Read part one, "Concorde engineers share supersonic stories 50 years after first flight".
A fatal day in Paris
When flight AF4590 crashed shortly after take-off from Charles de Gaulle Airport on 25 July 2000, killing all passengers and crew on-board and several people on the ground, the immediate thought was that it had been caused by a thrust reverser bucket accidentally deploying.
Schulkins says: “BA and Air France were aware of the catastrophic consequences should one deploy during take-off and they had tried to simulate handling the event over the years. Up until the accident, the problem had only occurred in-flight once and during an engine ground run on another occasion.”
The reality, though, was that the accident had been caused by foreign object damage to a tyre, which then exploded, puncturing a wing fuel tank. However, Schulkins believes that the accident helped to shine the spotlight on his employer’s findings even more brightly.
“As part of the non-advocate review, our reliability engineers used fault-tree analysis (FTA) to reanalyse the same systems that Rolls-Royce had analysed with failure modes, effects and criticality analysis (FMECA) in the 1960s,” he says.
“FTA confirmed what had been missed by FMECA. In my own opinion, the thrust reverser system needed to be redesigned to make the aircraft safe, and I assume that our engineers confirmed this and that BA and Air France used this knowledge to inform their final decision to take the aircraft out of service after the accident.
“The aircraft’s mystique was preserved in its final months in service and it was retired with great grace, but there were strong technical reasons why it couldn’t continue,” says Schulkins.
Event that shaped a career
Around the time of the AF4590 crash, Chris Elliott was working on a modification to Concorde’s cold air unit. The cabin air hardware was no different from that in any other contemporary aircraft.
“Smoke detectors fitted to Concorde’s toilets were suffering from false alarms – something that was not being experienced in other aircraft. This problem was traced to atomised oil droplets from the cold air unit, one of the few places where oil can contaminate the cabin air,” explains Elliott. “The rate of oil contamination was imperceptibly low, but turbine oil is nasty – teratogenic, carcinogenic and neurotoxic – and the false alarms were a nuisance.”
The fix required was pretty simple: the oil seals were spring-loaded onto the shafts and Elliott simply increased the spring loading. But what was simple turned out to have an enormous influence on his career.
“The fix hadn’t been deployed for long, and the replacement oil seals were being introduced, when I remember late one working day hearing the terrible news of the AF4590 crash going around the office. I was less than 10 years into my engineering career and had this dreaded feeling that somehow I had missed a detail which had led to the accident,” recalls Elliott.
“It was utterly unrelated to my little fix, of course, but the memory of that feeling has stayed with me and shaped the thoroughness with which I approach each job and which I believe is necessary when engineering a product,” he adds. “I still work in the aerospace industry, and, while having a reputation for calculated risk-taking, I also engage in gate-keeping activities to prevent avoidable mistakes.”
The regrets
Engineers working on various parts of Concorde over the years were dedicated and meticulous, yet they often didn’t get to experience the very feat of engineering they helped to shape and power.
One of Murray’s biggest regrets is not having had the chance to travel on the aircraft.
“I actually missed out on two free flights in one week. The first was a test flight to investigate a rubber vibration, but this ended up being scheduled for a Saturday when my wife and I were going away as an anniversary celebration,” he recalls. “That same week, our chief engineer told me that BA had given BAE six free, all-inclusive, return flights to New York as a ‘thank you’ for keeping the fleet going during the rubber repair programme. But since he thought I was going on the aforementioned test flight, I missed out.”
Political sensitivity
On 24 October 2003, a BA flight from New York arrived at Heathrow with a 5,000-strong crowd watching on, as Concorde touched down on a commercial flight for the very last time. More than 15 years on from the aircraft being retired from the skies and it’s still considered a sore point.
Schulkins says: “It was a highly political subject right until the end. BA was sensitive when it came to its relationship with Air France. Neither airline wanted to be seen to be the one to stop flying Concorde first.”
So sensitive was the nature of the Concorde project that many working on it over the years are still, technically, bound by confidentiality agreements and are only able to disclose so much information. This includes Schulkins himself.
“Looking back,” he says, “I don’t know why it was called a non-advocate review – I had never been involved in one before and haven’t since. At the end of our review we had all our documents collected up and taken away and IT files were deleted.”
The return of supersonic flights
In recent years, the question has been asked: will supersonic travel soar again?
“When it comes down to the figures, they just don’t add up right now. Only the very rich could justify the expense – and that’s why any existing projects we hear or read about are looking at building supersonic business jets,” says Schulkins. Ticket prices for Concorde’s final flight were £4,350 for a one-way trip and £8,292 for a return.
Another issue is that, given the engineering and mechanical problems Concorde faced over the years, there would no doubt be safety challenges, argues Elliott. There would also be technical challenges to overcome.
“Another issue is making the sonic boom disappear to allow aircraft to operate over land, so that it doesn’t cause structural damage,” says Schulkins. “The cost of this work is holding up current developments, but, if engineers can reduce the boom to a relatively quiet thud, then, in theory, supersonic passenger travel could return.”
Part three of our feature Remembering Concorde, on a potential supersonic comeback, will be published on Friday (1 March).
Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.