New rule designed to detect corrosion and cracking at early stage will affect most of US commercial fleet

The US Federal Aviation Administration has mandated age-related inspections for commercial aircraft that have been in scheduled service for 14 years or more. The new rule requires operators of aircraft with 10 or more seats to implement a damage tolerance-based supplemental structural inspection programme to detect corrosion and cracks at an early stage.

The FAA's ageing aircraft rule is planned to take effect in December 2003 and will affect most of the US commercial fleet, but will not apply to aircraft operated within Alaska. Complying with the new FAA inspections and maintenance record reviews is expected to cost operators $175 million.

There is "strong evidence" that cracks are not being detected during regular maintenance inspections, the FAA says. Justifying the rule, the agency says it is "taking a long time" for manufacturers of large transport aircraft to implement damage tolerance-based inspections voluntarily, and for small transport aircraft there are no provisions for inspections focused on cracks.

The timing of the first inspections depends on aircraft age at the time the rule takes effect. The first age-related check is required within four years of the effective date for aircraft in service more than 24 years, and within five years for those in service more than 14 years but less than 24. Aircraft less than 14 years old must be checked no later than five years after the start of their 15th year of service. Repetitive inspections are required every seven years for all three classes of aircraft. The average age of the US commercial fleet of more than 6,400 aircraft is 12 years.

The rule includes a provision that operators cannot keep aircraft in service for more than four years from the effective date unless they implement damage tolerance-based inspections. Any aircraft covered by the rule that has a design life goal established by the FAA becomes subject to the damage tolerance-based inspection requirement when it reaches that goal, and no later than December 2010. Operators of aircraft with nine or fewer seats will be able to use inspections that are based on service history.

Northwest Airlines plans to retain each of its 146 McDonnell Douglas DC-9s until they have accumulated 100,000 flight cycles, which will mean that only 20 will need to be retired by 2007. The airline's treasurer, Dan Mathews, says the airline plans to keep most of its DC-9s in service for another 15 years given the continuing "phenomenally" low levels of maintenance each aircraft requires.

Source: Flight International