mm43, graybeard;
The TCAS has numerous system inputs. One of the inputs is the stall warning system. I think the NAV TCAS FAULT message was triggered by a programmed inhibition of the TCAS warning.
When certain other systems require a higher priority in terms of pilot attention and aircraft systems/performance/energy, they inhibit warnings which would compromise such priorities. Here, the priority would be aircraft energy to recover from a stall, so a TCAS warning is set aside as the lesser danger and is inhibited during such an event. The AUTO FLT REAC W/S DET FAULT warning has the same source.
The BEA Second Report seems uncertain regarding the source. Even though the second reason, (altitude differences > viability of data) makes a bit more sense than the electrical notion, the above reason should be examined as possible or dismissable. The inhibition isn't strictly a fault and if the two messages, (stall/TCAS) were ever "in competition" for attention/energy, perhaps the TCAS would simply remain silent.
Anyway, just thinking...always hazardous!
Last edited by Jetdriver; 31st May 2011 at 23:26.