Aeroflot A321 near Venice on Aug 19th 2015, near collision with military formation

Last Update: February 2, 2017 / 16:23:50 GMT/Zulu time

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Photo of Aeroflot VQ-BOI, Airbus A321 — Aeroflot VQ-BOI, Airbus A321 (Photo credit: Anna Zvereva / Flickr / License: CC by-sa)

Incident Facts

Date of incident
Aug 19, 2015

Classification
Report

Cause
Near collision

Airline
Aeroflot

Flight number
SU-2597

Departure
Venice, Italy

Destination
Moscow Sheremetyevo, Russia

Aircraft Registration
VQ-BOI

Aircraft Type
Airbus A321

ICAO Type Designator
A321

An Aeroflot Airbus A321-200, registration VQ-BOI performing flight SU-2597 from Venice (Italy) to Moscow Sheremetyevo (Russia), departed Venice's runway 04R and was cleared to climb to 4000 feet on the standard instrument departure (SID) route ROSKA6X. Due to thunderstorms in the vicinity the crew requested to deviate around the weather by continuing straight ahead. Due to delays in communication and coordination the aircraft soon after entered the control zone of Treviso Air Force Base while remaining in contact with Venice Air Traffic Control.

A pair of military aircraft were climbing near the extended runway center line of runway 07 Treviso and were maneouvering to intercept final approach course of runway 26 of Treviso's Military Airport Istrana maintaining 4000 feet and in communication with Treviso Military Air Traffic Control. The military aircraft did not feature ACAS (TCAS).

The military aircraft remained unaware of the presence of SU-2597, while SU-2597 received a TCAS resolution advisory to climb.

The crew of the A321-200 complied with the resolution advisory and climbed the aircraft passing the military aircraft with an undetermined vertical and a horizontal separation of 0.5nm.

Italy's ANSV released their final report in Italian concluding the probable cause of the serious incident was:

the safety investigation determined as cause of the event a criticality in the immediate and direct communication between Venice civilian and Treviso military air traffic control, which does not permit to promptly and effectively handle air traffic separation in case of unpredictable mutual interference by traffic.

A marginally contributing factor was the inertia in reactions by both air traffic control teams.

The ANSV analysed that upon receiving the request by SU-2597 Venice Tower approved to continue straight ahead while climbing to 4000 feet. At the same time the coordinator of Venice Tower attempted to communicate with the coordinator of Venice Approach, located in the same building but one floor below, by phone to tell them about the deviation from the standard instrument departure route. The coordinator of Venice Approach however was involved in another coordination phone call, the phone call by Venice Tower connected therefore only 22 seconds after the tower had approved to deviate from the SID. Venice approach recognized a developing conflict with an unknown climbing target in the extended center line of runway 07 Treviso and amended the clearance for SU-2597 to "stop climb at 4000 feet" assuming the unknown traffic was departing Treviso and would continue to climb, thus not expecting that traffic to level off at 4000 feet. The ANSV stated, that had the unknown target continued to climb, separation criteria would have been met.

Treviso Military Approach recognized an unknown target (SU-2597) departing runway 04R of Venice and concluded it was a commercial flight that although appearing temporarily climbing slowly would continue his climb and thus no conflict would arise. Treviso Approach nonetheless attempted to raise the attention by Venice Approach via a phone call to Padua Control to inquire about that flight's intention and coordinate the flight, the phone call lasted for more than 70 seconds.

Venice Approach recognized that the unknown target was not continuing the climb and had levelled off at 4000 feet and issued a number of traffic advisories to SU-2597 in an attempt to defuse the developing conflict. At the same time the coordinate of Venice Approach tried to call Treviso Control's coordinator, whose phone was busy however with the coordination call to Padua.

In a last attempt to avert a possible collision Venice Approach radioed SU-2597: "2597, copied, the traffic is at your eleven o’clock, three thousand nine hundred feet, as your altitude, so o descend or climb", the crew replied: "AFL2597 TCAS RA".

The ANSV analysed that it had not been possible to positively establish the vertical separation at which the aircraft passed each other, only the horizontal separation could be determined at 0.5nm.

The ANSV analysed that the occurrence has highlighted a lack of assertiveness by both air traffic control teams. The airspaces controlled by either team are objectively complex and do not provide for much margin of space and time in case of an unpredicted mutual interference. This is made even more problematic by communication infrastructure that does not offer solutions appropriate to the time and space constraints, that - as this occurrence has shown - can be extremely reduced.

The ANSV recommended to both civil and military air traffic control to adopt technologies and procedures in the most appropriate manner to ensure timely and effective separation of aircraft in case of unpredictable reciprocal traffic.