I have had TCAS reset to STBY a couple of times during long (+4 hrs) flights. The TCAS is switched to STBY and the ND  displays an amber "TCAS OFF" notification. I can turn it back on by rotating the switch to TA/RA but I haven't been able to catch it prior to or just after the reset. I can't find a reference in FCOM1 or 2 or the QRH covering an uncommanded reset to STBY. Has anyone encountered this and is their anything I need to do to prevent this.

Are you flying online using a client such as vPilot?

 

 

Has anyone encountered this and is their anything I need to do to prevent this.

 

As Clarke mentioned, if you are using any other programs, ensure that they are not sending a command to turn the transponder to standby. You may also want to check your key commands in the sim to ensure you don't have a transponder on/off command being accidentally triggered.

Clarke and Kyle-

I'm flying stand alone and I'll check for an inadvertent keystroke command. Thanks for the suggestions and quick response, I'll let you know what I find. BTW, this started after installing the latest upgrade.

I've noticed this behavior on the ground but not in the air - often during pushback/startup the TCAS will reset to 'off.'   It happens periodically but not always, and has not been enough of a bother to dig into it, but I'll do so now.

I usually set TCAS to TA at engine start and advance it to TA/RA at the runway threshhold. I observed TCAS settings changing from TA Only to TA/RA without any keyboard or mouse input. It doesn't happen all the time but enough to make me curious. Now curious is one of my favorite conditions in the sim because I like to dig into the docs and try to understand what's happening. The TCAS operation I've experienced (see above post) while both on the ground and in flight can't be explained from reading the FCOM nor the QRH. Again, this falls under the heading of curious but certainly doesn't detract from my overall enjoyment of the T7. Honestly, the aircraft has been a complete joy to learn and operate - PMDG's best offering so far.

FS2Crew?

I usually set TCAS to TA at engine start and advance it to TA/RA at the runway threshhold. I observed TCAS settings changing from TA Only to TA/RA without any keyboard or mouse input. It doesn't happen all the time but enough to make me curious. Now curious is one of my favorite conditions in the sim because I like to dig into the docs and try to understand what's happening. The TCAS operation I've experienced (see above post) while both on the ground and in flight can't be explained from reading the FCOM nor the QRH. Again, this falls under the heading of curious but certainly doesn't detract from my overall enjoyment of the T7. Honestly, the aircraft has been a complete joy to learn and operate - PMDG's best offering so far.

The TCAS should not spontaneously set itself to standby or off without being commanded to do so, but the automatic switching of TA/RA to TA ONLY (or vice versa) is a normal feature of a real-world TCAS system, and is accurately emulated in PMDG aircraft.

 

RA is suppressed when the aircraft is within 1000 feet of the ground even when the TCAS mode is selected to TA/RA. This is done to prevent spurious RA commands from being issued when the aircraft is in a high traffic density area during the critical last part of an instrument approach or departure. Especially when approaching an airport that may be conducting simultaneous ILS approaches to parallel runways.

Thanks Jim, but this has been happening during the cruise portion of flight, at FL300 and above. I checked the FCOM and the conditions you mentioned are covered. Again the TCAS switches to OFF without any input. It happens infrequently so I'm not too concerned, just curious.

Funny enough this is a real world problem as well,lol..........but only at some airports.

 

For example at KJFK and KEWR we are told to disregard the TCAS OFF message if it appears during take off.

It is a nuicance message that goes away after a few seconds, they are investigating.

 

I have not noticed this problem on my PMDG.

A key stroke problem would have been my guess as well.

I discovered my problem (post 5) was my VA's ACARS software triggers my TCAS off during its nitiation sequence for some reason.