SYDNEY - A Qantas Airways A380 superjumbo aircraft bound for London has landed safely in Dubai after it was diverted due to an engine defect, a Qantas spokeswoman said on Friday.The aircraft with 258 people on board had an "oil quantity defect" in one engine and in line with standard procedure was shut off, she said, adding Qantas engineers would investigate the problem.Qantas A380's are equipped with four Rolls Royce engines.