Collision Avoidance vs. "See and Avoid" for GA

[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/Rep.../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 [phone]. 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.