Thank you for your response. I am referring to Loss of APU Detection of a fire . As i sed after we depart we have an engine fail ( severe damage) so according to QRH if APU is working we should start it. After that and before starting another approach we loose the fire detection of our APU and according to QRH we have to ( plant to shut down the APU as soon as practical ) means to me that LEGALLY i can keep it , otherwise it will state ( Shut down the APU ) . So I believe its a tricky item. Also according to Electrical redundancy of B777-300 we have two engine generators, two back up generators, one APU generator and one RAT.