Air Transport

US regulators are proposing to expand an airworthiness directive for Bombardier CRJ100/200s to reduce the risk of flap failure, after finding the original directive was ineffective in addressing the problem.

The original US Federal Aviation Administration directive, issued in January last year, was intended to deal with stuck-flap incidents in cold-weather operations. It required pressure tests of drive shafts in the flap mechanism and torque tests on flap actuators.

But the FAA is proposing a new directive to supersede the earlier one, and is calling for comments by 20 January.

"Since we issued [the original directive] we received a report that it was not effective in reducing the number of flap failures [on CRJs]," it says.

The new FAA directive will be largely in line with one issued by Canada's civil aviation authority on 18 August. It will retain the requirements of the previous directive, but add several corrective actions, including checking, repairing or replacing flap components after a flap failure and installing cockpit placards specifying new flap operating limitations. It also allows installation of modified flap actuators.

The directive requires revising the aircraft flight manual with a temporary revision clarifying maximum flaps extended speeds and incorporating maximum flap operating speed data. It also modifies operational limitations and requirements for zero-flap landing simulator training.

Meanwhile, two CRJ left main landing gear failures in December are being investigated by the US National Transportation Safety Board. The incidents, that left the aircraft damaged but did not cause any injuries, involved an Air Wisconsin CRJ200 that landed with its left main gear retracted at Philadelphia International airport and a Mesa Airlines CRJ700 that suffered a left main gear collapse on roll-out after landing at Chicago O'Hare.