It's not every day that Sydneysiders hear a bang in the distance from an A380 superjumbo flying overhead.
And it's certainly not usual for them to hear a thud on their rooftop moments later.
But that is what a northwestern Sydney home owner experienced late last year when an Emirates A380 bound for Dubai suffered an engine failure shortly after takeoff.
The surprise discovery is detailed in a report from air-safety investigators into the mid-air incident, which forced the Emirates A380 to return to Sydney Airport.
It reveals that the owner of the property at Riverstone was disturbed by a distant bang at about 10 pm on November 11, before hearing debris land on their tile roof.
The suspected engine debris measured only centimetres in diameter.
The home owner reported the incident to Quakers Hill police, who later handed the suspected pieces of engine debris over to air-safety investigators.
Releasing its final report on Monday, the Australian Transport Safety Bureau found the Emirates A380 suffered ''significant internal damage'' to one of its four engines.
The A380 had reached about 9000 feet on its way to Dubai when its pilots heard a loud bang and received a warning that the No.3 engine was overheating.
Moments later, the engine was shut down automatically.
The pilots turned back for Sydney and dumped fuel before landing safely at Kingsford Smith.
The investigators found the engine failure and in-flight shutdown were the result of the break-up and dislodgment of nozzles from its high-pressure turbine.
It resulted in ''substantial downstream damage'' and a breach within the turbine's casing walls. The problem with the nozzles had likely been caused by hotter than expected temperatures.
Apart from some metallic material shooting out from the rear of the engine, the bureau said there was no evidence that ''high-energy debris'' had escaped during the mid-air scare.
The incident was termed a ''contained engine failure'', in contrast to the ''uncontained failure'' which beset a Qantas A380 after takeoff from Singapore in late 2010.
The investigators noted that two other engines in Emirates' fleet of aircraft suffered similar problems in the weeks after the Sydney incident.
Shortly afterwards, the engine manufacturer, Engine Alliance, took steps to fix the problem, which included better monitoring.
The bureau said the manufacturer was continuing to better understand the ''initial onset of nozzle distress and potential for further design improvements''.
Engine Alliance is a joint venture between Pratt & Whitney and General Electric.
While the incident was enough to result in an in-flight engine shutdown, the investigators emphasised that the safety risks of continuing the flight were ''relatively low''.
At the time of the incident, passengers on board flight EK413 reported seeing a bright orange flash and felt the plane shake. No one was injured.
- Sydney Morning Herald