Posted on: 12 November 2010 by Mark Howells
The US Federal Aviation Administration (FAA) has finalised a rule designed to protect commercial aircraft from structural damage as they age.
The new rule – part of the FAA’s continuing effort to address aging aircraft issues – seeks to prevent “widespread fatigue damage” (WFD) by requiring aircraft manufacturers and certification applicants to establish a number of flight cycles or hours a plane can operate and be free from WFD without additional inspections for fatigue. Manufacturers have between 18 and 60 months to comply depending on the particular aircraft type.
Once manufacturers establish these limits, operators of affected aircraft must incorporate them into their maintenance programmes within 30 to 72 months, depending on the model of aircraft. After the limit is in the maintenance programme, operators cannot fly the aircraft beyond that point unless the FAA approves an extension of the limit.
“Safety is our highest priority. This rule provides a comprehensive approach to the problem of widespread fatigue in aging aircraft,” explained US transportation secretary Ray LaHood. “Requiring carriers to regularly inspect their aircraft for possible fatigue is essential to ensuring the highest levels of safety.”
“We’ve addressed the problem of aging aircraft with numerous targeted regulations and 100 airworthiness directives over the years,” noted FAA administrator Randy Babbitt. “This rule is a comprehensive solution to ensure the structural safety of today’s airliners and the aeroplanes of tomorrow.”
An aircraft’s metallic structures are stressed and can develop cracks when they experience repeated loads such as the pressurisation and depressurisation that happens on every flight. While airlines regularly inspect aircraft for cracks exceeding a certain size, WFD involves aircraft developing numerous tiny cracks, none of which would have raised concerns individually but which together run the risk of joining up and impairing the structural integrity of the plane.
The new regulation applies to airliners with a takeoff weight of 75,000 lb and heavier. It also applies to all transport designs certificated in the future. The affected models, totalling 4,198 US-registered aeroplanes, are listed in the rule.
The FAA is working closely with the European Aviation Safety Agency (EASA) and other national authorities to harmonise this rule with their regulations as much as possible. EASA is now developing rulemaking to address WFD, and the FAA participates in that process.