The F-16 contains many multiplex or mux panels. Mux panels contain multiplex transformers that are either enclosed in a sheet metal box or are mounted to a sheet metal plate. The mux transformers transmit digital avionic signals for the navigation, flight control, and weapons systems. Similar to any aircraft part, there comes a time when mux panels should be repaired or replaced.
Reason Number 1: Intermittent Problems in an Avionic System
Many of the mux panels that arrive for repair have intermittent problems. Intermittent problems are either listed as a cause for the repair by the customer or can be found by shaking the panel during testing. These problems are caused by one of the following reasons: (1) bad solder joints where mux transformers are attached electrically to the wiring in the panel, (2) winding issues inside the actual mux transformers, and (3) corrosion and moisture inside the mux panel. In most cases, the best and faster fix is to replace the mux transformers and the wiring inside the panel. The good news is that in most cases the sheet metal does not need to be replaced.
Reason Number 2: Wing Modifications
For the past seven years, InterConnect has seen a large increase in the F-16 community to replace or repair the wings. During this time, many users have decided to replace the wiring harnesses in the leading edge of the wing. Typically there are 13 wiring harnesses in each wing. Since the wiring harnesses are being replaced with new ones, it is a good time to replace the mux transformers and the wiring inside the 3 mux panels located in each wing. By doing this repair each wing is basically brought back to a new condition electrically.
Reason Number 3: Degradation of Digital Signals
Besides intermittent problems, at times, digital signals start to degrade in the wire run. The purpose of mux transformers is to amplify the signals throughout the whole circuit. One of the possible reasons for degradation of the signal can be problems within the mux transformers. In order to fix this problem, mux transformers are replaced throughout the whole circuit.
Reason Number 4: Age of the Aircraft
The final reason to replace F-16 mux panels is simply due to the age of the aircraft. Many F-16’s have been flying for over 20 years. During this time the mux panels have been subjected to moisture, temperature, vibration, and high G extremes. This type of environment can lead to many of the issues discussed above. At some point, mux transformers should be replaced due to the environmental conditions where they operate. The mux panels that are repaired more often than other are the left and right strake and wing leading edge mux panels. A good rule of thumb is to replace at least the mux transformers and wiring inside mux panels once the aircraft is 20 years or older.
In summary, F-16 mux panels are extremely important to the successful operation of the avionic systems throughout the aircraft. Failure to replace mux transformers can eventually lead to intermittent and problematic problems in the aircraft. The best and only solution is to replace the mux transformers and wiring inside mux panels.
By: John Ashour
