TCAS RA

[RAT 5]

To seek opinions: This could be reflected by a/c type or company or personal technique.

TCAS RA. Some years ago on B733 CL the QRH was disconnect A/P if necessary and follow RA guidance. I say if necessary because the RA could have been "maintain V/S". This could be either in climb/descent/level flight. Note A/T stayed engaged.
B738 NG. The manoeuvre now is to disengage A/T also. When a Boeing pilot was asked about this the answer was "to be consistent with the manual flight = manual thrust philosophy."
It was suggested that at high level, especially, this introduced a threat. You get a "CLIMB RA", haul back on the elevator and forget to add enough thrust. No need to go into space, but I suspect some might be over zealous at the thought of near death, hence forgetting thrust. Speed decays to very fast to stick-shaker.
You get a "Descend RA". Same action except it has happened that in one event pax & C/A were pinned to the ceiling. Once again you forget the thrust and smash the Mmo.
Or after the death defying descent you level off, check your heart rate and blood pressure, but forget to add power for level flight.

All the above errors I've seen performed in the sim by experienced crews. If leaving A/T engaged was a good idea on B733 CL is it really an improvement in safety to disconnect it now in Boeing SOP's? What is other types guidance and do airlines differ? I feel there should be more thinking to this than just a simple philosophy about manual flight.

[heavy_landing]

Think it's to be consistent - autothrottle may be engaged, for example when in LVL CHG/FLCH modes in descent, but won't move to maintain speed if CLIMB RA issued.

[Romasik]

Airbus keeps Autothrust ON...

[de facto]

RAT 5,

There is NO need in a RA to HAUL up or to be pinned down ....it should be flown accurately but gently..especially at high levels.
I see no issue with having the AT off,if you can t increase or decrease pitch gently without maintaining your speed then well...back to basics...
All the above errors I've seen performed in the sim by experienced crews
Maybe its time your Airline changes its recruitment sim sessions and add a few basic maneuvers without FD(yes oh my Lord) to weed out the addicts and ones unable to perform a maneuver as benign as an RA...

[de facto]

Claybird

Join Date: Mar 2009
Location: Roaming
Posts: 87
As De Facto said (were you away, De Facto btw? Welcome back), why 'haul up'?


I had a brief millenium post crisis,but thank you:E

[nitpicker330]

Yes Airbus keep Auto Thrust on BUT you must turn off the FD's.

[RAT 5]

And it's not always the case that FD commands are to be followed, there's criteria for that.

Guys: I did not suggest that one should haul back or stuff forward. Of course that is wrong technique. What I'm asking, quite simply, is why it can be deemed more safe to disengage the A/T during an RA? You are executing a 'life saving' manoeuvre perhaps at high level. Some people will panic and react thus; as has happened in real life. Both hands on the elevator and input delicate control commands to keep outside the crash box while looking out the window. With that technique & A/T engaged, in most cases, thrust will then look after speed. My curiosity is why change a perfectly good procedure for dogma? Has it been thought through thoroughly? If it is not a technique used by all types is it the best technique? An RA is certainly not a type specific manoeuvre.

Ref the above: in B737's you do NOT follow FD commands in an RA. Or have I misunderstood.

[de facto]

In the 737 NG i fly, RA pitch guidance must be followed not the actual FD.
The fact remains that if people get all panicked in a sim session following an RA,which is a basic and simple maneuver then well if it ever happened to them in real life,id rather be seated in the back of a chinese bus...more comfy on the G load for sure,,maybe not the lateral one though:E
Seriously,i take an RA as a dumb gentle maneuver,follow the guidance and dont think too much of the other aircraft...ie dont freak out...i had one over greece,we all survived and Pax didnt notice as even the CA were not aware of what had happened.

If people react in such a way,well yes then in a more complicated scenario such as a gradual loss of pressure may end up as a screaming of emergency descent over the PA as described in another thread here.

As long as your aircraft flies and you have oxygen ,no reason to panic,ESPECIALLY during your own airline regular OPC,i find it quite unacceptable from pilots that RAT 5 described as 'experienced crews'.

One hand is plenty enough to pitch an aircraft up or down,i use the left as it is connected to the elec stab trim,how convenient.
The right hand is on the thrust levers as intended by boeing to adjust the thrust.
Both hands on the elevator
Why?? even if you decide to leave the AT engaged,at least have a hand on the levers for feeling feedback of what the AT is doing.no?
The only time i would have both hands on the elevator would during the windshear maneuvers with AT disconnect at full thrust for more accuracy of manual inputs.

[vilas]

RAT 5
Your SIM instructors are not properly briefing pilots before conducting the exercise. There is a difference between terrain avoidance maneuver and TCAS RA. The pitch change required to fulfil RA demand is maximum 2 degrees in cruise,While it increase to between 5 to 7 degrees at speeds below 200kt. It is calculated at normal handling inputs.If the pilots knew this they wouldn't pull back harshly on the controls. If there are multiple threats the RA reversal can take place. So just pulling or pushing to its limit in one direction can compromise safety.

[grounded27]

Might be enlightening to hear from someone who has actually experienced an RA, sort of similar to the first combat experince of a soldier. With a previous airline we had structural stress damage as a result. No time to think, react is the only resolution.

[de facto]

grounded27 Might be enlightening to hear from someone who has actually experienced an RA, sort of similar to the first combat experince of a soldier. With a previous airline we had structural stress damage as a result. No time to think, react is the only resolution.


Refer to post #11.
With a previous airline we had structural stress damage as a result.

I dont know if I should be laughing or crying,what did your airline do ?retrained all of its pilots?
Yes there is no time to wonder about,however there is no need to overreact.

[grounded27]

Yes there is no time to wonder about,however there is no need to overreact

I agree, but have you had this experience?

[vilas]

grounde27
When you are faced with real RA you will react according to your perception of the maneuver. If you are not explained the mechanics of the RA requirement all you have is panic and fear. You do not save yourself because you pulled back with all your sreanght. As I mentioned you may have multiple threats and pulling or pushing in panic will put you in another's path. At .8Mach yoy need pitch change of max 2 degrees. How many Gs you need for that?

[de facto]

From my post #11

..i had one over greece,we all survived and Pax didnt notice as even the CA were not aware of what had happened

I agree, but have you had this experience?

What is it in my above post that dont understand?

I had one following an aircraft flying through its cleared level.

[AerocatS2A]

I agree, but have you had this experience?
I have. It's a non-event. You know don't you that you have 5 seconds to react to an RA? That's a long time to get a pitch change of about 2º established. Allowing for a couple of seconds to react, that is about 1º/second, or about a third of the pitch rate used to rotate during take-off.

[de facto]

I have. It's a non-event

It does require post flight paperwork though.:}
Ref the above: in B737's you do NOT follow FD commands in an RA. Or have I misunderstood.

In a 'preventative action' RA,ie 'monitor verical speed',you do continue on your actual path via the FD and must NOT fly into the area of RA pitch symbol.

The 'corrective action' RA you must pitch as close as feasible to the RA pitch guidance and not follow the FD.

[RAT 5]

Thank you guys, for your input, and we are in violent agreement. I mentioned no more than a real event where, perhaps due to the panic factor, an RA "descend, descend NOW" caused occupants in the cabin to be bounced off the roof.

[exeng]

Flying in Nigeria for 4 years I have had 4 TCAS RA's. In each event I have complied smoothly with the TCAS guidance and I doubt the pax have ever noticed - certainly no adverse comments.

My last 'nasty' would have been an RA but I avoided the traffic before it became an RA by climbing at max climb power (no traffic above). I had a TA during the climb and had to change my underpants shortly afterwards. Just like the sim actually where the traffic is on the nose at 4 miles and a thousand below - then the TCAS shows 800, 600, 400 - not nice.

Complete and utter mess and I won't post details here because the issue is still being investigated.

Some Captains, by the way, thought that I should have waited for the RA before reacting - most agreed with my actions - however I do see the other point of view. I knew nobody was above me at the time which in somewhere like LHR, FRA or JFK etc you cannot be sure of.

[vilas]

RAT 5
"An RA is certainly not a type specific manoeuvre." When it comes to Airbus FBW I am afraid it is type specific. It is mandatory to switch off APs and FDs but keep the ATHR on. If you keep FDs on the ATHR will not go into speed mode and during cimb in case of Descend RA your speed will increase with possible pitch up from high speed protection activation jeopardising the escape.

[RAT 5]

Thanks Vilas: I'm still operating in 'low tech' a/c. Your info is an education. My comment was motivated by the object of the exercise being to miss the other guy in a smooth controlled manner if possible, and not withstanding that I thought all elevators worked the same.
Safe flying.

[Teldorserious]

Your airline culled out all the thinkers who would have stopped after V1 if they had a fuel truck stuck under the wing...would have flown up instead of down, as what they saw outside the window is contrary to what the RA tells them to do.

So what are we talking about here...that a guy that's been culled out of thousands to take orders, unblinking, unquestioning, to robotic-ally to defer decisions aeronautical to the check list, to the captain, to the phone on the wall, NOW wants to say 'well gee maybe I can go up, instead of down?'

You chose not to make decisions and you were hired specifically not to, so this thread just jumps at me as 'well ok, now I want to be a pilot'.

[Denti]

Awww, you spoiled it. Already had the popcorn out, SSG is always soo much entertainment value. Nothing like a 16 year old that believes fervently in some whacko theories.

[grounded27]

Please I have no excuse for the crew, it was at altitude. You are crusing along, :mad: ATC talking in a forign language. Really? Cup of coffee in one hand and the daily news in another... Just thinking of the worst possible, I would not condem them.

[NSEU]

Have I missed something here, or are you honestly saying someone managed to overstress an aeroplane following a TCAS RA?

I seem to recall an MD11 (DC10?) out of Honolulu which made evasive manoeuvres due to traffic which warped the elevators. The aircraft was grounded in Sydney after engineers noticed that the elevator skin was wrinkled and the elevator ends were rubbing against the horizontal stabilizer. Apparently the damage went unnoticed during the transit in Nadi.

[framer]

Rat5 I agree with the posters who mentioned sim training/ briefing. If it is made clear that it is a low G manoeuvre with 5 seconds to react prior to the exercise then there is less chance of pilots over reacting. I have had a descend now RA at 3000ft in the aircraft with ATC telling us " negative maintain 3000ft" . I was an FO and PF and the Capt transmitted " negative TCAS RA" . We followed it to anout 2500ft and then after returning to 3000ft got a frequency change, the next controller asked us if it was a TA or an RA. We informed him RA. It was very simple and calm for us but I imagine if we hadn't had specific training in ignoring ATC in this situation it may have been a difficult decision to ignore them. It was actually a bit surreal as it was so much like the training we had recieved. It is also valuable to do them above FL 350 in the sim to demonstrate to the crew that the control inputs are very small and controlled.

[4468]

If I may add a few points here:

EXENG: If you had waited for your RA you would never have had to fly your max rate climb. Firstly because TCAS cannot demand one, but more importantly because, once RA is activated, any manouvres are coordinated with the threat a/c. They 'talk' to each other. (and very, very quickly too!!)

This coordination is also why you should NEVER manouvre in opposition to TCAS commands, REGARDLESS of what you may 'see' out the window! To do so will likely exacerbate the avoidance manouvre required! (Or ultimately cause a collision!)

Yes you have 5 secs to respond to a TCAS RA, but only 2.5 secs to respond to a reversal manouvre (which you may have triggered by not following what TCAS told you in the first place!)

Finally it's quite important to transmit your "TCAS RA" as soon as possible, because ONLY THEN will ATC stop attempting to 'control' you for collision avoidance!

The thoughts above were not just picked up in a sim, or from a study guide! TCAS makes calculations incredibly fast, and transmits that 'coordinated' information to both you and the threat extremely quickly too! A great piece of kit!

Always bear in mind TCAS will issue an RA whenever it thinks the closest point of approach of a target is closer than it's criteria allow. That doesn't NECESSARILY mean it is predicting a 'zero/zero' aka 'collision'!

In fact, that is a VERY rare prediction.

Finally (finally!) During a TCAS event, I believe TCAS information is instantly downloaded to a ground station?? Perhaps someone may confirm?

[Brian Abraham]

If so, you show a comical (and if you're actually a pilot, worrying) lack of understanding of TCAS.You suspect correctly john, SSG in a new suit (probably from an op shop). Not a pilot, nor understands anything aviation. Wait till he starts on the theory of helicopter aerodynamics. Thats besides the V1 rants and non thinking airline pilots.

[ManaAdaSystem]

TCAS can issue commands that exceed the performance capability of the NG.

Why do we turn off the autothrottle on the NG? Simply because you don't know what you will get if you don't. If you are climbing with N1, a manual TCAS descent will not change this. You will then descend with climb N1 and enter overspeed really fast. You will get the overspeed clacker and will have to figure out why, at the same time as you need to fly the aircraft inside the TCAS safe zone. A very common pilot reflex to overspeed is to raise the nose of the aircraft. Not a smart thing to do in this situation.

I've had 3 real TCAS RA's, excluding Monitor VS. Click, click, fly outside the killzone smoothly. The passengers or cabin crew never noticed anything.
Monitor VS are being modified into Maintain altitude (or something to that effect), since pilots don't understand that a Monitor VS doesn't tell you to do anything but monitor. They start to manouver and often will make the situation worse.

I'm not surprised some pilots overreact to RA's. It is normally new pilots, or pilots new to TCAS who do this. I used to think it was a fast, emergency manouver myself when I was first introduced to TCAS. I have had a 200 hr marvel in the right seat who tried to point the aircraft skywards after a TA, not sure what he would hav done with a RA.

[uksatcomuk]

PlanePlotter software now displays TCAS data in real time
Preesumably these will only be RA events.

[safelife]

No need to bounce anyone off the ceiling, a vertical speed of 1500 fpm will clear most RA just fine...

[ant1]

ManaAdaSystem, apart from for consistency reasons (AP off/AT off) yours is the right explanation, you want to be in control and not subjet to any surprises.

[sky-738]

Hand fly with throttle and York ,is your first lesson when fly.
When ra , 25seconds to impact. For a high speed flying object ,it is to much.maybe a little Change in attitude will Change the flying path and make you "safe". So what I think is be easy and not be panic.just follow the rules.

[TyroPicard]

john_smith
On the Airbus (not sure if its type specific or not: I suspect not) TCAS will only demand either a 1500fpm or 2500fpm ROC or ROD. Those are the only two possible options for climb or descent RAs.

Do you have an FCOM reference for that? Mine (A320 and330) say that the V/S is optimised to avoid.. and V/S changes are minimised.

[misd-agin]

If you have the new TCAS software that directs 90 degree turns you don't have to worry about climbing. :-/




Incident: LAN B788 and LAN B788 near Lima on Jun 11th 2013, near collision (http://avherald.com/h?article=4678db44)

[Fly3]

The latest TCAS is 7.1 and it does not issue turn instructions. I suspect that the crew who elected to turn did so without TCAS input. As the other aircraft was climbing their TCAS was almost certainly giving descend which they didn't do. That would explain why the first aircraft climbed 800ft when a "normal" RA would only require 500/600ft to generate "clear of conflict".

[DaveReidUK]

The latest TCAS is 7.1 and it does not issue turn instructions. I suspect that the crew who elected to turn did so without TCAS input.The AvHerald article doesn't actually say that the turn was linked to a TCAS RA.

[Uplinker]

Can I add my two pennorth, some of which has already been mentioned.

I am constantly surprised by pilots talking about the 'kill zone' and over stressing aircraft to 'escape' and thinking they are about to 'die', as if they are driving along a motorway and suddenly see a car coming towards them in the opposite direction. Nothing could be further from the truth.

Your TCAS is constantly interrogating all the aircraft around it, (can't remember how many, but it is dozens), and assessing them all for threats. It will give warnings (TAs) if it sees proximate traffic, and avoidance advice (RAs) if a conflict is predicted.

TCAS units all talk to each other. If an RA is required the two aircraft's TCAS units will talk to each other and agree a plan. One will decide to go up, the other down. One makes the final decision, and they both agree which one will be the master according to which one has the lowest squawk code. (If one aircraft cannot react properly, for example if it is on one engine, the other aircraft will double its avoidance if necessary. This is why you select TA only on your TCAS if you've had engine failure.)

TCAS will issue an RA to its pilots with 30 seconds to the predicted conflict. Look at your watch now and watch the second hand for 30 seconds. It's a loooong time! All that is needed therefore is a GENTLE climb, or descent, or maintain what you are doing, and the aircraft will pass harmlessly.

If some idiot decides to 'haul on the controls' they might well put themselves into conflict with other traffic above or below them, which might trigger further RAs and massively complicate what should have been a very gentle and controlled manoeuver. If some idiot decides to ignore both TCAS computers and make up their own avoidance or do the opposite of what they are told, then both units will recalculate their avoidance plan and this is where changes of instruction come from.

To sum up,

-Nobody is within milliseconds of crashing when a TCAS RA is issued.
-All that is needed is a gentle change of vertical speed - sometimes not even that, just maintain the vertical speed you are doing.
-Always obey TCAS RAs, do NOT do your own thing - do not make decisions based on what you might see out of the window. You don't know if the aircraft you can see is the conflict aircraft, and if you choose the 'wrong' aircraft you might do the wrong thing. Remember, the TCAS units are talking to all the other TCAS units around you, most of which you cannot see. TCAS will 'see' a conflict aircraft at least a minute before you will.
- don't panic - as long as you start to do what the TCAS IVSI display tells you within 2.5 seconds, (and you will be prepared to react already because you will have been warned by the TA), there will be absolutely NO drama whatsoever.
- there is no need to haul on the controls, the TCAS will give you warning with plenty of time for you to react safely and gently.

[DaveReidUK]

One makes the final decision, and they both agree which one will be the master according to which one has the lowest squawk code.

I believe it's the ICAO 24-bit address that's used as a tiebreaker, rather than the Mode A squawk.

[rudderrudderrat]

Hi john_smith,
TCAS will only demand either a 1500fpm or 2500fpm ROC or ROD.

See page 13:
http://www.skybrary.aero/bookshelf/books/106.pdf
"2000 ft/min.
1000 ft/min.
500 ft/min.
0 ft/min.
RA requires one of
these vertical speeds"

All of my TCAS warnings have been due to other traffic with big ROD / ROC approaching their cleared levels. If only they observed ICAO Recommendation:
"Unless otherwise specified in an air traffic control instruction, to avoid unnecessary airborne collision avoidance system (ACAS II) resolution advisories in aircraft at or approaching adjacent altitudes or flight levels, operators should specify procedures by which an aeroplane climbing or descending to an assigned altitude or flight level, especially with an autopilot engaged, may do so at a rate less than 8 m/sec or 1 500 ft/min (depending on the instrumentation available) throughout the last 300 m (1 000 ft) of climb or descent to the assigned level when the pilot is made aware of another aircraft at or approaching an adjacent altitude or flight level."
See http://www.skybrary.aero/bookshelf/books/1804.pdf

So with say 3,000 ft per min ROC, pilots will have to have started to change their VS towards 1500 ft per min before 2,000 feet to go - else it is too late and the AP mode will have changed to ALT*.

[Uplinker]

Hi DaveReid,

You might well be right, I was told it was the squawk. Anyway, the two TCAS involved do have a way of nominating which becomes the master.


Hi Rudderrat,

Yes, I personally think it's high time there was an autopilot or altitude capture software update installed to all aircraft which softened the rate of climb/descent as aircraft approached their cleared level to avoid the sort of nuisance TAs you refer to.

[JeroenC]

Or pilots use the VS mode- same like a turn indicator in your car: it's there for a reason, without surcharge.

[Aluminium shuffler]

Can's say about other types, Jeroen, but the 737 require complete manual flying, and I suspect all Boeings are the same. It sounds like Airbus advocate manual flight controls with autothrust. Certainly, using autopilot V/S modes is a no-no; it's too slow to respond and too likely to result in a SNAFU.

I have had two RAs (and plenty of TAs sorted by adjusting v/s pre-emptively). It really isn't a big deal, and requires just a very small attitude change. Like others said, if the cabin crew or pax notice it, then it's not been done correctly. But it is a message that needs training and sim experience to iterate.

[misd-agin]

One airplane heading north. One heading south. TCAS goes off. One a/c does a 90 degree. There is no airway change of 90 degrees for their route of flight.


Comment about the TCAS 'turn' mode was tongue in cheek.