The cable harness branches assembled in aircrafts can be separated by fix points into a number of cable harnesses between the adjacent fix points. One kind of these cable harnesses between the adjacent fix points, which has the assembly feature: one fix point being a mechanical protection and the other fix point being electrical connector, is defined as the end cable harness between the adjacent fix points(''the end cable harness'' for short) in this paper. The principle of determining the lengths of cable harness branches in prototype was revealed, it is proposed that the unit lengths of determining cable harness branches in prototype are lengths of cable harnesses between the adjacent fix points. And the process for assembly workers to determine the length of one cable harness between the adjacent fix points was abstracted as a kind of iterative approach in which its length was determined by justifying whether the process geometrical requirement and the process clearance requirement could be met or not under a given possible lengths. On the basis of that, the length model of the end cable harness was developed to calculate its maximum and minimum length values in the computer platform. To solve the model, the preliminary geometry model for this kind of cable harness was proposed by 6R robot arms, in which the end cable harness’s stiffness could be simulated by adjusting the ratio of lengths of the six rods. Then based on the minimum curve energy method, the refined geometric model was proposed where the center line of the main body of the preliminary geometry was refined to an arc with common end points and same length, the gap detecting precision was improved. Finally, the length model of the end cable harness was programmed in VR environment and the calculating result of an entire example was verified by experiments.
