Action
Final rule.
Summary
We are adopting a new airworthiness directive (AD) for all Fokker Services B.V. Model F.28 Mark 1000, 2000, 3000, and 4000 airplanes. This AD was prompted by a design review that revealed insufficient measures were taken to ensure the correct locking of the attachments of the fuel quantity tank units (FQTUs) in each wing tank. When an FQTU becomes loose, this could lead to insufficient clearance between the FQTU and the adjacent tank structure or other metal parts, and under certain conditions, create an ignition source inside the wing fuel vapor space. This AD requires modifying the FQTUs by applying sealant to cover the nuts, washers, and stud ends at the FQTU attachments in each main wing tank. This AD also requires revising the maintenance or inspection program, as applicable, by incorporating a fuel airworthiness limitation item and a critical design configuration control limitation (CDCCL). We are issuing this AD to prevent an ignition source in the wing fuel tank vapor space, which could result in a wing fuel tank explosion and consequent loss of the airplane.