What happened
On 15 June 2006, a Boeing 737-300, registration OO-TND, was performing a diversion to Nottingham East Midlands Airport due to deteriorating weather at its original destination, Stansted. The flight was conducting a Category IIIA automatic approach in low-visibility conditions.
During the final stages of the approach, at approximately 530 feet above the airfield, Air Traffic Control (ATC) transmitted a company message to the aircraft stating that the operator did not want the plane to land at East Midlands. In an attempt to clarify this message, the commander inadvertently disconnected the aircraft's autopilots. The commander then attempted to re-engage the autopilot, but only successfully engaged one autopilot in a specific mode that did not maintain the required approach parameters.
Because the crew did not initiate a go-around immediately following the loss of automation, the aircraft's descent continued unchecked. The Enhanced Ground Proximity Warning System (EGPWS) issued a 'SINK RATE PULL UP' warning between 87 and 59 feet, but the go-around was initiated too late. The aircraft struck the grass area to the left of Runway 27 near the threshold. The impact caused the right main landing gear to detach from the wing, resulting in damage to the flaps and the loss of hydraulic System A. The crew subsequently diverted to Birmingham Airport, where they performed a successful emergency landing with the nose and left landing gear extended.
The investigation
The AAIB investigation examined the aircraft's flight recorders, the ILS and airspeed indicator systems, and the hydraulic systems. The investigation also reviewed the maintenance of the airport's meteorological reporting and the ATC communication procedures. Investigators found that the commander's attempt to manage radio communications while flying a critical phase of flight led to a loss of situational awareness. Additionally, the investigation looked into the training and standard operating procedures (SOPs) regarding the crew's responsibility to call for a go-around during automated approaches.
Findings
- ATC transmitted an inappropriate message to the aircraft during a critical phase of a CAT III approach.
- The commander inadvertently disconnected the autopilots while attempting to respond to the ATC transmission.
- The crew failed to decide on a go-around when the automation was lost below 500 feet.
- The commander's situational awareness was compromised following the disconnection of the autopilots.
- The co-pilot did not call for a go-around until after the aircraft had already made contact with the ground.
- The aircraft's right main landing gear detached upon impact, causing significant structural and hydraulic damage.