such a situation (after cancellation of IFR, still in contact with ATC, doing the best one could do to actually make the descent…) got actually fined for such a „scratching at the edge“. All situations where I actually heard of a fine were pilots not knowing where they are and/or consciously trying to exactly follow the edge and were some NM or Ft of and/or trying to take a shortcut …
