WHAT IS FSA | FOR EDF LOVERS
By Ed Waldrep
FSA (Fan Swept Area) is the area of the opening where the air goes through the fan. In other words, find the area of the entire face of the fan, the subract the area of the motor/spinner/hub, the result is the FSA.
Here's an example
WeMoTec Mini fan 480
Fan Shroud ID 2.715"
Motor tube OD 1.27"
Max Area 5.79 sq. in.
Motor tube area 1.27 sq. in.
Fan swept area 4.52 sq. in[U].
Tailcone diam. 100% 2.4"
Tailcone diam. 95% 2.28"
Tailcone diam. 90% 2.16"
The inlets may look quite small but if you measure and calculate the area you may find plenty of area. 100% of the FSA is the goal, a bit under you'll be ok, a bit larger is OK. You can go way above that and possibly improve static thrust, but too large and the scale looks begin to suffer (look at the huge nacelles on the GWS Me 262 and you'll see what I mean, they're way oversized) and there's increased drag at higher speeds because too much air is going in.
EDF, Fan Swept Area in Knowledge