TCAS vs. ATC: who takes priority?

[TheCosmicFrog]

Hey again, still feeling inquisitive :8

I'm sure that there's probably one definite answer for this in the ol' Pilot's textbook, but I was just curious about it:

When it comes to traffic avoidance, who takes priority, ATC or TCAS?

If ATC says, "Callsign 1234, alert, traffic, cease ascent!"

...and the TCAS says, "Traffic, traffic, climb!"

...what must the PF do? I imagine this must be incredibly disorienting. I know I wouldn't like to be the PF in one of these situations!

Thanking you for any insight :)

[PT6A]

Very simple...

Follow the RA...

PT6

[SNS3Guppy]

TCAS. Always.

[Brian Abraham]

As PT6 says, comply with the TCAS. This is what can happen in circumstances where you don't Bashkirian Airlines Flight 2937 - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Bashkirian_Airlines_Flight_2937)

[ford cortina]

TCAS RA's ALWAYS......
Euro control have some info about TCAS here:
http://www.eurocontrol.int/ra-downlink/gallery/content/public/library/ICAO%20ACAS%20changes%2022Nov07.pdf

[adverse-bump]

Spotter Forum in 3, 2, 1...

[Fullblast]

Follow TCAS and declare "TCAS RA" to ATC, they stop transmissions/clearences up to your "Clear of conflict, resume .......".

That's in Euroland, guess somewhere else still using "TCAS Climb/Descent".

FB

[Iceman49]

Follow TCAS for vertical, and ATC for headings

[ITCZ]

Follow TCAS for vertical, and ATC for headings
Modify that.

Never turn when TCAS is issuing instructions. The TCAS software solution is based on 'wings level' and commanding rate of climb or descent.

Turn during an RA or TA and you throw your protection out the window.

"Traffic" or RA? Follow instructions. Don't turn. RA trumps ATC. Advise ATC iaw local AIP.

[bucket_and_spade]

ITCZ,

Hmmm, only just considered that scenario. So, if you're in a turn and get an RA, the automatics come out and you follow the RA command while rolling wings level?

Genuine question - I probably should have considered it before but RAs always seem to come when S+L in the sim.

Have you got a reference for a description of the wings-level software solution?

Cheers,

B&S

[Iceman49]

Our ops states: If a TCAS RA and ATC controller's breakout instructions occur simultaneously, comply with the TCAS vertical guidance and follow the controller's turn/heading instructions.

[Dont Hang Up]

For goodness sake!

This has been covered so many times!

TCAS is followed as the highest priority. Controllers know this and flight crews know this. Surely there is no longer anyone in any doubt?

Last time someone got this wrong people died.

[framer]

I got an RA recently, called "ABC 1234 TCAS climb" and ATC came back with "negative maintain niner thousand".......hard to believe I know but that was the response. I just said "negative abc1234 TCAS climb"

So it does happen where they put you in that position of deciding.Full report followed of course.

[Spodman]

If I misheard "ABC 1234 TCAS climb" as "ABC 1237 request climb" (and I think that could be most easily done), I would come back with "negative maintain niner thousand"... if I believed there was traffic above. Aust AIP says "TCAS RA..." which I have heard a couple of times (both false alarms obviously, I'm still in the business) and really got my attention.

If an ATC has still not yet grasped the situation, the pilot is supposed to respond to any such instructions with "UNABLE TO COMPLY, TCAS RA (thinks: f%$#wit...)", or something like that.Follow TCAS for vertical, and ATC for headings Sounds like a dumb idea. On the other hand, if I have compromised separation and think the TCAS is possible RA'ing as I speak, (heaven forfend), I would issue an alert and a suggested heading and not screw around with the levels. I would leave the levels to the TCAS.

If nothing else that should tell the crews that the guys on the ground have bolloxed it up and trust your technology:oh:

[AKAFresh]

I know the instruction must be followed over ATC instructions but my issue is whether you can continue the turn or must level the wings first and then Climb/Descend.


ITCZ you state that "Never turn when TCAS is issuing instructions. The TCAS software solution is based on 'wings level' and commanding rate of climb or descent. Turn during an RA or TA and you throw your protection out the window."


My Operations Manual clearly states:

"If an RA is given in a turn, the turn may be continued"


Can someone please clarify the action required (regarding roll) with a TCAS RA in a TURN please?

AkA.

[Cretan Airbus]

A TCAS RA always has priority, but not a TA. The RA virtually eliminates human ATC or pilot error. Just be mindful of aircraft that are not operating mode c transponders, or formation flights where only one aircraft has a transponder turned on (rare, but it happened to me once).

Be sure to send in the required operations report, which should alleviate any record of wrongdoing by the pilot.

Cretan

[Willoz269]

The bigger problem is that TCAS may solve an issue by issuing a climb and putting the aircraft at risk against a preceding higher traffic.

My suggestion has been to receive direct feedback of TCAS displays on the ATC radar console, particularly in approach, so the controller knows real time what instructions are being displayed to the pilots.

[Cretan Airbus]

TCAS is capable of giving an RA for multiple aircraft threats. It avoids putting you into another RA, but if it does, it will give the appropriate guidance. This is why you want to keep the RA vertical guidance in your scan during an RA, as it can change dramatically.

All of this is, of course, assuming that all target aircraft are equipped with at least a mode c transponder.

Cretan

[framer]

If I misheard "ABC 1234 TCAS climb" as "ABC 1237 request climb" (and I think that could be most easily done), I would come back with "negative maintain niner thousand"...
Good point. In the scenario we had, the communication was good, and the call wasn't mis-heard, we were approaching to land as well so a request for climb wouldn't have been what the controller was expecting either. I imagine that if we were depating and the controller had an expectation of us wanting further climb, then what you suggest is quite likely. The correct terminology for us is still "abc 1234 TCAS climb" ....maybe it will change soon to align with ICAO.

[Wizofoz]

Iceman,

That is specifically and only tp do with breakout instructions during a PRM ILS procedure. In all other cases, RA should be complied with with wings level.

HOWEVER, the response to a TA is "Manoeuvre as required". There is no TCAS instruction with a TA, and no limitation on lateral manoeuvring. Rules of the air still state that aircraft on a collision course should alter heading to the right, so I think a turn to AVOID an RA situation is an appropriate response.

[AKAFresh]

I know the instruction must be followed over ATC instructions but my issue is whether you can continue the turn or must level the wings first and then Climb/Descend.


ITCZ you state that "Never turn when TCAS is issuing instructions. The TCAS software solution is based on 'wings level' and commanding rate of climb or descent. Turn during an RA or TA and you throw your protection out the window."


My Operations Manual clearly states:

"If an RA is given in a turn, the turn may be continued"


Anyone care to comment on this;

Can someone please clarify the action required (regarding roll) with a TCAS RA in a TURN please?

AkA.

[Capt Pit Bull]

Use the search function.

[bucket_and_spade]

I think we've more than agreed on what takes priority - what a few have asked for, myself included, is a reference or expansion from those posting earlier about the TCAS software solution and its assumptions.

Of course, with a bit of legwork we can find the info elsewhere ourselves but as we're on the subject and some people here have hinted at some knowledge of the subject, it's perfectly reasonable to ask for more info on this thread.

Anybody?

Cheers,

B&S

[ITCZ]

Of course, with a bit of legwork we can find the info elsewhere ourselves but as we're on the subject and some people here have hinted at some knowledge of the subject, it's perfectly reasonable to ask for more info on this thread.
Oh dear. Can of worms opened!

I bring two perspectives to this problem. First, the perspective of someone who pursued the qualification of journeyman mathematician but never put it to 'professional' use. Second, as a professional pilot.

So, take a reasonable grounding and interest in mathematics, an imperfect knowledge of avionics and properties of electromagnetic waves, and a particular interest in not hitting other aeroplanes, and this might be the result.

or.... Caveat Emptor!

The algorithm used in TCAS computers is from the branch of mathematics some call Probability. Having first detected a likely bearing and range to a target, the TCAS unit then has to decide, using probability mathematics, which of the reported replies are likely to be aeroplanes. In the same way that VOR's may scallop, and surveillance radars might paint flocks of birds or lorries as targets, not every whisper-shout return the transponder reports to TCAS might be an aeroplane at the calculated range, bearing, and relative altitude.

The algorithm matches three or four valid replies or more, selects those that are most probably an aeroplane travelling in a straight line.

An aeroplane that is travelling in a straight line, can be computed faster and a projection of its future location made, using fewer such returns and the solution found much faster than for an aeroplane that is turning.

Once it determines that a series of valid returns are matched using probability mathematics to be aeroplanes, the algorithm makes forward projections based on current vehicle states, and issues alerts as required.

If for some strange reason you wanted to confuse the TCAS computers of other aeroplanes in the same airspace, then a good party trick would be to either (a) accelerate or decelerate, and/or (b) make a rapid turn.

Because then you are making your aeroplane behave in a way that the other proximate, probably Mode S, aeroplanes will think is a 'very un-aeroplane like' manner.

That is, you no longer fit the model of 'aeroplane-like-behaviour' that other TCAS II computers use to filter out multipath returns, etc.

Also, out of the range, bearing and relative altitude information that TCAS algorithms filter, understand that it determines range not by GPS coordinates transmitted -- TCAS can independently calculate range from signal gain in the whisper-shout transmissions between transponders. Squaring the range returns, and finding the asymptote of the resulting parabolic curve is the input to range calculations and closest point of approach. And (thankfully) I can point you to one internet paper on the subject confirming in mostly plain language that asymptotic values of range-squared are too low to track a turning target.

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA163354&Location=U2&doc=GetTRDoc.pdf

Humans (ATC, pilots) can separate aeroplanes by changing their speed, their heading or their altitude. TCAS sought an automated solution too 'see' further than pilots and simultaneously calculate more potential threats than an ATC. When melding mathematics, electronic and avionics engineering, it was far easier to implement a fully automated solution based on vertical speed and altitude than accelerate/decelerate, lateral separation, or turning. Simpler with existing technologies.

When avionics can be made of newer computing technologies that are not simply bigger and faster Von Neumann machines (fer chrissake they still have MODES!!!), we might see other mathematical and technical solutions to collision avoidance.

As I said, that part is the formulation of a trained, but amateur, mathematician. You are free to discount it all as a load of b0llocks if you like. Now lets talk as professional pilots.

so I think a turn to AVOID an RA situation is an appropriate response.
I disagree.

When we were introduced to the rules of the air, we were taught right of way, and overtaking, who is it that has the other on his right, etc.

Conflict? Resolve by turning. Primacy of learning, what ever you call it, or maybe its how we solved conflicts in two dimensions on the surface. Aeroplanes cannot stop,so... Turn!

Take a look at any airprox or TCAS event recorded in any State's accident/incident database and you will find they are replete with pilots that turned in response to a threat of midair collision.

Key point: In response to.

Some of those turns made the situation worse.

As someone said before, any search on TCAS training materials (there are some excellent ones by Eurocontrol) and you will quickly find that the TCAS software tracks many more targets than it displays, and probably more than most pilots can process (which is about seven, plus or minus two, but thats another topic).

A 'lesser of Rate One or 25 deg AoB' turn probably fits, within the TCAS algorithm of moderate turn.

But anything more than that, such as the kind of turn that might be considered by a pilot that thinks they need to 'do something' in response to a TA, or 'do something' extra in an RA, is in my mind making it harder for the TCAS system to do a job that it does very, very well. Using altitude and vertical speed.

Thus far, noone here has suggested that they firewall the power levers, or slam them shut, throw out the airbrakes gear and flap, as a collision avoidance manoevre. Fair enough too -- what would that achieve?

Much the same as turning. Might work if the aeroplane you have eyeballed is the right threat, and only threat. Otherwise great potential to make things worse. Turning does not fit the definition of aeroplane like behaviour in the probability mathematics that is the heart of the system that is alerting you and protecting you.
My Operations Manual clearly states....
My training organisation has instructed self and colleagues not to initiate a turn in response to a TA or RA.

As a working pilot that follows instructions from above, that is what I do. As someone with a background and an interest in the underlying maths and tech, I believe I understand some of the reasons behind that instruction.

.... "If an RA is given in a turn, the turn may be continued"
Amateur mathematician says: That sounds reasonable. Your turn onto an ATC heading or following an LNAV track is probable at or much less than rate 1 or 25 deg AoB. Moderate. And you are not considering initiating a turn in response to a threat, you are in un-accelerated flight.

Pilot says: It is also your instructions in your FCOM. Follow those instructions. :ok:

[bucket_and_spade]

ITCZ,

Oh dear. Can of worms opened!

Indeed. You're no doubt referring to some of those on this site who post "do a search" more often than any other reply. Often valid, sometimes not. I suggest that the detailed response ITCZ has posted is not available in another Proon thread.

Anyhoo...

In a previous life I seem to remember doing a geeky physics degree so will use this now-very-shaky knowledge to try and get the gist of the .pdf you posted!

Thanks for your detailed reply :ok:

B&S

[Wizofoz]

ITCZ,

A very well written and obviously knowledgeable response.

As such, my question is just that, a request in the hope of gaining knowledge, and in no way a challenge.

What ARE you advocating in response to TA? My manual (and, indeed, the Boeing manuals from my last three employers) all say, in various ways, "Attempt to acquire the traffic visually and maneuver as required".

Do you advocate a vertical man oeuvre BEFORE progressing to an RA? This would seem counter productive as there is no guarantee the other aircraft won't react in the same way.

Do you advocate simply waiting for an RA? This seems risky, as it is predicated on the other aircraft either doing nothing, or correctly following HIS RA. In at least two cases, the collision of the 757 and the AN124, and the near miss of two JAL aircraft, the situation ensued where one aircraft followed the RA, whilst the other followed an ATC instruction, with catastrophic and very near same results.

I hear what you are saying about multiple targets, but it's reasonably rare we get close enough to ONE target to generate a TA. Where, in the realms of probability, does the likelihood of getting a TA, using it as a guide to visual acquisition, visually acquiring the WRONG target, then turning towards the ACTUAL, but as yet unseen target actually lie?

[JEP]

From EUROCONTROL - "When ATC meets TCAS II"

http://www.eurocontrol.int/msa/gallery/content/public/documents/ACAS_Bulletins_10_disclaimer.pdf

More information is found here EUROCONTROL - ACAS II Bulletins and Safety Messages (http://www.eurocontrol.int/msa/public/standard_page/ACAS_Bulletins_Safety_Messages.html)

Educating stuff even for PPL-amateurs like me.

[Capt Pit Bull]

OK. The reason I said use the search function is because I and many others have spent probably days answering TCAS related questions on this board.

And tbh, I'd leave it at that if the subject wasn't so incredibly safety critical. Though I am forced to wonder about the mandated theoretical training that aircrew are suposed to have received. I get the impression that it still isn't happening for a significant proportion of the profession.

So, here goes:

Lets start with response to a TA.

1. Don't make up your own avoiding manouevre because you've received a TA. Some very serious incidents have occured where crews have got themselves (unduly) concerned about separation, manouevred as a result, and ended up causing a reduction in separation rather than an increase. In a TA, you have no legal basis for breaking your ATC clearance.

2. HOWEVER... this is often interpreted as meaning that you should do nothing to change your flight path. This is incorrect. You can - and probably should - manouevre in response to a TA, but only insofar as it is permissable by your ATC clearance.

Rationale: Statistically, most RA's these days are 1,000 foot level offs. If you get an RA, there is a good chance thats its because you are approaching your cleared level with an inappropriate vertical speed, OR, you are being sensible, but the other aircraft has a high rate. Everyone OUGHT to be following the guidance of not exceeding 1500 fpm within 2,000' of the cleared level, but my contacts in the ATC world tell me (with a hint of dismay I might add) that there are still way too many aircraft that either don't know or choose not to follow this guidance.

Hence, in most RA's, there is at least one aircraft that hears "TRAFFIC TRAFFIC" when they have an excessive vertical speed as they approach their cleared level. If they have any sense, the crew will use part of their 10-15 seconds to punch VS and spin the pitchwheel to a more sensible value, in addition to doing anything else.

At this point someone will probably accuse me of promoting reckless behaviour because their SOP doesn't mention this. My response: The fact that you are having a TA doesn't mean give yourself a lobotomy. If you find yourself with a big vertical speed and a TA, and you REALLY want to frighten yourself, just keep that high VS going. You're on course for an altitude crossing RA - and if the other aircraft is non TCAS, and god forbid on a different freq, or has TCAS but doesn't follow it (yes, its still hapening) you could be looking at a last minute reversal ....at best...

Whereas a prompt reduction in VS will defuse this into something less stressful, like a corrective RA that is not altitude crossing, or better still a preventative RA, or best of all no RA at all, thereby saving yourself a bunch of paperwork.

Of course you are still legally required to maintain a minimum 500 fpm towards you cleared level, so don't level off in response to a TA, but reducing your rate is a very very wise thing to do. Better still, reduce it before you even get a TA in the first place...

Onwards then, to consider turning in response to an TCAS RA.

1. You should never initiate a turn based on information from TCAS. This is sometimes taken to mean that you should not turn during a TCAS encounter. This is most emphatically not the case; you are perfectly entitled to turn as long as you are not doing it solely because of TCAS.

2. It is often sugested that the aircraft you are looking at may not be the one that TCAS is worried about. This is very important to appreciate, but people often miss the point.

You see, in the earlier days of TCAS the guidance used to be that if you had visually identified the intruder and did not feel the RA was needed, you didn't have to follow it. At our airline, our in house guidance was follow the RA anyway, because .... the aircraft you are looking at may not be the one TCAS is worried about.

But can you see how this is not the same as looking at an aircraft and deciding a turn will help?

The first case involves looking at an aircraft and deciding it isn't a threat. As such, if its the wrong aircraft, not following the RA is going to be dangerous.

The second case involves looking at the aircraft and deciding its a threat. If you're looking at it, and its on a constant relative bearing, and its getting bigger, really, who cares if its the one TCAS is generating an RA on or not? If its a threat, then a turn may well help (more on that later). So we follow the RA (because thats definitely a good idea, whether there's one aircraft or two), and the decision about whether to turn or not goes into the melting pot of knowledge and judgement.

3. In addition to visual spotting, you could well be offered avoiding action by ATC. Current (in the UK at least, can't speak for the rest of the world) training for ATCOs is: Don't attempt to change the flight path of either aircraft once you become aware a TCAS RA has occured. Up untill the magic words "TCAS RA" are heard though, the ATCO remains responsible for attempting to provide separation, however they are strongly advised NOT to offer last minute vertical avoiding action, (statistically we pilots don't tend to get "TCAS RA" mentioned until well into the RA). As such giving you a turn ought to be more likely.

In this case, it is an ATC instruction and as such you are obliged to comply, however of course once an RA starts (and it may have started before you receive the avoiding action from ATC) then YOU, not the ATCO, are solely responsible for collision avoidance. The turn you've been offered now becomes advisory. I would suggest though if you've got any sense, you'll follow it.

4. But what about aircraft performance? It is often mooted that TCAS performance inhibitions are invalidated by turning, and that therefore to turn during an RA is to ensure that your aircraft will plummet like a dead sparrow etc etc...

This viewpoint is not without truth. Yes, your aircraft might have marginal performance to complete the RA and turning might compromise that. However, for most aircraft in all RA's, and all aircraft in most RA's, the RA will be easily achievable and a turn will be possible without difficulty.

Notwithstanding that, if your performance is marginal, you must sacrifice the turn in order to meet the RA. The RA is your main defence, the turn is incase the other bloke decides to be an idiot (or is non TCAS).

As an aside, even if you are NOT turning, your performance may be marginal, and you may not be able to fully comply with your RA even if the wings are level. I draw the line at rehashing that arguement (its only a few weeks old, use the search facility). If you can't comply fully with the RA, get as close as you can, whatever you do don't manouevre in the opposite sense.

5. To turn or not to turn....

OK, so we've established that you could be in an RA, with possibly an advisory turn from ATC, and / or your own visual perception that a turn might help.

Do you, or do you not, make the turn?

No simple answer for this. I'm not going to attempt to list them all, but there are clearly risk factors with either course of action, I know this'll wind up those who feel that every situation must have a 'correct' response and that everything else must be wrong. I'm not going into details here, ultimately its a judgement call.

One thing I will say is this though. Don't even think of looking at the traffic display to decide if you should turn during an RA. Really, its a bad idea at ANY time, and you shouldn't be doing it, but during an RA most TCAS installations surpress 'other traffic' blips so its a doubly bad idea.

6. If you are on a collision course, is a turn likely to help?

It depends. Whether a turn will actually help or not is a function of geometry. Obviously if you turn a long time before the collision point, you will change your flight path and miss the other aircraft.

Whereas, if you don't turn, and TCAS has not worked for whatever reason (other crew kept manouevring opposite, or didn't have TCAS etc), then there remains the possibility that even though you think you are going to collide, that your vertical judgement is wrong. You might be lucky, and miss one another by a few feet vertically.

In this case, if you have just started to turn, you are going to make matters worse. There is a period of time, as you roll the bank on, where you are making your aircraft bigger vertically, so you are more likely to overlap the intruder and hit him.

I recently read a study that suggested that as the time to impact decreases to less than 10 seconds you very rapidly reach the point where you do more harm that good by rolling into a turn.

So, for a turn to be effective, you have to grasp the bull by the horns and get on with it early during the encounter.

7. What about pitching to avoid an intruder visually?

For completeness, you should be aware that humans are almost useless at judging relative altitude. Read this for some background: http://www.pprune.org/tech-log/58559-perception-relative-altitude.html

This is one reason why its a bad idea to disregard an RA in favour of visual spotting. If you don't have an RA (10 day TCAS MEL perhaps) then your best bet is a turn, not a pitch.

In summary:

TA - Comply with your ATC clearance as normal. If you have a big vertical speed, strongly consider reducing it but still comply with your clearance. Turn as normal for navigation or if given a heading. If its an 'avoiding action' turn make it immediately.

RA - Whatever else you do Don't manouevre opposite the RA. Your RA will almost certainly be achievable and if so, you are required to follow it. If your RA is not achievable, get as close to it as you can whilst protecting the stall envelope. This applies even if it means you have to break your ATC clearance.

Turn if you think it will help, based either on ATC avoiding action or visual spotting. Do not use your interpretation of the traffic display to inform your decision to turn.

pb

[Capt Pit Bull]

never mind

[AKAFresh]

Capt Pit Bull...

Thank you very much for you detailed reply. Much Appreciated! :ok:

AkA.

[Wizofoz]

Capt Pitt Bull,

A great reply fully of factual information and plain old common sense. Indeed, approaching level off is where most TAs and RAs occur, and as such a vertical response (or, in fact, sound vertical management to avoid it in the first place). I avoided such an RA recently. A very light 777-300ER going up like a homesick angle, actually went into ALT mode 2000' below the level off, still doing over 2000fpm. The only way to reduce it's VS was to disconnect the AP which I duly did.

Most of the responses, however, are rather heavy on the assumption of immediate ATC availability and high traffic density. I spend a lot of time CPDLC over India, using dodgy HF in Asia, or OCTA in Modadishu airspace. Night before last I was no-coms for over an hour out of Jakarta, up to 40NM off course avoiding CBs. In these sort of circumstances, had I detected opposite direction traffic which was going to infringe, a right turn as per rules of the air would, in my opinion, have been the correct thing to do right up to the point of having to comply with an RA.

I believe we are negative training these days, teaching people to sit and wait for an RA to save them. It works if everyone does the right thing, it can lead to tragedy if someone doesn't.

[Graybeard]

ITCZ: "Having first detected a likely bearing and range to a target, the TCAS unit then has to decide, using probability mathematics, which of the reported replies are likely to be aeroplanes. In the same way that VOR's may scallop, and surveillance radars might paint flocks of birds or lorries as targets, not every whisper-shout return the transponder reports to TCAS might be an aeroplane at the calculated range, bearing, and relative altitude..."

Those words could be misinterpreted. Relative bearing is not part of the collision avoidance calculation. Range, rate of closure, and altitude difference are used to calculate the CPA, closest point of approach. Bearing is used only to provide a display to the pilot to aid in acquiring traffic visually, and it lacks accuracy, for lots of reasons. Plus or minus 15 degrees is the certification standard in the forward sector. There is no requirement for bearing accuracy behind.

GB

[ITCZ]

Those words could be misinterpreted. Relative bearing is not part of the collision avoidance calculation......Plus or minus 15 degrees is the certification standard in the forward sector.
Agree.

The TA that is 'painted' 1 o'clock, may flash by you at your 11 o'clock :eek: Imagine if you had turned left!

Capt PB, nice post. Humbly agree with all.

"Attempt to acquire the traffic visually and maneuver as required".
A valid instruction. The problem is that many pilots interpret the instruction "maneuver" in a limited fashion.

Maneuver is not solely turn left/right.

Maneuver includes accelerate/decelerate. Increase/decrease vertical speed (Decrease V/S being recommended in many advisories on this topic).

Why do pilots want to limit themselves to one form of maneuver? It seems very unimaginative and very undisciplined in light of all the time and expense we incurred learning to navigate in three dimensions!

I believe we are negative training these days, teaching people to sit and wait for an RA to save them.
I sometimes wonder if the problem is bigger than that.

When I was doing ground school for CPL and IFR, we learned basic operating principles of, and limitations of: pressure altimeters, magnetic compasses,
gyroscopic AI, non directional beacons (quadrantal errors, turning errors, coastal refraction....), VOR (site error, scalloping.......) etc

Maybe that WW2 technology was easier to comprehend...

.... or maybe the technically oriented people that became pilots at those times had an interest in the underlying technology.

My father's generation used to pour over copies of "Power Mechanics" to understand the gadgets of their time, to a level of how does it work?

Now we have FMS with manufacturer supplied databases, IRS's that initialise using TSO'd GPS, and TCAS that use arcane mathematics to filter targets and predict threats, with interfaces that are familiar to a generation of pilots that grew up with Von Neumann machines in the form of microcomputers, we have a pilot population that tends to unconditionally accept anything that is displayed on an LCD or LED display.

We are now a generation that has very little interest in the underlying technology that make our gadgets work. If it has an effective user interface, thats about it.

That might be ok if you are joe public using an iPhone or a digital television. I don't see how it is ok for an airliner pilot to not have at least a basic idea of the principles of operation, and limitations of, every bit of kit fitted to his or her aeroplane.

[waren9]

which to follow?

stall warning
gpws
tcas
atc

in that order

[Vee1Kut]

Interesting thread...I would have to imagine many in here would see the RA...then talk to ATC, then go to the SOPs manual, call dispatch, discuss it with the flight attendants, flip a coin, consult some Tarot cards, take a poll from the passengers, get a show of hands.....lord knows it's better to have a midair, then make a turn, change altitude and risk having call ATC on landing....