Probability of conflicting traffic?

[Mariner9]

Somebody on a recent thread stated that in his/her view, see and avoid was a load of hogwash, and that collisions were primarily avoided by the statistical unlikelyhood of flight paths converging.

That got me thinking about the number of times that I've seen conflicting traffic, and had to manoever to avoid it (apart from joining/in the circuit). As far as I can recall, that has only happened to me on three occasions in my 170-odd hours (each of which was a conflicting glider as it happens)

There was also one occasion where I didn't see conflicting traffic approaching until the last second when it flashed past on a reciprical course about 100' to port same level (if you flew a Rockwell Commander near Goodwood last July it could have been you)

There's also a chance that I have also been in near-conflicts that i haven't seen at all

Assuming I have seen everything, on the basis of my observations we might expect to be in a conflict situation every 40 hours or so. However, the majority of my flying hours are in the S. West, with only 30-odd in SE bandit country, where given the increased traffic density, conflict chances are likely higher.

Anyone care to add their experiences to see if we can come up with an average?

[englishal]

I've had a number.....1 in 40 hours sounds about right, I had one during my PPL which was opposite direction, about 100m right, same level......

I was flying a G1000 aircraft with Traffic display in the US a few weeks ago, I realised that the traffic I saw compared to what was on the screen was about 30%....The nice lady informing me of "traffic traffic" went off a number of times...... Sods law says that the traffic is ALWAYS converging......

Damn useful device, shame its not available here...

[Genghis the Engineer]

I can say with certainty that there are at-least two occasions in the last 1000hrs when see-and-avoid in VFR saved my neck.

1 in 500 hours is pretty significant by my count.

G

[High Wing Drifter]

Somebody on a recent thread stated that in his/her view, see and avoid was a load of hogwash, and that collisions were primarily avoided by the statistical unlikelyhood of flight paths converging.

In 200 odd hours I can recall the need to avoid five times; three were very close and to be honest one was so close and quick that we flashed past each other before either got a chance to react and that was over WCO, an early lesson in not flying over landmarks or beacons!

After seeing Farnborough's radar screen, I'm much resigned to the fact that I simply have not seen at least half the traffic that was probably visible to me, and I reckon I'm pretty diligent when it comes to lookout.

[hugh flung_dung]

Quite a few near'ish (usually gliders) and 1 VERY near - maybe 2 spans away, passing at 90 degrees L-R, 28/Aug last year, N of Bournemouth, T tail (PA38?) - in a few thousand hours.

I'm a believer in the "big sky small aeroplane" theory, lookout is important and helps but it cannot fully protect you.

One common failing with students when they see a close "bogey" - they don't turn towards so they can keep it in sight.

HFD

[IO540]

Those you spot are not on a true collission course.

An aircraft on a true CC will appear completely stationary. In 600hrs I've never had one of those (evidently, as I am writing this) but have seen plenty which I felt a need to avoid. They might have missed by 50-100m, which looks very close.

The only foolproof solution, for those who think it's worth paying for, would be mandatory Mode C and TCAS.

[Saab Dastard]

I've had one VERY VERY close one in a little over 100 hours. Were it not for the mark 1 eyeball and quick reactions on the part of the FI sitting in the RHS I would not be here today.

That was SE England, not far from Pulborough, at about 2500 feet, >10K vis. about 3 years ago.

As IO540 says, the ones you don't see are the ones that will hit you!

The FI (not me) estimated that we missed by less than 30 feet - and that was AFTER taking last-second avoiding action (we dived, just as well the other aircraft didn't).

SD

[IO540]

Flying around MID at 2400ft is not a lot better than flying in a circuit

Otherwise, if one flies around at reasonable levels, say 3500ft+ rather than 2000ft where a lot of people like to sit, there is very little traffic.

Abroad I fly at 8500/9500 or higher. Best MPG is at 8500 or so.

One can get very hung up about this. Statistically there is no support for it though, and I would never pay the £15k-20k for a TCAS. Especially not until transponders are mandatory. A radar altimeter, less than half the price, for those DIY approaches into [name your favourite English/Welsh airfield with a perpetual cloud cover and a dodgy NDB] would be a lot better

[booke23]

I'm surprised you got back to the airfield with your pants still clean saab after the 30ft incident!

In my 100 hrs I have not had any close calls like the above. Although I was flying north of Bournemouth one Sunday a few weeks ago and had to turn to avoid 3 aircraft in 40 mins. All at the same level, closest was about 200m horozontally....although we both had seen each other.

It's very true that it's difficult to see aircraft on an collision track......I also know that alot of collisions happen because one or both aircraft were in each others blind spots.

I always try to keep a good lookout, but theres alot to be said for climbing higher.......I find that even at 4000ft theres much less traffic.

Also I usually talk to the nearest radar unit if I can.......they can be a good help at times. If I'm flying from A to B in a straight line I'll ask for a RIS......Although often it's easier said than done getting a RIS!!

[Johnm]

I've had two fairly close encounters both with gliders in my 300 odd hours.

I also fly as high as I can and choose odd levels eg 2200 ft or 1900 ft in the crowded SE where TMA is down to 2500 and many seem to pick 2000 or 2400.

One interesting observation from an IMC holder, flying North about 500ft above a thin layer of Stratus with a RIS I got a lot of opposite direction traffic info and never saw any despite a careful look out for it (and pop up traffic). I can only assume it was below the layer and I was above. It's safer on top

[chevvron]

Climbing out of Halton in an AX3 passing about 2000ft, just turned to go down the valley towards Amersham when a Citation appeared from over my right wing (classic blnd spot) and turned left to cross in front of me, cunningly keeping his reg from my view. it seemed close, but was probably 300m or more. Obviously he'd seen me, was he 'carving me up' I wonder?

[stiknruda]

This year's end of season display pilots' seminar had a very interesting presentation about this entire subject.

In short, I'll tell you what my chum and I were so amazed by that we even talked about it on the way home....

Statistically, by a huge factor, most air to airs happen in the circuit. Of those 60% are run down from behind - Mrs Breakneck you may have a point, so I suggest that you acquire a faster aeroplane!

Stik

[Laundryman]

I'm running at about 1 in 25 to 30 hrs three this year each time the same flying school (big well known organisation too) they teach a lot of commercial pilots so maybe these guys have got their heads down practicing IFR. It does make me apprehensive in case I miss seeing one until too late. Always ask my passengers to keep a sharp eye out, its good to have to pairs of eyes on the job even if they are in the same aircraft.

[IO540]

The problem is that lookout has a limited effectiveness.

I've often flown under an RIS, with 3 passengers, and we were all looking out for traffic reported to us. Most of it we never saw.

Also, at best, the angle of view from a cockpit is limited. You could be going at 100kt and another plane descending at 180kt could fly into you from say your 4 o'clock.

People don't like to be told that the "old Mk1 eyeball" (to quote the traditionalists) is actually pretty useless....

In reality, mid-airs are extremely rare. If they were common, something would have to be done about it. Just as well, since most people really do believe that keeping a lookout avoids hitting something. Those that you spot (and perhaps try to avoid) would nearly always not have been on a true collision course anyway.

The only potentially effective way is mandatory Mode C transponders, and TCAD/TCAS which starts at about £15k. Even then, you won't spot most of the reported traffic but at least you can take your own avoiding action.

I agree the circuit is the most dangerous place. Which is why I don't like overhead joins. One is asking several pilots at once to all head for the same area, all at 2000ft AGL. Usually, one cannot spot all of those who are known (from the radio) to be arriving at the same time. In those conditions, I've aborted the join and came back later. But there isn't a solution to this, if several planes really do arrive at the same time. Not under VFR. Under IFR you just put them into holding patterns so in effect they are doing overhead joins but at different levels

[High Wing Drifter]

IO540,

The only potentially effective way is mandatory Mode C transponders, and TCAD/TCAS which starts at about £15k. Even then, you won't spot most of the reported traffic but at least you can take your own avoiding action.

I think this would create more problems. I agree that technology solves IFR problems, but remain suspicious that for plain old vannilla VFR, technology seems to add complexity and procedures for dubious returns. As has been said, most mid airs are in the circuit and any half decent TCAS system would be going absolutely banannas as it approaches the ATZ! Yes you can switch it off, but that is another line to the checklist, something else to miss and something to distract. TCAS is a good idea for an airliner where seperation is ATC maintained 99.73% of the time and any Resolution Advisory is a rare eye-widening event. For the VFR bimbler in the open FIR you can fly pretty close once viz is established without feeling in danger and Resolution Advisories would be common place and needless in most cases. I'll wager that it would become next to friggin useless once you have tired of the number of alerts vs the number to real potential VFR conflicts.

[DubTrub]

I find that even at 4000ft theres much less traffic

At 800 feet there's even less. And before someone mentions the military...

Also, never fly at "exact" height/altitude, and never over a VOR or NDB honeypot.

[funfly]

I've often found myself looking at an aircraft approaching from my left (say at 10 or 11 oclock) and maybe heading towards me or across in front of me although not necessarily on a collision course - maybe at a different height.
The rules of the air say I should turn to my right but that assumes he will also move to his right. In my experience these aircraft zoom past and don't seem to have spotted you at all so what would others do in this situation?

[MichaelJP59]

Which is why I don't like overhead joins. One is asking several pilots at once to all head for the same area, all at 2000ft AGL. Usually, one cannot spot all of those who are known (from the radio) to be arriving at the same time. In those conditions, I've aborted the join and came back later. But there isn't a solution to this, if several planes really do arrive at the same time. Not under VFR.

I often worry about this. Someone reports overhead join, descending on deadside, but you have no real way of knowing where they are if you're also approaching.

So far I've tended to wait until I think it's clear, but once I reported joining overhead and someone else did a few seconds later. Just carried on, but I did feel as though I was trusting to luck even though I was keeping a look-out. There are plenty of blind-spots even on a good visibility aircraft.

[Penguina]

Statistically, by a huge factor, most air to airs happen in the circuit. Of those 60% are run down from behind

Where you just don't stand a chance of saving yourself.

I've had a couple in my 150 hours. One was indeed in the circuit, in bad viz and it persuaded me not to be such a silly billy and continue flying in such weather!

The other was very lucky indeed. Finding the cloudbase seemed to be lowering a bit, I descended 100ft or so to be on the safe side. 30 seconds later someone emerged from the cloud roughly at the height I had been maintaining previously.

On neither occasion would my eyes have helped me, I'm afraid to say.

[ShyTorque]

Highwingdrifter,

"I think this would create more problems. I agree that technology solves IFR problems, but remain suspicious that for plain old vannilla VFR, technology seems to add complexity and procedures for dubious returns. As has been said, most mid airs are in the circuit and any half decent TCAS system would be going absolutely banannas as it approaches the ATZ! Yes you can switch it off, but that is another line to the checklist, something else to miss and something to distract. TCAS is a good idea for an airliner where seperation is ATC maintained 99.73% of the time and any Resolution Advisory is a rare eye-widening event. For the VFR bimbler in the open FIR you can fly pretty close once viz is established without feeling in danger and Resolution Advisories would be common place and needless in most cases. I'll wager that it would become next to friggin useless once you have tired of the number of alerts vs the number to real potential VFR conflicts."
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Sorry - but have you ever flown an aircraft equipped with TCAS or received instruction in its use? Because you are 100% WRONG! I fly a commercial helicopter thus equipped. We are required to fly in Class G most of the time, often IFR or changing between IFR/VFR or vice versa. We do NOT, repeat NOT use RA mode but TA mode only. To be honest, I don't EVER want to go back to flying without it because I know how good it really is.

I don't understand your point about TCAS distraction - if you are possibly about to have a mid-air collision - what else is more important than knowing about it and acting to avoid it? NOTHING!

Judging by the number of times that we encounter other aircraft and hold right of way i.a.w. the Rules of the Air, but have to take serious avoiding action because nothing is done by the other pilot, TCAS very certainly helps us spot conflicting aircraft MANY times more often than other pilots spot US. We carry extra white strobes and HISLs and switch on the forward facing searchlight when appropriate, but it IS most often US taking the avoiding action.

Once you have used TCAS for some time you begin to realise just how many aircraft there REALLY are out in class G and how often you potentially get very close to other aircraft. There must be a lot of pilots flying around UK in blissful ignorance - because they don't SEE all the other aircraft they asssume they just aren't there!