TCAS II - 2Q's

[cool blue]

I'm updating my knowledge of TCAS, to TCAS II version 7 [or later] using an ops manual training questionaire, and an authority issued circular on the subject, dated 2000. Of the 30Q's, two remain which I'm unsure of [Q1], or stumped on [Q2].

Q1. An RA FAIL message on the ND indicates:

a. failure of the radio altimeter input
b. an indicator fault which stops the display of an RA
c. the data tag cannot be computed

Q2. The enhanced advisory INCREASE DESCENT nominally calls for a vertical speed increase to:

a. 2000 fpm
b. 3000 fpm
c. 2500 fpm


Re:Q1, 'b' is my best guess, as there is an automatic self-monitoring sytem, but, if correct why not 'a' or 'c' specifically? Is it that the message would be NO TCAS[a] and TA ONLY[c]?

Re:Q2, The circular indicates that, nominal climb/descent [& climb/descent, crossing, climb/descent] RA's are issued for 1500-2000 fpm. Also, that maintain climb/descent RA's will be nominally issued for 1500-4400 fpm. I have no information for enhanced RA's.

Anyone?

Thanks in advance,

CB

[Crash & Burn]

G'day,

My honeywell TCAS II manual states the following:

"RA FAIL will appear when the TCAS cannot post Resolution Advisories"

Further on it mentions that loss of vertical speed information will result in a RA fail indication although the wording suggests that this isn't the only case you'd get a RA FAIL indication. Doesn't really help much with the answers given in your question though!

"INCREASE DESCENT - INCREASE DESCENT" = Increase descent to that shown by the green arc on the RA indicators, from 2500 to 3000 FPM

Cheers

C & B

[Capt Pit Bull]

With reference to answer (a) - A radalt failure would put the TCAS into TA only mode.

By way of an example, when we do a cat 3 briefing on my type one of the items is a RAD ALT test. Push the button and note indicated rad alt of 40 feet and an autoland failure annunciation. However, if you glance at the TCAS it will be seen to have gone into TA only mode. Thus its best to have a glance at the TD for conflicts before doing the rad alt test.

For (b) in principle, IIRC, the RA fail flag means that the display in question can't show the RA, rather than TCAS can't generate an RA. I.E. you could have 1 display RA failing, but the other one working. IIRC, when you have a situation where there is no display capable of showing the target RA, OR no vertical speed information available anywhere in the aircraft (so you can't see if you have acheived the RA) then the syustem should go to TA only.

For (c) The phrase 'data tag' usually refers to the relative altitude / vertical speed arrow. Obviously this is absent when the intruder has no altitude reporting, but there is no specific flag that will appear somewhere else on the display. I.E. the answer is a distractor.


As C&B said, enhanced RA's are green banded for 2500 - 3000 fpm. Crap question really.

CPB