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RAT 5
20th Oct 2007, 15:48
I read the recent thread on TCAS RA & GPWS conflicts. Enlightening, but no definitive answer. AS always, 10 pilots 10 opinions. I suspect that the trained reaction would takeover, i.e react to the RA and only realise afterwards about MSA. There's not too loong to think about an RA yes/no. I would not be surprised if there was an odour after such a rapid combination of life threatening scenarios.

May I ask another TCAS question:

Recently there was an ACAS11 bulletin N0.9. from Eurocontrol. There is a paragraph on page 3 discussing 'Degraded Performance'. This refers to the a/c. It implies that during an Emergency descent, and thus the a/c would not wish to respond to an RA climb, the TCAS should be set to TA only. Thus all avoidance will be done by other a/c. I've checked my curent SOP's and previous airline SOP's and none include setting TA only for an Emergency Descent.
The bulletin goes on to say that "the use of TA only mode is described in the following note that will included in the next version of ICAO PANS-OPS Doc. 8168 due in Nov 2007". Perhaps this is considered to become a new procedure and will take effect in 2008, hence nothing in SOP's to date.

Does anyone know more?

md-100
20th Oct 2007, 16:06
well, I guess I would keep the TCAS in TA/RA... and if a RA is fired.. I will execute it.. even if I had to stop or smooth the descent...
I prefer to breath 20 sec more of oxygen than not breathing anymore !!

we dont have any SOP on that.

ANd about selecting TA... well I dont know... I would like to hear "trafic trafic" as the last words in my life ( I ll prefer:: "honey honey.. you are the best!!":)!!!

md-100
20th Oct 2007, 16:10
correction!!
i would NOT NOT NOT like to hear "traffic traffic""

Willit Run
20th Oct 2007, 16:36
In many of our emergency procedures, we have an item that tells us to select TA only. For instance; engine out performance when heavy. I think it would be appropriate to select in most any real emergency. After all, you are in the midst of trying not to crash, why put added difficulty into the already bad day.

ok, let me have it!

411A
21st Oct 2007, 00:35
In many of our emergency procedures, we have an item that tells us to select TA only. For instance; engine out performance when heavy. I think it would be appropriate to select in most any real emergency. After all, you are in the midst of trying not to crash, why put added difficulty into the already bad day.

Absolutely correct, in my considered opinion.
Far too may folks seem to 'rely' on TCAS as though it were infallable...sadly, sometimes it is not.
TCAS is simply another tool in the safety toolbox.

flyboyike
21st Oct 2007, 03:27
Interesting question there. TCAS isn't mentioned in any of our emer procedures. Perhaps it should be.

Denti
21st Oct 2007, 09:25
Interesting issue, i just re-checked our current SOP regarding emergency descent and it doesn't say to select TA ONLY, however we were told to just that during type rating oh so many years ago and were are still told to do so during our recurrent checks.

Of course the one engine out procedures tell you to switch to TA ONLY.

ATC Watcher
21st Oct 2007, 10:50
I will not ague the engine out procedures, ( the TA in there ,as I learned recently,was mostly to prevent " coordinated" climb RAs ) , but would like to go back to the original question : during an emergency descent :
From an ATC point of view :
After having witnessed many such events trained in the sim , with different airlines, and relating this to my own geographical area , I would advise a turn of 15 min max 30 degr ( to get you out of the traffic on the same track below ) squawking as soon as possible A7700 ( to warn all other ATC ( civil and/or military ) units below of what you are doing ) and finally keep the RA on, as, if this is happening near an point of convergence , ( FFM, SPI, or TRA to take some European examples ) you are most likely going to meet a lot of people on your way down. I believe also that with the rate you are going to descent , you are more likely going to get RAs like " monitor vertical speed" , of "Adjust vertical speed ", and the others will coordinate their RAs accordingly.
As someone else said earlier , better breathe O2 a few seconds more and keep on breathing in the end. .

Maude Charlee
21st Oct 2007, 12:28
I would have to agree about the likely RA that would be given in the emergency decent. At such a high rate of descent, I cannot believe that with 2 mode S equipped a/c, that the one performing the emergency decent would be given any resolution which involved anything more than an adjustment to the rate of descent, and certainly not a climb.

RAT 5
21st Oct 2007, 19:20
Thank you your replies, inlcuding ATC watcher. Remember this thread was triggered by an ACAS 11 memo from Eurocontrol and it seems to be proposing, even stating, that this will become the procedure in PANs OPS due to be published soon.

They lumped all a/c degraded performance scenarios together, only giving engine failure operations and emergency descent as 2 examples of applicable TA only operations. Thus, if it is adopted, then company SOP's will lag behind, naturally.

Regarding the turn off airways, we had been briefed that NATS expected an emergency descent straight ahead and let TCAS & ATC sort out the problem. I can just imagine the bells ringing, when 5 a/c all south bound from Scotland into the various London airports, all on // radar headings, and then 1 one the maggot on the screen suddenly storms off stage-right like a bowling ball on acid.

Anyway, we shall have to wait and see the outcome of Eurocontrol proposals.

We had also been advised that in less crowded free-fly European airspace a slight turn off the airway should be considerd. Either way the old 90 degrees peel off seems to have been binned.