Ejection seat manufacturer Martin-Baker has promised that lessons have been learned from a fatal accident that claimed the life of a UK Royal Air Force Red Arrows display team pilot after a coroner was sharply critical of the company.
Flt Lt Sean Cunningham was killed on 8 November 2011 when the Martin-Baker Type 10B1 Mk1 ejection seat fitted to his BAE Systems Hawk T1 was accidentally activated while the aircraft was still on the ground at RAF Scampton, in the east of the country. The main parachute system then failed to deploy properly and Cunnigham remained attached to the seat.
Two maintenance errors had gone unobserved by both engineers and pilots including Cunningham, says Central Lincolnshire coroner Stuart Fisher in his narrative conclusion to the inquest. The latter problem meant that the seat firing handle was slightly out of position, and when its safety pin was inserted to immobilise the handle, the pin did not engage with its housing, leaving the ejection system effectively live.
Fisher says Cunningham was in the process of going through routine pre-flight checks when the ejection seat was "unintentionally activated by him". The seat’s two drogue parachutes deployed correctly, but thereafter the seat failed to operate as it was intended to. "In consequence he failed to separate from the seat and his main parachute failed to deploy,” says the report.
This type of seat, if the ejection sequence operates precisely as designed, is capable of blasting pilots clear of a stationary aircraft and parachuting them to earth safely. However, Martin-Baker says an over-tightened shackle bolt was responsible for the main parachute's failure to deploy.
Fisher blames the manufacturer for not making its maintenance instructions clearer: “They [Martin-Baker] failed… to provide any written guidance as to how to appropriately secure the drogue nut to its bolt, confining their guidance in this respect to the need to ‘pass the bolt through drogue shackle and scissor shackle, secure with locknut’."
The implication in the coroner’s findings is that there was no warning to the RAF about the possible consequences of over-tightening the bolt. But additionally, the coroner says Martin-Baker had been aware since 1990 of this potential error and had warned other seat users of the risk, but not the RAF.
Martin-Baker says the RAF had huge experience with the Type 10B1 Mk1 ejection seat, which it points out has saved more than 800 lives. “We supplied the seat to Hawker Siddeley [now part of BAE Systems] in 1976. Since then, for the last 35 years, the seat has been used and operated by the RAF,” it says.
The manufacturer adds, however, that changes have taken place: “In light of this incident, lessons have been learned and we have taken steps to alert all our customers worldwide who still use this type of seat, of the risk of over-tightening the shackle.
"Furthermore, our designers, working closely with military experts have developed a new type of shackle bolt and firing handle housing, which both Martin-Baker and the military authorities consider will prevent the re-occurrence of the circumstances that led to this tragic accident."
The manufacturer says that as of the end of January, Martin-Baker seats "have saved 7,436 lives, seven in this month alone”.
Air Cdre Terry Jones, for the Ministry of Defence, paid tribute to Flt Lt Cunningham and promised the service would learn lessons from the incident. He says: "There have been a number of lessons for us and others to absorb and correct, and we have made – and will continue to make – every effort to ensure that such a tragic accident cannot occur again."
Source: FlightGlobal.com
