Question regarding MEL dispatch (A320)
 

Hello folks...

Consider this scenario:

During taxi, a friend of mine saw that the TCAS TRAFFIC selector (THRT/ALL/ABV/BLW) litteraly fell from it's place. Somehow the thing broke on it's base... The TCAS was then stuck on ABV mode.

Such situation is not covered by our MEL... But it's something that does not affect the airworthiness of the acft, thus, AFAIK, a GO ITEM.

​​​​​How could the acft be further dispatched in such situation? Would that become NEF item?

Would have thought this kind of scenario would be considered an Airworthiness issue as the TCAS availability is not fully available as per design. If stuck in ABV then only threats between if I remember right -2700ft and +9000ft would be displayed.

So personally would apply the MEL that renders the TCAS system inoperative and get a TCAS control panel ordered ASAP.

Making it a NEF (non-airworthiness item) would likely result in repairs not happening too fast as in my experience material/logistics departments often don't react too quickly to this kind of deferred defects/hold items.

This thread will become one of those 50/50 arguments. At the end of the day, when the authorities walk onboard for a ramp check, what do you think they would say when you've been flying around all day with a switch missing?

TCAS warnings not affected.
TCAS procedures strictly prescribe NOT to use the display for avoidance manoeuvres.
ABV/BLW extends the DISPLAY range from 2000 to 6-8000 feet in the chosen direction, the opposite one remains at 2000.
The older units still display targets ONLY +/- 2000 anyway.

The deciding fact is actually the words DURING TAXI = MEL restrictions do not apply, thus:
A) Commander understands the functionality of the system is not degraded (see above) in any way and proceeds with the flight.
B) He reports the status of the switch to MCC at some stage,
C) where the experts decide what happens before the next leg. In accordance with their manuals and Quality Assurance protocols.

During taxi it is no MEL issue any more. MEL does only apply until off-blocks.

For me it does. Our manual specifically says for failure occuring after off block but before take off:
Apply ecam, if not successful
Apply COM, if not successful
Call mx for procedure, if not successful
Apply Mel, if not pilot deferable, go back to gate

MEL does apply. You could invoke "enroute MEL "