Is it possible for an Airbus A380 to operate with eight of the largest geared turbofans instead of four Trent 900 engines? Would it be fuel efficient? What would be the total thrust of the engines?
The current largest geared turbofan is the PW1100G. The highest thrust variant is the PW1130G which provides 147.28kN of thrust. Eight of these would provide 1178kN total thrust.
The Trent 900 provides 340kN of thrust, the 4 engines on the A380 provide a total of 1360kN of thrust. This means that 8 PW1130G engines would leave the A380 a bit under-powered.
Would it be efficient? Probably. Most of the efficiency of an airplane comes from the engines. The PW1100G are newer and more efficient than the Trent 900 engines. There would be some losses due to higher installation drag but probably not enough to offset the efficiency.