Description

On 6 February 2013, an Airbus A320-200 (G-EUUK) being operated by British Airways on a scheduled passenger flight from London to Helsinki under callsign BAW79H was instructed to go around from an approach to runway 04L at destination by ATC. An Embraer 190 (OH-LKO) being operated by Flybe Finland on a scheduled passenger flight from Warsaw to Helsinki under callsign FCM746K and ahead of the A320 on the same approach was then obliged to also commence a go around due to no landing clearance being issued. Having been instructed to fly runway heading, the Embraer 190 then did so on a track which was abeam that of a Boeing 717-200 (OH-BLQ) being operated by Blue1 on a scheduled passenger flight from Helsinki to Stockholm under callsign SAS717 which had just taken off from the parallel runway. Short Term Conflict Alert (STCA) activations occurred as the proximity between the Embraer 190 and the other two aircraft reduced and loss of the prescribed minimum separation subsequently occurred against both of them. The conflictions occurred in day Instrument Meteorological Conditions (IMC).

Investigation

The event was investigated by the Safety Investigation Authority Finland (SIAF). Sufficient data was obtained from ATC radar, voice and from STCA recordings and no aircraft data recorder was sought. However, problems were encountered in obtaining recorded data from the ANSP traffic management system which is used to plan the preliminary approach sequence. It was noted that a succession of explanations about why this was not available had been received from Finavia. Initially they had been told that it was “not recorded” and but subsequently that although there was recorded data, there was “no operational data used by air traffic controllers”. Then, after the Investigation had received confirmation from the manufacturer of the equipment that actually it did retain a recording of operational data, Finavia stated that “due to a technical malfunction at the time of the occurrence, this information was not available”.

It was noted that the TWR Supervisor had decided that the “desired sequencing for arriving traffic was 5nm”. It was established that a Norwegian Boeing 737-800 inbound from Alicante and the A320 were both tracking towards the approach to landing runway 04L from the southwest with the Boeing ahead. The responsible controller in the ARR-E position had decided to bring the Embraer 190, which was approaching from the south, onto the 04L ILS between the two. Speed control instructions were used but it became apparent that, although they had been followed by all three aircraft involved, with the A320 eventually flying as instructed at minimum speed, the minimum separation could no longer be maintained and the A320 was instructed to go around when 4nm from the threshold. Subsequent examination of the radar recording showed that the separation between the three aircraft on final approach had been less than the target 5nm throughout.

By the time the A320 was instructed to go around, the Embraer 190 was already on TWR-W frequency and had been advised to expect a late landing clearance. At a range of 0.5nm, the Embraer crew requested a landing clearance but the TWR-W controller advised that the runway was still occupied (by the landed Boeing 737, which had been previously instructed by TWR-W to “turn to the right” when convenient). The TWR-W frequency was then busy for 16 seconds because of an exchange between the controller and the 737 crew about their reasons for using the full runway length. At the conclusion of that exchange, the controller issued a landing clearance to the Embraer crew who responded by advising that they had already commenced a go around. The Investigation noted that this landing clearance had been issued prior to any transmission from the 737 crew that their aircraft was clear of the runway.

Shortly afterwards, the TWR-W controller, having observed that the Embraer was too close to the A320, then instructed the former to turn right but after the TWR Supervisor pointed out that the Boeing 717 was departing from the parallel runway 04R, this instruction was changed back to runway heading. About ten seconds later, the STCA activated because of the reducing 2nm separation of the Embraer from the A320 which was flying 80 knots faster at the same altitude, 3000 feet. No action was taken by the TWR-W controller but, ten seconds later, the ARR-E controller instructed the A320 to commence a left turn onto heading 335°. The minimum separation (CPA) between these two aircraft was 1.5nm when both were at 3000 feet.

Some 35 seconds after the first STCA activation and approximately 20 seconds after the CPA between the Embraer and the A320, a second STCA activation was generated by the proximity of the Embraer and the Boeing 717 which had just taken off from runway 04R as they flew parallel at a lateral separation of 0.9nm reaching a CPA when both at 3000 feet. These two aircraft flew parallel for 1 minute and 10 seconds until the ARR-E controller, to whom the Embraer had been transferred, turned the aircraft left at 3000 feet. The STCA activation continued until the 717 passed 4000 feet in the climb with the controller responsible for it, RAD-W, although aware of the proximity and having noticed the resulting STCA activation and alerted the TWR-W controller, took no action to increase separation by turning the 717 to the right.

It was noted that when the TWR-W controller queried with the Norwegian 737 crew why they had been unable to use an exit earlier than the end of the runway when their initial guidance from TWR-W was changed from exit “when convenient” to “expedite” later in the landing roll, the crew had cited the fact that the runway surface was slippery. This statement was consistent with the frozen deposits observed and braking action measured in respect of the runway shortly before the aircraft landed.

It was noted that although the prevailing weather was snow showers which led intermittently to loss of visibility from the TWR, in the presence of Advanced Surface Movement Guidance and Control System this had not been a relevant factor in respect of the investigated events.

A review of the actions of all the flight crew involved did not find any evidence that they had contributed to the two loss of separation events in any way. In respect of the actions of the controllers, it was considered that:

• controllers are not sufficiently familiar with the features of STCA alerts and noted that the EUROCONTROL document “Guidance Material for STCA” requires that training should include operational instructions during STCA alerts.

• as well as functioning as an aid to assist the safe control of traffic, it appeared that the SMR may also have been being used to establish that a runway was free without confirming this over the radio. In this respect, it was noted that “using the SMR does not alter the air traffic control’s separation responsibilities, nor can it be used to ascertain that the runway is free when clearing an aircraft onto the runway after another one has landed / departed”.

• the instructions on missed approaches and non-standard go-around clearances in the ATC Operations Manual are “difficult to understand and presented in a somewhat unsatisfactory manner”.

• although operations with one runway for arrivals and the other for departures, i.e. segregated parallel operations, are normal at Helsinki, they are not as tightly regulated through Operations Manual procedures as the relatively rarely used system of independent parallel approaches.

It was determined that under the ESARR 2 severity classification, the investigated event met the criteria for a 'Serious Incident' (A).

In respect of Probable Cause, the Investigation found that:

• The Serious Incident between the (A320) and the (E190) developed when, after having told the (A320) to go around, the arrival controller cleared it to maintain heading 040. As a result, the (E190) no longer had sufficient airspace for flying a missed approach procedure in accordance with the published procedure.

• The Serious Incident between the (E190) and the (B717) developed when, after the E190 had aborted its approach, the TWR controller first cleared it to fly heading 050 and a little later heading 040. As a result of this the (E190), flying on the extended centreline of RWY04L, flew too close to the (B717) that had departed from the adjacent parallel runway.

Contributory Factors were identified as including:

• The arrival controller’s delayed decision making (when) an un-typical traffic situation (prevailed)

• The failure of the TWR and APP controllers to prioritise their tasks

• Shortcomings in coordination between ATC working positions

Four Safety Recommendations were issued as a result of the Investigation as follows:

(1) that Finavia Corporation should augment the Helsinki-Vantaa AT Ops Manual with an operational instruction (for response to) an STCA Alert.

(2) that Finavia Corporation should take measures which make it possible to use the SMR at Helsinki-Vantaa ATC to ascertain that the runway is free when clearing an aircraft onto the runway after another one which has landed/departed.

(3) that Finavia Corporation should specify and augment the instructions in the Helsinki ATC Ops Manual as regards missed approaches and non-standard go-around clearances.

(4) that Finavia Corporation specify the instructions on segregated parallel operations with regard to when the criteria of segregated parallel operations are no longer met.

The Final Report of the Investigation was published on 27 January 2014 and subsequently made available in English translation.

Further Reading

• Loss of Separation
• Urgency Instructions and Clearances
• ATCO Actions in Case of Loss of Separation
• Loss of Separation - ATCO-induced Situations
• Loss of Separation - Pilot-induced Situations
• Surface Movement Radar
• Continuation Bias
• Parallel Runway Operation
• Guidance Material for STCA, EUROCONTROL, 14 December 2006