GENERAL REQUIREMENTS

INSULATION GAP

The insulation gap (referenced from the first point of contact of the conductor to the terminal) shall be less than two (2) wire diameters, but shall not be imbedded in the solder joint. The wire contour shall be visible at the end of the insulation.

NASA-STD-8739.3 [9.1.1], [9.1.2]

GENERAL REQUIREMENTS

INSULATION GAP (SPECIAL EXCEPTION)

When characteristic impedence or other circuit parameters may be affected (i.e. high-voltage, high-frequency terminations, etc.), the insulation clearance requirements may be modified. All variations shall be documented.

NASA-STD-8739.3 [9.1.4]

GENERAL REQUIREMENTS

INSULATION GAP
MULTIPLE TERMINATIONS

Conductor insulation clearances are not required to be equal for applications involving the termination of multiple (common) conductors to a terminal in parallel orientation.

NASA-STD-8739.3 [9.1.3]

UNACCEPTABLE

IMPROPER INSULATION GAP (C)

The insulation gap (referenced from the first point of contact of the conductor to the terminal) is greater than two (2) wire diameters. Excessive insulation gap may present a birdcaging or shorting risk.

NASA-STD-8739.3 [13.6.2.a.2]

GENERAL REQUIREMENTS

INSULATION SLEEVING

Sleeving shall completely cover and fit snugly around the terminal and the wire insulation and overlap the wire insulation by a minimum of 5 mm (0.20 in.), or two (2) insulated wire diameters, whichever is larger.

NASA-STD-8739.3 [9.8]

UNACCEPTABLE

IMPROPER INSULATION SLEEVING

The sleeving shall not be pierced, split, charred or otherwise damaged, and shall completely cover the terminal and overlap the wire insulation. The sleeving shall fit snugly around the terminal and the wire insulation.

NASA-STD-8739.3 [9.8]

GENERAL REQUIREMENTS

TERMINAL FILL

Conductors shall be in full contact with the terminal and each other. They shall be mounted as close to the base as allowed by the insulation or body shape and not wrapped onto each other or extend beyond the top of the terminal.

NASA-STD-8739.3 [9.1.9]

UNACCEPTABLE

EXCESSIVE CONDUCTOR FILL

The number of conductors shall not exceed the capacity of the terminal post. Conductors shall not extend above the top of the terminal post.

Best Workmanship Practice

GENERAL REQUIREMENTS

SERVICE LOOPS/STRESS RELIEF

Wire/harness terminations shall exhibit an even distribution of conductor dress and tension throughout the cable and harness, to prevent stress to the terminations.

NASA-STD-8739.3 [9.1.5], [9.1.7], [13.6.1.h]
NASA-STD-8739.4 [4.3.5.c], [19.6.1.e.3]

UNACCEPTABLE

INSUFFICIENT SERVICE LOOP

The termination exhibits an uneven dress length of individual conductors, which may result in a concentration of stress on a single conductor.

NASA-STD-8739.3 [13.6.2.a.10], [13.6.2.a.17]
NASA-STD-8739.4 [4.3.5.c]

GENERAL REQUIREMENTS

WRAP ORIENTATION

Conductors may be wrapped clockwise (CW) or counterclockwise (CCW) to the terminal, but the curvature of dress shall be such that the wrap will tighten against the terminal if the conductor is pulled.

NASA-STD-8739.3 [9.1.8]

UNACCEPTABLE

IMPROPER WRAP ORIENTATION

The conductor's curvature and direction of dress are improper, and the wrap will loosen against the terminal if the conductor is pulled. This will eventually weaken the solder joint.

NASA-STD-8739.3 [13.6.2.a.10]

PREFERRED

BIFURCATED TERMINALS

Conductors shall enter the slot, perpendicular to the posts, and make positive contact with at least one post corner. Wires shall be placed in ascending order, with largest on the bottom, and wrap directions shall alternate.

NASA-STD-8739.3 [9.3.2]

PREFERRED

BIFURCATED TERMINALS
SOLDERED ASSEMBLY

The lead profile is discernable, with wire and terminal interface completely wetted. The solder is smooth and shiny, and fillets the entire wire/lead and terminal interface.

NASA-STD-8739.3 [10.2.2], [13.6.1]

ACCEPTABLE

BIFURCATED TERMINALS
BOTTOM ROUTE

The uninsulated conductor end shall enter the terminal from the bottom, be brought through one of the side slots at the top, and wrapped as required for a side route termination.

NASA-STD-8739.3 [9.3.3]

ACCEPTABLE

BIFURCATED TERMINALS
STRAIGHT-THROUGH TERMINATION

Single conductors may be terminated straight-through, providing the conductor is in contact with the base, exhibits proper insulation clearance, and has no end overhang.

NASA-STD-8739.3 [9.3.2]

ACCEPTABLE

BIFURCATED TERMINALS
TOP TERMINATION

The conductor is in contact with both posts. Any space between the posts has been filled with filler wire or by doubling. Top termination is not recommended for flight hardware.

UNACCEPTABLE

BIFURCATED TERMINALS
TOP ENTRY-PARTIAL FILL

The top route termination has unfilled space between the posts and the conductor, and no filler wire or doubling has been used to fill the gap.

Best Workmanship Practice

ACCEPTABLE

BIFURCATED TERMINALS
WRAP DIRECTION

When multiple conductors are connected to a terminal, the direction of bend of each additional conductor shall alternate and the termination shall alternate posts.

NASA-STD-8739.3 [9.3.2]

UNACCEPTABLE

BIFURCATED TERMINALS
END TAIL OVERHANG

The end tail shall not extend beyond the diameter of the terminal base, except when physical clearance is adequate. End tail overhang may violate minimum electrical clearance.

NASA-STD-8739.3 [9.3], [13.6.2.a.10]

PREFERRED

HOOK TERMINALS

The conductor is wrapped in full contact with the terminal for a minimum of 180 º and a maximum of 270º, and is attached to the hook within the 180º arc. Insulation clearance is less than one (1) wire diameter, and wire end does not protrude.

NASA-STD-8739.3 [9.1], [9.4]

PREFERRED

HOOK TERMINALS
COMPLETED ASSEMBLY

The lead profile is discernable, with wire and terminal interface completely wetted. The solder is smooth and shiny, and fillets the entire wire/lead and terminal interface.

NASA-STD-8739.3 [13.6.1]

ACCEPTABLE

HOOK TERMINALS-WRAP LOCATIONS

The conductor(s) are wrapped in full contact for a minimum of 180º. Wraps alternate direction and do not overlap. Terminations are located more than one wire diameter from hook end, with majority located within the 180º arc (hook).

NASA-STD-8739.3 [9.4]

UNACCEPTABLE

HOOK TERMINALS
IMPROPER WRAP LOCATION

The termination is not located in the 180º arc of the terminal, with the wrap located less than one wire diameter from the hook end.

NASA-STD-8739.3 [9.4], [13.6.2.a.10]

PREFERRED

PIERCED/PERFORATED TERMINAL

The wire passes through the eye of the terminal, is wrapped in contact with both sides of the terminal, and does not overhang the terminal edge. Insulation clearance is less than 1 wire diameter.

NASA-STD-8739.3 [9.5]

PREFERRED

PIERCED/PERFORATED TERMINAL
SOLDERED ASSEMBLY

The lead profile is discernable, with wire and terminal interface completely wetted. The solder is smooth and shiny, and fillets the entire wire/lead and terminal interface.

NASA-STD-8739.3 [13.6.1]

ACCEPTABLE

PIERCED/PERFORATED TERMINAL
SIDE ENTRY

The wire passes through the terminal eye, and exhibits a quarter turn (90º) wrap in contact with the terminal face. Termination exhibits proper insulation clearance (C).

NASA-STD-8739.3 [9.5]

ACCEPTABLE

PIERCED/PERFORATED TERMINAL
ZIG-ZAG TERMINATION

The wire passes through the terminal eye and exhibits two (2) quarter turn (90º) zig-zag wraps in contact with both terminal sides. Termination exhibits proper insulation clearance (C).

NASA-STD-8739.3 [9.5]

UNACCEPTABLE

PIERCED/PERFORATED TERMINAL
SIDE ENTRY

The wire passes through the terminal eye, but exhibits a wrap that is less than 90º and which is not in contact with the terminal face.

NASA-STD-8739.3 [9.5], [13.6.2.a.10]

UNACCEPTABLE

PIERCED/PERFORATED TERMINAL
SIDE ENTRY

The wire passes through the terminal eye, and exhibits a quarter turn (90º) wrap in contact with the terminal face, extending over the terminal edge.

NASA-STD-8739.3 [9.5], [13.6.2.a.10]

PREFERRED

TURRET TERMINAL

The conductors are parallel to each other and to the mounting base. Conductors are mechanically secure, wrapped a minimum of 180º to 360º, non-overlapping, with the first conductor in contact with the terminal base.

NASA-STD-8739.3 [9.2]

PREFERRED

TURRET TERMINAL
SOLDERED ASSEMBLY

The lead profile is discernable, with wire and terminal interface completely wetted. The solder is smooth and shiny and fillets the entire wire/lead and terminal interface.

NASA-STD-8739.3 [10.2.2], [13.6.1.]

ACCEPTABLE

TURRET TERMINAL

Conductors have been mechanically secured to the terminal with a minimum of 180º wraps. Multiple conductors may be installed in a single slot, if wrapped to the post without overlap.

NASA-STD-8739.3 [9.2.1]

ACCEPTABLE

TURRET TERMINALS
BOTTOM ROUTE

The uninsulated conductor end shall enter the terminal from the bottom, be brought through the side slot at the top, and wrapped as required for a side route termination.

NASA-STD-8739.3 [9.2.2]

MANDATORY

TURRET TERMINAL WRAP
CONDUCTOR SIZES<AWG 26

Conductor sizes AWG 26 and smaller shall be wrapped a minimum of 1/2 turn (180°), but less than one (1) full turn (360°) around the post.

NASA-STD-8739.3 [9.2.1.b]

MANDATORY

TURRET TERMINAL WRAP
CONDUCTOR SIZES > AWG 26

Conductor sizes larger than AWG 26 shall be wrapped a minimum of 1/2 turn (180°), to a maximum of 3/4 turn (270°) around the post.

NASA-STD-8739.3 [9.2.1.a]

UNACCEPTABLE

TURRET TERMINALS
IMPROPER WRAP

Conductors and part leads shall be mounted as close to the terminal base, as allowed by the insulation or body shape, and shall be in full contact with the terminal and each other.

NASA-STD-8739.3 [9.1], [13.6.2.a.10]

UNACCEPTABLE

TURRET TERMINALS
TOP MOUNTING

Components shall be mounted parallel and in contact with the mounting surface, unless specified otherwise in the engineering documentation.

NASA-STD-8739.3 [8.3.1], [13.6.2.a.5]

SPECIAL APPLICATIONS

CONTINUOUS RUN CONNECTIONS
BIFURCATED TERMINALS

The wire shall pass between each set of terminal posts, contact each terminal base, and exhibit stress relief. The wire ends shall be attached to the first and last terminal with a 90° to 180° wrap.

NASA-STD-8739.3 [9.3.4]

SPECIAL APPLICATIONS

PIGGYBACKED/STACKED COMPONENTS

Multiple discrete components may be terminated in a piggybacked/stacked configuration, with the largest component mounted parallel to and in contact with the mounting surface. All components shall be stress-relieved and staked.

Best Workmanship Practice

SPECIAL APPLICATIONS

CONTINUOUS RUN CONNECTIONS
PIERCED/PERFORATED TERMINALS

The wire shall pass through each terminal eye, contacting both sides of each terminal, exhibit stress relief, and shall be terminated to the first and last terminal with a 90° to 180° wrap.

Best Workmanship Practice

UNACCEPTABLE

CONTINUOUS RUN CONNECTIONS
PIERCED/PERFORATED TERMINALS

The wire passes through each terminal eye, but does not contact both sides of each terminal.

Best Workmanship Practice

SPECIAL APPLICATIONS

CONTINUOUS RUN CONNECTIONS
TURRET TERMINALS

The wire shall wrap around each terminal, contact each terminal base, exhibit stress relief, and be terminated to the first and last terminal with a 180° to 270° wrap (depending on wire gauge).

NASA-STD-8739.3 [9.2.3]

UNACCEPTABLE

CONTINUOUS RUN CONNECTIONS
TURRET TERMINALS

The wire does not wrap 360° around each inner terminal or exhibit sufficient stress relief.

NASA-STD-8739.3 [9.2.3]