For single engine approach for NPA in A320
 

Is that must be in landing configuration before pass the FAF in NPA？What is SOP said in your company?
If so, means that only use CONF 3 in NPA?

If no level off expected during final approach, delay CONFIG FULL until established on final descent. If a level of is expected, use CONF 3. This isn't specific to NPAs and whether you used CONF FULL or CONF 3 would depend on exactly how the approach was coded.

The problem in OEI is with selecting flap full in level flight i.e. at platform altitude. It has too much drag, the thrust will go to MCT causing problems with directional control and maintaining speed. So if landing in full the final flap should only be selected once established in final descent. Second problem could be with the NPA having step down descent. In that case obviously flaps to be maintained at three till the level step and then it's too late to change configuration so just land in Flap3.

All approaches are CDA, so flaps full once you’ve started the final descent.

You’re missing the point, you need to adapt to the context of the situation to achieve the safest outcome. Which is possible while balancing the different requirements.

There are three requirements that have to be considered and balanced, different weightage depending on the operational/environmental context. (e.g.: OEI 2D approach, OVW, ISA+30)

1. There is no requirement to fly a 2D approach with an Early Stabilized approach speed technique. ref: FCOM/PRO/NOR/SOP/Approach/Approach General/Approach Speed Technique. Nowhere it is mentioned that the crew should or must opt for an early stabilized approach, nor is it necessarily recommended. Early Stabilized approach may be beneficial under certain conditions in order to improve vertical guidance and/or to manage the workload more effectively - but never at the expense of safety.2. ref: QRH One Engine Inoperative - Straight In Approach does not imply an early stabilized approach, rather supporting the notion that Flaps Full should not be selected in level flight before or after the FDP for performance reasons. But this doesn’t mean you should be dragging the aircraft in level flight with L/G down @ Flaps 3 unnecessarily. (see 3)

3. ref: FCTM/PRO/AEP/ENG/One Engine Inoperative Landing:Now add Overweight and ISA+XX to increase the complexity and reduce the performance margins, and you’ll see that you cannot have a dogmatic prescribed model on how to configure your aircraft - you need some adaptation and flexibility.

Except in the FCTM PR-NP-SOP-190-CONF

“(…)This technique is is recommended for non-precision approaches (LOC FPA, NAV FPA and TRK FPA) (…)”

Dear SB,

You are completely right. Missed that paragraph… thanks!
In any case the same message stands: we cannot look at things in isolation. The notion of delaying the L/G still stands.

Brgds

What it means is with OEI on ILS or fully managed NPA decelerating approach can be considered but without vertical guidance not recommended.

It is recommended, not a must.....some companies were doing decelerated NPAs with selected guidance

By all means! I personally adapt the strategy to the characteristics of the NPA to be flown and the condition of the aircraft at the moment, weights, wx, and so on. This is also the way we teach it. Gathering all the inputs from the manufacturer in order to deliver the safest and most efficient outputs in terms of execution of the maneuver.