What happened
On January 12, 2007, a Gulfstream G-IV SP operated by the Swedish Air Force was taxiing at Berlin Tegel Airport. The aircraft, carrying four crew members and four passengers, was preparing for an IFR flight to Bremen. While taxiing via taxiway NE, the crew was advised by the ground controller that they could use runway 26L for departure, which would allow for an earlier takeoff.
As the aircraft approached the CAT-II/III holding point for runways 26R/L, the ground controller handed the aircraft over to the tower frequency. During the transition, the tower controller issued a clearance to line up on runway 26L without explicitly addressing the need to cross runway 26R. The copilot, expressing uncertainty, requested confirmation regarding crossing the runway.
Upon hearing the request, the pilot in command noticed several aircraft on final approach. Realizing the potential conflict, the pilot intervened on the radio to clarify that the aircraft needed to cross runway 26R to reach 26L. The tower controller then corrected the instruction, directing the aircraft to hold short of runway 26R. The aircraft came to a stop before the CAT-I holding point, avoiding any immediate danger of a collision.
The investigation
The BFU examined the communications between the crew and the controllers, as well as the operational procedures at the time. The investigation noted that the tower controller assumed the Gulfstream G-IV SP was taxiing on taxiway SE, based on previous experience at the airport and the presence of another aircraft on that same path.
Physical visibility from the tower was partially obstructed by a structural pillar in the glazing, making it difficult to see the aircraft on taxiway NE. Furthermore, the investigation found that the tower controller did not incorporate information from the surface movement radar into their situational awareness during the clearance process.