Air Asia Indonesia Lost Contact from Surabaya to Singapore

[tubby linton]

The flight augmentation computer ( FAC ) fulfills several functions independently of the engagement status of the FLT CTL/FAC pushbutton switches.
These functions are necessary for :
- the control of the speed scale on the primary flight displays ( PFDs ).
- the adaptation of gains of the flight management and guidance computer ( FMGC ) and elevator aileron computer ( ELAC ).
- the distribution of signals for the FMGC control laws
- the protection of the flight envelope in automatic flight ( speed limits for the FMGC, alpha-floor for the autothrust )
- the display of the rudderposition input.

Turning off both of the FACS leads to Alt Law and you have lost - VSW, VLS, S, F, Green Dot, Speed Trend, VMAX, VFE, VFE NEXT from your PFD. If you are not very speed aware it would be easy to inadvertently stall the aircraft. I would not be seeking to start climbing the aircraft at this point
The inop systems follwing a FAC1+2 failure are-
WNDSHEAR DET
F/CTL PROT
FAC 1 + 2
AP 1 + 2
A/THR
CAT 2
The PFD picture would be no Flight Director,(Red FD flag),and no limit speeds on the speed tape. The aircraft would be in alternate law with no autopilot or autothrust.The aircraft would be in trim so hands off it would continue on its previous trajectory.
The FCTM states-
Outside the normal flight envelope, the PF must take appropriate preventive actions to avoid losing control, and/or avoid high speed excursions. These actions are the same as those that would be applied in any case where non protected aircraft. The flight crew should consider descending to a lower altitude to increase the margin to buffet. Descending by approximately 4 000 ft below REC MAX ALT reduces significantly the occurrence of stall warning in turbulence.