Summary
The FAA proposes to adopt a new airworthiness directive (AD) for Boeing Model 737-300, -400, and -500 series airplanes modified in accordance with STC ST00127BO. This proposed AD would require installation of bonding straps to the safe side harnesses of the digital transient suppression device of the fuel quantity indicating system. This proposed AD is prompted by the results of fuel system reviews conducted by the STC holder. We are proposing this AD to prevent unsafe levels of current or energy from entering the fuel tank, due to hot short faults or threat conditions associated with the safe side harness assembly, which could result in a fire or explosion of the fuel tank.