1/20/2011 Near Midair - AA B-777 & 2 C-17s

[Hacker15e]

Lets not forget the C-17s were in TA only and weren't taking part in the resolution advisory calculations. From what I've read, the AA plane actually had a reversal of commands; first a "descend now", then an "increase descent", and finally a "climb now". There was actually ZERO vertical separation when it was all said and done. Why that happened, no one really knows yet.

It was night. I sure as hell can't tell whether or not someone is at my altitude or on a converging course at night. And how do we know they weren't in a cloud layer.

And yes...the TCAS worked. Mostly. The TCAS RA on the 777 commanded a descent, then an increased rate of descent, then a reversal to a climb. THUG11, the flight of two, had their transponders set to TA only and couldn't receive RAs; there was no "negotiation" between the systems of each aircraft. The 777 was on its own for avoiding the C17s.

OH lordy! The 777 was on it's own! The C-17s were only in TA! DOOOM! Are you guys listening to yourselves? Seriously -- to listen to some of the points of view I read and hear, it is amazing that aircraft were ever able to fly without having a midair before TCAS was invented. Who cares if they're on different radio freqs -- my radio has never been able to look out the window and alert me to traffic. Night ops? Yes, this was over the United States, and they had these big red things flashing on them, along with a couple other colors going, too. Again, this is why there are windows and people in that room at the front of the jet to look through them.

It's not such a small point that the RA commands provided confusing and contradictory guidance. You ask "why that happened", and I think that's a very easy answer -- because TCAS is a very imprecise tool that reacts comparatively slowly (compared to what a pilot would do under similar circumstances), especially if the other aircraft is maneuvering (or if the TCAS containers aren't talking to one another, of course). This is EXACTLY why pilots need to remember that TCAS is an aid to clearing. Say that again -- TCAS only supplements the pilot's responsibility to look outside and miss stuff. Yes, even at night. I have flown with a number of USAF pilots (from non-tactical backgrounds) who in practice rely completely on the hits on the display to cue their visual search, and that's only IF they are actually conducting a visual search to begin with. More often, it's the "Traffic" call that makes them look up from their magazine or stop fiddling with the FMS.

Don't get me wrong -- I like what TCAS does. It's a great backup. It has alerted me to stuff I did not see a number of times -- I'm not going to claim that I have perfect visual lookout (and my old man eyes are juuuust starting to fail anyway!). It's nice when you're in the soup and it gives you SA on what's going on around you that you would not otherwise have. Just like every other piece of avionics, though, I assume that it's trying to kill me and inherently don't trust it. It is only a part of my SA building.

Flying in a big aircraft with a multi-pilot crew and all sorts of fancy toys doesn't ever negate what your primary responsibility is as an aviator, nor abrogate the skills and habit patters that you were using to fly 150s around to get your PPL.

 

[dasleben]

OH lordy! The 777 was on it's own! The C-17s were only in TA! DOOOM! Are you guys listening to yourselves? Seriously -- to listen to some of the points of view I read and hear, it is amazing that aircraft were ever able to fly without having a midair before TCAS was invented. Who cares if they're on different radio freqs -- my radio has never been able to look out the window and alert me to traffic. Night ops? Yes, this was over the United States, and they had these big red things flashing on them, along with a couple other colors going, too. Again, this is why there are windows and people in that room at the front of the jet to look through them.

It's not such a small point that the RA commands provided confusing and contradictory guidance. You ask "why that happened", and I think that's a very easy answer -- because TCAS is a very imprecise tool that reacts comparatively slowly (compared to what a pilot would do under similar circumstances), especially if the other aircraft is maneuvering (or if the TCAS containers aren't talking to one another, of course). This is EXACTLY why pilots need to remember that TCAS is an aid to clearing. Say that again -- TCAS only supplements the pilot's responsibility to look outside and miss stuff. Yes, even at night. I have flown with a number of USAF pilots (from non-tactical backgrounds) who in practice rely completely on the hits on the display to cue their visual search, and that's only IF they are actually conducting a visual search to begin with. More often, it's the "Traffic" call that makes them look up from their magazine or stop fiddling with the FMS.

Don't get me wrong -- I like what TCAS does. It's a great backup. It has alerted me to stuff I did not see a number of times -- I'm not going to claim that I have perfect visual lookout (and my old man eyes are juuuust starting to fail anyway!). It's nice when you're in the soup and it gives you SA on what's going on around you that you would not otherwise have. Just like every other piece of avionics, though, I assume that it's trying to kill me and inherently don't trust it. It is only a part of my SA building.

Flying in a big aircraft with a multi-pilot crew and all sorts of fancy toys doesn't ever negate what your primary responsibility is as an aviator, nor abrogate the skills and habit patters that you were using to fly 150s around to get your PPL.

You're way off base here, Hacker. If this was a planned exercise, 2,000' laterally wouldn't be a big deal by any stretch. Unexpected, unplanned loss of separation, at night, in possible IMC, with a jet that can't aggressively maneuver? It's a problem.

By the way, I don't disagree that see and avoid is rule #1, however, this was not an intentional formation exercise done in VMC.

 

[TFaudree_ERAU]

I disagree with you about your analysis of TCAS. Unless its telling you to dive at the ground, you follow the commands. It is NOT an imprecise tool. Contrary to what you are saying, it's thinking WAY more quickly than you can, and it's (supposed to be) coordinating with the conflicting traffic. It DOES take precedence over what you see out the window or are being told over the radio.

Have we forgotten Überlingen? I'm guessing those two crews should have been relying primarily on their eyes and only using the TCAS as "advice".

 

[dasleben]

I disagree with you about your analysis of TCAS. Unless its telling you to dive at the ground, you follow the commands. It is NOT an imprecise tool. Contrary to what you are saying, it's thinking WAY more quickly than you can, and it's (supposed to be) coordinating with the conflicting traffic. It DOES take precedence over what you see out the window or are being told over the radio.

Have we forgotten Überlingen? I'm guessing those two crews should have been relying primarily on their eyes and only using the TCAS as "advice".

Very true. TCAS II has proven itself extremely reliable, and a disregard for RAs has cost lives. For Hacker15e, the contradictory commands more than likely came as a result of 1) the two C17s having their TCASs in TA only (i.e., no "You climb, I'll descend" negotiation going on), and 2) C17s possibly changing altitude. The main thing that makes TCAS II work is the two-way interrogation and resolution maneuvers, which the C17s had disabled.

To add, in the civilian world, disregarding RAs because you're Macho Man Randy Savage and don't need it, will probably cost you your job, and for good reason.

 

[Chief Captain]

Why would a C17 be TA only? What's the advantage of disabling the RA's?

 

[derg]

The industry bought TCAS with a lot of spilled blood.


Sent from my TRS-80

 

[MercFE]

Why would a C17 be TA only? What's the advantage of disabling the RA's?

Engine out? I know that our RA computations are based on four engine climb performance. Therefore, we switch the TA when we have an engine failure, to avoid impossible climb commands.

Don't know anything specific to this situation, just the only time I can think of going TA.

 

[dasleben]

Engine out? I know that our RA computations are based on four engine climb performance. Therefore, we switch the TA when we have an engine failure, to avoid impossible climb commands.

Don't know anything specific to this situation, just the only time I can think of going TA.

My guess was to avoid RAs in formation...is that normal?

 

[thepotato232]

Hacker's exactly right in saying "see and avoid" is Priority One regardless of what you're flying and who you're flying it for. He's also exactly right in saying that at 2000' of separation, it's not time to crap your pants and pull out the rosary, it's time to be a pilot and get the Hell out of the way.

What makes this such a big deal is the circumstances. There are very good reasons the military requires so much training and briefing for close-in formation flights. All pilots need to be on the same page, and have a reasonable expectation of what the others will do. The foundations for flying in that environment are built in flight training, and are added onto continuously, up to and including the flight itself. Even his example of the tight traffic pattern took place within a controlled, coordinated environment. Large, sluggish aircraft getting within 2000' of each other with no prior coordination, with closure rates approaching a thousand knots, operating in a controlled environment under IFR (possibly IMC) is a BIG DEAL. It means something has gone wrong. There has been a breakdown on some level of safety barriers, and it warrants further investigation. Responding to incidents in this manner is a big part of why air travel is so much safer now than it was in the Good Old Days.

And Hacker can happily note that all parties made the standard right turn to avoid traffic. Whether this was pilots reverting to basic procedures or (more likely) a last-minute save by ATC, it's reassuring to see that the human element was not written out of the scenario in favor of absolute reliance on TCAS.

 

[dasleben]

And Hacker can happily note that all parties made the standard right turn to avoid traffic. Whether this was pilots reverting to basic procedures or (more likely) a last-minute save by ATC, it's reassuring to see that the human element was not written out of the scenario in favor of absolute reliance on TCAS.

It was a turn by ATC, according to the NTSB's docket. ATC stood out of the way while the 777 maneuvered with the RA.

By the way, here's some decent reading on TCAS II, in case anyone has any questions as to how it works: http://www.faa.gov/documentLibrary/media/Advisory_Circular/TCAS II V7.1 Intro booklet.pdf

As TFaudree_ERAU said, it's actually rather precise, and very reliable.

 

[PositionAndHold]

OH lordy! The 777 was on it's own! The C-17s were only in TA! DOOOM! Are you guys listening to yourselves? Seriously -- to listen to some of the points of view I read and hear, it is amazing that aircraft were ever able to fly without having a midair before TCAS was invented. Who cares if they're on different radio freqs -- my radio has never been able to look out the window and alert me to traffic. Night ops? Yes, this was over the United States, and they had these big red things flashing on them, along with a couple other colors going, too. Again, this is why there are windows and people in that room at the front of the jet to look through them.

It's not such a small point that the RA commands provided confusing and contradictory guidance. You ask "why that happened", and I think that's a very easy answer -- because TCAS is a very imprecise tool that reacts comparatively slowly (compared to what a pilot would do under similar circumstances), especially if the other aircraft is maneuvering (or if the TCAS containers aren't talking to one another, of course). This is EXACTLY why pilots need to remember that TCAS is an aid to clearing. Say that again -- TCAS only supplements the pilot's responsibility to look outside and miss stuff. Yes, even at night. I have flown with a number of USAF pilots (from non-tactical backgrounds) who in practice rely completely on the hits on the display to cue their visual search, and that's only IF they are actually conducting a visual search to begin with. More often, it's the "Traffic" call that makes them look up from their magazine or stop fiddling with the FMS.

Don't get me wrong -- I like what TCAS does. It's a great backup. It has alerted me to stuff I did not see a number of times -- I'm not going to claim that I have perfect visual lookout (and my old man eyes are juuuust starting to fail anyway!). It's nice when you're in the soup and it gives you SA on what's going on around you that you would not otherwise have. Just like every other piece of avionics, though, I assume that it's trying to kill me and inherently don't trust it. It is only a part of my SA building.

Flying in a big aircraft with a multi-pilot crew and all sorts of fancy toys doesn't ever negate what your primary responsibility is as an aviator, nor abrogate the skills and habit patters that you were using to fly 150s around to get your PPL.

Adding to what others have stated. TCAS is an exact science for a variety of reasons. But the biggest is not creating multiple conflicts when responding to a single RA. If you think you have the traffic and start a steep descent, well past what TCAS is telling you to do, you might find yourself pulling hard the other way to avoid the guy you are now descending rapidly towards. Or you might think you've got the traffic insight, and you're looking at a similar but wrong target and plow into the plane TCAS is screaming about. It's not mearly an aid, it is mandatory to respond to an RA in the maner TCAS is commanding. If pilots out there are being trained to do any thing else, it's crazy.

 

[Roger Roger]

Seriously -- to listen to some of the points of view I read and hear, it is amazing that aircraft were ever able to fly without having a midair before TCAS was invented.

Two points.
One, the skies (at least the parts of them frequented by large heavy jets full of people) are a lot more crowded than they were in the Good Old Days.
Two, they didn't fly without midairs. In the days before TCAS there were quite a few really nasty midairs that killed a lot of folks.

 

[MercFE]

My guess was to avoid RAs in formation...is that normal?

Not sure about other platforms procedures... However, when we air refuel, our transponder is turned off. Only need the one return for ATC, and avoids all traffic calls while you have the tanker visually.

 

[MercFE]

While I think TCAS is a GREAT tool, I have come to believe that it is hardly an exact science. Like any system in our aircraft, it is subject to having issues. The theory and design behind it might be exact, but all pilots must expect it to fail or give erroneous readings at any time. Ultimately, the PIC is the one responsible for the safety of the flight.

As an example, we have had two of our aircraft place TCAS returns in the wrong location on out display. We have repeatedly reported these issues to maintenance, with little to no effect on finding a solution. We will give them all the info we can about planes in traffic patterns and passing at altitude, only to have sign offs such as, "targets displayed properly outside 20 miles."

Neither of the aircraft has ever given an RA against one of these targets. However, neither plane has been placed into a position where it would need to either.

 

[Hacker15e]

Adding to what others have stated. TCAS is an exact science for a variety of reasons. But the biggest is not creating multiple conflicts when responding to a single RA. If you think you have the traffic and start a steep descent, well past what TCAS is telling you to do, you might find yourself pulling hard the other way to avoid the guy you are now descending rapidly towards. Or you might think you've got the traffic insight, and you're looking at a similar but wrong target and plow into the plane TCAS is screaming about. It's not mearly an aid, it is mandatory to respond to an RA in the maner TCAS is commanding. If pilots out there are being trained to do any thing else, it's crazy.

I know what most FOMs say, and what the FAA recommends. I'm not advocating to regularly just blow off RAs. Hell, I'm not even advocating to do it every once in a while. Probably not even 1 out of 1,000 times in the operating environment that most of you are talking about (I'm completely excluding my operating environment because it obviously does not apply in any way to commercial operations in the US NAS or even ICAO airspace).

What I am saying is that if pilots are merely a slave to what the TCAS container is saying -- both in terms of data displayed as well as commands issued -- and not using all the tools available to build their SA and then operating their aircraft appropriately, then that is what is crazy.

With respect to "exact science", all I can say is that I have about 6 years experience flying TCAS I and II-equipped aircraft (both slow and fast movers), and I have seen it be less than precise on numerous occasions. Mostly they were displayed errors in both azimuth and altitude, and calls for RAs based on predicted maneuvering out of the other aircraft that never happened or happened differently than predicted. Or, it was displays not showing aircraft that were squawking, or the opposite -- showing phantom traffic that did not exist. In the fighters, especially, we were the ones messing with the TCAS-equipped aircraft and causing them to get all hot and bothered; TCAS doesn't predict the speeds and climbing / maneuvering capability of a fighter, and because the system lags, we could be setting off RAs even when we weren't remotely any conflict for the other aircraft. More than once I have had aircraft climb or turn into me while following an RA -- a situation where I saw them the entire time, and they obviously did not see me.

As an aside, in fighter and combat operations, I give TCAS even less importance in my SA heirarchy for a number of reasons. Let's not forget that TCAS is trying to maintain some relatively large miss distances between aircraft as well as command relatively smooth and light G maneuvering to do it. In a potentially very crowded environment (for example, a 'stack' over a target where aircraft are at 500-foot altitude increments doing circles of various radii, speeds, and directions) and filled with non-squawing aircraft (like every #2 of a formation), not only does TCAS sometimes try and make me climb/descend into someone else's airspace to 'avoid' someone who is not going to hit me because of established altitude deconfliction, but it also doesn't see all of the idiotic wingmen out there who are moseying around at other-than-their-assigned-altitude and not even appearing on the TCAS display. In that situation, I go to STBY or TA, and only use the display for helping get my eyes on something I haven't been able to pick out of the sky yet visually. So, for the purposed of this discussion, I'm completely disregarding those types of experiences because we just don't see that in common carrier operations.

Again, look at the conflicting commands seen in this exact situation and look at the lines on the admittedly non-scientific map posted -- there's direct evidence that the system isn't perfect. Even if we flew in a perfect world where every aircraft was flying around with a TCAS II or better system on board (and obviously we know that is far, far from the truth), this would not be a perfect system. Bearing in mind that there are a whole crap-ton of aircraft operating in the National Airspace System that aren't so well equipped, then it's just not possible to christen the system as the Saviour. Is it good? Yep. Does it provide value? Absolutely -- I think it's a magnificent system and I really like flying aircraft that are so equipped. In no way, though, does it replace my duty as an aviator to clear my flightpath, nor does it replace my responsibility to build and maintain SA, and respond appropriately to possible conflicts. TCAS is a single piece of information in building that SA.

But, hey -- if the FAA's printed information on it says it's perfect and precise, then I guess it is, right?

 

[TFaudree_ERAU]

Out of curiosity, what change number were you guys running? Change 7 has taken care of a lot of the false alarms.

 

[ProudPilot]

I don't quite get your question, but yes, TCAS works at all altitudes as long as both aircraft are properly equipped.

Not sure what you're getting at by talking about a trend. Controllers make mistakes, that's why we have multiple levels of safety (procedures, TCAS etc.) to ensure there's no loss of life.

The system worked as designed. Personally, I think ALL aircraft should have TCAS.

Yeah, it'll be ADS-B, In eventually.

 

[Hacker15e]

Out of curiosity, what change number were you guys running? Change 7 has taken care of a lot of the false alarms.

Gotta admit, I have no idea offhand. I'd have to go look it up to give you a legitimate answer. Most of my time in TCAS-equipped aircraft is in the military, and it can be a very odd place in terms of equipment and software that may be standard across the board in the civilian world. Some places are very up to date on changes like that, and many others (especially my corner of the world, the fighter and trainer business) can take years to implement such changes.

If it's improving, then that is fantastic to hear. I like things that make flying safer -- I really do.

I know that sometimes my posts sometimes may contextually present a cavalier attitude, that I'm some hair-on-fire crazy risk taker. I am actually a pretty cautious and calculated aviator (side note: isn't that one of the warning flags -- when a pilot says "I really am a safe pilot", it means that he isn't, right? ), and not about taking any risks that the situation does not demand. Y'all have to realize that I've spent 17 years in a combat-mission oriented environment that involves lots and lots of flying consisting of ordinary day-to-day operations that would probably scare (or at least appear pretty extreme to) many civilian pilots. It is a very mission-focused environment, too, which runs contrary to most civilian operations (and even contrary to what is specifically taught and encouraged by the FAA -- I think that's one of the 'hazardous attitudes' according to the FAA!).

I fully realize that. I realize that the mentality which is appropriate for successful combat operations is not the same for safe commercial flying operations. When I comment on these situations (and I'm sure you can go back and find years of such poking-sticks-in-the-cage from my posts on similar topics on JC) it is to show that there is a different perspective out there.

Remember that airmanship is a journey. None of us have all the information, so as airmen we're constantly on a journey to seek out new information and experiences to add it to our bag of tricks. Why do you guys think I'm a participant on a forum that primarily discusses a type of flying that I'm not really involved in yet? I'm on APC and FI as well....along with a number of other forums that discuss differing types of aviation that I'm interested in but neither experienced nor active in. The discussions on this forum and others provide me with a lot of information and "experience" (de facto) that I wouldn't otherwise be exposed to where I "normally" work. IMHO, such interactions are helping build my knowledge and awareness, and ultimately my judgment and airmanship.

My presentations of the differing perspective of a military tactical pilot should hopefully bring similar perspective to your worldviews.

 

[TFaudree_ERAU]

I completely understand and REALLY respect where you're coming from. Even in the civilian world, there are pilots doing the same type of flying in which one pilot may feel comfortable and the other not. I mentioned the 91 vs. 135 factored runway distances as an example; mikecweb and I have taken a Lear 55 (a notorious runway hog) into a Caribbean runway that would make some 55 drivers crap their pants at the mere thought of it. We did it because the book said we could do it, and we felt confident in our abilities to do it.

I fully agree with you that visually clearing the airspace is priority number one when it comes to keeping metal from bending, but when, for whatever reason, that falls through, TCAS is where I'm putting my money. AC 120-55C has a lot of good info about TCAS. While it DOES start off by saying that see-and-avoid is the number one rule of traffic avoidance, it then goes on to basically say, over and over again, that "serious injury or death may result from not adhering to TCAS resolution advisories."

And stop climbing that fighter jet at more than 1,500 fpm in RVSM airspace and you won't get all those RAs

 

[jtrain609]

There may be a different perspective out there, and you may have survived all these years of combat ops.

But what is considered an acceptable level of safety for you is completely inappropriate for part 121 airlines that have passengers in the back that only understand that their level of risk is incredibly, incredibly low. Airline gigs are boring, slow paced, boring, safe, boring, mundane, and boring, which means they're safe.

So perspective is fine, but really, what you guys do for normal ops is 100% unacceptable to airline ops.