Summary
The FAA is revising an earlier NPRM for an airworthiness directive (AD) that applies to all Short Brothers Model SD3 airplanes. The original NPRM would have required installing additional fuel tank bonding jumpers, performing an in-place resistance check of the float switches, inspecting certain internal components of the fuel tanks, and performing related corrective actions if necessary. The original NPRM would have also required revisions to the Airworthiness Limitations section of the Instructions for Continued Airworthiness, and to the airplane flight manual procedures for operation during icing conditions and fuel system failures. The original NPRM resulted from fuel system reviews conducted by the manufacturer. This action revises the original NPRM by adding service information. We are proposing this supplemental NPRM to prevent ignition sources inside the fuel tanks, which could lead to fire or explosion.