Originally Posted by
FlyingStone
If evacuation is already in progress, it surely makes more sense to have the step to fire the second bottle in the Evacuation NNC rather than having to go back to the Engine Fire on Ground NNC for that step?
Discharging of the second bottle used to be the memory item (on the 737 at least), but that usually delayed the decision to evacuate the aircraft, while waiting 30 seconds, then discharging the second bottle, then waiting if it had any effect. That is why NTSB recommended that Boeing develops the new checklist, which now redirects you to Evacuation NNC before firing the second bottle, and you fire the second bottle only while people are already jumping down the slides.
Thanks, this makes a lot more sense. The thing is, I read in another thread that Boeing removed the second bottle discharge because it was found to be ineffective and could even interfere with the first bottle, making it less effective. I didn’t realize it was removed due to the delay in the evacuation process. So, Boeing calls for evacuation immediately if the first bottle doesn't put out the fire, even though the second bottle could still do the job. But yeah, I understand we need to expect the worst-case scenario here.