TCAS RA

[I-FICO]

Assumption: TCAS RA are only on vertical plane.
What kind of Resolution advisory can I get from TCAS if I fly at my service cruise altitude towards another aircraft cruising at the same altitude?
Does the TCAS take into account that I can't climb anymore or not fast enough as it could command?
And what about the other conflicting traffic?
Is there any improvement to this technology?

Thanks for your reply..

[Fly3]

You will find that all aircraft are certified to around 800ft above their normal max cruise altitude. This allows you to react to a TCAS RA even at max alt. Try it next time you are in the sim and you will find that it is not an issue as speed can be traded for altitude.

[clivewatson]

Fly 3 - I have no idea if you are correct about the 800ft over Max Cruise certification, but I would warn you about trading speed for altitide when flying at or close to your Max Cruise Level.

Buffet Margin IS an issue!!

[rudderrudderrat]

Hi clive,

From Airbus FCTM SI 060 P3/4

If a RA is generated: • The flight crew must always follow the TCAS RA orders in the correct direction, even: ‐
If the TCAS RA orders are in contradiction with the ATC instructions ‐
At the maximum ceiling altitude with CLIMB, CLIMB or INCREASE CLIMB, INCREASE CLIMB TCAS RA orders ‐
If it results in crossing the altitude of the intruder.

I think you'll find it's cheaper to nibble into the buffet margin rather than hit the other aircraft.

[muduckace]

but I would warn you about trading speed for altitide when flying at or close to your Max Cruise Level.

I do not think this is an issue when it is the only resolution to avoiding a head on crash, I would hope you would prefer to recover from a stall with your aircraft intact over the obvious other option.

[Fly3]

Buffet margin is only an issue if you have been stupid enough to climb to max alt when you are very heavy rather than optimum alt which is the norm.

[FE Hoppy]

Type dependant.

My type won't give climbs or increase climbs above FL340.

[clivewatson]

Buffet margin is only an issue if you have been stupid enough to climb to max alt when you are very heavy rather than optimum alt which is the norm.

Fly 3, I don't want to get into an argument with you. In my post I mentioned that Buffet Margin is an issue. I don't think you can dispute that. As FE Hoppy points out, his type inhibit TCAS Climb RA's above FL340 probably for this very reason.

I would also add that there could be a number of NOT stupid reasons to fly at altitudes above that which may be optimum on the day. Surely also you acknowledge that buffet margins vary widely from type to type, and that it is not necessarily stupid pilots who find themselves flying with narrow margins.

Like I said...it's just an issue, but please feel free to have the last word.

[Fullblast]

Technically speaking, when a TCAS is fitted in an aircraft the software takes account of the flight envelope of the aircraft, so it's quite unlikely to have an RA that will bust some limitations, anyway, if you really can't comply, at least stay where you are and don't react in opposite direction, it's gonna save your ass anyway, maybe !!!

FB

[fellman]

Yes, TCAS RAs are only in the vertical plane.
If an aircraft is at its service ceiling, this can be taken into account by TCAS which can be "climb inhibited".
In the scenario described by I-FICO there are three possible outcomes depending on which aircraft declares an RA first and the Mode S addresses of the two aircraft.
1. Own aircraft stays level (told not to descend) and the other aircaft descends.
2. Own aircraft told to descend and the other aircraft climbs...
3. ...unless the other aircraft is also climb inhibited, in which case own aircraft descends and the other aircraft stays level.