TCAS RA during ILS approach.
Hi!
I would like to share with you fellow aviators what happened to me recently during a flight, and hear your thoughts on what I think is quite an interesting situation.
Sunny day, little to no wind, in a medium business jet of the Citation family.
The event took place at an airport in France, after about one hour of flight.
We are in the approach phase, ready to begin the ILS procedure, still in contact with the approach controller. At about 15/20 miles from the airport we are able to see a target on the TCAS around the airport area, that at the moment does not seem to constitute a problem, being out of our approach path.
No information about any other traffic is given by the controller.
The FO, myself, and the captain do not speak french, and perform all the required communication with the ATC in english, as per company SOP.
After being cleared to perform the ILS we are handed over to the tower frequency.
We are unable to establish visual contact with the other traffic, that is a couple of miles off to our right.
We are instructed to continue the ILS and to report 3 miles. In the mean time the controller keeps talking in french with what we suppose being the other traffic: far from standard communication is used, since the frequency is blocked for a long time.
We don't understand a single word of that conversation and we are not aware of the position and the intentions of the other traffic.
We try to communicate with the tower to obtain informations, but we are unable, due to the frequency being congested by the small traffic and the controller still transmitting.
We receive the first TA, "traffic, traffic".
We still don't have the traffic in sight.
We are at about 8 nm, established on the glide, AP on, when we receive the RA, "descent descent".
The FD is commanding an increase of the rate of descent.
The terrain well in sight, the pilot flying disconnects the AP and follow the FD indications. The pilot not flying executed the standard call out: "Tower, XXX TCAS descent" on the frequency, that is still blocked.
After a few seconds we are clear of traffic, and find ourselves about one dot and a half below the glide slope, speed still under control, and in sight with the terrain and the airport environment.
We decide to proceed to the landing.
Only on the ground, after touchdown, the tower seems to understand that something happened.
The controller later acknowledged there was a mistake in the separation of traffics due to a deviation of the small traffic from the clearance given (?).
ASR filed, still waiting for the feedback from the french side, not holding my breathe.
A few considerations.
At about 1000 feet radio the TCAS RA function is automatically inhibited, and only TA is available.
The TCAS is not linked with the GPWS: the descent instruction received during the ILS at about 3000 ft of height left us a little bit surprised.
Luckily we were in VMC, but the very same circumstances in IMC could have lead to a much more "interesting" situation.
Your thoughts?
How does it work on your planes, is the TCAS linked somehow with the GPWS to give proper indications in case of RA in these particular conditions?
How would you behave in case of marginal weather conditions?