. Protect personnel from the shock hazard resulting from equipment that experiences an internal power failure l Prevent the accumulation of static charges that could produce radio interference or be an explosion hazard due to periodic spark discharge BONDING FOR LIGHTNING PROTECTION Close-riveted skin construction that divides any lightning current over a number of rivets is considered adequately bonded to provide a lightning discharge current path. Control surfaces and flaps should have a bonding jumper across each hinge. To protect the control cables and levers, additional jumpers should be connected between the control surface and the structure. The length of a discharge path through the control system should be at least 10 times the length of the path of the jumper or jumpers. All external electrically isolated conducting objects (except antennas) should have a bonding jumper to the aircraft to ensure a low-impedance path. This is done so the voltage drop developed across the jumper system by the lightning discharge is minimized. The bonding jumpers must be kept as short as possible. When practical, a bonding jumper should not exceed 3 inches. ELECTROSTATIC DISCHARGE Learning Objective:   Recognize the hazards to electrostatic discharge-sensitive devices, to include proper handling and packaging techniques. The sensitivity of electronic devices and components to electrostatic discharge (ESD) has recently become clear through use, testing, and failure analysis. The construction and design features of current microtechnology have resulted in devices being destroyed or damaged by ESD voltages as low as 20 volts. The trend in this technology is toward greater complexity, increased packaging density, and thinner dielectrics between active elements. This trend will result in devices even more sensitive to ESD. Various devices and components are susceptible to damage by electrostatic voltage levels commonly generated in production, test, operation, and by maintenance personnel. The devices and components include the following: . All microelectronic and most semiconductor devices, except various power diodes and transistors . Thick and thin film resistors, chips and hybrid devices, and crystals All subassemblies, assemblies, and equipment con- taining these components/devices without adequate protective circuitry are ESD sensitive (ESDS). You can protect ESDS items by implementing simple, low-cost ESD controls. Lack of imple- mentation has resulted in high repair costs, excessive equipment downtime, and reduced equipment effectiveness. The operational characteristics of a system may not normally show these failures. However, under internal built-in-test monitoring in a digital application, they become pronounced. For example, the system functions normally on the ground; but, when placed in an operational environment, a damaged PN junction might further degrade, causing its failure. Normal examination of these parts will not detect the damage unless you use a curve tracer to measure the signal rise and fall times, or check the parts for reverse leakage current. STATIC ELECTRICITY Static electricity is electrical energy at rest. Some substances readily give up electrons while others accumulate excessive electrons. When two substances are rubbed together, separated or flow relative to one another (such as gas or liquid over a solid), one substance becomes negatively charged and the other positively charged. An electrostatic field or lines of force emanate between a charged object to an object at a different electrostatic potential or ground. Objects entering this field will receive a charge by induction. The capacitance of the charged object relative to another object or ground also has an effect on the field. If the capacitance is reduced, there is an inverse linear increase in voltage, since the charge must be conserved. As the capacitance decreases, the voltage increases until a discharge occurs via an arc. 10-15