What happened
On July 15, 2006, a Thai International Airlines Boeing 747-400, registration HS-TGY, was taxiing at Madrid-Barajas Airport for a scheduled flight to Rome. During the taxi maneuver, the flight crew inadvertently entered taxiway I-8, an area undergoing construction work. Due to the ongoing works, the taxiway centerline had been displaced, and a NOTAM was in effect restricting the use of this taxiway to aircraft with a wingspan no larger than an Airbus A-321.
As the aircraft proceeded through the construction zone, the crew noted the narrowing path and expressed concern regarding clearance for the right wing. Despite the co-pilot attempting to apply brakes, the right winglet of the Boeint 747-400 struck the T-tail of a parked Embraer EMB-135, registration F-GOHC. The impact caused the T-tail of the Embraer to detach and fall to the ground. The Boeing 747-400 sustained damage to its right winglet, while the Embraer EMB-135 suffered major structural damage. There were no fatalities, though the crew of the Embraer was on board at the time of the collision.
The investigation
The CIAIAC investigation examined the aircraft's flight data, airport signage, and air traffic control (ATC) procedures. Investigators found that the flight crew was following a modified taxi route suggested by ATC to avoid congestion, which led them away from the standard published path. The investigation also reviewed the airport's signaling, noting that a horizontal ground sign at the junction was not in full compliance with standard norms, as the directional arrow was at a 45-degree angle rather than 90 degrees.
Furthermore, the investigation identified that the aircraft's onboard Jeppesen charts lacked the necessary detail to navigate the complex taxiway network at Madrid-Barajas effectively. The investigation also noted that the cockpit voice recorder (CVR) data for the immediate moments of impact was lost because the device remained powered for over two hours following the event, allowing the relevant audio to be overwritten.
Findings
- The primary cause of the accident was that the flight crew failed to adequately assess the clearance between the aircraft's right wing and the parked Embraer EMB-135 after inadvertently entering taxiway I-8.
- The aircraft entered a restricted area where construction work had reduced the available taxiway width, making it unsuitable for a large-span aircraft like the Boeing 747-400.
- Air traffic control surveillance was reduced because the ground movement frequencies for the South sector had been unified, leaving only one controller monitoring the area.
- The flight crew's onboard charts were insufficiently detailed for the complex taxiway environment at the airport.
- The ATCO was focused on other aircraft in a different sector at the moment the collision occurred and was unable to intervene.