Loop Back Method

The Loop Back Method is a hybrid of the various IFD methods.  From the IFD-Alpha Method, lets assume, for example, that all of node 1 is not interconnected within the UUT, and also some of the test points on node 1 are at the extremities of the UUT ie on the tail plane of a large aircraft.  In the schematic shown below, it can be seen that some of the test points on node 1 have been forced to be interconnected by a shorting link of some kind (shown in Orange on the left).  Without these loop backs, the connections at what are shown as loop backs, on the left, would need dedicated test points and cable runs, as shown in Orange on the right.  This would increase the test point count, node count and make the ITA more complex.  However, the method shown without the Loop Backs, provides better flexibility for isolating faults; it is a compromise based on test point count, length of cables, compex ITA, and the testing methods needed to isolate the fault.

 

 

Using Loop Backs may restrict the ability for isolating faults to a specific test point.  Therefore, it might be possible to create difference loop back configurations, to allow in-depth diagnostics.