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| Date: | Friday 12 April 2013 |
| Time: | 18:11 |
| Type: |  Airbus A319-111 |
| Owner/operator: | TAP Air Portugal |
| Registration: | CS-TTD |
| MSN: | 790 |
| Year of manufacture: | 1998 |
| Engine model: | CFMI CFM56-5B5/P |
| Fatalities: | Fatalities: 0 / Occupants: |
| Other fatalities: | 0 |
| Aircraft damage: | None |
| Category: | Serious incident |
| Location: | 20 NM south-east of Zurich Airport -
 Switzerland
|
| Phase: | En route |
| Nature: | Passenger - Scheduled |
| Departure airport: | Lisboa-Humberto Delgado Airport (LIS/LPPT) |
| Praha-Václav Havel Airport (PRG/LKPR) | |
| Investigating agency: | SUST |
| Confidence Rating: |  Accident investigation report completed and information captured |
Ryanair flight FR3595, a Boeing 737-800 (EI-ENK) and TAP Air Portugal flight TP706, an Airbus A319-111 (CS-TTD), were involved in an ICAO Category A airprox incident near Zurich.
TAP 706 and RYR 3595 were cruising in Swiss airspace under the control of the Zurich Area Control Centre (ACC). At 16:00:53 UTC, while at FL 370, the crew of TAP 706, with the radio callsign "Air Portugal seven zero six", an A319 on a scheduled flight from Lisbon (LPPT) to Prague (LKPR), reported to the Zurich ACC Upper Sector M4 air traffic controller (ATCO). The crew of RYR 3595, with the radio callsign "Ryanair three five niner five", (a B737 on a scheduled flight from Pisa (LIRP) to Lübeck (EDHL) also reported to the ATCO just a short time later at 16:01:11 UTC, while at FL 360.
At 16:10:43 UTC the crew of RYR 3595 requested clearance to climb to FL 380 due to extpected turbulence; though without mention of their radio callsign. The ATCO replied as follows: "Six Delta Whiskey, climb three eight zero". This was the radio callsign for flight RYR 6DW, an aircraft belonging to the same aviation operator reporting to the sector shortly before. The crew of flight RYR 3595 responded to the clearance for flight RYR 6DW as follows: "Flight level three eight zero, Ryanair three five niner five" and initiated a climb. Neither the ATCO nor the crew of RYR 6DW did respond to this readback of RYR 3595.
At 16:11:37 UTC the ground-based short-term conflict alert for Sector M4 reported an impending conflict between TAP 706 and RYR 3595. After the crew of RYR 3595 answered in the negative to the ATCO's immediate query as to whether they were at FL 360, he instructed them to descend immediately.
The traffic alert and collision avoidance system on both aircraft generated resolution advisories (RAs) shortly afterwards; these were immediately followed by both crews.
At 16:11:49 UTC, the closest point of approach between the two aircraft was reached: 0.8 NM horizontally and 650 ft vertically.
Causes:
The serious incident is attributable to the fact that the crew of a commercial aircraft initiated a climb without clearance, which lead to a dangerous convergence with another commercial aircraft.
The following factors were identified as the cause of the serious incident:
- The crew initiated the climb on the basis of a clearance which had been issued to another commercial aircraft belonging to the same aviation operator.
- The air traffic controller did not realise that the clearance issued was not read back by the crew for which it had been intended.
The following was identified as a contributing factor to the serious incident:
- A request by a flight crew for clearance to a higher flight level without specification of their radio callsign;
- The issue of altitude clearance by air traffic control without verification of the crew which had made the request;
- Absent reaction of another crew to whom the clearance was addressed to;
- Insufficient attention was given to the prevailing weather conditions when the decision to combine sectors was made.
Accident investigation:
 |
|
Sources:
STSB
History of this aircraft
Other occurrences involving this aircraft
| 10 October 2016 | CS-TTD | TAP Air Portugal | 0 | Santiago de Compostela Airport (SCQ/LEST) |  |
non |
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 14-Oct-2025 11:23 | ASN | Added |
Corrections or additions? ... Edit this accident description
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