Bob,

Your calculation is correct for area ratio. However, the intake and compressor designs assume zero restriction or infinite area ratio to the surrounding. If we take this as 100% air volume available at the intake to the compressor, then any restriction you placed in front of the intake will reduce the air volume accordingly. From your information, you are restricting or reducing the intake air volume by 33%. What this means is that you are reducing the intake area by 33% and this will have direct effect to increased EGT and reduced thrust output. From experiment, an average FOD screen with 25% restriction will reduce thrust by about 10-15%. With higher restriction, engine ramping is also affected and you may experience hesitation or flaming during acceleration if ramping value is not changed.

Regards,
Kraivuth S.
PST Jets