Boeing has stated that it is confident the rupture that tore a hole in the roof of a Southwest Airlines 737-300 would never occur on its 737-Next Generation aircraft it now produces.
Paul Richter, Boeing’s chief project engineer for the 737-300/400/500 models, said the design of the lap joint installed on all classic 737s models built between 1993 and 2000, where the 1-by-5-foot hole opened up due to fatigue cracks in the metal emanating from the fastener holes, or lap joints, was specific to these vintage aircraft.
The Federal Aviation Administration (FAA) is expected to issue an airworthiness directive that all airlines operating this vintage aircraft and type to immediately inspection their aircraft that have flown more than 30,000 take-off and landing cycles.
Richter said the lap joint that failed was an improved design, developed after Boeing determined that an earlier version of the lap joint could result in the cracking along the inside row of fastener holes.
Boeing had recommended that the improved lap joint’s fatigue performance would allow airline to delay any sort of inspection requirements until the fleet approached roughly 60,000 cycles. However the Southwest aircraft had flown only 40,000 cycles, which has led Boeing to declare that all aircraft that have clocked more than 35,000 cycles will have to be inspected within five days. The FAA will require repeat inspections every 500 cycles, also. For a low cost carrier, this could mean every three months – an expensive additional cost alongside rising fuel costs.
Meanwhile Southwest confirmed it had found cracks on two more 737-300s yesterday. Both are now out of service.