The Weekly Reflektion 49/2024
Accidents and incidents are often attributed to human error and in many cases, this may be the case. Why people did what they did, and why they considered it rational in the situation and circumstances they were in, needs to be understood before we play the human error card. Sometimes a more detailed investigation discovers that it was not human error at all.
Was your last accident attributed to human error?
RAF Chinook ZD576 and the memorial to the 29 people killed in the crash
On 2 June 1994, a Royal Air Force (RAF), Chinook helicopter crashed on the Mull of Kintyre, Scotland. All 29 people on board were killed. The helicopter was carrying senior intelligence experts on their way to a conference outside Inverness in Northern Scotland. Due to the nature of the flight, terrorist involvement was suspected, however there was no evidence of any explosion or sabotage.
The crew were flying on Visual Flight Rules (VFR) that require a minimum visibility of 5.5 kilometres above 260 km/h, or minimum visibility of one kilometre if travelling slower. In the event VFR conditions are lost, an emergency climb must be immediately carried out and Instrument Flight Rules (IFR) established. Witnesses in the area stated there was fog and therefore poor visibility, hence it would have been expected that the crew took immediate action and transferred to IFR. The helicopter crashed into a hillside 250 meters above sea level. RAF Chinooks were not equipped with Flight Data Recorders (FDR) or Cockpit Voice Recorders (CVR) so there was little information to establish what happened and why.
In 1995, an RAF board of inquiry ruled that it was impossible to establish the exact cause of the accident. This ruling was overturned by two senior reviewing officers, who stated that the pilots were guilty of gross negligence for flying too fast and too low in thick fog. This verdict was controversial and was disputed, including by the officer who was responsible for the pilots’ training. He could not understand why the pilots would deviate from the VFR procedures when visibility was obviously impaired. Further investigation highlighted problems with the FADEC (Full Authority Digital Engine Control) that had been integrated into all RAF Chinooks. An official document written 9 months before the crash described the engine software as ‘positively dangerous’. Other crews had experienced problems with the FADEC system, and some had refused to fly Chinooks with the system installed. A ground test of the FADEC system in 1989 had resulted in severe airframe failure requiring the system to be redesigned. The possibility of human error could however not be ruled out. Fatigue was identified as a potential factor since the crews had been on flight duty for 9 hours and 15 minutes, including 6 hours flying time.
A Parliamentary inquiry conducted in 2001, found the verdict of gross negligence on the part of the crew to be ‘unjustified’. In 2011, an independent review of the crash cleared the crew of negligence and accepted that the RAF had falsely declared compliance with regulations in relation to the aircraft’s authority to fly. The 2011 Report made a key statement that is relevant to all incidents where there is doubt on the causes.”The possibility that there had been gross negligence could not be ruled out, but there were many grounds for doubt and the pilots were entitled to the benefit of that doubt. The Reviewing Officers had failed to take account of the high calibre of two Special Forces pilots who had no reputation for recklessness.’