"Tail Code Key” Parametric Testing for MIL-STD-1553B Bus"
“Tail Code Key” is a method of enhancing MIL-STD-1553B bus maintenance quality by means of performing real time parametric testing on the bus. If functional testing results with “go” and “no-go”, which could be scaled as grade 100 and grade 0, “Tail Code Key” is a parametric test that will deliver a grade somewhere between 0 and 100.
Three important benefits are gained from the detailed grade:
The ability to detect failures before they impact functionality.
Physical location of failure on the bus.
Detection of single failure events during flight.
“Tail Key Code” is a set of numbers that are measured during flight in real time, 50 times a second. These numbers serve as a code - quality code. The code varies as a direct result of the quality of the bus.
If the bus connectors or wires degrade over time and usage, the measured code would change. Technicians get an early warning for problems that should be fixed before they fail the bus.
If single failure events occur during flight from physical stress or temperature changes, these single events impact the code, thus escape the tolerated margins. These events are recorded for repair. These single events downgrade the avionics communication quality exactly when they are critically needed. Typically such failures would not be traceable when the mission is complete.
Once the mission is done, bus problems are very hard to debug and require special equipment to pinpoint the exact physical location of the problem. In many cases the location is not found because the test is performed on wheels in 1G and in room temperature. Analyzing a recorded key code unveils the location of the problem.
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