What aircraft was involved and where did it happen?

The accident on null involved a aircraft, registration I-ATMC, at IT.

What was the probable cause of the accident?

The fundamental cause of the airprox was the decision to authorize two converging aircraft to occupy the same flight level. This was exacerbated by a flawed controller handover and a failure to account for wind-induced variations in ground speed.

TCAS alert triggered by separation loss between two Alitalia air…

An airprox event occurred near the Campagnano VOR when two Alitalia flights were authorized to the same flight level, leading to a reduction in minimum separation.

What happened

On January 22, 2001, at approximately 17:50 UTC, two Alitalia aircraft were involved in a Type B airprox near the Campagnano VOR. The first aircraft, an ATR 72 with registration I-ATMC, was operating flight AZA 1122 from Ancona Falconara to Rome Fiumicino. The second aircraft, an MD-80 with registration I-DACV, was operating flight AZA 1752 from Catania Fontanarossa to Rome Fiumicino.

Both aircraft were cleared to flight level 110. As the aircraft approached the VOR, the TCAS on both airframes issued alerts. The pilot of I-ATMC reported a TCAS alert and subsequently climbed to approximately 500 feet above flight level 110. Simultaneously, the pilot of I-DACV received a TCAS instruction to descend, which they executed. During the encounter, the separation between the two aircraft dropped to 2.5 NM, which is below the required minimum of 3 NM.

The investigation

The ANSV investigation examined radar tracks, radio communications, and Flight Data Recorder (FDR) data. The investigation focused on the sequence of instructions provided by air traffic controllers in the TN2 and TN1 sectors. The inquiry looked into the handover process between the outgoing and incoming controllers in the TN1 sector and evaluated the impact of wind components on the aircraft's ground speeds.

Findings

The primary cause was the authorization of both aircraft to fly at the same flight level while converging on the Campagnano VOR.
An imperfect handover occurred between the outgoing and incoming controllers in the TN1 sector.
The outgoing controller failed to note the authorization for I-DACV to descend to flight level 110 on the flight progress strip, which could have alerted the incoming controller to the potential conflict.
The outgoing controller did not account for how the wind component—a 10-knot north wind—would affect ground speeds, specifically how it would favor I-ATMC and disadvantage I-DACV, thereby complicating the planned arrival sequence.
The incoming controller's workload was increased by the need to manage simultaneous communications from other aircraft.

Safety action

ENAV was advised to sensitize air traffic controllers on the importance of complete and standardized handovers.
ENAV was advised to emphasize the importance of timely and accurate updates to flight progress strips.
ENAC and ENAV were advised to encourage flight crews and controllers to complete required Air Traffic Incident Report (ATIRF) forms.

TCAS alert triggered by separation loss between two Alitalia aircraft