A320 landing performance difference unreliable airspeed & dual adr fault
While having a close look at my performance calculations I have noticed that there is a difference between DUAL ADR FAULT (ADR 1+2, ADR 1+3 or ADR 2+3) and UNRELIABLE AIRSPEED.
I thought the scenario for UNRELIABLE AIRSPEED respective to Landing Performance is that you have a DUAL ADR FAULT leading you into ALTN LAW and CONF 3 for landing. Therefore your LD is slightly increased.
On the other side a DUAL ADR FAULT leads you also into ALTN LAW and CONF 3.
Comparing both calculations shows me a difference of about 100m in factored LD:
FACTORED LD without failure: 1750m,
with UNREALIABLE AIRSPEED: 2050m,
with DUAL ADR FAULT: 1950m (no matter wich 2 ADR I choose)
Where does this difference come from? In my opinion it should be rather the same distance.
Thanks for the advice!