AIRLINES are to be forced to introduce a raft of new checks on their older aircraft to ensure they are free of potentially dangerous faults. But individual aircraft manufacturers will be left to decide what those checks should be, and critics warn they will not be frequent enough.
A ruling from the US Federal Aviation Administration (FAA) that comes into force in March 2003 will require extensive extra checks to be made on all American airliners over 14 years old. A similar ruling is being considered by the Joint Aviation Authorities, the umbrella body that coordinates air safety across 36 European countries.
The US Congress instructed the FAA to introduce extra checks on old planes some 11 years ago, when they passed the Aging Aircraft Safety Act. This followed a number of high-profile accidents involving ageing aircraft. In 1988, a 5-metre section of roof was torn off a 19-year-old Aloha Airlines plane while it was cruising at 24,000 feet. A flight attendant was killed but, miraculously, the plane was landed safely.
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According to the FAA鈥檚 own figures, more than 88,000 cracks were discovered on US airliners between 1991 and 2001. The cracks ranged from 5 millimetres long to more than half a metre. But finding cracks and other age-related faults can be a hit-and-miss affair because it often relies on simple visual inspections.
Airlines had expected the FAA to specify standard checks for detecting metal fatigue in ageing components and structures, and maintenance measures to combat corrosion damage. Instead, aircraft manufacturers have been left to come up with a list of checks themselves. These will then be passed on to airlines to act on. The plane makers will have four years to produce the new check lists from March 2003. Airlines will then have a year to implement them.
After its first round of checks, an ageing plane will not have to be re-checked for seven years. This is good news for airlines wanting to minimise the time aircraft must be taken out of service for checks. But critics believe the gap is too long because the likelihood of a crack causing an accident rises steadily with increasing age.
鈥淩epeat inspections should be sooner,鈥� says Gail Dunham, president of the National Air Disaster Alliance, a passenger safety lobby group. 鈥淎ccording to the FAA鈥檚 own projections, the danger of a fatigue-related accident goes up by an order of magnitude every ten years.鈥�
Others are dismayed that the ruling does not call for specific checks for wiring faults, which have led to numerous fires on older aircraft. Often, damaged insulation is to blame. 鈥淢ost of the problem is tied to what happens to wire insulation when it gets old and cracks,鈥� says Gary Slater, an aerospace engineer at the University of Cincinnati, Ohio, and a former member of the FAA鈥檚 Aging Transport Systems Rulemaking Advisory Committee, which advises the FAA on ageing-related engineering issues. Faulty insulation is believed to have caused a spark inside the fuel tank of TWA 800, a 25-year-old Boeing 747 that exploded off the coast of New York in 1996, killing 230 people.