A Nimrod spy plane which crashed in Afghanistan, killing 14 British servicemen, had a serious design flaw, an inquest heard yesterday.
A senior engineer from BAE Systems, the British defence and aerospace firm, said his predecessors, who made the Nimrod some 40 years ago, also failed to fit a fire protection system on a key area of risk on the aircraft.
Nimrod XV230, a 37-year-old aircraft, exploded in mid-air near Kandahar on September 2, 2006, shortly after undergoing air-to-air refuelling.
The tragedy is believed to have been caused by fuel leaking in one of the plane's dry bays, then igniting on contact with a hot air pipe, the inquest into the deaths has heard.
The hearing in Oxford was told yesterday that a section of hot air pipe in XV230's dry bay seven was not lagged to protect it from igniting fuel in the event of a leak from a fuel pipe below it.
Although the hot air pipe is insulated in most parts of the aircraft, it remains uncovered in dry bay seven.
Andrew Walker, the coroner, said: "What we have here amounts to a serious design flaw, because we could have a single point failure (where just one fault could cause a serious problem)."
Martin Breakell, BAE's chief Nimrod engineer, agreed, although he stressed that this scenario would be unlikely.
Mr Breakell, casting his mind back 40 years to the engineer's decision not to lag this section of pipe, added: "Why did he leave it off? What was going through his mind at the time?"
Michael Rawlinson, for 13 of the 14 families, asked why, as a potential fire zone, dry bay seven did not have any fire suppressant system fitted.
Mr Breakell, asked by the coroner if he considered this to be a serious failure, said: "It is a serious failure."
Tom McMichael, head of airworthiness at BAE's Military Air Solutions, said that if the evidence was correct, the Nimrods had, at the time of the tragedy, been flying in an unairworthy state for 37 years.
Mr McMichael said because dry bay seven was potentially a single-point failure area, it should have been fitted with a fire-suppressant system. The fact that it was not meant the aircraft should never have been passed fit to fly, he said.
Mr Walker, pondering on the decisions of those who passed the Nimrod airworthy four decades ago, asked: "Was it not a serious possibility that no-one recognised the risks associated with this aircraft?"
"It is a possibility," replied Mr McMichael.
An "acceptance conference", to decide the Nimrod's airworthiness, took place in August 1968 and it was declared fit to fly.
The coroner said: "So, at the end of the acceptance conference, on the evidence as it stands, this aircraft was not airworthy."
The inquest continues.