How close is too close?

[Vance Harral]

There's no ulterior motive in this poll, and probably no useful conclusions to be drawn.  I'm just generally curious, and figured I and others might be surprised by the responses.  Note that there is no universally "correct" answer, and I'm explicitly requesting that respondents refrain from criticizing other's votes.

Assume you're flying in a relatively busy metropolitan area, and you recognize converging traffic, that winds up passing "close" by you.  At what point does the event change from an everyday occurrence you've forgotten by the time you're tying down, to a scary story you tell for weeks/months/years after?

For the purposes of this poll, it doesn't matter whether you initially acquired the threat visually or on ADS-B, and it doesn't matter how/if you maneuver to avoid them.  Assume we're talking about piston single speeds here - maximum closure rate of 300 knots in the worst case, head-on scenario; but more realistically in the range of 100 knots.

At what point does your sphincter tighten, and you feel compelled to "do something": maneuver, cuss, yell on the radio, whatever?

[N201MKTurbo]

If I have it in sight, not hitting it is good. 500 feet is OK. 
 

It is the ones I don’t see that scare me not the ones I have in sight.

[M20F]

  On 9/3/2024 at 9:19 PM, N201MKTurbo said:

It is the ones I don’t see that scare me not the ones I have in sight.

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It is the ones that I get a traffic alert on that I still can’t see ever or I see after no factor that scare me.  I like the technology but ignorance was bliss.

[Skates97]

  On 9/3/2024 at 11:08 PM, M20F said:

It is the ones that I get a traffic alert on that I still can’t see ever or I see after no factor that scare me.  I like the technology but ignorance was bliss.

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I agree, if I can see them and what they are doing I'm not concerned. When I see them on my tablet and can't find them anywhere... that's a different story.

[Vance Harral]

  On 9/3/2024 at 11:08 PM, M20F said:

It is the ones that I get a traffic alert on that I still can’t see ever or I see after no factor that scare me.

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  On 9/3/2024 at 11:14 PM, Skates97 said:

When I see them on my tablet and can't find them anywhere... that's a different story.

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I respect these fears, provided the person expressing the concern understands display zoom scale.

I also find them frustrating, because every single "near miss on the tablet without visually acquiring" incident I've had, was one in which the threat target appeared out of nowhere, then disappeared from the display altogether a few seconds later.  I've had about a dozen of these in the last 5-ish years.  I'm 95% sure they were all ghost targets caused by failed ADS-R/ownship reconciliation, rather than real threats.  Because of this, I'm no longer startled when a threat suddenly appears on the display at my same altitude, and I'm not particularly concerned about it.  I do look outside intently, but that's the limit of my panic.

If I ever die in a MAC that I "should" have seen coming, I suppose it might be because of complacency about ghost targets.

[M20F]

  On 9/3/2024 at 11:25 PM, Vance Harral said:

I respect these fears, provided the person expressing the concern understands display zoom scale.

I also find them frustrating, because every single "near miss on the tablet without visually acquiring" incident I've had, was one in which the threat target appeared out of nowhere, then disappeared from the display altogether a few seconds later.  I've had about a dozen of these in the last 5-ish years.  I'm 95% sure they were all ghost targets caused by failed ADS-R/ownship reconciliation, rather than real threats.  Because of this, I'm no longer startled when a threat suddenly appears on the display at my same altitude, and I'm not particularly concerned about it.  I do look outside intently, but that's the limit of my panic.

If I ever die in a MAC that I "should" have seen coming, I suppose it might be because of complacency about ghost targets.

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I am not talking about fake targets.  I get 2-3 a year where I am like where the heck are they, we are all going to die, then I see them finally passing me (no factor) when we both were danger close to each other a few moments ago.   
 
There are a few I just never see, real planes just never see them even though they are in the inner ring.  
 
30yrs ago ignorance was bliss is all.  

[hubcap]

As I understand it…these “false” targets are sometimes our own ADSB signal causing the alarm. One of the members of our board was actually an engineer involved in setting up the WAAS GPS system. He explained to me how it creates a false threat but it was too technical for me to really understand.

[AIREMATT]

  On 9/4/2024 at 2:07 AM, hubcap said:

As I understand it…these “false” targets are sometimes our own ADSB signal causing the alarm. One of the members of our board was actually an engineer involved in setting up the WAAS GPS system. He explained to me how it creates a false threat but it was too technical for me to really understand.

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 Maybe I don’t understand, but ADB-B uses a tail number in the data. I am able to have my EFB ignore my own tail number, so I don’t seem to have ghost targets in my likeness show up on my iPad. Are there other ghost targets that are appearing for some of you?

[M20F]

  On 9/4/2024 at 2:07 AM, hubcap said:

As I understand it…these “false” targets are sometimes our own ADSB signal causing the alarm. One of the members of our board was actually an engineer involved in setting up the WAAS GPS system. He explained to me how it creates a false threat but it was too technical for me to really understand.

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When you get a plane type, heading, collision rate, and a N number that isn’t yours it isn’t a false threat. 
 
False positives come from when you are running a Stratus and relying on somebody else’s ship to send a ping so you get inbound data.  If you are running a GTX345 or the like you aren’t getting false pings. 

[Shadrach]

  On 9/3/2024 at 9:06 PM, Vance Harral said:

At what point does the event change from an everyday occurrence you've forgotten by the time you're tying down, to a scary story you tell for weeks/months/years after?

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Any situation where separation was provided solely by “big sky theory”

[hubcap]

  On 9/4/2024 at 2:22 AM, M20F said:

When you get a plane type, heading, collision rate, and a N number that isn’t yours it isn’t a false threat. 
 
False positives come from when you are running a Stratus and relying on somebody else’s ship to send a ping so you get inbound data.  If you are running a GTX345 or the like you aren’t getting false pings. 

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I have gotten false positives on my Garmin. I have called ATC to see if they showed the target …..negative. I don’t know what causes it, but it’s exciting.

[Vance Harral]

  On 9/4/2024 at 2:22 AM, M20F said:

False positives come from when you are running a Stratus and relying on somebody else’s ship to send a ping so you get inbound data

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Portable ADS-B receivers are more susceptible, but they're not the only reason for ghost targets.  You can get ghosts even with a panel-mounted ADS-B in/out transponder, and even when Foreflight knows the N number of your ownship.  Most manufacturers of traffic displays have a little treatise on it.  Foreflight's is at https://support.foreflight.com/hc/en-us/articles/225240087-Why-do-I-see-a-false-or-ghost-traffic-target-in-ForeFlight-Mobile .  Garmin's plays it closer to the vest, but if you dig, you can find some posts about this from Garmin employees on Beechtalk and elsewhere.  In my experience, ghosts seem to be correlated with maneuvering.  I do a lot of maneuvering as a CFI, and my recollection is that ghosts tend to show up during steep turns, steep spirals, lazy 8s, etc.  I'm sure whatever processing takes place in the stack is biased toward straight and level-ish flight.

 

[201er]

I didn’t like the choices of the poll. Anything measured in nautical miles or hundreds of feet is hardly a “close call”. 3nm is about the farthest you can even spot GA traffic as a dot. 1nm you can tell if they’re a high wing or low wing. It’s somewhere between reading the N number and 1nm that qualifies as a close call but it’s hard to put a measurement on it.

[Skates97]

  On 9/3/2024 at 11:25 PM, Vance Harral said:

I respect these fears, provided the person expressing the concern understands display zoom scale.

I also find them frustrating, because every single "near miss on the tablet without visually acquiring" incident I've had, was one in which the threat target appeared out of nowhere, then disappeared from the display altogether a few seconds later.  I've had about a dozen of these in the last 5-ish years.  I'm 95% sure they were all ghost targets caused by failed ADS-R/ownship reconciliation, rather than real threats.  Because of this, I'm no longer startled when a threat suddenly appears on the display at my same altitude, and I'm not particularly concerned about it.  I do look outside intently, but that's the limit of my panic.

If I ever die in a MAC that I "should" have seen coming, I suppose it might be because of complacency about ghost targets.

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Not talking false targets that just appear and disappear. There are times that you track it for miles converging and either because of ground clutter, view blocked by wing/cowl/etc they aren't seen. I those cases I change heading until I either find them or no longer on a collision course. Those are the ones that make me nervous. 

[Vance Harral]

  On 9/4/2024 at 3:21 AM, 201er said:

Anything measured in nautical miles or hundreds of feet is hardly a “close call”.

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Yours is a fine opinion, but not one shared by a few of my flight instruction clients, folks in FBO lobbies, and various posts on various aviation boards.  Hence the original motivation for the poll.

The criticism of poll choices is fair, but polling is a complicated endeavor.  One must provide broad enough choices to span the range of possible responses, but not so many choices that the granularity prevents determining if there's any kind of consensus.

So far, the poll seem to be settling in the "I can read the N number" range.  I'm not too surprised at this, given that the sample group is comprised largely of pilots who own fast, complex singles, and have significant flying experience.  My guess is that I'd get somewhat different answers from a student pilot audience.  There's also the issue of what people say makes them nervous in the comfort of their office on the ground, vs. what actually does make them nervous in the air.  A number of pilots I've flown with don't seem to really have any idea how far away another aircraft is, and can't estimate how long it would be to impact if they were actually on a collision course.  This is especially true when their only information about the threat is its depiction on a traffic display.

[201er]

  On 9/4/2024 at 3:40 AM, Vance Harral said:

Yours is a fine opinion, but not one shared by a few of my flight instruction clients, folks in FBO lobbies, and various posts on various aviation boards.  Hence the original motivation for the poll.

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1nm is about the width of the Hudson River and we fly opposite direction same altitude that far apart and it is a daily non-event. Definitely not a wet your pants, talk about it in a decade type of event.

On the other hand reading their N number is actually too close.

 

Says that 12” letters can be seen from 120-525 feet. Where are the poll choices for distances like 500, 1000, 2000 feet? That’s the difference most of us would diverge on based on personal levels, not miles.

[M20F]

  On 9/4/2024 at 3:40 AM, Vance Harral said:

There's also the issue of what people say makes them nervous in the comfort of their office on the ground, vs. what actually does make them nervous in the air. 

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In other words you don’t agree with your own poll results and want to keep debating what has generally been a concise message from the forum.  @201er I think nailed it. 
 
I am not certain your intent at this point.  

[Vance Harral]

  On 9/4/2024 at 6:32 PM, M20F said:

In other words you don’t agree with your own poll results

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As I said in the OP, there's nothing to agree or disagree with, and no particular conclusion to be drawn.  I'm just curious to see what people say bothers them, and thought others might be as well.  I'm definitely not going argue that the poll indicates anything at all about what's safe, or how pilots should behave or feel.

Replies are dying down, and the results are predictably bell shaped.  Looks like most folks "draw the line" somewhere inside of one mile lateral and inside 500' vertical.  But it's worth noting that as of this writing, 3 out of 26 respondents are uncomfortable with other airplanes inside 2nm lateral and/or 1000' vertical.  So even here in a group of Mooney owners, roughly 1 in 10 pilots have pretty conservative feelings relative to the median.

For what it's worth, this roughly mimics my flight instruction experience.  I fly with 10-20 different clients per year, and a small handful of them are bothered by airplanes that seem to me to be too far away to worry about.  If they ask me something like, "Didn't that seem close to you?", I say no, and try to have a respectful conversation with them about why.  It's possible some of them change their opinion as a result of those conversations.  But human nature being what it is, I think it's more likely they conclude I'm fatalistic, and/or not very smart.

[Shadrach]

  On 9/4/2024 at 6:57 PM, Vance Harral said:

 2nm lateral and/or 1000

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I would say that this is unrealistically conservative.  It would be very difficult for me to operate in and around the eastern seaboard and expect this kind of separation.  For this reason, I am almost always in contact with or monitoring an ATC freq. <2nm separation, same altitude is common place in an around the Balt/Wash metro area.

[PeteMc]

Again, the reason I don't like polls is that you end up giving points to an answer you're not totally in agreement with.

For me it has a lot to do with the big picture and are we converging or are they just crossing over or under me at 1000'.  I've been in a Pattern where someone was was doing a Overhead Pattern Entry to a Tear Drop entry.  He was 500ft above and no more than 1000ft laterally as he passing behind me.  He had called me in sight and I could see him just fine, and based on his track, I knew I was indeed the person he called in sight and was indeed going to pass behind me.   

Close? Yes.  Too close?  I don't think so based on the situation and we both had each other in sight. Technically he could have been 500ft directly overhead, but (I'll assume) he was smart enough to go behind me for some extra cushion of safety.  Had there been someone else behind me, I would hope he (we all) would aim to go above the gap between the planes rather than right over one.  It just adds that little extra bit of safety. 

(And, of course, he was not an commercial operator with the 1000ft restriction.)

[Paul Thomas]

If I have a visual on them, I'm rarely bothered by other traffic. The ones that make me nervous are those that I can't see when we are on a converging course but thankfully, it's typically pretty easy to keep some separation.

I've only been nervous about traffic I could visually see twice:

1. I think it may have been my second solo flight while I was doing touch and goes. While on downwind, someone in an acrobatic airplane decided to join up and do some formation flying and show his superior airmanship. My instructor saw it from the ground, was not amused by that guy's antic, and had a talk with him. For a while, that made me nervous about uncontrolled airports, especially that specific airport. I don't think I ever soloed there again as a student pilot.
2. . We were leaving Oshkosh on an IFR departure with my friend flying. I asked him to lower the nose due to traffic, but he didn't. We kept climbing, so I asked more sternly and ended up having to take over the controls. The other traffic did not seem to see us till too late and we were too close, close enough that I could have identified the other pilot. What made me nervous was the lack of reaction from my friend and once the other pilot started descending, I had to take over the airplane because we would have gone from too close to likely collision.

I had another encounter where it was too close, but it didn't make me nervous because we always had an out. I was flying with a friend who was a newer pilot. She was on short final when a 172 starting moving about the hold short line. I kept an eye on it and it started rolling toward the runway when we were over the fence. Even in a 150, it was too late to slow down and let them depart, especially at the speed they were moving. She went around, we flew side by side as they climbed out and departed on upwind. We rejoined the downwind and landing without issues. We never heard them on the radio; I'm not sure if they were on the wrong frequency or had their radio off. The 172 belonged to a flight school.

[Yetti]

When ATC calls with an urgent voice you can hear beeping in the back ground and telling you to climb Immediately.   I believe I went right also as well as climbing.

[EricJ]

  On 9/4/2024 at 7:43 PM, Yetti said:

When ATC calls with an urgent voice you can hear beeping in the back ground and telling you to climb Immediately.   I believe I went right also as well as climbing.

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I've had that happen, too, and I'd already been watching the slower traffic that I was catching up with for a while, so when ATC called with the alarms going off I just said, "traffic in sight" and did whatever it was that they were asking.   That seemed to restore calm.   

[201er]

  On 9/4/2024 at 6:57 PM, Vance Harral said:

Replies are dying down, and the results are predictably bell shaped.  Looks like most folks "draw the line" somewhere inside of one mile lateral and inside 500' vertical.  But it's worth noting that as of this writing, 3 out of 26 respondents are uncomfortable with other airplanes inside 2nm lateral and/or 1000' vertical.  So even here in a group of Mooney owners, roughly 1 in 10 pilots have pretty conservative feelings relative to the median.

If they ask me something like, "Didn't that seem close to you?", I say no, and try to have a respectful conversation with them about why.  It's possible some of them change their opinion as a result of those conversations.  But human nature being what it is, I think it's more likely they conclude I'm fatalistic, and/or not very smart.

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Sure, I'm "uncomfortable" sharing the sky with anyone at all from any distance I can see them. However, that doesn't constitute a "close call" or "a scary story you tell for weeks/months/years after". I kind of doubt anyone has a scary story they recall from years ago of another GA sized plane passing a shocking 1, 2, or 3 nautical miles away from them! You're closer to other planes every day in the traffic pattern.

Heck, the FISK arrival at OSH puts you 1/2 mile in trail. Uncomfortable? Yes. Memorable? Sure. Requiring a change of clothes? I don't think so.

91.111 Operating near other aircraft.

(a) No person may operate an aircraft so close to another aircraft as to create a collision hazard.

I don't think from a mile away you could argue there's a collision hazard. Only the potential for a collision hazard. At the same time, it may be more than 120-525 feet where you can read 12" letters that is a collision hazard.

At a 300 knot max closing speed, that's 12 seconds for a direct head on from 1nm apart. However, it's almost never head on at same altitude at cruising speed. So that's 18 seconds at pattern altitude if both planes are going 100 ktas. So it works out that you need about 500-3000ft of horizontal separation (when you have 0 vertical) to have around 10 seconds to see and avoid another airplane in most circumstances like in the pattern or a not head on convergence at cruise. None of those options were represented so it's no wonder most had to vote for the same option because it is closer to representing their point than the other extreme but still quite far off.

[Hank]

ATC called out opposite direction traffic once, about 5 seconds after I watched a white Mooney with a red tail go directly under me in the opposite direction. Based on altitude, he was IFR because I was at 8500 outside AVL, heading back to WV.

To keep my eyes on him, I had to lean my head against the window . . .

But it wasn't scary. My wife spotted him first.