Mandatory Action on RA's

[Jump Complete]

Just read in the new Flight International (page 14) that there is a proposal from the JAA that 'takes away from pilots the option of doing nothing in response to an RA, and forbids action in the sense opposite to the advisory. The new rule requires that response to an RA shall be "it shall never be in a sense opposite to that required by the RA, (shall) be in the correct sense required by the RA even if this is in conflict with the vertical element of an air traffic control instruction, (and shall) be the minimum possible to comply with the RA." '

I dont fly for an airline, so I was wondering what those who do think of this, how does it differ from the current rules? How reliable is TCAS, and what if the controller is clear one
shouldn't (say) descend in response to a RA? Surely it is conceivable that he may have a situation that he knows that the RA response isn't the right move?

[Cobbler]

JC, I think what the JAA are proposing is already common practice among most airlines, certainly in Europe and the US. In fact, the mid-air between the DHL and Siberian over Switzerland was caused (in the last instance) by the Siberian aircraft acting against his RA, while the DHL followed his.

Pilots already say "TCAS Climb / Descent" to ATC when following an RA; this should stop ATC from issuing further (vertical) avoiding action.

[cdb]

I don't know about JAA rules, but what you have described already matches CAA guidelines - there was a SI issued about this not so long ago. As your profile says you're an ATPL holder, I'm surprised you haven't seen it.

As controllers, if we see a loss of seperation developing, we will continue to give avoiding action as we have always done, however once we are informed that a TCAS RA has been triggered, we will give no further instructions, only traffic information, until the situation has been resolved and the aircraft are back under our control.

Remember that the picture we see is up to ten seconds out of date, because of scan rates, transmission and processing delays. As far as TCAS being "wrong", its probably theoretically possible but we work on the principle that it's infallible if followed.

Hope that helps

cdb

Edit. Cobbler New guidelines are not to give ANY avoiding action, vertical or horizontal, once informed of the RA. I believe this is because of concern that the angle of bank used for an avoiding action turn could decrease the climb rate below what is required to satisfy the RA.

[BOPralph]

Eurocontrol has all the good info in one spot..

http://www.eurocontrol.int/acas/Legislationandguidancemike.html
.don't think that will work as a link - I'm a technophobe

Many, much, lots of important words. Get it wrong and .....

Another new point is that PANS-OPS now states that visual acquisition is no longer an acceptable reason not to follow an RA. We should trust in ACAS, not our poorly adapted human visual system.

That said, I should not focus too much on one element of this defence system.

We should fully understand how the system is going to defend us, and realise that it is interdependant. It's not just our aircraft that is affected, someone else is being 'electronically' shouted at as well. Just follow the RA promptly and accurately.

[Cough]

Never remove the pilot element... My opinion.

If in any doubt about that then check the latest CHIRP (http://www.chirp.co.uk/new/Downloads/html/FB73.htm). Scroll to TCAS RA incident and have a ponder....

I say this as my QRH now contains no discretion!:uhoh:

[BOPralph]

The "chirp" highlights my point...

"fully understand how the system is going to defend us, and realise that it is interdependant."

The problem in this incident was not the correctness of TCAS procedures, it was that a faulty mode 'C' squawk was not silenced.

And the "pilot element" does remain - do not do anything that would jeopardise the safety of the aircraft.

[coracle]

The new MATS Pt 1 ammendment for controllers suggets that during a TCAS R/A that we should not issue avoiding action whether it would be in the vertical OR horizontal plane!!!!

[AlanM]

More of a "MUST NOT" than a "SHOULD NOT".......


Supplementary Instruction no1 2005 in CAP 493
On being informed that an aircraft is manoeuvring in accordance with a TCAS Resolution Advisory (RA), a controller must not issue control instructions to that aircraft which are contrary to the RA communicated by the flight crew. This includes avoiding action in the horizontal plane, as the controller must not attempt to modify the aircraft’s flight path.