6.  Prevent accumulation of static charge. 1.  Bond or ground parts to the primary aircraft structure,  where practicable. 2.  Make bonding or grounding connections in such  a manner that no part of the aircraft structure is  weakened. 3.  Bond parts individually, if possible. 4.  Install bonding or grounding connections against  smooth, clean surfaces. 5.  Install bonding or grounding connections so that  vibration, expansion or contraction, or relative  movement in normal service does not break or loosen  the connection. 6.  Install bonding and grounding connections in  protected areas whenever possible. Figure 4-110.  Hardware combinations used in making bonding  connections. 4-63 jumpers carry a substantial amount of ground return current, the  current rating of the jumper should be adequate, and it should  be determined that a negligible voltage drop is produced. The use of solder to attach bonding jumpers should be avoided.  Tubular members should be bonded by means of clamps to  which the jumper is attached. The proper choice of clamp  material minimizes the probability of corrosion. When bonding  Electrolytic action can rapidly corrode a bonding connection  if suitable precautions are not observed. Aluminum alloy  jumpers are recommended for most cases; however, copper  jumpers can be used to bond together parts made of stainless  steel, cadmium-plated steel, copper, brass, or bronze. Where  contact between dissimilar metals cannot be avoided,  the choice of jumper and hardware should be such that  corrosion is minimized, and the part most likely to corrode  is the jumper or associated hardware. Parts A and B of  Figure 4-110  illustrate some proper hardware combinations  for making bonding connections. At locations where finishes  are removed, a protective finish should be applied to the  completed connection to prevent corrosion. To be sure a low resistance connection has been made,  nonconducting finishes, such as paint and anodizing films,  should be removed from the surface to be contacted by the  bonding terminal. Bonding jumpers should be kept as short as practicable, and  installed so that the resistance of each connection does not  exceed 0.003 ohm. The jumper should not interfere with  the operation of movable aircraft elements, such as surface  controls; normal movement of these elements should not  result in damage to the bonding jumper. The following general procedures and precautions are  recommended when making bonding or grounding connections. General Bonding and Grounding Procedures Cadmium plated steel locknut Cylindrical surface Aluminum washers Cadmium plated steel screw Cadmium plated steel lockwasher Copper terminal Clamp Cadmium plated steel locknut Cylindrical surface Aluminum washers Cadmium plated steel screw Cadmium plated steel lockwasher Copper terminal Clamp Cadmium plated locknut Aluminum alloy or corrosion-resisting steel conduit Aluminum washer Cadmium plated steel screw Cadmium plated steel lockwasher Aluminum washer Clamp Structure Aluminum washer A. Copper jumper connection to tubular structure B. Bonding conduit to structure C. Aluminum jumper connection to tubular structure