Swedish investigators are doubting an ATR 72-200 crew's claims that they did not notice a serious runway excursion during landing at Trollhattan airport, an incident which went unreported by the pilots and was only revealed by the discovery of lighting damage.
The RAF-Avia turboprop – converted to a freighter – had been arriving from Szczecin on 9 October. It was a training flight, with the pilot in the left seat under the supervision of an instructor captain in the right.
Swedish investigation authority SHK says the ATR approached runway 33 in darkness under a 17kt crosswind from the left.
It drifted to the left of the centreline and its main-gear wheels exited the side of the runway onto the grass. The aircraft struck an edge light during the excursion before it swung back onto the runway.
While such incidents must, under European Union regulations, be reported within 72h, the inquiry says the crew filed no such report.
Airport personnel found the damaged edge light two days later during a routine weekly check. Closer inspection, a few days later, determined that the light had been run over and there were tyre tracks leading off the runway into the grass.
Analysis of the tyre tracks' width showed they were 4.1m apart and that the only recent arrival which matched this measurement was the RAF-Avia ATR 72.
The airport manager informed the carrier of the incident and the pilots filed "more or less identical" reports dated 18 October – nine days after the event – stating that the landing was carried out "without any deviations", in crosswinds from 250-290° at 16-18kt.
SHK says one of the pilots, in a subsequent interview, informed that the aircraft drifted "slightly to the left" during landing, owing to insufficient aileron deflection into the wind, while the other pilot claimed he did not remember anything of the incident.
But SHK has expressed doubt over this stance. It says it "finds it unlikely" that the crew failed to notice the aircraft had veered off the runway, not least because of the "clear line of lights" at the runway edge which would have been in the pilots' view.
The pilots said they conducted a routine check of the aircraft after the flight and found nothing out of the ordinary, and the technical logbook was signed without any remarks.
RAF-Avia has an "open reporting culture" which "encourages free and honest reporting" with a non-punitive policy, according to its safety-management system manual, says SHK.
"The fact that the runway excursion was not reported by anyone in the crew could, of course, be an indication that there are shortcomings in the reporting culture within the company, despite the directives in the operator manuals," it states.
"However, it has not been possible for SHK to investigate more closely or clarify why the incident was not reported.
"Nor has SHK identified anything during its investigation in the operator’s approach to incident reporting that would deter the staff in this regard."
RAF-Avia's own internal investigation into the incident was completed two months later, on 13 December. It found that ailerons were not applied against the crosswind, causing the aircraft to drift briefly off the runway into the grass.
None of the three crew members, which included a technician in the jump-seat, was injured and the aircraft (YL-RAI) was undamaged.
Latvia's civil aviation agency carried out an audit of RAF-Avia over the course of 3-12 January this year, at its Riga and Frankfurt Hahn bases. During this period the operator suffered an excursion involving a Saab 340B at Savonlinna in Finland.
RAF-Avia's response to the two serious incidents has been acceptable, according to the Latvian authority's findings, but it has still recommended tightened safety measures such as an improved reporting culture.
SHK adds that the carrier has indicated that it will implement special training measures on handling of the ATR 72 during crosswind landings, as well as other operational changes, and has started regularly downloading quick-access recorder information for flight-data monitoring.