As the helicopter passed around 250 feet, the 53-year-old experienced pilot transitioned to forward flight, pitching the nose down and the landing gear retracted. The helicopter started to turn right and then more so, despite the pilot applying immediate corrective inputs. The blue and white helicopter reached a height of around 430 feet ft before descending with a high rotation rate and the pilot tried to recover normal flight.
The helicopter struck the ground on a stepped concrete surface, coming to rest on its left side. The impact with the ground damaged the lower fuselage and the helicopter’s fuel tanks which caused a big fuel leak. This fuel ignited shortly after the helicopter came to rest and an intense post-impact fire rapidly engulfed the fuselage. All five people in the helicopter perished in the disaster.
The full Air Accidents Investigation Branch report into the accident has now been published and makes stark reading for the helicopter manufacturer. The report indicates that those onboard experienced a deceleration force exceeding 30 g when the helicopter hit the ground and all the occupants suffered significant impact injuries; for one person, these were likely to have been fatal.
First responders arrived at the accident site within one minute of the helicopter striking the ground and they attempted to gain access to the cockpit and cabin. However, as the helicopter was on its side, the strength of the cockpit windscreen combined with the rapid increase in the power of the fire, they were unable to get in. The helicopter was rapidly engulfed by fire and the occupants who survived the initial impact, the AAIB report says, died from inhaling the products of combustion.
One of the conclusions of the investigation found that in simulator trials confirmed to the investigation that the loss of yaw control was irrecoverable.
This crash tragically took the lives of all five on board: the then Leicester City owner and Chairman Vichai Srivaddhanaprabha, pilots Eric Swaffer and Izabela Roza Lechowicz, as well as Kaveporn Punpare and Nusara Suknamai.
The AAIB was able to identify the source of the catastrophic failure and crash which was that a critical duplex bearing, which connected the control shaft running along the length of the tail to the rotor blades, seized. This seizure of the bearing was the result of fatigue, cracking, pitting, shearing, friction, grease degradation and heat generation.
The AAIB report lists a number of causal factors for this crash, including:
Seizure of the tail rotor duplex bearing initiated a sequence of failures in the tail rotor pitch control mechanism which culminated in the unrecoverable loss of control of the tail rotor blade pitch angle and the blades moving to their physical limit of travel.The unopposed main rotor torque couple and negative tail rotor blade pitch angle resulted in an increasing rate of rotation of the helicopter in yaw, which induced pitch and roll deviations and made effective control of the helicopter’s flightpath impossible.The tail rotor duplex bearing likely experienced a combination of dynamic axial and bending moment loads which generated internal contact pressures sufficient to result in lubrication breakdown and the balls sliding across the race surface. This caused premature, surface initiated rolling contact fatigue damage to accumulate until the bearing seized.
There are a number of issues arising from the report involving the manufacturer Leonardo, including the inactions listed below, leading to the bearing seizure and tragic crash:
Not sharing critical flight test results with the company which made the duplex bearing, in order to confirm that the bearing that they had chosen was actually suitable for use in the tail rotor. Had Leonardo shared the results, the bearing may not have been chosen.Not requiring the routine inspection of critical parts removed from service (such as the duplex bearing) to confirm that they were in the condition that they expected them to be in based on their design. Had Leonardo done so, they would have found that the bearings were more damaged than expected and ought to have concluded that they needed to change their original design.Not fully considering possible risk reduction and mitigation measures for the duplex bearing – which had been identified as a critical component by Leonardo during the design phase. It was recognised by Leonardo, the report notes, that if the bearing failed it could lead to the death of multiple occupants onboard. Had they included one of those mitigation measures, simply changing the thread direction of a key component, it is likely that the severity of the accident would have been reduced.
Former Leicester City owner Vichai Srivaddhanaprabha purchased what he believed to be a state-of-the-art helicopter. Leonardo’s non-performance of key measures, raises serious questions about the safety of the company’s aircraft.
Aiyawatt Srivaddhanaprabha, who lost his father, Vichai Srivaddhanaprabha, commented: "I am deeply saddened by the course of events. Almost five years after my father’s passing, this report provides concerning evidence against Leonardo. My father trusted that he had bought a safe helicopter from a world-renowned manufacturer. Had he known what we know now he would never have risked his life in this machine. The pain this causes me and my family is immeasurable and as a family, we continue to struggle every day with our grief at the loss of my father. He was a great inspiration to me personally and we all loved him very much.”
The families of three of those lost in the crash – Vichai Srivaddhanaprabha, Eric Swaffer, and Izabela Lechowicz – have retained leading litigation specialists’ Stewarts. The family of Vichai Srivaddhanaprabha are now considering their legal recourse against Leonardo. Litigation has already been commenced in Italy on behalf of the families of Eric and Izabela.
Eric and Izabela were life partners and soulmates. Both were recognised and highly respected throughout the global aviation industry for their exemplary piloting skills. Both were also qualified instructors and examiners on a range of aircraft. Eric spent most of his career lobbying and advising on matters of safety in the rotary wing industry.
The report confirmed there was nothing either Eric or Izabela could have done to prevent this disaster, it stresses that effective control of the aircraft was impossible following the loss of the tail rotor. For the families, it has been important for the memories of Izabela and particularly Eric, who was piloting the helicopter, to have been cleared of any possible implication in the accident.
Deborah Sutton, mother of Eric Swaffer said: "This of course is every mother’s worst nightmare and time is not healing. Eric and Izabela were an inseparable couple, devoted to each other and to their flying. Without them there is an enormous hole in our lives. I think of them daily and miss them more than I can say.”
Peter Neenan, a partner in the aviation team at Stewarts, said: “This report is a frightening tale of missed opportunities.
The report confirms that the helicopter manufacturer, Leonardo, did not accurately model the forces affecting the helicopter during their design, did not provide the right information to the bearing manufacturer, did not then measure the forces actually affecting the helicopter, did not involve the bearing manufacturer to validate their assumptions despite not having the software needed to model the forces on the bearing, did not implement a routine inspection requirement for these bearings to identify and replace them during their degeneration prior to any risk of seizure and did not require discarded bearings to be examined to see whether their design assumptions were valid.
This was all done in circumstances where Leonardo had recognised that the duplex bearing was a critical component and that the failure of this component could be catastrophic for the helicopter and likely to result in the death of those onboard.
Nevertheless, and despite that concerning warning, they then also did not implement sufficient mitigation measures within the wider tail rotor control system to avoid a catastrophic loss of control of the helicopter from such a failure. Some of those measures would have been as simple as changing the thread direction on component parts, a measure that they had already implemented for an earlier variant of this helicopter, the AW139."
