Why do people freak out about ADS-B and mid-air collisions?

[wombat]

I like ADS-B too.  It is helpful.  But we should be clear that the risk it's helping to mitigate isn't a very big one to begin with.    The system was not designed to help mitigate the risk of mid-air collisions, it was designed to help with the cost of ATC RADAR maintenance costs.

 

It's not that ADS-B is worthless or useless, but the reduction in risk it provides is minimal.

Maybe think of it like this:   Looking at your ADS-B is about the same level of accuracy as getting a report from ATC of other traffic when they are not seeing you directly but using RADAR.    If you are in the traffic pattern, it's effectively useless.   Like when ATC says "Airport is at 12 O'clock, 10 miles, multiple targets in the pattern, report airport in sight."  Once they are done with that, it's up to you and your eyes.

[EricJ]

5 hours ago, wombat said:

I like ADS-B too.  It is helpful.  But we should be clear that the risk it's helping to mitigate isn't a very big one to begin with.    The system was not designed to help mitigate the risk of mid-air collisions, it was designed to help with the cost of ATC RADAR maintenance costs.

 

It's not that ADS-B is worthless or useless, but the reduction in risk it provides is minimal.

Maybe think of it like this:   Looking at your ADS-B is about the same level of accuracy as getting a report from ATC of other traffic when they are not seeing you directly but using RADAR.    If you are in the traffic pattern, it's effectively useless.   Like when ATC says "Airport is at 12 O'clock, 10 miles, multiple targets in the pattern, report airport in sight."  Once they are done with that, it's up to you and your eyes.

I would disagree with this.   Down here we live in some of the most crowded airspace in the country.   ADS-B helps me immensely in managing traffic, including very close traffic.   I regularly fly as a safety pilot in "the stack", which very often has instrument students and others stacked in a hold every 500 feet from about 4000 to often 7000 or 8000 feet, in uncontrolled airspace managing separation only by self-reporting using an ad-hoc protocol.   Conflicts are not unusual, and it'd 1000x harder (or at least more stressful) without ADS-B-in.   You're in a small space with multiple diverse aircraft separated vertically by a maximum of 500' and often (or even usually) less than that due to inattentive students or incorrect altimeter settings or whatever reason.  I was there a couple weeks ago in the stack with two helicopters, a King Air, and some other single engine recips.    One of them, which wasn't one of the local large flight school airplanes, kept maneuvering into our altitude.   Since we were maneuvering to maintain the holding pattern we could not always keep them in sight.   ADS-B-in was the only reason we were able to maintain situational awareness with that traffic and the others.     I won't go in there without functional ADS-B-in because the collision risk is just too high without it.

Many of the uncontrolled fields around here often have a lot of traffic in the pattern due to flight school overflow from other fields.   The risks are real.

It's been a while since we've had a mid-air collision around here, though, I think the last ones were not long before ADS-B came into common use, which I think is notable and likely causal. 

Edit:  I take that back, there was a collision between a flight-school helicopter and a flight school airplane in the pattern at a Class-D field here a couple of years ago. 

[wombat]

I've heard that before.    I find it hard to believe ATC is letting IFR traffic self-separate using ADS-B only with vertical spacing of 500 feet.  Can you tell me exactly where this happens and some times I might be able to see this on FlightAware so I can see it for myself?

The rate of mid-air collisions has not changed significantly since ADS-B adoption has increased significantly.  The rate of mid-air collisions is very small, and even out of those things that might kill you as a pilot in an airplane it's quite small.

So why is it that you think this is such a large risk when it is in fact so small?   And why do you fixate on ADS-B being a 'solution' to this problem?

Edited 6 hours ago by wombat
Making my first paragraph less inflammatory; I'm not out to win, I'm out to find the truth.

[MikeOH]

UGH, I tried to stay out of this one, but I can't help myself!

1) ADSB was NOT designed to be an active traffic AVOIDANCE system (i.e. NOT a TCAS substitute)

2) I have personally, on multiple occasions, observed MAJOR discrepancies between reported position and ACTUAL position of traffic (see number 1)

3) It is another tool in the toolbox.  It is not, IMHO, a necessary tool, but can be useful as a strategic tool.  I like getting the 'lay of the land' when approaching an airport and appreciate the 'big picture' it provides while in cruise.

4) No way I would use it for tactical use in a traffic pattern.  It is NOT reliably accurate (see number 2).  Doing so, again IMHO, would be providing a false sense of security.  I want my head on a swivel looking OUTSIDE, not managing the distraction of 'head's down' time while in critical airspace like a busy traffic pattern.  However, as others mentioned, having a second person monitoring the ADSB display is also useful.

5) Looking at factual accident data shows mid-airs are way down the list of fatal accident causes.  I await some statistical proof that those numbers drop even further before entertaining that a cause/effect relationship has truly been established.  Anecdotes and the absence of an accident in the last x years when mid-airs are so infrequent to begin with is not convincing.

[EricJ]

1 hour ago, wombat said:

I've heard that before.    I find it hard to believe ATC is letting IFR traffic self-separate using ADS-B only with vertical spacing of 500 feet.  Can you tell me exactly where this happens and some times I might be able to see this on FlightAware so I can see it for myself?

1. The traffic at "the stack" is not IFR.   ATC is not involved.  It is typically IFR training flights or proficiency/currency flights with either instructors or safety pilots.    This happens over the Stanfield VOR (TFD) to shoot either GPS, VOR, or ILS approaches into Casa Grande (CGZ) runway 5.  The protocol is pubished here:
   
   https://aftw.org/wp/wp-content/uploads/2021/05/AFTW_Stanfield_VOR_Procedures_Rev6.pdf

1 hour ago, wombat said:

The rate of mid-air collisions has not changed significantly since ADS-B adoption has increased significantly.  The rate of mid-air collisions is very small, and even out of those things that might kill you as a pilot in an airplane it's quite small.

Many, if not most, of the safety precautions we take as aviators are to mitigate risks with very small (and sometimes very, very, very small) probabilities, but significant consequences.  This one is no different.   I hope you are not suggesting that all of the other safety precautions we routinely take to mitigate small risks are inappropriate.
 

1 hour ago, wombat said:

So why is it that you think this is such a large risk when it is in fact so small?

I do not think it is a large risk, although I think it may be larger in the airspace that I fly than in some others, and I also think it not outside the usual order of risk magnitude that we routinely mitigate with similar safety measures.   I also think that for many of the "small risks" we take as aviators we use many tools to mitigate them, especially those with large consequences.   You'll have to forgive me if I extend those practices to avoiding mid-air collisions as well.

1 hour ago, wombat said:

And why do you fixate on ADS-B being a 'solution' to this problem?

I don't think I've ever heard anyone serious, here or elsewhere, suggest that ADS-B is a solution to mid-air collisions.   I've no idea what makes you think I think so or that I am "fixated" on it being so.