Pilots onboard a FedEx McDonnell Douglas MD-11F struck trouble in the skies over Sydney on the weekend, issuing a Mayday call and aborting the final approach. FedEx flight FX9075 was in the final stages of a seven-hour plus flight from Singapore on Saturday night and descending over Botany Bay when a "flight control malfunction" occurred.

MD-11 mayday call follows one month in the maintenance sheds

The operating aircraft, N576FE, is a 29-year-old MD-11 freighter that arrived at FedEx after flying for Garuda Indonesia and now-defunct VARIG. Saturday's flight down to Sydney was the plane's first flight in over a month after a spell in the maintenance sheds in Singapore. The jet took off from Singapore's Changi Airport just after lunchtime (local time) on Saturday and was eight miles out when trouble hit.

"We're going to require the full length of the runway." the FedEx pilot warned Sydney ATC. Sydney's main north-south runway is 3,962 meters long.

Safe landing on the second approach for FedEx MD-11

Sydney Airport regulars will be familiar with the MD-11s approach into Sydney Airport - the tracking in from the southwest, the diversion out over the Royal National Park, and the turn over the water to line up for the final northerly approach over Botany Bay.

Flight tracking websites show the jet had passed over Kurnell and was midway across the bay when it aborted the landing, veering left over Sydney's southern suburbs before heading out to sea and lining up again. The FedEx pilots safely landed the plane on the second attempt. In situ emergency services vehicles watched and waited but were not required. The jet came in overspeed at around 227 miles (365 kilometers) per hour

"We really appreciate the help," the pilots told Sydney ATC after the landing. The Sydney Morning Herald has obtained some audio grabs of the conversation between the pilots and ATC. Some of that audio is inaudible, but the conversation is clear in other parts. "We had a flight control malfunction, a flaps disagreement issue ... a flight control issue."

"Very well handled," replied the air traffic controller.

Flap problems behind the FedEx Mayday emergency

Flaps are hinged panels mounted on the trailing edge of the wing. They are used to increase or decrease the wing's surface area, which in turn can increase both lift and drag and reduce the stall speed. Using flaps helps control a plane's takeoff and landing.

Possible problems onboard the FedEx MD-11 on Saturday evening include flap asymmetry (where there is a difference between left and right side flap positions); split flaps (where the flaps may be symmetric, but either the inner flap or outer flap pair has not reached the commanded position); and stuck flaps (where one flap fails to do as commanded, causing the opposite flaps to stop automatically).

The high-speed landing suggests the MD-11 made have encountered a stuck flap scenario. In this case, a go-around is usually required while pilots work through the checklists and recalculate landing speeds and length of runway needed.

In a statement, the Australian Transport Safety Bureau said, "The ATSB is gathering further information into the circumstances of an occurrence where an MD-11 freighter aircraft conducted a missed approach and issued a mayday call while on approach to land at Sydney Airport on Saturday evening."

Over some 60 hours on the ground, N576FE took to the air again on Tuesday afternoon (local time). At the time of publication, the jet is operating FX9837 between Sydney and Guangzhou.