What happened
On September 21, 2004, a Korean Air Boeing 747-400F, registered HL7467, departed Oslo Airport Gardermoen for Incheon International Airport. During the takeoff roll, the aircraft began to autorotate at approximately 120 knots. The aircraft eventually became airborne at 165 knots, but the crew experienced an excessive pitch-up attitude, which reached 19.5 degrees at 200 feet.
During the flight, the crew identified that the aircraft balance was incorrect and contacted their operations center via SATCOM. After receiving updated data, the crew relocated several cargo pallets to adjust the center of gravity. Despite these efforts, the aircraft landed at Incheon with the center of gravity still 7.2% aft of the allowable limit. During the landing rollout, the nose of the aircraft lifted at 60 knots, causing the loss of nose wheel steering. The crew subsequently stopped the aircraft on the runway and shut down the engines.
The investigation
The Norwegian Safety Investigation Board (NSIA) examined the loading procedures and the flight data. The investigation focused on how the aircraft was loaded with a center of gravity significantly aft of the permitted limits. Investigators reviewed the roles of the Load Master, the ground handling services, and the flight crew's verification process. The investigation also looked into the lack of specific aircraft weight and balance reference data available in the cockpit.
Findings
- The primary cause of the unstable takeoff was a loading error where the Load Master mistakenly used the Mean Aerodynamic Chord (MAC) percentage as the Index Unit (IU) value.
- This error resulted in the aircraft being loaded with a center of gravity 4.8% aft of the aft limit during takeoff.
- The error went undetected by the Load Master, the ground service supervisors, and the flight crew during the manifest review.
- The flight crew lacked access to specific cockpit placards or Pilot Operating Manual information regarding the required Standard Operating Mass and Index Unit values for this specific aircraft.
- The aircraft's training curriculum did not include recurrent training for manual mass and balance calculations or simulator training for handling out-of-limit center of gravity conditions.