Hong Kong’s Air Accident Investigation Authority is probing a hydraulic failure aboard an Atlas Air Boeing 747-400F.
The incident, which the AAIA grades as ‘serious’, occurred on 17 June as the aircraft (N406KZ) departed from Hong Kong’s runway 25L at 04:09 local time bound for Anchorage.
“During the take-off roll, the crew experienced a slight yawing and shimmy sensation when the aircraft accelerated between 80kt [150km/h] and 100kt,” says the preliminary report into the incident.
“However, in the absence of cockpit indications and other cues that would suggest the aircraft’s flyability was compromised, the take-off continued normally with normal gear retraction.”
About 26min into the flight, as the aircraft levelled off at its cruising altitude of 29,000ft, the crew received an alert related to the hydraulic system.
After following the appropriate checklist and dumping fuel, a PAN-PAN call was made, and the aircraft made an ILS approach back to runway 25R.
The landing was normal and there was no loss of directional control. However, the hydraulic fluid in systems #2 and #4 rapidly fell to zero during the landing roll.
Smoke was also spotted coming from the tyres, but since brake temperatures were within the normal range the crew shut down the engines and waited for ground support personnel.
An examination revealed that the #9 and #10 tires were shredded, with parts of the wheels missing. Several hydraulic lines in the right-hand wing landing gear wheel well were fractured and punctured, and the fluid in the #1, #2, and #4 hydraulic systems was completely gone.
“In addition, some damage was sustained by the lower forward fuselage, lower right-wing sections and components/systems inside the wheel well,” says the AAIA.
Cirium fleets data indicates that the N406KZ was originally delivered to Nippon Cargo Airlines in December 2007. The jet is still owned by the Japanese cargo carrier, which leased it to Atlas Air in 2019.
