Collision Avoidance vs. "See and Avoid" for GA

[italianjon]

I was asked for my opinion on a particular technology (PCAS - Portable/Passive Collision Avoidance System) by a colleague at work. A company (internal) pilot opinion survey had revealed that whilst people knew about the technology, none had fitted it to their aircraft. My colleague asked the question; given that this technology offers 'a decent amount of benefit for the cost' why was this the case?

I will not offer my opinion here as I intend to show this thread to my colleagues and do not want to 'set the tone' or prejudice the outcome in any way.

So, I would be extremely grateful to hear opinions on this, broadly along the lines of

1) Do you know what it is?
2) Do you have it?
3) Would you buy/fit it?
4) If so, why, if not, why not.

[gpn01]

I guess this is an example...
Zaon Portable Collision Avoidance System - PCAS XRX Onyx - MyPilotStore.com (http://www.mypilotstore.com/mypilotstore/sep/4612)

So, answering the questions:

1) Do you know what it is?
See URL above - I didn't but I now do

2) Do you have it?
Nope

3) Would you buy/fit it?
No

4) If so, why, if not, why not.
No panel space, no power.

Most importantly though I presume it requires everybody else to also be equipped with a similar device for it to work (e.g. like Mode-S, FLARM or TCAS). Unless there's complete interoperability between the various technologies then there's a great risk that it won't spot the other guy (particularly if they don't have any device on board).

[chrisN]

Gpn, I don’t think you’re quite right about everybody needing it. AIUI, Zaon etc. requires everyone to have a transponder on, but not necessarily to have their own Zaon. Flarm, on the other hand, does indeed need everyone else to have FLARM to be detected. The full scale TCAS requires everything else to have a transponder to be detected, but only gives automatic conflict resolution to mode S equipped aircraft (when the two TCAS’s “talk” to each other).

No doubt an expert will be along to correct me if any part of this is wrong.

Chris N.

[Wrong Stuff]

1) Do you know what it is?
Yes

2) Do you have it?
No

3) Would you buy/fit it?
Probably not

4) If so, why, if not, why not.
- It's a bit more clutter in the cockpit.
- There's a danger it may give a false sense of security and keep eyes inside the cockpit rather than outside.
- Quite a few aircraft don't have transponder fitted or turned on.
- The perceived risk of a mid-air collision is greater than the US accident statistics show the real risk to be.

Aviation Consumer did a review of the top 10 safety investments sometime last year and the traffic warning boxes didn't make the list. In the US there are about 10 midairs a year and they have about a 50% survival rate. From memory, in the UK there seems to be about 1 a year with a similar survival rate. Put simply, there are a lot more common ways to kill yourself than hitting another aircraft, and you're better off spending the money trying to avoid those real risks.

The top ten most effective safety investments according to Aviation Consumer:

1) An instrument rating
2) A real, thorough flight review
3) Add a rating
4) Fuel totalizer
5) In-cockpit weather link
6) Progressive maintenance
7) Seatbelt harness for older aircraft
8) 406 MHz ELT
9) Cabin airbags
10) Vortex generators

It's interesting the top three are all pilot-training related.

[Africrash]

We have a Zaon in one of our aircraft at work, I would certainly not buy one for my own aircraft, my current experience suggests the unit may not display traffic position correctly, to the extent it could result in avoiding action in the wrong direction!

Nice idea but I will wait till they get them right and look again, CTAF radio works better right now.

Crash

[ShyTorque]

4) If so, why, if not, why not.
- It's a bit more clutter in the cockpit.
- There's a danger it may give a false sense of security and keep eyes inside the cockpit rather than outside.
- Quite a few aircraft don't have transponder fitted or turned on.
- The perceived risk of a mid-air collision is greater than the US accident statistics show the real risk to be.

This viewpoint is often held by people who have never flown with a transponder based warning system. Conversely, I've never heard a pilot who HAS used one of these sytems say that they are no good. Keep eyes inside the cockpit rather than outside? They most definitely DON'T if used properly, namely incorporated as part of a proper lookout scan. A glance inside at the screen takes less than a second. As soon as this equipment indicates a possible threat the eyes are most definitely outside.

I have good vision (still 6/5) and often spot other aircraft well before my second pilot BUT after using TCAS and TAS (about 8 years now, 4 different aircraft types) my eyes have literally been opened to how many other aircraft can pass close by unseen (even in what would be classed as excellent visibility, the problem being lack of contrast).

Also, unaided lookout simply can't see through that lump of cloud between you and the aircraft that is going to hit you from above and behind, or immediately below and climbing towards you.

Some who firmly believe that the sky is usually clear and their own unaided lookout is perfect might just be the ones who most need TCAS/ TAS help. They might perceive the threat of collision to be less than it is, simply because they aren't seeing how many other aircraft are actually around them.

My type of ops require often VFR to IFR and back to VFR, most of it in class G airspace. Whatever the conditions, almost on every flight I encounter at least one aircraft who fails to comply with the rules of the air, especially with regard to giving way to an aircraft on the right. Assuming that everyone has passed the air law exam, that leaves two possibilities. Firstly, some pilots know the rules and ignore them, or secondly, some do fail to see other conflicting aircraft. I know I might not have seen some of these aircraft so early myself without TCAS to assist me, obviously some I do see perfectly without, or I probably wouldn't still be around writing about it after thirty one years of flying for a living. It's just as possible that I have failed to give way to other aircraft myself because I failed to see them.

The risk IS out there because the human eye is far from infallible, as more experienced pilots come to realise. Yesterday I spotted (quite late / close) a metallic red Jetranger with white registration lettering (I won't post the reg here), flying westbound, south of Bovingdon and north of the LHR zone yesterday, coming in from my left. That aircraft flew a steady course and passed immediately in front of my aircraft at the same altitude, so my right of way. I maintained course as long as was safe then slowed rapidly to let him past; it seemed he hadn't seen me at all but I had seen him, so had Heathrow Special controller. However, he was one of those not transponding at all and perhaps not talking to someone who might have given him traffic info on my aircraft.

An ex-colleague of mine has suffered mid air collisions twice, both times in helicopters and both times with two pilots on board. Once from above and behind, an aircraft descended onto him, inside regulated airspace. Another time another helicopter hit him from below. A good lookout on his part wasn't good enough on either occasion, because the other aircraft were both out of his field of view. He has developed an exceptionally good lookout (!) but is also very enthusiastic about the benefits of TCAS, which also works when a mere unaided lookout cannot.

[Fright Level]

I fly with TCAS at work and it's invaluable. Outside of controlled airspace, which is where most GA aircraft operate, it's useless as until the very last microlight has one fitted it's a distraction.

In VFR flight, nothing should distract from lookout. A device like this has added risk of a false sense of security. Not for me, not even as a back up aid.

[ShyTorque]

FL,

Then please just make sure you fly with Mode C selected, so I can use my TAS to tell me you're there at twenty miles range. Rather than wait for both of us to hope to spot each other at 4 or 5 miles, which is about the limit of human eyesight where light aircraft are concerned in most cases. :p

BTW, TAS gives me absolutely NO sense of security, just the opposite. Which is why I look out as much as anyone else when VFR. Controlled airspace gives me a slightly better feeling of security.

[gpn01]

ChrisN said: "Gpn, I don’t think you’re quite right about everybody needing it."

Unless it has an active element to it (e.g. it's own radar) then I don't see how it could work (typical example being Cessna flying with PCAS vs glider not equipped with anything). Happy to stand corrected on this. I do sense that PCAS/TCAS/ADS-B/FLARM means we're going to go down the 'Mode-S' thread again!

[Fuji Abound]

In VFR flight, nothing should distract from lookout. A device like this has added risk of a false sense of security. Not for me, not even as a back up aid.

Ah yes, the visual waveband receiver, requires certification every two years or less depending on age, hopeless at tracking a moving object with no relative motion, generally lazy and unreliable but in its day all we had. Of course it wouldnt be certifiable today but lives on with grandfather rights.

[Tony Hirst]

ItalianJon,

Long time no see, how are you?

To answer your question I've had the Zaon MRX. The past tense due to being in another part of the world now. It isn't snake oil. It works well. It provides minimal information (relative height and distance) so does not encourage an eyes in mentality. It is tiny and the batteries last a fair time.

They are passive receivers only - they eaves drop on transponder conversations between aircraft and ground stations. The distance is calculated based on power output assumptions. These assumptions are used to identify the host aircraft transponder and separate it from others. Occasionally the host's transponder may not be powerful enough and may be confused as another aircraft and generate spurious same height 0.1nm warnings as I had in IMC on approach to Exeter after being warned about near by corp jet. Was not happy with that, possibly bad placement by me. Despite that I think this unit is useful for IMC, but once you are in a radar environment I think you are best served by switching it off. If you are like me and reasonably diligent, I think there is less value in VMC and I rarely used it as such.

Hope that helps.

[A and C]

As usual the velcro fitted boxes with power from the cigar lighter are leading the way! The only problem being that it is yet another wire to trip over when you get out of the aircraft.

Such a pitty that the autoritys won't enable the TIS system that is avalable in the USA. The system works by data linking ground radar transponder returns via the mode S transponder to the map screen in the GPS.

If this was avalble them the take up of mode S transponders would be much higher because aircraft owners would see some return for fitting the mode S.

[chrisN]

Gpn, AIUI, a transponder squawks every time it is interrogated. A mode A or C does so every time a radar head anywhere in ground-air range sweeps it, which is most of the time, anywhere. A Zaon etc. “hears” that squawk every time, and assesses proximity by its signal strength or something.
A mode S only squawks when it is told to. The “S” means that ATC can select when they want it to or not. For GA aircraft with S outside CAS, that is much less frequent – say once per second instead of umpteen times per second (hence requiring less battery capacity for a particular flight length – one of the much-vaunted claims by the CAA to justify it for gliders etc.).
TCAS generates its own interrogations. See below, as others have posted in the past:
[quote] TCAS Function:

TCAS works its way through the Roll Call, sending Selective Interrogations to those aircraft. This gives it a picture of all Mode S aircraft in the vicinity. As aircraft move out of range, their announcement signal eventually gets weak enough to be ignored so they are dropped from the roll call.

It then does a Mode C "All call" sweep, to catch non mode S aircraft. Note, it only cares about altitude, so its sends Mode C interrogations only - However, . . . [snip] - non altitude encoding aircraft still reply to Mode C calls, just with an empty frame, so the existence and range to the target can still be derived.


Other Mode S / TCAS tricks for interference reduction.

Whisper / Shout.

TCAS sends its mode S interrogations at variable power levels. In a nutshell, it 'Whispers' at low power to the target, if no reply is received it transmits progressively more power, eventually 'Shouting'. Its uses a successful transmission as a benchmark for its next attempt, and progressively adjusts power to the minimum required to maintain contact.

TCAS interference Limiting Mode.

Lengthy topic, more pilot oriented, will post if anyone interested (Its already written for an email query I received, so no trouble).

-----------------------------------------
[snip] . . . just to clarify a couple of points.

At present TCAS and Mode S ground stations operate completely independently. A ground station would see TCAS squitter or air to air surveillance as interference and visa versa.

Mode S ground stations do not use the squitter data but transmit an All Call interrogation to find out who's out there which will also include its interrogator identity code. This then gets included in the transponder reply. All Mode S interrogations and replies are parity encoded so that the data is only used if it contains the expected aircraft address or interrogator code.

The way that Mode A/C systems reject interference is to interrogate a number of times and only believe the reply if it gets the same information more than once (There's also some clever decoders that correlate replies on amplitude and angle of arrival.)

At the moment the only link between TCAS and ground based Mode S is that the transponder will generate a message to the ground station that contains the RA information if one is generated. This is of limited use to co-ordinate actions, it wouldn't arrive in time, but could be used to clearly identify the aircraft concerned on the display. At present there's not many operational Mode S stations outside the US and even these don't use this feature. However, most of Europe will be updating to Mode S in the next couple of years.

Lots more proposed for Mode S in the future, see the Eurocontrol web-site for info on 'Enhanced Surveillance' and ADS-B using 1090 extended squitter.
---------------------------------------
As before, no doubt an expert will be along to correct me if any part of this is wrong.

Chris N.

PS – where I wrote squawk, that should probably be “squitter". And of course, neither TCAS nor Zaon etc. can detect a non-transponder-equipped flying device of any sort - glider, paraglider, LAA non-electric type, or whatever. Nor falling parachutists. Nor birds. Nor radiosonde balloons.

[IO540]

gpn01

Yes, the £10k and up "TCAS" systems are active interrogators. Your aircraft (if thus fitted) emits an omnidirectional burst every so often, triggering nearby transponders. Only Mode C or S transponders return a useful return though.

Actually "TCAS" is a wrong term as it implies the pilot gets an RA (resolution advisory) which is a voice telling him to climb or descend. The GA kit is not certified to do that. I think TCAD is a more correct name; you just get a screen showing other traffic, and warnings if somebody is getting dodgy. But the pilot decides what to do about it.

The cheapest Zaon box is IMHO crap because you get no azimuth info. If you fell asleep it might wake you up... The next one up (c. £1000) gives you rough azimuth info and should work well. I have flown with a couple of the latter; one kept picking up the aircraft itself, plus traffic, and the other one worked apparently well.

The problem is that it isn't easy to install it neatly - it really needs fixed wiring and a decent mounting surface, and the fixed wiring is a "grey area" in certification terms. I installed a Garmin 496 for its TAWS function (to get a "GPWS" functionality) and the resulting very neat wiring took the avionics man all day to do, and that was after I prewired a lot of cables with special connectors. In fact the 496 could have been mounted completely out of sight (with its on/off switch hot-wired or whatever) but I put it on the yoke and it forms a useful emergency backup GPS.

The whole issue of installing "portable" kit neatly, using what is inevitably fixed wiring and connectors, is a grey area (because the kit you are installing is not approved for a fixed installation, not coming with Approved Data) and needs a very friendly avionics shop and some technical knowledge, for fitting special inline connectors in the cables, so the "portable" kit can be removed for the Annual and then put back in. A lot of people have done it, but most wouldn't, and it needs to be done in a way which would enable you to get the Annual done at even the most anally retentive shop. Easier on the N-reg.

[gpn01]

Thanks all for the various clarifications. My point was simply that devices of this nature do not pick up other aviation that isn't carrying some sort of transmitting device (glider, microlghts and hang-gliders spring to mind).

[SNS3Guppy]

Actually "TCAS" is a wrong term as it implies the pilot gets an RA (resolution advisory) which is a voice telling him to climb or descend.


Incorrect. Only TCAS II does that.

TCAS 1 does not.

[flyme273]

1) Do you know what it is? Yes
2) Do you have it? No
3) Would you buy/fit it? Have considered.
4) If so, why, if not, why not.
Not sure if this product is sufficently dependable. Would prefer azimuth info, but install problem with the larger unit.

Would like to have an affordable fix install TCAS, (maybe install the sensors with the wing-tip lights?) I'm convinced it's necessary, especially when low sun, coastal fog or industrial haze/ inversion. Eyes are not good enough. Anyone who believes their look-out is sufficent for fast jet conflict has never been there.

[Kyprianos Biris]

1) Do you know what it is?
YES

2) Do you have it?
NO

3) Would you buy/fit it?
NO

4) If so, why, if not, why not.
Because I am against portable stuff in the cockpit.
I am doing an exception only with the Garmin296 as a back up GPS / VFR advisory moving map and I use it only with its battery to avoid loose cables in the cockpit.
Also I believe these devices are not accurate enough.
For traffic awareness you need a device that shows you relative bearing and altitude with accuracy so you know where to look for instantly.

[scooter boy]

I really love my BF Goodrich TCAS.
I used it this morning, I like it very much.
Does it give me a false sense of security - absolutely not, it does enable me to locate traffic that my eyeball struggles to and makes me feel safer when in the soup.
It overlays on my G1000 MFD so there is no loss of situational awareness.
I still look outside, in fact it speeds up acquisition of traffic so much I have more time to scan the rest of the sky when VFR.

A safety plea - if you have a mode C transponder then please switch it to ALT, it lets those of us who have this great technology see eachother and also see those who don't have it.

SB

[robin]

Does it give me a false sense of security - absolutely not, it does enable me to locate traffic that my eyeball struggles to and makes me feel safer when in the soup.
It overlays on my G1000 MFD so there is no loss of situational awareness.
I still look outside, in fact it speeds up acquisition of traffic so much I have more time to scan the rest of the sky when VFR.


Yes - you can find those who are squawking.

I was flying in the Bristol area and they identified a target (which I'd already seen) but not the 3 microlights in my 12 o'clock

Yes, advise those with transponders to use Mode C, if so equipped, but always bear in mind that the majority of very light aircraft are flying below 3000' and won't be transponding and may not even be radio-equipped. Either that or they may not be on your frequency.

Mk1 eyeball isn't perfect but, in reality, is your only equipment for a lot of flight modes...

[SNS3Guppy]

Even TCAS equipment doesn't always spot other aircraft. Not infrequently I see other aircraft pass close by, whom I know full well are squawking mode S, and yet they don't appear on the TCAS. Make no assumptions, and don't let the equipment do the looking for you.

It's called "see and avoid" for a reason...not "monitor and avoid."

[IO540]

I see other aircraft pass close by, whom I know full well are squawking mode S, and yet they don't appear on the TCAS

Why? They should. IF they are actually squawking, and your installation is not masked by the airframe etc.

[SNS3Guppy]

Why? They should. IF they are actually squawking, and your installation is not masked by the airframe etc.


Exactly.

This isn't exactly an amature installation, and the condition in which I see traffic missed occur when I'm looking right at the traffic and it's the only traffic around. It happens, and I've seen it on a fairly wide variety of equipment, installations, and circumstances. Even the costliest and best installations still miss traffic. Go figure.

Point is that the law is see and avoid. This applies in IFR flight every bit as much as VFR. If you can possibly see it, you're responsible to be looking for it.

Use all the other equipment and gimmicks you like (and if they're available, you should)...but there's no substitute for the Mark 1 eyeball. See and avoid like your life depends on it.

Because it does.

[ShyTorque]

TCAS has never been a replacement for see and avoid and was never intended to be. I've never met a pilot who actually thinks that it is. Certainly, any pilot using it regularly soon discovers the limitations of the equipment and knows where to place the information it gives, as far as prioritites are concerned. I consider mine an extra pair of eyes, nothing more.

I wonder if those who say they don't want it at any cost would also object to anyone in the other seat pointing out other aircraft, similarly would they not bother with an ATC radar service because they would object to being advised of other traffic? Both of these also provide assistance to 'see and avoid' but similarly are not infallible.

TCAS I offers basic collision avoidance information to pilots as an aid to ‘see and avoid’. The main difference from TCAS II is that it does not generate 'Resolution Advisory' (RA) warnings. Because of this principle difference, TCAS I systems are less costly and smaller, making them attractive for those operating at low levels and/or outside controlled airspace where extra information to assist with ‘see and avoid’ is most welcome.

[englishal]

but there's no substitute for the Mark 1 eyeball
Oh no, lets not start that debate again :ugh:

Personally when cruising at 300kts and someone is coming at you at 300 kts, my eyes won't see them until it is too late ;)

[SNS3Guppy]

Oh no, lets not start that debate again

Personally when cruising at 300kts and someone is coming at you at 300 kts, my eyes won't see them until it is too late


You may relax. Nobody has started any debate, as there's none to be had. There is no substitute for looking for traffic.

You'll note that I previously correctly stated that one should use all the resources available to look for traffic, as well one should. None of them relieve one of the responsibility to be heads up and looking for traffic. Even at 600 knots closing speed.

TCAS has never been a replacement for see and avoid and was never intended to be. I've never met a pilot who actually thinks that it is.


I surely have. More often than not, when I hear someone alerted to traffic, the response on the radio is "Got 'em on TCAS." Not "Traffic in sight."

Gimmicks don't replace the eyes. They supplment them, but don't replace the responsibility, requirement, and duty to stay eyes-peeled for traffic.

[JBGA]

Ask any glider pilot flying around in the Alps about the value of FLARM and you will get a unanimous answer. In a sport where mid-air collisions are one of the most popular ways to die, people gladly spend hundreds of pounds and make room on their panel and in the glider for the equipment and batteries.

There aren't enough mid-air collisions in power planes to get people interested in collision avoidance. In my experience, power pilots are more worried about engine failures or crashing in to a hillside in bad weather, probably because that's the most popular way to die in a power plane. If you could make a box that helped prevent engine failures or CFIT people would be snapping them up in their thousands.

[ShyTorque]

I surely have. More often than not, when I hear someone alerted to traffic, the response on the radio is "Got 'em on TCAS." Not "Traffic in sight."

Do you think that means the crew aren't looking for the traffic? I very much doubt it.

And they will "Get 'em on TCAS" before visually aquiring it, that's the whole point of the equipment, as an aid to lookout.... :ugh:

The equipment fitted to the aircraft I fly for a living works out to 20 miles. There is no way that the human eye will see other traffic at that range, no matter what the owner of the eye might claim and pre-warned is pre-pared.

Next time you ask for a radar information service, why not ask ATC to delay telling you about other traffic until just after you've seen it; perhaps giving you a heads up in good time is not sporting enough? :E

[SNS3Guppy]

Next time you ask for a radar information service, why not ask ATC to delay telling you about other traffic until just after you've seen it; perhaps giving you a heads up in good time is not sporting enough?


Now why introduce such stupidity into the conversation? Why not just turn off the TCAS for that matter?

One uses all the tools at one's discretion. These tools never relieve one of the responsibility to see and avoid, however.

I know a lot of pilots who believe otherwise.

In the general aviation, lower altitude, more congested airspace arena where not only is more traffic, but ground clutter, reduced visibility, and other distractions to acquiring traffic a factor, the issue of seeing and avoiding is even more critical; far more so than what we may see at FL410.

For the general aviation pilot who relies upon a gimmick that may or may not work, may or may not see other traffic, and in which other general aviation airplanes may or may not be visibile or even equipped with an electrical system, a false sense of security may be imbued and may lead to a false sense of security. Add to that a device which doesn't report the whole picture or give an adequate pictorial display, and you may just have more of a distraction than it's worth.

Personally, I wouldn't own one. I use TCAS II, it's useful, but I couldn't afford to put it in my own aircraft, and wouldn't bother with TPAS or other cockpit gimmicks available today. My eyes work reasonably well, however. Your own mileage may vary.

[ShyTorque]

Now why introduce such stupidity into the conversation? Why not just turn off the TCAS for that matter?


Perhaps you don't understand the smilies? Obviously, turning off the TCAS would be just as stupid, so I assume you are joking, just as I was...

These tools never relieve one of the responsibility to see and avoid, however. I know a lot of pilots who believe otherwise.

I'm surprised at that last sentence. The VFR rules are quite clear, at least the UK ones are.

[SNS3Guppy]

Don't be surprised. Yes, the rules are clear. Never the less, just as the burgeoning generation of glass-and-gps trained pilots is leading to the inability to navigate between two blades of grass when the GPS is turned off, the use of equipment that is sold as having the ability to spot traffic has lead to even more lax use of the eyes in the cockpit.

"Got em' on TCAS" isn't simply a lazy response. Too often it's a report that marks the end of the effort to spot the traffic.

See and avoid applies under IFR just as VFR; the responsibility is never relieved.

TCAS is an excellent tool, with lesser versions becoming progressively less useful as the price tag and capability decreases, but it's never more than just that; a tool.

A few years ago I took a checkride in a King Air 200 with an FAA inspector. I had borrowed the airplane, which was well equipped. It included TCAS. When he climbed aboard, he saw the TCAS and groaned. We departed his home field, which was located in a heavy training area in a busy metropolitan city airspace, and immediately had a TCAS screen full of warnings, displays, and threats. Even with the threat ring reduced to a minimum, there was still a constant run of traffic alerts and warnings as we worked our way between multiple airports out to a "practice area" for air work. Even there we had more nuisance warnings than help, and the TCAS served as more of a distraction than an aid. It also called for attention often enough that the temptation to go heads down and look for it on the TCAS was a detriment to safety; the inspector turned it off.

We've used them extensively in airline service, charter, various government work, and in the fire service. I've seen them become a help, and not uncommonly, a hinderance which in some cases has compromised safety instead of enhancing it. Even in fairly hard-core visual operations, I've seen people fall victim to the tendency to let the TCAS spot traffic for them.

"Got 'em on TCAS" isn't an acceptable response to ATC. "Traffic in sight" is acceptable, as is "negative contact." But not "Got 'em on TCAS." That doesn't mean a lot to a controller, nor can the controller be assured of what you've "got" on TCAS.

"XXX traffic two o' clock and two miles, three thousand, opposite direction."

"XXX, got 'em on TCAS."

"Riiiiiiiiiight...turn left heading two seven zero, descend and maintain one thousand five hundred, report traffic in sight."

[ShyTorque]

SNS, I think we might be separated by a common language here because this discussion seems to be going round in circles and I think we are mainly singing the same song.

I've seen people fall victim to the tendency to let the TCAS spot traffic for them.

In what capacity have you seen people 'fall vicitim'? I initially got the impression that you are an airline pilot; your profile doesn't mention in what capacity you operate or what licence you hold.

I have seen some pilots over-concentrate on spotting a TCAS 'target' that will not conflict, almost as if they try to prove to themselves how good their eyesight is. Meanwhile, they neglect the rest of the sky. Is this what you allude to? If so, I agree but this is a training issue, not a fault of the equipment. Just like over-concentrating on anything else inside the cockpit or getting distracted.

I've been flying TCAS 1 / TAS equipped aircraft for almost a decade, most of it outside controlled airspace, both single pilot and multi crew. I previously flew more than twenty years before that without it. All the instruction manuals I've read have stressed that avoiding action must NOT be taken on TCAS / TAS derived information alone, it is an aid to aquiring visual contact, no more. I repeat, TCAS must be used properly, it's a simple tool or aid to be used as part of a lookout scan, definitely not to be used as a replacement for lookout.

Every pilot I've met has been intelligent enough to realise that the equipment is far from infallible; i.e. if other aircraft aren't squawking they don't appear on TCAS. Similarly, an ATC service can only do so much, especially outside CAS. Some aircraft present a poor radar return and a controller may sometimes not be in a position to pass on timely advice on a 'late spot'.

Having said that, I would NEVER turn off something that might just save my neck and that of my passengers. I might turn down the audio warnings as low as they go via my headset control but would never turn off the box itself. A TCAS screen full of diamonds is not a distraction; it just reminds me to keep looking out of the windows.

[bookworm]

"Got 'em on TCAS" isn't an acceptable response to ATC. "Traffic in sight" is acceptable, as is "negative contact." But not "Got 'em on TCAS." That doesn't mean a lot to a controller, nor can the controller be assured of what you've "got" on TCAS.

Can the controller "be assured of what you've got" when you report "traffic in sight"? Moreover, can the controller be assured that it will stay in sight?

[italianjon]

All, Thanks for these replies it is showing some interesting themes...

I think the main point that is coming out is that these are all equipment and should be used as aids and information sources to assist the pilot - but do not replace a good lookout.

Also I think comment regarding FLARM in the alps raises an interesting issue. In the Alps people are flying closer together, there have been more incidents of aircraft occupying the same bit of airspace at the same time and therefore people choose to install this technology. But because of the terrain etc. more aircraft carry FLARM that don't therefore the solution works. However there is no mandate to carry it, it is purely an example of how the flying population recognise a danger and take their own approach to do it.

In the 'congested' skies over the UK, (I put that term in inverted commas because can you argue that the UK skies are as congested as a valley in the Alps?) there is, maybe, not the collision risk that is present in the Alps and therefore people feel that they get no benefit from installation in skies such as the UK.

Please keep the replies coming... it is good stuff.

I think there is enough for me to throw my 2 pence in the ring: -

1) Do you know what it is? - Yes

2) Do you have it? - No

3) Would you buy/fit it? - No

4) If so, why, if not, why not.

I think there are other alternatives already available that if used correctly can help and have minimal cost, for example actually using the ATC services available, ensuring the aircraft is flown properly (e.g. in trim etc) allows more time for look out, taking a friend flying and asking them to assist with the lookout (also alleviates boredom), thinking about the altitude and where you are flying (everyone fliew at 2,500 and 3,000 feet for example, so fly at 2750; if you are above the transition altitude use the correct FL even if VFR and if you are flying along a line feature, even if you are not using that feature to navigate recognise the fact that other pilots will... fly on the correct side etc. Doing your downwind checks before you fly the circuit, then all you need to do is look out while you're in the circuit (Don;t forget the Reds, Greens, Blues on Final tho)

Anyway, my 2 pence worth!

As I said keep 'em coming this is a really good debate!

[IO540]

ISTM that the most common thread among pilots who can afford the installed TCAS is that they won't install it until transponders are mandatory for VFR.

[chrisN]

Italianjon, in UK class G airspace, it seems to be the case that most GA power typically cruises at 1000 to 2500 feet, and most glider cross country flying is in weather conditions where gliders will normally be higher than that. Statistics show that glider/glider collisions are one of the three big fatal collision causes, accounting for typically one fatality a year. Glider/other GA collisions happen at far lower rates – about four in the last 30 years, not all fatal. So, FLARM for gliders in class G in the UK make sense to me, and is making sense to growing numbers of glider pilots, and we are fitting them voluntarily. So far, in small but growing numbers. Worldwide, I understand that over 9000 units have been sold.

In terms of risk analysis, and bang for the buck, I believe it is the right place for us to spend money. I believe that widespread adoption of FLARM for gliders will save more lives than the equivalent amount of money spent on mode S. Not only that, but as I and others have repeatedly pointed out, FLARM is physically achievable in most gliders, whereas mode S Power and space requirements preclude it for many, as well as there being few EASA-approved installation schemes.

For some gliders, transponders may have worth while benefits for their cost. I am planning to fit one, partly because I fly close to controlled airspace where it is a choke point for GA traffic to skirt round Stansted, and partly because sometimes I want to penetrate controlled airspace myself. I have solved the power problem in my glider, but not the EASA-approved installation.

I have a simple response to airline or GA power pilots who think we should have interoperability between gliders and the rest. If they think it worth spending money on, they can spend it, by fitting FLARM. It is the only thing in the foreseeable future which will assist in detecting most gliders. If they don’t think it worth the money for them, why should anyone think it’s worth only some glider pilots spending far higher costs on mode S, for the limited number of gliders where it is actually practicable?

If they don’t want an extra piece of equipment in the cockpit, which gives no interoperability with transponder equipped aircraft but does with the low threat of glider collisions, why do they think gliders should fit transponders which give no interoperability with other gliders, although that is where the biggest threat of glider collisions remains?

By the way, I totally agree that any of these electronic aids must be used to aid, and not replace, “see” and avoid. I also agree with those who recognize that the eyeball on its own is a very imperfect collision avoidance tool. We can never overcome blindspots with eyeball alone, and human beings seem incapable of perfect lookout even where blindspots are not a factor. I saw a safety presentation which showed that most collisions involving gliders are from behind one of them. Only one pair of eyes, and sometimes not even that, had the chance of seeing and avoiding. Collision geometry such as the rearmost higher glider catching up lower glider in front can result in blindspots for both pilots. Whatever the cause, certainly that has happened.

Chris N.

[edited - few, not necessarily no, EASA-approved glider installation schemes]

[Flying Binghi]

the inability to navigate between two blades of grass when the GPS is turned off

LOL, now thats funny ;)

[bookworm]

In terms of risk analysis, and bang for the buck, I believe it is the right place for us to spend money. I believe that widespread adoption of FLARM for gliders will save more lives than the equivalent amount of money spent on mode S. Not only that, but as I and others have repeatedly pointed out, FLARM is physically achievable in most gliders, whereas mode S Power and space requirements preclude it for many, as well as there being no EASA-approved installation schemes.

As I've argued in other places, I think it's a crying shame that a 1090ES-based system with FLARM's power and weight requirements has not been developed. There's no technical reason why 1090ES has to be too heavy, costly and power hungry. But you've convinced me that FLARM for gliders is a pragmatic solution in the real world, where regulation and certification are once again aviation's worst enemy. I'd draw an analogy with aviation regulators' failure to embrace GPS as a hugely cost-effective safety measure leading to the sub-optimal situation we now have with a proliferation of different UIs and cables strewn across the cockpit, and an overall sub-optimal safety situation. The market won out while the regulators were still trying to get their act together.

I have a simple response to airline or GA power pilots who think we should have interoperability between gliders and the rest.

I wonder if synergy is possible at the level of the receiver? Can we make a FLARM receiver that decodes and displays 1090ES (ADS-B out or Mode S responses) or a system of the sort that italianjon describes that can also receive FLARM output?

[Flying Binghi]

I wonder if synergy is possible at the level of the receiver? Can we make a FLARM receiver that decodes and displays 1090ES (ADS-B out or Mode S responses) or a system of the sort that italianjon describes that can also receive FLARM output?

LOL ...bookworm, all you need then is a pilot that is able to decode the display :D

[Whiskey Kilo Wanderer]

As mentioned in ‘another place’ where the same question was posed, I use the small Zaon unit. With all its limitations, it is better than nothing. I fly a relatively slow aircraft (the sort that gets bird strikes on the trailing edge of the wings), most other traffic overtakes me, so there is even less chance of me seeing them, although I hope they see me. When my unit starts to display, it reminds me to increase my look out. When it starts to beep too much, say in the circuit, I mute it.

I suspect the answer to the original question is that anything that helps awareness of other traffic is good. It’s a case of Mk1 Eyeball + LARS etc. + TCAS or cheaper equivalent + FLARM all the things that you can afford, power and use without too much distraction from the job in hand. My 2.5p’s worth (old money).

Safe Flying,
Richard W.

[chrisN]

Bookworm, I agree that in retrospect it seems a pity to my (non-tech) eyes that a 1090ES-based Flarm system was not developed, but we are where we are; it wasn’t. Maybe to do with easy marketing without official certification? Dunno, but there we are.

Glad you agree that, even without 1090ES, at least it helps with some categories of collision.

Regards – Chris N.

[bookworm]

Maybe to do with easy marketing without official certification?

Yes, I think using the ISM-band helps, as does the fact that it cannot meet a certification requirement so it doesn't even try: a 1090ES solution would be tempted into trying to meet the requirements for a Light Aviation Mode S transponder. I really think it's worth keeping an eye on Australia -- they seem to be leading the way on 1090ES.

[SNS3Guppy]

Can the controller "be assured of what you've got" when you report "traffic in sight"? Moreover, can the controller be assured that it will stay in sight?


That's not really relevant. A controller who hears a pilot report the preceding aircraft in sight gives separation responsiblity to the pilot making the report, whereas a pilot reporting seeing an aircraft on TCAS does not provide that latitude. Further, I've seen far too many pilots who are satisfied when they see an object on TCAS. Additionally, most operations manuals give mandatory RA reaction to TCAS, taking that discretion from the pilot.

The July 2002 collision between a Tupolev and a B757 over Germany involved two aircraft equipped with TCAS, in radar contact, talking to a controller. A chain of events occured, including several mistakes, which lead to the collision, but the fact remains that even with professional crews operating advanced collision avoidance equipment, getting radar advisories are still not immune. Further, taking evasive action based on what you don't see, be it based on TCAS or based on what the controller tells you, still does not make you immune, or necessarily improve your odds.

http://www.humanfactors.uiuc.edu/Reports&PapersPDFs/humfac04/nuneslaur.pdf

[ShyTorque]

SNS, Was a visual sighting made by the crew of either aircraft? I think probably not in that case, with tragic consequences. Which is one reason the instruction manuals of alerting systems other than TCAS 2 forbid avoiding action based on derived information alone, i.e. not until a visual sighting is made.

Another reason is that an out of tolerance transponder / encoder can give a false altitude to TCAS; I've seen this on a number of occasions where a GA aircraft has gone past at a different relative altitude to that shown on the TCAS display.

The original poster will obviously not be using TCAS 2; if he did choose another system he would presumably read the instructions and use the equipment properly, and with due regard to its limitations, just like any other piece of on-board equipment.

[SNS3Guppy]

Another reason is that an out of tolerance transponder / encoder can give a false altitude to TCAS; I've seen this on a number of occasions where a GA aircraft has gone past at a different relative altitude to that shown on the TCAS display.

As have I, to say nothing of spurious readings that miss traffic completely, or miss based on operational practices. Many times I've watched traffic come by at FL350, a thousand feet separated, with nothing at all on TCAS...but the next aircraft to pass is right there. It happens. Why, I don't know, but it does.

I arrived over a fire years ago when TCAS had just been installed in the lead aircraft. I reported my altitude, I was above the lead, he could easily have looked up and seen me. However, he reported that he couldn't clear me into the fire because two aircraft were circling the fire directly above us, shadowing our positions, but at a higher altitude. We could clearly see that wasn't the case, but he was comparing the altitude we reported in to what he was seeing on TCAS, and making the riduculous assumption that two identical aircraft were above us, exactly the same altitude above us, on opposite sides of the fire orbit. It took some convincing to get him to actually look for himself before we were cleared in to drop.

Conversely the introduction of TCAS has been largely an improvement in that arena, where 30 or more aircraft can be working in a very small area with nearly nil visibility, close to terrain, on up to five or more frequencies, with a vastly disimiliar mix of single engine airplane through large multi engine airplanes through helicopters, in low visibility and rough conditions...the heads up provided by TCAS has proven to be both a help and a hinderance at times...and that's one place where one does NOT want to respond to an RA, because terrain always wins the conflict.

The original poster will obviously not be using TCAS 2; if he did choose another system he would presumably read the instructions and use the equipment properly, and with due regard to its limitations, just like any other piece of on-board equipment.


The point is that while TCAS II offers the best situational awareness, display, aid presentation of information, even it has limitations...especially in a particularly dense traffic area. Further, while one may be alerted to traffic and then see traffic in that area visually, one may very well be deluded into thinking because one target is displayed and one sees one target, then one has acquired all the traffic that's there. This is an extremely dangerous assumption, but one that's easy to make, and often made, where traffic reporting services or equipment is available. One must always assume that what one sees is the least of one's worries, and continue to look for the traffic that's not displayed or not seen. It's not the traffic you see that kills you. It's the other guy.

If one isn't looking, as though one's life depends on it, one IS the other guy.

Other displays which don't offer a 360 degree situational display with relative traffic positions and vertical closure rates and elevations offer precious little information and tax the pilot for keeping situational awareness on all the traffic. This is a hazard, and can be a distraction from seeing traffic which may be a conflict which isn't displayed.

TPAS and some of the other innovations do have their limited benifits, but I wouldn't invest in one for my personal flying as I don't feel they offer adequate information, reliability, or service to make their distraction or cost worth the while.

Many of us who have to sit for eight hours with the sun in our eyes at high altitudes will put up sunshades or clip charts to block the sun...which does prevent visual acquisition. And the truth is that ones eyes quickly fade to empty field myopia at high altitudes with no field definition...we're seeing a spot three feet in front of our face and don't know it, when we look out that window for traffic into the haze cloud, and distance. We have radar separation in some cases (though for much of the world, precious little), we report positions through HF relay stations, but we still watch the TCAS closely, look out the window and back in again (to prevent empty field myopia) frequently...or we should.

I don't know how many have ever been in and out of the clouds, flying IFR, and had a non-reporting airplane blow by the windscreen close enough to see the brand of sunglasses worn by the other pilot, but I have...several times...even when talking to ATC and squawking a code, and using all the resources available to me. I look for traffic when in the cloud and out, when VFR as well as IFR, as though my life depends on it. It very much does.

I'm not convinced of the usefulness or viability of the cheaper traffic systems designed for general aviation cockpits. With the increasing capabilities of the displays and avionics suites that are rapidly becoming available to the average private pilot, there's no reason that better traffic information can't be integrated into these displays every bit as much as they are on a corporate or airline aircraft. The little velcro-to-the-panel displays with an arrow and a number are very near useless in comparison, and in my opinion, detrimental. It's just far too easy to see traffic displayed, see "an" airplane out there somewhere, and think that's it. Like I said, it's the one we don't see that's the dangerous one, and we could very well be that dangerous one if we're too busy playing with gimmicks that offer limited utility and poor display information, when we could be exercising our necks and our eye sockets in a vigiliant effort to spot the other guy.

The old mexican joke is about a cab ride in mexico city, when the bichito (cab) driver blows through every red light he comes to, and stops at ever green light. The tourist finally asks why the cab driver stops at the green lights, and the cab driver replies "my brother might be coming the other way."

I spend a lot of time looking for that brother in flight...especially the one who's letting his traffic display or his radio do the traffic scan for him.

One of my biggest pet peeves, or annoyances on the radio is the guy who says "Lincoln traffic, Cessna XXXXX six miles south at four thousand, over the bean plant, any inbound traffic please advise."

Any inbound traffic? No. Just us guys with no radio, no electrical system, the ones who can't hear you...but still have eyes to look...

[robin]

When my unit starts to display, it reminds me to increase my look out.

Try flying near to Spamfield or to an LAA rally and see how often you get an alert.......

That attitude will cause you grief sooner or later.

[ShyTorque]

SNS, Sorry but having read your last posting I'm beginning to lose track of what point you are actually trying to make, except there is other traffic out there. So here's where I bow out of this discussion, thanks.

[SNS3Guppy]

Point trying to make? Not that complicated, really.

You stated that discussions about TCAS or TCAS II don't apply, as this is a private pilot forum.

Point is that while those are the best options and most other lesser systems are a waste, even the best systems have no assurance. Whereas even the best systems haven't prevented incidents, don't put too much faith in the cheap ones, either. Especially one's with limited and unclear display information.

Pilots who use TCAS to find traffic are much like pilots who use radios to find traffic for them. Call out and ask if there's any traffic out there...it's a stupid call, and a lazy one. Much like "got 'em on TCAS."

Not that complicated at all. But you're right, there is traffic out there.

TPAS and the other cheap efforts at TCAS aren't really worthy of one's time or effort or expense, are more prone to errors, to creating a distraction, and to confusion, and offer too little information in a non-intuitive format such that they contribute little to situational awareness.

That, and some examples were given. Clear?

[gpn01]

Would another thing, in addition to looking out, be to check NOTAM's for activity ? e.g.....

Q) EGTT/QWGLW/IV/M/AW/000/999/5136N00048W005
FROM: 08/07/19 09:30 TO: 08/07/27 17:00

E) MAJOR GLIDING COMPETITION (INC X-COUNTRY RTE). INTENSE ACTIVITY
WI 5NM RAD 5136N 00048W (WYCOMBE AIR PARK (BOOKER AD),
BUCKINGHAMSHIRE). UP TO 40 GLIDERS AND 6 TUG ACFT MAY PARTICIPATE.
GLIDERS WILL NORMALLY OPERATE BELOW THE INVERSION LEVEL OR BTN THE
TOPS OF ANY CU CLOUD AND 500FT AGL.
AFTER LAUNCH MOST ACFT WILL BE CONCENTRATED IN THE AIRSPACE AROUND
THE AD AND UPWIND OF THE SITE OR ON THE FIRST LEG OF THE DAILY
X-COUNTRY RTE. FOR DAILY OPS INFO ON ACTIVITY CONTACT GLIDER CONTEST
CONTROL. TEL 01494 529263. RTF 130.1MHZ. AUS 08-07-0168/AS2.

LOWER: SFC
UPPER: 5000FT AGL
SCHEDULE: 0930-1700

Scary to watch a light aircraft fly right through a gaggle of gliders earlier today. The gliders aren't equipped with TCAS, PCAS, ADS-B or Mode-S and they all managed to avoid each other by using mark-one eyeballs.

Never quite sure why, when events such as this are NOTAM'd, that pilots elect to fly right into an area of quite intense aerial activity.

[JBGA]

Never quite sure why, when events such as this are NOTAM'd, that pilots elect to fly right into an area of quite intense aerial activity

Because they are either a) oblivious, or b) have no respect for gliding competitions and other similar events ??

[robin]

Probably haven't even read the NOTAMs

I was up at Wycombe for Air Expo and heard someone asking to pass through the ATZ when it had been clearly NOTAM'd as restricted for the event.

The girl on the radio sounded as if this had not been the only time this had happened.

[IO540]

A lot of people, myself included, tend to ignore notams of 'high activity' events, or some high speed military flights, or survey flights, etc, on the simple grounds that these could happen anywhere without being notamed.

One has to watch out all the time.

And it helps to fly high; most UK GA flies below 2000ft and flying at 3000+ reduces the traffic density by orders of magnitude. Above the cloud if possible because there sure as hell won't be any gliders up there (well not for long ;) ) and it's easy to avoid marked gliding sites.