vilas,
With slats in 2+3 positions speed increment will be minimum and if required it will be easier on landing distance in overweight landing procedure.
Why would you want to Land overweight if the second SFCC failed? There is no requirement to LAND ASAP, and surely you would be looking for a suitably long runway somewhere else.
As far as your point about false ADR signal is concerned it is not likely to happen as the MEL requires all ADRs to be serviceable.
See the explanation in MEL with ADR2 inop 34-10-02B.
"FOR TAKEOFF
Takeoff in CONF 1+F is not permitted.
Note:
When the ADR 2 pb-sw is set to OFF, and if the aircraft is in CONF 1+F, the SFCS n°2 Flap channel is unable to crosscheck the airspeed coming from the ADR 1 with the ADR 2 airspeed coming from the SFCS n°2 Slat channel. This may lead to an uncommanded flap retraction during the takeoff. As a consequence, takeoff in CONF 1+F is not permitted when the ADR 2 pb-sw is set to OFF."
Please explain how SFCS No 2 can cross check anything if it is US.
Hi sonicbum,
I don't know what the chances are of any of those you list failing, but the premature retraction of the flaps during the take off phase is considered to be a more serious problem and easily avoided by not permitting 1+F take off.