A320 cargo smoke and ventilation doubt
Hi i want to clarify something about Airbus320 cargo smoke and ventilation...I am new to the aircraft... if anyone could help...
Air from the cabin goes via the inlet isolation valve to the aft cargo compartment, driven by an extraction fan...
Now lets say that there is smoke in the cargo compartment.. checklist says Aft isolation pb off..and then agent discharge...and land ASAP
ventilation chapter says air from cabin comes to cargo compartment with the help of extraction fan and then thrown outside...so that menas the same air is not circulated back....
Now putting isolation PB to off closes all the inlet and outlet valves and stops extraction fan..thereby isolating the cargo compartment...now if we close the valves the air is trapped and with the help of extinguisher it can be extinguished..
Lets say we do not close the isolation valve so in that case also smoke filled air cannot come in the cabin..and if extraction fan runs that smoke air will be thrown out..
Now are we closing the valves to deprive them of oxygen so that it dosent ignite more...or some other concept...
THanks if someone coulp put some light to it..
also in B747 SAA flight 295..investigation revealed that crew followed the checklist and there in that combi aircraft the cargo compartment air filled in the cabin also...somehting of that sort...i was watching the mayday episode...and somehow was confused with our aircraft...
Regards