My first TCAS RA in Vatsim

[Thiago Simões]

Interesting how after many years, I got my first TCAS RA in Vatsim today over the Black Sea, during cruise.

I was flying westbound on FL340 and the other guy was flying eastbound on FL340 as well.. No big deals as we have TCAS 😉

I had time to take a screenshot when recovering from the "DESCENT!!! DESCENT!!!" manouver 

 

 

 

Edited July 10, 2022 at 07:54 PM by Thiago Simões

[Lauri Uusitalo]

Unfortunately, as far as I know, these RA instructions are not synchronised between clients?

[Lars Bergmann]

3 hours ago, Lauri Uusitalo said:

Unfortunately, as far as I know, these RA instructions are not synchronised between clients?

Correct.

[John McMurdo]

On 7/12/2022 at 11:46 AM, Lars Bergmann said:

Correct.

Does that mean that the RA could be advising the same manouver in both aircraft?

[Lars Bergmann]

36 minutes ago, John McMurdo said:

Does that mean that the RA could be advising the same manouver in both aircraft?

Yes.

[Daniel Mckee]

..both aircraft using the same jet airway?

 

[Thiago Simões]

On 7/12/2022 at 5:30 AM, Lauri Uusitalo said:

Unfortunately, as far as I know, these RA instructions are not synchronised between clients?

I didn’t know that. Well this is not supposed to happen but I have to say using the PMDG 777 and following the “TRAFFIC” followed by “DESCENT, DESCENT” manouver during cruise was pretty realistic. I saw the traffic passing just above my head very fast. Was epic to experience that online for the first time. Specially during cruise where is very unlikely to happen.

 

I then spoke to the other pilot that said his navigation was showing he should be in FL350 and not FL340, but for some reason he missed that.. he was a beginner in Vatsim so I just continued with no complaints as the main point of having a traffic, receiving alert and a RA happened as it would in RL. 

 

[Thiago Simões]

On 7/14/2022 at 3:23 AM, Daniel Mckee said:

..both aircraft using the same jet airway?

 

Yes, this is completely normal considering you are flying a both ways airway. One way airways will have arrows indicating it’s only possible direction of flight

[Daniel Mckee]

On 7/20/2022 at 1:32 PM, Thiago Simões said:

Yes, this is completely normal considering you are flying a both ways airway. One way airways will have arrows indicating it’s only possible direction of flight

Aware of which way arrows go but unfortunately I could not see actual route in your post😉I would be interested if you would advise same so I can have a look; cheers

[Tobias Dammers]

On 7/14/2022 at 12:50 AM, John McMurdo said:

Does that mean that the RA could be advising the same manouver in both aircraft?

It could mean that, but in most cases, the correct evasion maneuver is obvious even without coordination, so it usually still works out OK.

AFAIK, it works like that IRL too, when a TCAS system responds to a non-TCAS threat: no coordination is possible, but the TCAS still calculates and advises an evasive maneuver. Not as good as the coordinated case, but better than nothing.

[Thiago Simões]

On 7/23/2022 at 2:56 AM, Daniel Mckee said:

Aware of which way arrows go but unfortunately I could not see actual route in your post😉I would be interested if you would advise same so I can have a look; cheers

I'm sorry about the screenshot quality 😒 for some reason it saves in very low quality when I press V.

Here is where it happened between HAKAN and GUMRU, in a both ways airway (UT310). You can see UL621 and UP975 are examples of one way airways.

 

 

[Daniel Mckee]

Thank you for the screenshot. In this airspace should aircraft using UT310 have different altitudes assigned depending on the direction?

 

[Andreas Fuchs]

Turkey is using the standard flightlevel assignment procedure, the eastbound aircraft should have been at an odd level. Maybe that aircraft was actually at an odd level, but due to the "altitude-bug" in MSFS it was at a different altitude for other users of the network.

Edited August 4, 2022 at 05:49 PM by Andreas Fuchs

[Tim Wells]

The problem exists because live weather is not exactly the same in all sims (or if users are not using live weather).  My barometer may be different than yours.

If you're flying at FL360 and I'm at FL350 in the opposite direction, and the barometer doesn't match, then the planes appear to be too close in both simulators, even though each plane is at the correct altitude in their own sim.

STD altitude is contributing to this, because each plane is using that standard barometric pressure for the altitude.  In real life this works because the barometric pressure is always going to be the same in a given area.  In the simulator, barometric pressures will vary by sim or weather application.

A possible solution for this might be to use the indicated altitude whenever STD is enabled.

TCAS is not fully implemented in the simulators and VATSIM. The plane sees the injected traffic and it simulates an RA. However, there is no communication between the TCAS units on the planes, like you would have in real life.  I've seen RAs not make any sense, for example the traffic is above me but it told me to climb, or it tell planes to go towards each other (lower to climb and higher to descend).

In my opinion, TCAS RAs should not be followed on VATSIM, as they can make things more difficult for the controller.  When flying a plane that automatically executes an RA, the TCAS should be kept in TA mode only to prevent it from reacting to the RA.

In order for TCAS to be properly implemented, it would require the simulator and/or plane to have a way of injecting a proper TCAS RA.  The VATSIM servers could decide which plane should go in which direction and send the RAs to the planes.