ANOTHER PATTERN COLLISION - NOT M20

[carusoam]

3 hours ago, Pinecone said:

 

Agree with most of what you say.

But a good number of people have experience with 3 miles per minute, or faster, low to the ground.  Heck, the A-10 easily does that, and it is slow.

No doubt… there are people around here that do have high speed and close quarters experience…

There are even videos of MSers driving race cars at speed around major racetracks… 

Very often, in controlled environments… (more or less)

 

There is a similar situation in recent MS history of a fighter jet running over a GA plane somewhere near its airport…

 

I do love the A10 and its pilots for what they do…

if he was doing 180…  this pic would have had just his tail in it…  

(Early morning, SNF, a little more than a decade ago…?)

-a-

[Sue Bon]

48 minutes ago, ilovecornfields said:

Ideally, at the 10 mile final call you would think “Oh, there’s someone else coming in on a straight in. Better keep and eye out for them.”

My first reaction to this sentence was a defensive one, but you are absolutely right. 100%. Situational awareness includes anticipating potential problems that might currently be ten miles away. Thank you for that.

[jaylw314]

I'd point out until we have good ADSB data and correlated the timing, it's unclear to me what "I see you, you're behind me" actually means:

• The 152 pilot could have still been on base, saw the 340 was still off in the distance, and judged he had plenty of room to turn to final, given how difficult it is to judge the speed of someone heading in your direction.
• The 152 pilot could have already turned to final, and only spotted the 340 behind him once he was mostly through his turn.  He may not have had a visual on the 340 until starting his turn, figuring he had plenty of room

Note that the only indication the 152 pilot would have had of how fast the 340 was going before turning to base was the time between the 10 mile and 3 mile call.  It's not clear to me how busy the pattern radio was in the preceding minutes, but unless you use your notepad and timer for every call in the pattern, it might be disingenuous to conclude the 152 pilot should have been aware how abnormally fast the 340 was going.

I've been doing straight in landings on the last few trips given the wind, and I usually make announcements at 12 miles, 6 and 3.  Each time I announce I'm coming in "straight in traffic permitting."  Whenever there's more than 2 planes in the pattern, or the timing doesn't feel good, I just abandon it, turn out to the left and spend the extra 2 minutes joining the pattern normally.

[Mooneymite]

1 hour ago, Marauder said:

For those of you flying heavy iron, does TCAS ever provide false alerts? 

 

Rarely, but occasionally.

Usually a "seemingly" false alert is triggered by a target without altitude reporting.  TCAS may be reacting to a target thousands of feet away vertically, but without mode C, "how do it know"?

[Pinecone]

3 hours ago, GeeBee said:

The latency may be "minimal" compared to weather, but what is if you have two aircraft closing at 4 miles a minute? Remember, those electrons have to go, from the airplane, to antenna, through a data network, to the ATC facility, through their data network, then........back through all that again. TCAS....well that's plane to plane with their own processors which is why it works so good. 

AFAIK, ADB-S is plane to plane, no ATC involvement.

If one plane is not ADB-S, but within range of an ADB-S ground station, the ATC info from the transponder through the ground station.

[kortopates]

Your post has me wondering how my TAS plays with TIS-B in my Lynx 9000. I’m going to read up on it.

Also, I agree that in ADS-R situations where 1090 or 978 are retransmitted to the opposite receiver through a ground station, there would be some sort of latency potential. I thought that one selling point of ADS-B was the direct plane to plane was also occurring. In other words, if a 1090ES plane is broadcasting out, a plane able to receive 1090ES, doesn’t require a ground station. It’s supposed to be truly plane to plane. I get that right?

I remember my primary reason for getting TAS was to locate non ADS-B compliant planes (i.e. Mode C guys) and give me coverage when I am too low to receive an ADS-B ground (in my area, I usually don’t receive FIS-B in until I am around 800 AGL).

I guess I need to freshen up my understanding of the technology and the limitations.


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i agree, there is no latency between two ads/b equipped aircraft; even transmitting on separate bands when they have dual band receiver. That’s why i commented above that we would only have it with something other than air to air ads-b broadcast, such as ads-r, which is exactly what GeeBee described even though he didn’t call it by any specific technology - so i think we are mostly all on the same page. But with most of my pattern work being under a class B veil where all us of are ads/b equipped i don’t think I have ever seen latency in any form.

Inspired to review this, i see Asd-R is only used by receivers that are NOT dual band receivers, since the ground station rebroadcast a 1090ES message out on 978 and vice versa only to aircraft that can’t receive both bands. Since it’s a re-broadcast at the ground station, there really isn’t any appreciable latency that i can find - it’s echo’d right back to the plane after a transmit.
So that just leaves non-abs-b traffic which we can pick up via TIS-B, also being transmitted from ground station. TIS-B “may” include additional aircraft that aren’t broadcasting their position (none ads-b ) when being tracked by FAA SSR Radar - and with those not only do we have a latency issue but we have much less accuracy in position and their 3-D velocity vector.
But Ads-b targets are broadcasting their position every second with a position accuracy of 0.05 nm and velocity vector accuracy of within 10meter/sec per the TSO’s - with no appreciable latency.


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[jaylw314]

1 hour ago, EricJ said:

That's not latency, that's outages.   In other words, you get some updates that display, then for whatever reason (terrain gets in the way, interference, whatever, there are lots of possibilities), your receiver isn't able to process subsequent updates for a while (because it doesn't receive them, they contain errors, etc., etc.), and then finally when it gets a reliable update it has to jump the displayed position from where it was at the last known position.

The actual latency, i.e., the time from when an aircraft calculates its position to when it is transmitted, received, and displayed on another airplanes display, is very, very short for the direct airplane-to-airplane case.   The amount of time between updates can be random, though, due to outages, terrain, interference, or other reasons, or if you're getting updates only from the ATC broadcast towers.   For the case of getting updates from the broadcast towers, the latency is still pretty small, essentially still real-time in most cases, but will naturally be a little longer than the direct airplane-to-airplane case.   

Just a reminder, if you're low enough that you can't pick up a ADS-R tower, UAT only gets UAT air-to-air traffic, and 1090ES only gets 1090ES traffic.

A good reason to get a dual-band ADSB-In receiver

[ilovecornfields]

7 minutes ago, jaylw314 said:

I'd point out until we have good ADSB data and correlated the timing, it's unclear to me what "I see you, you're behind me" actually means:

• The 152 pilot could have still been on base, saw the 340 was still off in the distance, and judged he had plenty of room to turn to final, given how difficult it is to judge the speed of someone heading in your direction.
• The 152 pilot could have already turned to final, and only spotted the 340 behind him once he was mostly through his turn.  He may not have had a visual on the 340 until starting his turn, figuring he had plenty of room

Note that the only indication the 152 pilot would have had of how fast the 340 was going before turning to base was the time between the 10 mile and 3 mile call.  It's not clear to me how busy the pattern radio was in the preceding minutes, but unless you use your notepad and timer for every call in the pattern, it might be disingenuous to conclude the 152 pilot should have been aware how abnormally fast the 340 was going.

I've been doing straight in landings on the last few trips given the wind, and I usually make announcements at 12 miles, 6 and 3.  Each time I announce I'm coming in "straight in traffic permitting."  Whenever there's more than 2 planes in the pattern, or the timing doesn't feel good, I just abandon it, turn out to the left and spend the extra 2 minutes joining the pattern normally.

I wouldn’t expect the guy in the 152 to know how fast the 340 was going, but I would expect him to know there was a potential conflict and ensure it was resolved before committing himself to base/final. He KNEW someone was on final before he turned base. When there is uncertainty, assuming the least dangerous alternative isn’t usually good for your health. 

Again, not tying to blame the 152. I think what the 340 did was clearly “wrong” but I also know people will do stupid things so when there’s a potential threat (someone else in the pattern that might arrive on final at the same time as me) I try to do everything possible to mitigate the threat and I certainly don’t want to put myself in situations where my options become increasingly limited.

Maybe it’s too much to expect that from the 152 pilot, but it certainly should be something a good instructor would teach before letting someone fly solo. Maybe since I’m not a CFI I don’t “get it” but we spent a ton of time on situational awareness and knowing where everyone was in the pattern before my first solo.

[jaylw314]

11 minutes ago, ilovecornfields said:

I wouldn’t expect the guy in the 152 to know how fast the 340 was going, but I would expect him to know there was a potential conflict and ensure it was resolved before committing himself to base/final. He KNEW someone was on final before he turned base. When there is uncertainty, assuming the least dangerous alternative isn’t usually good for your health. 

Again, not tying to blame the 152. I think what the 340 did was clearly “wrong” but I also know people will do stupid things so when there’s a potential threat (someone else in the pattern that might arrive on final at the same time as me) I try to do everything possible to mitigate the threat and I certainly don’t want to put myself in situations where my options become increasingly limited.

Maybe it’s too much to expect that from the 152 pilot, but it certainly should be something a good instructor would teach before letting someone fly solo. Maybe since I’m not a CFI I don’t “get it” but we spent a ton of time on situational awareness and knowing where everyone was in the pattern before my first solo.

I agree with all that, I was just pointing out a nuance nobody's commented on yet  

[kortopates]

Just a reminder, if you're low enough that you can't pick up a ADS-R tower, UAT only gets UAT air-to-air traffic, and 1090ES only gets 1090ES traffic.
A good reason to get a dual-band ADSB-In receiver

Very true. Here in my SOCAL neighborhood we pick up the ground station on the ground. But i know it’s not universal.

I wonder what percentage of planes don’t have dual band In since even most portable receivers have it.

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[RobertGary1]

On 8/19/2022 at 4:50 PM, DCarlton said:

ADSB is great but I don't think it would have helped with this one.  Same with the collision at KVGT.  The tower couldn't even stop that one.  

Why not? I get a big red box on my screen and a voice saying “traffic 12 o’clock below”. Seems effective. Amazing how often I’ve gotten close to planes in the middle of nowhere enroute and only know about them because of ads-b. Never saw them. 

[EricJ]

2 hours ago, kortopates said:

i agree, there is no latency between two ads/b equipped aircraft; even transmitting on separate bands when they have dual band receiver. That’s why i commented above that we would only have it with something other than air to air ads-b broadcast, such as ads-r, which is exactly what GeeBee described even though he didn’t call it by any specific technology - so i think we are mostly all on the same page. But with most of my pattern work being under a class B veil where all us of are ads/b equipped i don’t think I have ever seen latency in any form.

Inspired to review this, i see Asd-R is only used by receivers that are NOT dual band receivers, since the ground station rebroadcast a 1090ES message out on 978 and vice versa only to aircraft that can’t receive both bands. Since it’s a re-broadcast at the ground station, there really isn’t any appreciable latency that i can find - it’s echo’d right back to the plane after a transmit.
So that just leaves non-abs-b traffic which we can pick up via TIS-B, also being transmitted from ground station. TIS-B “may” include additional aircraft that aren’t broadcasting their position (none ads-b ) when being tracked by FAA SSR Radar - and with those not only do we have a latency issue but we have much less accuracy in position and their 3-D velocity vector.
But Ads-b targets are broadcasting their position every second with a position accuracy of 0.05 nm and velocity vector accuracy of within 10meter/sec per the TSO’s - with no appreciable latency.


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FWIW, there is always "latency", as it takes time to collect, modulate, transmit, propagate, demodulate, interpret, and display a target on a display.   A common goal for the engineers is to get the latency low enough to make it appear real time to a human observer.   I think you're right that for all of ADS-B (the airplane-to-airplane transmissions), ADS-R (rebroadcasts from a tower) and TIS-B (processed targets broadcast from a tower) the latencies are low enough that they will all appear essentially real-time with low latency on an EFB or cockpit display.    TIS-B is likely the longest latency, and I don't know what the numbers are, but I suspect they're still pretty low.

ADS-R is still very useful since terrain and interference and other factors may prevent reception of direct transmissions from other airplanes even within your range of expected reception.   My Stratux is dual-band ADS-B-in and feeds the displays on my EFBs, while I have a UAT ADS-B-in in-panel receiver that feeds my panel GPS display which includes that traffic.   It is not at all unusual that I will have traffic that appears on my EFBs that doesn't appear on the panel display and vice versa.   There are no wireless technologies that are 100% reliable, so this isn't unexpected, but it does help illustrate that all of it is useful and more may be better as far as display/processing options, and it all has to be augmented by looking out the windows, too.

So those occasional dropouts or outages or blockages or whatever you may want to call them that interrupt reception of ADS or TIS signals for traffic display may appear as "latency", but really aren't.   They will affect the reliability of the display of some targets, and in my experience it is not at all unusual for targets to be intermittent on my EFBs or the panel display, so relying on them heavily for separation is not a great idea.   It's an awesome and extremely useful thing to have in the cockpit and I'm grateful for it, use it all the time, and it's probably saved my butt once or twice and helps out constantly.

Websites like flightradar24 or others often have the benefit of lots of diversity reception from large numbers of ground receivers that may all be reporting the same target, so that dropouts and outages are rare except for very remote areas.    So the tracks used from websites for incident analysis are likely to be more reliable than what somebody might see in real-time in an airplane.

All of that might have very little to do with the current incident, although it may be how the 152 pilot knew that the 340 was approaching quickly.   

[BravoWhiskey]

180kts is big iron approach speed isn’t it?  Not that I really have a clue what was going on in either pilot’s mind but I think they both knew where the other traffic was.  I think both made faulty assumptions. Maybe the 152 thought he was lower and in pattern so the 340 would slow down or wasn’t going as fast as he was?  Maybe the 340 thought he’d have no problem beating then 152 in if he firewalled it and the 152 would extend downwind?   When the 340 called 10 and 3 miles I think I would have been confused by the timing there.  Personally, when I am 15 and 10miles out I double check my speeds and time before reaching my final approach or pattern speed and altitude.  It helps me figure out where I can fit in the pattern or if straight in is appropriate.  And of course make sure I’m not to fast for landing.  That 340 was certainly coming in hot.

Edited August 21, 2022 by BravoWhiskey

[GeeBee]

Bottom line is this. You don't know what equipment the other aircraft has. 1090ES or UAT. Without that knowledge (as well as knowledge of your own equipment) you don't know what your latency issues you are dealing with. It is nice stuff, better than nothing but I don't trust it implicitly. 

 

[larryb]

My observation at uncontrolled fields is that pilots often talk at each other but not with each other. Each one dutifully announces their intentions. And when a conflict develops they keep announcing their intentions rather than calling up the conflicting aircraft by N-number and mutually working out a plan.

[carusoam]

Sometimes…

Pilots in the traffic pattern…

Are working at max cog capacity…

Some people are challenged by making position calls as their extra capacity is running low… (this becomes audibly apparent)

Toss on Gumps checks…

It can get pretty difficult to do the extra math for another plane doing something non-standard…

Hence… the reason why traffic pattern entries have been refined over the years…

 

The oddity of this TYPE of accident….

It isn’t just a momentary meeting at the intersection to be aware of….

It is the entire final approach that lasts about one minute…. (For the C152)

 

If the C152 reaches final approach prior to the speed demon…

The 152 has a minute to finish and be rolling out….

The speed demon is going to be on the same glide path, following the same centerline… until he slows down, alters course, OR makes contact…

Closure rate

Obstacle recognition

Reaction time

Control inputs

 

Given this set-up… the collision is more likely to happen, than not…

The slow plane is going to be in the way for nearly a full minute….

The fast plane is covering ground at nearly 3X the speed of the slow plane…

 

Both pilots committed to being on the same line in 3D space for an eternity….

Yikes,

-a-

[DXB]

It's easy to imagine myself in the shoes of the guy in the 152 here, much less so in the place of the 340 making the 10 mile straight in when there's obviously traffic established in the pattern making standard position reports.  As my experience has built up, I've announced plenty of straight in approaches 10 miles out "if there's no one in the pattern at X" while looking and listening carefully to make sure there's no one in the pattern - the second I see or hear someone there, I consider it my responsibility to announce a change in plan and enter the pattern in a way that gives them priority.  Not wanting to be right but dead, I've also given way to plenty of 10 mi straight in traffic while I'm already in the pattern, usually by extending my downwind, but I'm in a bad mood while doing it and consider the person coming straight in to be an a-hole.  This accident is a good reminder for me not to give in to temptation to exacerbate the traffic conflict out of irritation at being cut off (of course don't know the 152 pilot's state of mind in this situation, just my own in similar ones).   Changing the behavior of the 10 mi straight in type folks is probably a lost cause, and a worse than useless one to take up until one is safely on the ground.  

[ilovecornfields]

Well, this is certainly timely! A Mooney Special Letter on ADS-B and traffic alerting.

SL_22-03.pdf

[Raptor05121]

20 hours ago, BravoWhiskey said:

180kts is big iron approach speed isn’t it?  Not that I really have a clue what was going on in either pilot’s mind but I think they both knew where the other traffic was.  I think both made faulty assumptions. Maybe the 152 thought he was lower and in pattern so the 340 would slow down or wasn’t going as fast as he was?  Maybe the 340 thought he’d have no problem beating then 152 in if he firewalled it and the 152 would extend downwind?   When the 340 called 10 and 3 miles I think I would have been confused by the timing there.  Personally, when I am 15 and 10miles out I double check my speeds and time before reaching my final approach or pattern speed and altitude.  It helps me figure out where I can fit in the pattern or if straight in is appropriate.  And of course make sure I’m not to fast for landing.  That 340 was certainly coming in hot.

Not even that. The airliner I fly has a Vref of 129-145kts (depending on weight). Sometimes approach will have us hold 170kts until a 5 mile final for metering which is out of flap configuration for us and need you to be quick to react and slow down to Vref.

That light single was a full 10 knots faster than what airliners 15 times his weight consider "fast"

Edited August 22, 2022 by Raptor05121

[AH-1 Cobra Pilot]

Is it OK to be on a 1-mile final in front of someone on a 3-mile final?  On the carrier, we shot for landings 40 seconds apart.  So, our separation was less than 2 miles, and with the time to roll back, raise the hook, taxi off the landing zone being just a little less than slowing to exit a taxiway, that should be enough room for people to manage, even if a bit stressful.

I do wonder what the toxicology report will find.  I suspect the C-340 pilot was impaired.

The bottom line for me and my students will be this:  If you find yourself in this situation, LAND! 
1.  Survival is much more likely if you are already on the ground. 
2.  You cannot guess what some knucklehead behind you will do, and he is just as likely to turn into you as any other direction.
3.  Your trainer does not have the power/performance necessary to escape, especially when you are already slow and dirty.
4.  If someone behind you is that fast, he cannot land anyway, and will likely end up high over your touchdown point.

[EricJ]

1 hour ago, ilovecornfields said:

Well, this is certainly timely! A Mooney Special Letter on ADS-B and traffic alerting.

SL_22-03.pdf 282.62 kB · 8 downloads

My IFD has aural alerts for traffic but since I fly in a very high-traffic area I had to turn it off to keep it from constantly alerting.   

[Pinecone]

42 minutes ago, AH-1 Cobra Pilot said:

Is it OK to be on a 1-mile final in front of someone on a 3-mile final?  On the carrier, we shot for landings 40 seconds apart.  So, our separation was less than 2 miles, and with the time to roll back, raise the hook, taxi off the landing zone being just a little less than slowing to exit a taxiway, that should be enough room for people to manage, even if a bit stressful.

I do wonder what the toxicology report will find.  I suspect the C-340 pilot was impaired.

The bottom line for me and my students will be this:  If you find yourself in this situation, LAND! 
1.  Survival is much more likely if you are already on the ground. 
2.  You cannot guess what some knucklehead behind you will do, and he is just as likely to turn into you as any other direction.
3.  Your trainer does not have the power/performance necessary to escape, especially when you are already slow and dirty.
4.  If someone behind you is that fast, he cannot land anyway, and will likely end up high over your touchdown point.

 

Tower can clear traffic to land with, IIRC, 3000 foot separation through the landing roll.

In the USAF we would land on left or right half of the runway with pretty close spacing.  I can't remember what it was though, but 3000 feet sounds familiar.

[0TreeLemur]

Yes, an interesting and timely SAIM posted by @ilovecornfields.   Anyone experienced with TSO-C195b?

Does an iPad running and EFB that makes aural call-outs through the audio panel meet the TSO?

 

[Marauder]

Yes, an interesting and timely SAIM posted by [mention=15779]ilovecornfields[/mention].   Anyone experienced with TSO-C195b?
Does an iPad running and EFB that makes aural call-outs through the audio panel meet the TSO?
 

My Lynx 9000+ with ATAS meets the requirements of C195b.


I have an iPad that gets traffic from a GDL-52. My Aspens, GTN and Lynx all get traffic from the Lynx. What I have found is that I will get traffic warnings on the iPad not based on conflict but based on proximity to me.

The stuff that is connected to the Lynx will all trigger at the same time when the ATAS triggers with the voice warning. The big difference is that it won’t trigger unless there is a conflict. What that means is my iPad won’t trigger on a plane that is 3 miles away and heading towards me, while the Lynx ATAS will. As I mentioned earlier, it has been 100% accurate over the past 5 years. I don’t get nuance warnings even if in the traffic pattern unless there truly is a conflict. An example of that was a warning on final when a plane entered the runway with me about a mile out.

I just read through the TSO. There are a lot of requirements that need to be met to ensure any failure mode doesn’t compromise the integrity of the system. I doubt an iPad system can meet it but I am checking on the GDL-52 specs.


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[M20F]

7 hours ago, AH-1 Cobra Pilot said:

I do wonder what the toxicology report will find.  I suspect the C-340 pilot was impaired.

I suspect (or at least hope) you were impaired when you wrote this.