The accident occurred on 19 April last year during the course of an exercise in the area. After practising dive attack manoeuvres, the pilot was returning to Vidsel to land. He received permission to carry out a landing circuit at low level.
Shortly afterwards he experienced an explosion which blew off the aircraft canopy. The pilot felt for the ejection handle but did not manage to locate it before he was ejected from the aircraft and landed unharmed.
The Swedish Accident Investigation Board (SHK) has carried out an investigation into why the ejector seat operated without the pilot himself pulling the handle. SHK in its report concludes that the shape of the handle, its positioning and the low level of force needed to operate it, had caused the pilot’s legs, encased in the inflated G-suit, involuntarily to press the handle upwards, so causing the seat to be ejected.
"That was the message that we had expected. We came to the conclusion shortly after the crash that this was the cause", says Johan Svetoft, Commander, Air Combat Flying School.
Criticism of quality work
The Accident Investigation Board draws attention to the fact that shortcomings in the design of the ejection handle in the JAS Gripen C and D variants had been known but not acted upon, and directs criticism towards some aspects of the quality work carried out by the manufacturer, SAAB, and by the Swedish Defence Materiel Administration, FMV.
The Swedish Armed Forces are also criticised for not having identified the problem. Over the course of the ten years preceding this accident there had been nine deviation reports relating to the problem of making the handle safe when displaced from its normal position.
"One reason why this did not attract more attention is that the reports have been spread over such a long period. Another reason could be that the problem was covered in the normal procedures in the instructions that we have for the seat. The instructions explain how to make the seat safe if the handle is inadvertently lifted", says Johan Svetoft.
A questionnaire answered by 123 Gripen pilots shows that 15 percent of pilots had experienced problems in making the seat safe after landing. The problem of making the seat safe has not normally led to any report being raised, simply because the problem has been documented and known.
Action to be taken
The Swedish Armed Forces are now taking action to detect more easily any pattern in the deviation reports that arise.
"We are currently making changes to the entire flight safety database and changing the coding of incidents and the causes of deviations. This will make it easier to detect problems of the kind we have here, even though a long time may elapse between each report", says Johan Svetoft.
Subsequent to the crash, the manufacturer SAAB has conducted trials of modified ejection handles in order to reduce the risk of inadvertent operation. The Swedish Armed Forces have also introduced restrictions and changes in the pilots’ flight instructions. Replacement ejection handles will subsequently be fitted to the versions of the JAS 39 Gripen concerned.