Aircraft Vertical Separation Question

[SRENNAPS]

Hi,

I normally post on Military Aircrew, however the question I have is more appropriate for here, I think. Hope I am correct.

I was flying back from a city in Sothern Germany yesterday when I spotted another aircraft (an A320 I think) flying forward of us and to our left. Being a spotter I went to reach for my camera. However, almost immediately, the aircraft passed directly over the top of us at an angle of about 90 degrees. I would suggest that the aircraft was approximately 100 – 150 feet above us. There were audible gasps from many of the passengers that witnessed the event.

Having spent 30 years in the RAF and due to the nature of my work and holidays etc, I have been flying hundreds of times. However, I have never seen anything pass that close.

The aircraft was initially clearly visible (to us the passengers) due to a lovely blue sky and the contrails of the other aircraft. The question that I have is this:

With today’s technology and sophisticated ATC methods is it now the normal for aircraft to pass, vertically, that close??

Thanks

[Crazy Voyager]

As far as I know vertical separation in that area between RVSM equipped aircraft (which I'm quite sure these were) is 1000 feet.

[wiggy]

I would suggest that the aircraft was approximately 100 – 150 feet above us

I very very very much doubt it...ATC certainly wouldn't allow that and even if they stuff up TCAS (the collision avoidance system on the Flight Deck ) would also be demanding 1000' separation - and demanding a fairly healthy avoidance manoeuver if that distance was going to infringed that seriously.

As C.V. has stated it's 1000' vertical separation for airline traffic at cruising levels over most (all?) of Europe these days, which can look very close, even to those of us with lots of years up front, civil and/or military.

There were audible gasps from many of the passengers that witnessed the event

Add in a high closure rate, and perhaps the element of surprise and it can certainly produce a "startle" factor!!!

[SRENNAPS]

Thanks for the replies Crazy Voyager and wiggy.

Wiggy, I accept your comments in total and understand your scepticism.

To be honest if I had not seen it with my own eyes I would not have believed myself. Put it this way, I could clearly see things like access panels and the lines of the undercarriage doors. Not sure I could see those from 1000 feet. I just wish I had got my camera ready in my hand.

If it is of any consolation on my ability to judge distances I have flown in the back seat of a Tornado in close formation with another Tornado (perhaps you have seen my video on You tube), been part of plenty of AAR refuelling sorties in VC10s and Tristars and done several sorties in a Chinook in escape and evasion sorties with Hawk aircraft. The only point that I am trying to make here is that I am not a complete novice when it comes to being in close proximity of other aircraft and I will go to my grave 100% believing that it was no where near 1000 ft separation. Thanks anyway

[wiggy]

I could clearly see things like access panels and the lines of the undercarriage doors. Not sure I could see those from 1000 feet

You can (even given the average eyesight I have these days). We spend a lot of time 1000' above/below parallel traffic on the Atlantic routes and you'd be surprised what you can see ( but in light of your experience probably not suprised that we sometimes get complaints from passengers about us flying "within touching distance" of another aircraft).

If it's any consolation from personal experience I know how difficult it is to "put a number" on separation distances ( and I speak as someone with a few years in the Air Defence game, decades ago, so I've done my fair share of tanking, close formation, and Vis idents). FWIW we get a numerical display on the flight deck of the altitude difference from nearby aircraft and 1000' can look very close.

If you were within 150 feet of conflicting traffic the Flight deck TCAS would have been demanding an avoiding manouever for several seconds prior to the "merge" and whilst the manoeuvre is meant to be gentle if the miss distance really was getting down to 100-200 feet you would have been well aware of any avoiding action....I doubt you'd have been reaching for a camera.

Sorry to be sceptical.

[BOAC]

The actual minimum vertical separation is planned at 600' in RVSM airspace, not 1000'.

[SRENNAPS]

wiggy,

Thanks again for your reply and no need to apologise for being sceptical. You are probably right.

However, the only other point that I will make is that I have done a huge amount of flying since I was 18 years old and due to me being a sad old spotting git I spend 95% of every flight glued to the window…even in the dark I have flown in some of the busiest air spaces in the world and I have seen many, many aircraft in “close” proximity, passing both above and below the aircraft that I am in, but I have never, ever, seen an aircraft that close to me unless it was intentional. I really wish I could provide the evidence to you of what I saw, but sorry I can’t.

Thanks again

[Denti]

It is a common thing. At cruising altitudes things appear a lot closer than they really are. A lot of that has to do with the lack of anything to compare to and of course with the air quality in itself. There is nearly no humidity, no pollution to speak of.

It can sometimes appear frighteningly close even to us who do that flying thing for a living. Seeing access panels, gear doors or tires is absolutely normal.

[Doug E Style]

If your aircraft had been turning away from the other aircraft, even if only slightly, the position of that other aircraft relative to the wingtip of your own would have made the apparent difference in height look much less. I have been in a holding stack 1000' below a bigger aircraft whose turns were a little wider than ours and as we both turned it really did look like we were flying wingtip to wingtip even though I knew we had 1000' separation.
Incidentally, 100' is roughly the wingspan of an A320.