What happened
On August 6, 1999, a Socata TB 21 was conducting a VFR flight from Landsberg/Lech to Paderborn-Lippstadt. As darkness fell, the pilot decided to divert to Frankfurt to land, refuel, and drop off a passenger. Because the pilot did not anticipate flying at night, no flight plan had been filed, and he lacked specific night flight authorizations.
During the approach to runway 07R, the pilot requested to join the right downwind leg, which was granted by the tower controller. Simultaneously, an Airbus A320-211 was cleared for takeoff from runway 18. The controller asked the pilot of the Socata TB 21 if he could see the departing aircraft; the pilot responded with "roger," which the controller interpreted as an acknowledgment of the traffic, though the pilot did not explicitly confirm visual contact.
Despite being instructed to turn into the base leg, the pilot of the Socata TB 21 continued flying parallel to runway 07R, intending to wait until passing the runway threshold to begin his turn. This delay resulted in a dangerous proximity to the departing Airbus A320-211, with the minimum separation recorded at only 0.2 nm (approximately 370 meters). The crew of the Airbus A320-211 aborted their initial climb and initiated a descent to avoid a collision.
The investigation
The BFU investigation focused on the separation procedures and communication between the pilot and air traffic control. The investigation examined the lack of a flight plan, the pilot's lack of night flight authorization, and the controller's specific arrival plan. The investigators also reviewed radar data to reconstruct the flight paths of both aircraft and analyzed the timing of the instructions issued by the tower.
Findings
- The pilot of the Socata TB 21 failed to follow the controller's instruction to turn into the base leg, mistakenly believing he should wait until passing the runway threshold.
- The controller failed to inform the pilot of the Socata TB 21 about the specific arrival and landing procedure being implemented, which involved a conventional visual crossing.
- The pilot's response of "roger" to the question regarding the departing traffic was ambiguous and did not clearly confirm visual identification of the Airbus A300-211.
- The controller did not anticipate the speed at which the Socata TB 21 would traverse the length of runway 07R.