The departure off Rwy 20C in Singapore has a height requirement of 4000A at position SUDPO. This height is quite challenging for widebody jets and thus it is normal to do a derated takeoff and transition to full Climb thrust to meet that restriction. Prior to this major incident, I heard a QF A380 report prior to departure that they would probably be unable to make the SUDPO height so SIN ATC co-ordinated with Batam to have the restriction removed. This departure does cause the engines to be worked very hard and will no doubt be a factor mentioned in the ATSB report.