Boeing 738 failures

Hi to all,I am still an enthusiast simpilot of the B738 that is until now, according to me, one of the best addons for FS9 (i.e. all fuel flows and N1 regimes agree almost perfectly with the Continental B738 FCOM tables).Just a curiosity I often use the failure generator for training purpose but while I can always trigger V1 failures engine fires etc, I've noted that some failure doesn't work i.e. if I seklect an "hydraulic pump failure" nothing happens (the only possibility I've it's to switch off the pump manually) and so for others i.e. "birdstrike" "nosegear" etc. any idea for that? I can't remember if this could be 'cause I've installed the B744-B744F too...Any idea?Best regardsCiaoAndrea