What happened
On 23 April 2001, a Boeing 747-436, registration G-CIVB, was undergoing pushback from stand T4 at London Heathrow Airport for a scheduled service to Delhi. The pushback, performed using a towbarless tug, experienced an initial delay due to the need to replace a faulty tug. During the maneuver, air traffic control instructed the crew to push to a south-facing position to accommodate another aircraft.
Following the engine start sequence, the aircraft came to a halt near stands T6 and T7. Once the aircraft brakes were set to the park position and the towbar was disconnected, the tug driver began reversing the vehicle to secure the towing gate. During the completion of the 'After Start Checklist', the flight crew used non-standard phraseology to communicate with the ground crew regarding clearance.
Before the headset operator could provide a final visual signal and disconnect, the aircraft began to taxi. As the aircraft accelerated, the tug driver attempted to move the vehicle before jumping clear to avoid the moving aircraft. The flight crew felt a jolt, realizing they had struck the tug, and immediately applied the brakes and shut down the engines.
The investigation
The investigation, conducted by the operator's safety team, established that the aircraft began its taxi movement before the ground crew had confirmed they were clear of the aircraft's path. The inquiry examined the communication between the flight crew and the headset operator, noting that the exchange relied on non-standard terminology. The investigation also reviewed the operator's established pushback protocols and the actions of both the tug driver and the flight crew during the terminal phase of the maneuver.
Findings
- The aircraft began taxiing before receiving final visual clearance from the ground crew.
- Both the flight crew and ground crew failed to adhere to standard pushback procedures and used non-standard phraseology during communications.
- There were identified deficiencies in the operator's written pushback procedures for both flight and ground personnel.
- The communication between the cockpit and the ground crew lacked the necessary clarity and unambiguous timing required for safe operations.