Summary
We propose to adopt a new airworthiness directive (AD) for all Fokker Services B.V. Model F28 Mark 0070 and 0100 airplanes. This proposed AD was prompted by reports that debris from the parking brake shut off valve (PBSOV) could create a partial blockage of the restrictor check valve in the hydraulic return line of the PBSOV. This proposed AD would require replacing the restrictor check valve with an improved valve that has a filter screen. We are proposing this AD to address the unsafe condition on these products.