Few surprises in US FAA's final CRJ flap AD

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US FAA officials as expected have issued a final airworthiness directive (AD) aimed at mitigating the number of Bombardier CRJ100/200 stuck flap incidents that have been linked to cold weather operations.

The regulator in October 2007 proposed amending an August AD on CRJ100/2000 flaps to include requirements that operators of the type in the USA provide simulator training covering reduced- or zero-flap landings for pilots, and perform several additional maintenance actions.

These actions called for a pressure test of the flexible drive shaft in the flap mechanism to check for leaks within two years or 4,000 flight hours after the AD was approved. They also called for operators to perform a low-temperature torque test of the flap actuator within two years of the AD.

In a final AD issued today and effective February 15, the FAA has retained the requirements of its original AD, and incorporated actions in its August notice of proposed rulemaking (NPRM).

It has also revised the AD to clarify that new or repaired actuators with 2,000 or fewer flight hours since the pinion seals were replaced are excluded from certain actions, following a request from Delta Air Lines regional subsidiary Comair.

The agency notes that one of the factors found to be contributing to the flap problem “is lack of training in operating an airplane when flap failure occurs in-flight, such as in freezing conditions”.

“Due to the unsafe condition, we determined that these training requirements, in conjunction with the other requirements of this AD, are necessary to safely operate the airplane; and you must comply with them if you are an operator,” it adds.

Bombardier recently told ATI that a newly redesigned flap system is about to be tabled for certification. The company has also engaged flap actuator manufacturer Eaton to work on additional modifications of the system.

The work with Eaton, which is scheduled to begin in February, will further enhance the system’s reliability, and is being done “in the spirit of continuous improvement”, says Bombardier.

The FAA notes that once this new seal is developed, approved, and available, it “might consider additional rulemaking”. However, operators may request an alternative method of compliance if the request includes data that prove that the new action would provide an acceptable level of safety.

Until then, maintenance actions outlined in the AD “are intended to mitigate the potential of flap failures utilizing the solutions that are currently available”, says the regulator.

The FAA estimates that the AD will affect 684 CRJ100/200 regional jets, and that it will take about 27 work-hours per aircraft to comply with the basic requirements of the directive. Based on an average labor rate of $80 per work-hour, the agency estimates the cost of the AD to the US operators to be nearly $1.5 million or $2,160 per regional jet.