On 29 December 2011, an ATR72-200 being operated by Golden Air on a scheduled passenger flight from Oulu to Helsinki for airline Blue1 was about to land on runway 22R at destination in accordance with a valid landing clearance when a Saab 340 being operated by Latvian carrier RAF-AVIA Airlines on a cargo flight from Helsinki to Mariehamn for Nordflyg and taxiing for departure from runway 22R was observed to enter the runway. A go around had already been initiated when ATC called to instruct a go around for the same reason.
An Investigation was carried out by the Finnish SIB. ATC radar and R/T recordings and Flight Data Recorder (FDR) data from the ATR 72 were available but the Cockpit Voice Recorder (CVR) from the Saab 340 had been overwritten and it was noted that this fact had “significantly hampered the investigation of multi-crew co-operation” on the Saab flight deck.
It was established that runways 22R and 22L had both been in use as usual during the busy afternoon period, each controlled by a dedicated TWR controller, TWR-W and TWR-E respectively. Although it had been raining at the time, there was no low cloud and normal daylight visibility had prevailed at the airport so that neither in flight nor surface visibility - the latter observed as 6km - were a factor in the investigated event.
The Saab 340 was taxiing for departure from runway 22R and - see the diagram below which shows the complete taxi route taken - had received an initial taxi clearance from TWR-E of “via ‘CL’ cross runway15 taxi to ‘Y’ hold short of runway 22L” which was read back incorrectly as “via ‘Y’ to runway 22L crossing approved” but not corrected by ATC. As the aircraft, having crossed runway 22L, reported that it was approaching holding point ‘WD’, TWR-E told them to contact TWR-W but this instruction was not read back. The crew then mistakenly changed to the frequency of Helsinki Radar where they were told they were on the wrong frequency and directed to call TWR-W. The Investigation considered that it was possible that the landing clearance to the ATR 72 was given whilst the Saab crew were on the wrong frequency and thus could not have been heard. The TWR-W controller was waiting for the Saab to check in on their frequency but when this did not happen, they switched on the red stop bar lights at holding point WD so as to make certain that the aircraft would not taxi onto runway 22R and one minute later, the controller cleared the ATR-72 to land on runway 22R.
The route taken by the SF34 shown in red (Reproduced from the Official Report)
During the brief absence from both TWR frequencies, the commander of the Saab, acting as PF slowed the taxi speed as the illuminated stop bar ahead, positioned about 80 metres before holding point ‘WD’, was approached. The co-pilot checked in with TWR-W and the controller responded with “one landing” which the co-pilot read back as “Landing”. Having reportedly understood this as a line up clearance, the PF then proceeded to cross the stop bar (which neither pilot subsequently claimed to have noticed) and enter the runway. The co-pilot stated that he had been “uncertain of the clearance” but had not attempted to confirm it with ATC. The PF stated subsequently that the co-pilot had confirmed that the approach was clear by saying ‘right side clear’. However, the co-pilot stated that although this check was normal practice and was carried out with a complimentary check of the Airborne Collision Avoidance System (ACAS) display, he had exceptionally not made this check on this occasion. The Investigation noted that the 45° angle of the taxiway access via ‘WD’ to the runway precluded a left seat pilot from making an effective visual check of the final approach themselves.
It was established that the arriving ATR 72 having made an Instrument Landing System (ILS) approach to RWY 22R and acknowledged the landing clearance from TWR-W, had been instructed to go around as the Saab was observed entering the runway but by the time this instruction was given, the go around had already been initiated by the crew on sight of the aircraft ahead. FDR data showed that the minimum height reached by the ATR 72 had been 108 feet agl and that the aircraft had subsequently cleared the top of the Saab 340 by approximately 150 feet.
The Investigation concluded that there had been “shortcomings in the Saab 340 pilots’ multi-crew cooperation and communication” insofar as when the co-pilot was not certain whether they had been cleared to enter the runway, the crew had not sufficiently communicated in respect of the possible mistake nor sought to confirm the matter with ATC. They had then taxied across the illuminated stop bar and “did not apply multi-crew cooperation regarding the fact that the approach sector was clear”.
In particular, the language proficiency of the Saab pilots was observed to have been “limited as regards understanding air traffic control clearances or communicating with the ATC in English” despite the fact that both held valid ICAO language proficiency licence endorsements based on tests which had been performed in the Czech Republic in 2011.
The failure of both TWR controllers to use standard phraseology and respond to incorrect or non read back of ground taxi clearances by the Saab 340 crew was noted, with the latter being explicitly contrary to the applicable regulations.
Stop Bar illumination policy at Helsinki was noted as discretionary in normal daylight visibility and ATC were exceptionally permitted under their procedures to permit an aircraft to cross an illuminated stop bar if the stop bar lights cannot be switched off due to a technical malfunction. It was also noted that at the time of the incident, the surface movement radar installed at the airport did not include a runway incursion alerting system.
The Investigation formally identified the Probable Cause of the investigated Serious Incident as:
- the misinterpretation of the traffic information by the flight crew of (the Saab 340) who then taxied their aircraft across the illuminated stop bar and onto the active runway 22R without an air traffic control clearance.
It was additionally found that Contributing Factors were:
- inadequate multi-crew cooperation on board the (Saab 340)
- the use by ATC of subsidiary phraseology in addition to standard phraseology
Safety Action taken during the course of the Investigation by the Latvian CAA to support an improvement in the operational safety standards of RAF-AVIA was noted. This had included a temporary suspension of all the operator’s Saab 340 operations between 19 March and 29 April 2012 to allow fleet pilots to complete “language and refresher training and proficiency checks”.
Five Safety Recommendations were made as a result of the Investigation as follows:
- that the Latvian Civil Aviation Agency ensure that the pilots of RAF-AVIA Airlines are familiar with the procedures related to stop bars.
- that the Latvian Civil Aviation Agency make certain that RAF-AVIA pilots possess sufficient multi-crew cooperation skills.
- that Finavia Corporation emphasise the importance of disciplined radiotelephony communications in air traffic control operations and that Finavia focus particular attention on correct read-backs.
- that Finavia Corporation make certain that air traffic controllers include the pertinent air traffic control clearance, as applicable, when they complement the standard radiotelephony phraseology with traffic information.
- that Finavia Corporation study the possibilities of introducing a system that alerts air traffic controllers of runway incursions.
It was also proposed that the EAPPRI should be utilised at all Finnish aerodromes for the purpose of improving runway safety.
The Final Report was published on 30 January 2013