A final airworthiness directive (AD) to be issued by the US Federal Aviation Administration on 31 January targets wiring issues that could potentially cause the failure of ice protection systems on the Bombardier Q400.
Within 400 flight hours or 60 days of the mid-February activation date of the AD, US operators of Q400s will be required to inspect certain alternating current (AC) power wire bundles for damage, making repairs if needed, and segregating the wire bundle into two separate bundles with Teflon tubing.
The FAA said the AD, initially issued by Transport Canada on 20 December, was prompted by multiple reports of the loss of certain alternating current (AC) systems and the tripping of associated circuit breakers. The failure was caused by burned AC power wire bundles, the FAA said.
"All AC systems and AC generators could be affected by damage to this AC power wire bundle resulting in the loss of ice protection systems for the angle of attack vanes, pitot probes, engine inlets or windshields," said the FAA in the AD. "In icing conditions, the loss of the ice protection systems could affect continued safe flight."
The FAA accelerated the activation time for the inspections from the 600 flight hours and 90 days as mandated by Transport Canada in December.
"In developing an appropriate compliance time for this AD, we considered the degree of urgency associated with addressing the unsafe condition, the upcoming inclement weather conditions, and the maximum interval of time allowable for all affected airplanes to continue to operate without compromising safety," the agency said.