What happened
On January 20, 1999, a Boeing 747-400 arriving from Delhi was performing a manual approach to runway 25 L at Frankfurt Airport. The crew intended to conduct a CAT I landing based on earlier weather reports. The approach was flown from above the glidepath, which placed additional pressure on the crew. During the descent, the aircraft's sink rate was initially low, and the autopilot was disconnected at 3,000 ft AGL to allow for manual control.
During the final stages of the approach, the crew was distracted by a technical issue involving hydraulic system No. 4, which required them to work through a checklist. At approximately 800 ft AGL, the crew extended the flaps from 25° to 30°. This configuration change caused the aircraft to rise above the glidepath and subsequently increased the sink rate to 1,450 ft/min. Despite the ground proximity warning system (GPWS) issuing eight consecutive "sink rate" alerts, the crew did not initiate a go-around until the aircraft made unintended contact with the ground approximately 1,000 m before the touchdown zone, on the paved surface of an old runway extension.
The pilot initiated a go-around, and a second landing was performed automatically on runway 25 R under CAT III conditions. During this second landing, a tire on the main landing gear, which had been damaged during the initial undershoot, caught fire but was quickly extinguished by airport fire services.
The investigation
The BFU investigation examined the flight data recorder (FDR), cockpit voice recorder (CVR), and radar data. The investigation established that the ILS for runway 25 L was functioning correctly within tolerances. Analysis of the CVR revealed significant deficiencies in Crew Resource Management (CRM) and Crew Coordination Concept (CCC), noting a lack of constructive dialogue regarding the deteriorating weather. The investigation also reviewed the coordination between the airport operator (FAG) and air traffic control (DFS) regarding the transition between CAT I and CAT III operational modes.
Findings
- The primary cause of the undershoot was an unstable approach that was not aborted with a timely go-around.
- The crew failed to recognize that visibility had rapidly deteriorated due to encroaching fog banks, despite receiving updated runway visual range (RVR) information during landing clearance.
- The crew continued a manual approach despite not being qualified for CAT II or CAT III operations.
- The simultaneous management of a hydraulic system failure and the configuration change (flaps 25° to 30°) increased cockpit workload and contributed to the loss of glidepath control.
- Deficiencies in CRM and CCC resulted in a lack of situational awareness and a failure to analyze the aircraft's condition (such as the damaged landing gear) following the initial ground contact.