A320 Interesting flap configuration
 

A320 has a rather interesting scenario in its auto configuration between flaps 1 and flaps 1+F.

The description of the scenario as per the FCOM goes as follows

When the flaps are at FLAPS 1(I.e slats extended and flaps retracted) and air speed reduces to less than or equal to or 100 kts then the flap configuration changes to FLAPS 1+f (I.e slats extended and flaps extended to 10).

Now this scenario is possible only when you land with configuration 1, which happens in a unique scenario in case of reverser unlocked. Can any of the Bus drivers throw light on why Airbus came up with this rather weird automatic configuration change?

Stall recovery?

To allow for F1+F for takeoff? So the software does it on landing with F1?

Stall recovery? I hope not. 100kts is too low a speed for stall consideration, I guess.

Flaps 1+f landing is the preferred landing configuration in case of reverser unlocked. So in this case according to the schematic shown in the FCOM, flaps would retract to 1 when speed decelerates to 100 kts. Wonder why? And this is the only scenario I can think of, after a lot of research, that this auto extention happens.

I think you have that backwards... Flap 1 for approach (but only when reverse deployed (IAE/PW)/4doors open (CFM) otherwise its a flap 3 approach.) Then when rolling out the flap will extend. Its in my bucket of 'who cares' because it isn't going to disturb anything at that stage during the landing roll and I hope to never see it in my career!!

Ed to add - I think the 100kt is there just to differentiate between departures (when you need 1+f) and arrivals (when only 1 is needed) when you have some more of the obscure Airbus style failures!!

Yeah my bad, that's what I intended to convey but ended up typing the other way around :).

I know, it's a trivial one and neither do I hope to encounter one while flying, but the fact that airbus planned something as peculiar as this is intriguing.

Bkdoss
It is not weird. With only Slats out there is increase in body angle which will compromise tail clearance during take off rotation. Flap decreases the body angle. In the air with only slat at1 the body angle is 7 degrees while with flap1+F it is 4 degrees.Also in the case with G+Y fail with zero flap the approach body angle is about 8 degrees instead of normal 3 degrees. All aircraft use some trailing edge and leading edge flap combination for take off but airbus made the change in the air config. to only slat1 thereby reducing drag during manoeuvring for approach. For reverse inop When you select Flap1 Confg. for approach you land only with slat1 and flap zero but as the speed drops below 100kts. it will extend flap as per system design and not because of requirement.