a320 unrel spd config 1 ==> alt law
 

Hi,

just had unreliable airspeed this morning. As we had BUSS, we turn off all 3ADRs, and the aicraft reverted to Direct Law. But when we set Flps 1 for appr, it reverted to Alternate Law.

I can’t find any explaination in the books. Does any one know?

Thanks

Hi nj314,

This was discussed last year. See flying-buss-avionics-smoke-simulator

Post #17 by Cripple identified a block of MSN frames 4200 - 4800 with this behaviour. Several of our Simulators behave the same way - yet there is nothing in our FCOM. :ugh:

Golden
You won't find it anywhere except yours truly. It is given in Modification Operational Impact160015N. Here it is:

With L84 and L93 ELAC standards, when an ADR is faulty or off, the ELAC unduly rejects the associated IR. When all ADRs are faulty or off, the ELAC unduly rejects all IRs. Therefore with all ADRs off it reverts to direct law instead of alternate law. ELAC L96 Standard corrects this misbehaviour.
Cheers