TCAS Drill

[nickcolonial]

Would anyone comment on TCAS drill on your airline and aircraft? Would be nice to see any differences from Airbus or Boeing folks!

[ifleeplanes]

Disconnect the a/p and a/t follow the TCAS regardless of ATC instructions to the contrary. Announce TCAS climb/decent as required and when clear return to the previous cleared level informing ATC. I fly Boeing.

[Bill Smith]

Follow the RA !!

Aircraft type shouldn't come into it.

[ifleeplanes]

I think he was after HOW we follow it...not if we follow it

[FlightDetent]

AP off, flight director off. Then it is all the same, verbatim. I have transferred to the bus 3 months ago and the difference is such:

on a 737 you disconnect the autothrotle and fly away from the flight directors to respect RA commands keeping manual control of the thrust/energy. When clear, you have the flight director to help you regain previous trajectory, if desired.

on a bus, you want to keep the autothrust to simplify the manouevre. So you deselect the flight director which trips the A/THR to a basic mode for energy control. When clear, you fly the aircraft manually where you want it and then rengage the automation.

However, I find the 737 classic RA command display (read area shown over attitude indicator) superior over the VSI command on the 320. Because what you do, is fly the aircraft on pitch reference so you want a pitch command. To me this feels more pilot minded compared to the VSI displays that stem from the way TCAS actually works and calculates - comparing relative velocities.

Mind you, this is not a B. vs. A. issue, the more advanced Boeing models have TCAS command presentation similar. It seems that someone was trying hard how to put the TCAS display into 737 class. cockpit with least hardware re-arrangements and happened to hit the sweet spot.

I wonder what the TCAS diplay is in a NG fitted with PFD/ND. I understand they have altitude tape and VSI pointer. Do you guys have it 777 like or the old style?

FD.
(the un-real)

[xetroV]

I wonder what the TCAS diplay is in a NG fitted with PFD/ND. I understand they have altitude tape and VSI pointer. Do you guys have it 777 like or the old style?
The PFD/ND style of the 737NG is similar to that of the 777. It is okay, except for the vertical speed indication, which is so narrow that it actually hinders accurate V/S read-out. I believe the same insane lay-out is used by Airbus, and Fokker, which have all tried to squeeze the old style round VSI into a narrow vertical window on the PFD. A much better solution is the vertical V/S arrow used for the MD-11 PFD.

The RA information for a 737NG is a combination of a truncated V-bar in the attitude indication, showing the pitch angles to avoid, and a red tape in the V/S indication, showing the V/S values to avoid. (The old style display uses the same indications, except it also includes a green fly-to V/S arc on the VSI. The MD-11 doesn't offer any pitch indications, but it does show red and green area's on the vertical speed tape. Since its V/S display is so much clearer than the Boeing/Airbus solution, this works equally well.)

[Seat1APlease]

I'm not sure about the return to cleared level bit, that might re-start the warning.

Our procedure was to tell ATC we are back under their control and let them give a climb/descent clearance.

[ifleeplanes]

By the time you have manouvered away from the treat and it away from you, if you return to the original level the threat would have gone. TA is approx 40sec and RA approx 20 secs from CPA...the manoever and return takes far longer than the 20 secs. If you dont go back to the old level you could be setting yourself up for a further conflict at the new level your at....especialy in RVSM airspace with 1000ft clearance between opposing levels.

[Seat1APlease]

OK so you're cruising at 90 inbound to a waypoint with traffic below you same direction at 70, and ATC mistakenly clear you down to 70 instead of 80

As you descend through 80 the thing goes off, you reduce descent rate or climb back to 80 and the warning stops, what do you do now?

The other traffic is still below you at 70 as only one of you should have got a climb/descent and in any event if you have manoeuvred the TCAS will still be protecting you at whatever level you have settled at.

[Vee One...Rotate]

Hope you don't mind an interested lowly PPL student sticking his nose in.

Imagine you are commanded by TCAS to perform a certain action to avoid a collision...but whilst executing the action the a/c is brought into conflict with another a/c (different to the first). Is the modern TCAS system designed to deal with multiple threats and combine available info on each to arrive at the most suitable instruction to give? What is the saturation point? Slightly pessimistic of me to think of this perhaps...!

Just intrigued :confused:

Regards,

V1R

[End_of_Descent]

Vee One...Rotate,

if I remember the numbers correctly, TCAS can coordinate RAs with up to three individual intruders simultaneously. Hence, up to three red squares are possible on the TCAS display. Additionally, up to eight aircraft can be shown as (yellow) traffic advisory symbols on the TCAS display.

EoD

[ifleeplanes]

In the case you mention ATC should pick up on the fact and reclear you to the new level when you tell them that the conflict has finished......what happens if on the other side of the fence you are at FL 330 heading east and get a conflict the demands you decend ...the RA is resolved and your now at say FL320 but still westbound, and now on a head on into another aircraft happily heading east 10 miles away at FL 320.

Also TA/RA conflicts dont usualy happen to conviently cease at a specific level ie 310/320/330 etc much more likely to be at 312/323/334 etc etc.

Many RA will occur during the climb / decent....what would you do then? What would you do if it was just a reduce rate command?Level off at whatever FL you happen to be at when the RA ceased? Or once the RA had finished would you then re-comply with the initial climb / decent clearance? I think I would certainly take the later option.

SOPs cannot cover every eventuality but they are there to try and cover the majority. In your example ATC should realise the problem when you advise them of the RA and instruct you to maintain the new flight level when you inform them the conflict has ceased. TCAS is also meant as a back up to visual collision avoidance, right of way rules and ATC clearance. In the mean time you should try and recomply with your initial clearance once the conflict has ceased.