readers' stories
Carbon s r a e f e r fib by Martin Hone
A
RECENT tragedy involving an RV-6 at Gatton Airpark has re-enforced the tragic consequences of getting it wrong at low level, but also highlighted some unintended consequences of builder modifications and use of high tech materials. Not only did we lose a good friend and neighbour and our beloved Harvey, the RV-6, but the subsequent clean up raised serious issues of which most, if not all, builders will be unaware. Unusually for a case like this, the Australian Transport Safety Bureau (ATSB) became involved and, as the builder of the aircraft, I was contacted and asked if the aircraft carried any oxygen cylinders or carbon fibre components. My answer at the time was “No, it was a regular VFR Vans RV-6”. With that, the ATSB conducted its investigation, which involved speaking to witnesses and inspecting the damage. It was about a week later, after the police had released the wreck back to the family for disposal, that I happened to mention to one of the ATSB officers that there had, in fact, been a small amount of carbon fibre, because of a recent modification. During an Annual Inspection, I had reinforced my original aluminium cooling plenum design with a single layer of carbon cloth and added an expansion joint to prevent cracks in the top plate. With that admission, the ATSB became very concerned about possible contamination and, as a consequence, the Environmental Protection Agency became involved. What should have been a simple trip to the tip suddenly became Chernobyl. The problem? It seems that carbon fibre, once damaged in a high impact crash and burned in a post-crash fire, develops similar properties to asbestos - and we all know what that means. I contacted the SAAA TC network and was given information concerning the problems of carbon fibre - all of it news to me and, I dare say, to most of RA-Aus members. Links to investigations conducted by the US FAA and DOT showed that these bodies are very much concerned with the health hazards posed to fire fighters, investigators and clean-up personnel following the extensive use of carbon fibre composites in the Airbus and Boeing commercial transports. “The potential health risks associated with fires involving fibre-reinforced polymer composites include the fibrous dust and airborne particles released during burning which can be
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Carbon fibre, once damaged in a high impact crash and burned in a post-crash fire, develops similar properties to asbestos inhaled and deposited in the deep lung region and the sharp fibre fragments which can penetrate the skin. As the organic resin burns off, the continuous, reinforcing fibres are exposed to a turbulent, oxidising environment which causes them to break up and erode into small micro fibre fragments. The concentration of respirable airborne micro fibres increases when the accident involves fire and impact or explosion. In addition, the toxic chemicals produced from the combustion of the organic resin may be ad-
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sorbed on respirable fibres and enter the respiratory system with acute or chronic effects.” The fear is that the fibres are in the same range of size and shape as those of asbestos. None of the reports I have read produced a definitive assessment of the dangers, but the US Navy, NTSB, FAA and Britain’s RAF have all adopted guidelines which include wearing self-contained breathing apparatus and full body suits when dealing with crashes to minimise exposure. The obvious question for us is - what about