Airworthiness Directives; Airbus Airplanes

We propose to adopt a new airworthiness directive (AD) for all Airbus Model A300 series airplanes, Model A300 B4-600, B4-600R, and F4- 600R series airplanes, and Model A300 C4-605R Variant F airplanes (collectively called Model A300-600 series airplanes), and Model A310 series airplanes. This proposed AD was prompted by a report of yellow hydraulic system failure, including both braking accumulators, due to failure of the parking brake operated valve (PBOV). This proposed AD would require replacement of a certain PBOV with a different PBOV. We are proposing this AD to address the unsafe condition on these products.