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The "Mk 1 Eyeball" / lookout / see and avoid are almost totally useless

Now that I have a TCAS 1 system installed, I can see for myself what other TCAS owners have been telling me for years: most traffic is never spotted even if you know where to look.

This is the case no matter how many people are in the cockpit and looking out for the reported target.

I would put the "invisible traffic" figure at 90%, minimum.

The traditional Mk 1 Eyeball (a British RAF expression, I believe) seems to be mostly useless.

Shoreham EGKA, United Kingdom

I would put the "invisible traffic" figure at 90%, minimum.

I can't confirm that! When it's on TCAS and within reasonable range (5NM or less) we usually can see it. The invisible ones are most often the ones ATC warns us about: "traffic in your two O'clock position 2 miles, right to left, type and altitude unknown." 90 percent of those we never see, the few ones we spot are usually flying extremely low.

With TCAS it is imortant that you reduce distracting clutter from the screen by adjuting the settings to reasonable values. Make range dependent on your speed: During cruise (TAS > 400kt) I usually set 20NM range, during approach 12 NM and on final 6 NM. In vertical mode, we only use "normal" in cruise which means only targets between 3000ft below and 3000ft above will be shown.

But the real dangerous traffic is that, which neither ATC nor your TCAS will find because it is not squawking and hard to see due to it's size and colour: Gliders, (motorised) paragliders (have encountered those up to FL100) and microlights. How many of those we see or don't see we will never know...

EDDS - Stuttgart

altitude unknown." 90 percent of those we never see, the few ones we spot are usually flying extremely low.

That specific thing (my bold) I concur with. There is a strong correlation between non-mode-C traffic and very low flying (say below 1500ft) traffic. The place you will meet them is in the circuit

But the others seem hard to spot. I did wonder if the installer connected the antennae backwards, so targets on the left are shown on the right etc. He did not have any test equipment, despite being an "Avidyne dealer". But I see known targets in precisely the right place when approaching an airport.

I too fly with the vertical setting in NORMAL which is about 3000ft above and below.

Shoreham EGKA, United Kingdom

Remember transiting up from Cranfield, about 3000 feet, four of us, and myself flying. Guy in RHS asks if I have the helicopter in sight. I mumbled, looking, and yes I have. It continues straight for us, he nudges me and asks again do I have it. No, I answer, but looking. To this day I remember it whizzing past my left window, about 150 feet away, exact level, with the shouts of my startled pax, wondering why I had not taken evasive action, and how close I had come to killing them all!!!!!!

Fact is, I did not see it, and I doubt he saw us, he certainly did not take any evasive action.

It was close, but actually I think the closer they are, the more difficult it can be to pick them up visually, certainly in cruise. A helicopter heading straight for you, is actually pretty difficult to see, particularly against a changing skyline.

I am looking at these units, but not sure about actual accuracy, for the stuff that you really require to see. Agree, the circuit is probably most dangerous..

Fly safe. I want this thing to land l...
EGPF Glasgow

I dont think it does work. With the size of most GA aircraft, and their converging speeds, what wasnt there one minute ago, might be there the next. I know they say dont spend too long with your head in the cockpit, but you have to sometimes and you cant spend the entire flight swivelling your head around looking for traffic. Plus we fly for pleasure and sometimes it's nice to look out the window at the scenery below occasionally.

I have one of those ZAON MRX things, which I accept isnt a substitute for a visual scan, but I also try and make use of a traffic service where I can to 1) try and make the flight as safe as possible 2) free me up to do other things, including enjoying the scenery around me. Thats not to say I dont lookout - I do, as much as I can, but I accept the old MK1 eyeball has it's limitations too and you have to put some faith into equipment/ATC/blind luck, and just being incredibly extra careful around very active airfields, circuits and VOR's.

Swivelling one's head around, in one continuous movement, however slow, does little good. I remember seeing (actually even translating) a magazine article that recommended scanning stepwise, i.e. a fixed gaze extreme port, rest just a second and LOOK, than 15 or so degrees clockwise, and so on until extreme starboard.

[[edit: I feel confident the Mk I operator's manual might well suggest similar technique. Copy, anyone? ]]

I've always done it like that, but have no base for comparing the results.

EBZH Kiewit, Belgium

Quite an informative paper on the subject, here

"our data suggest that the relatively low (though unacceptable) rate of mid-air collisions in general aviation aircraft not equipped with TCAS is as much a function of the “big sky” as it is of effective visual scanning"

I think that means - look out of the cockpit as much as possible and rely less on technique


"our data suggest that the relatively low (though unacceptable) rate of mid-air collisions in general aviation aircraft not equipped with TCAS is as much a function of the “big sky” as it is of effective visual scanning"

I think it that means they agree with Peter's original POV... that look out is not terribly effective and is of limited utility in relation to luck.

The two times I had near collisions, I didn't see the aircraft until it was close. On one occasion I was able to take evasive action, and it actually did prevent certain head-on collision. On the other occasion I did not have time to take action but collision would not have occurred regardless. One save due to look-out, one save due to big sky.

The only time I had a near collision was above a layer of scattered/broken cloud at about 1000 ft, descending into the downwind leg circuit of my home airfield in between the gaps, and then we encountered a plane scud running right through the ATZ while not maintaining any radio contact on our frequency ! I was not P1 on that leg, but the lesson I learnt was that in poor viz / clouds at circuit height, was to descend deadside on the unofficial instrument approach, using a close by VOR, and staying on a radar LARS service for as long as possible before switching over to the A/G frequency. To be honest if I was P1, I would have done that anyhow, but I should have suggested this to the guy flying P1.

Regardless, the MK1 eyeball was only helpful at the very last minute and had I had a decent TCAS system on board, maybe I would have had some warning.

The TCAS on my plane works well and I am most conscious of how useful it is at low level.

EGTK Oxford
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