Collaboration increases war-fighter support

Chris Tatro (left), an electronics technician with the 523rd Electronics Maintenance Squadron Radio Frequency Shop, tests aircraft boxes for problems as Jeff Cummings (center), shop supervisor, and Sami Mansour, 523rd EMXS director, look on.
By Bill Orndorff
309th Maintenance Wing
November 24, 2010

Collaboration between the 416th Supply Chain Management Squadron, the 523rd Electronics Maintenance Squadron (Avionics) and two area businesses is saving the Air Force money and keeping F-16s flying.

The collaboration is solving intermittent problems with electronic component boxes that help control the aircraft.

"There are numerous boxes in the aircraft avionics suite referred to as Line Replaceable Units -- LRUs -- which contain printed circuit boards and other Shop Replaceable Units or SRUs," said Sami Mansour, 523 EMXS director. "Aging electronic LRU chassis often pose huge maintenance and cost challenges for aviation operations."

The boxes would sometimes malfunction in flight, even though they had tested as "good" or "no-fault-found" in electronics bench tests before and after being installed in the aircraft. Some aircraft boxes failed so often that they were labeled as a "bad actor," and were sitting on shelves. And since the problem couldn't be found, the boxes were left to be cannibalized, condemned or have parts swapped.

"The problem is similar to a 'check engine' light coming on in a car," Mansour said. "The certified mechanic is unable to find the cause, so he re-sets the light and sends you on your way. That could be an intermittent fault -- something, somewhere in the car stops working, if only for a few nanoseconds, but the mechanic couldn't duplicate the problem. An intermittent failure rarely synchronizes with the test time in conventional automated test equipment."

As aircraft age, some connections in the LRU chassis loosen or develop micro-cracks that cause intermittent faults under the vibration and temperature extremes of flight.

"We had a large number of boxes, I would say 70-plus that found their way into a holding cell where they were tested by the Air Force technicians," said Chris Tatro, 523rd Electronics Maintenance Squadron (Radio Frequency Shop) electronics technician. "They threw every part at them they could, they did everything to their best knowledge, trying to troubleshoot them and found it had nothing to do with them -- the box itself had those problems internally."

With $2 million in maintenance costs incurred annually on F-16 AN/APG-68 Radar Modular Low Power Radio Frequency (MLPRF) units --- including as much as $30,000 for replacement ribbon cables -- the 523rd and the 416th began looking for a solution.

In August 2006, at the request of the 416th, the F-16 Reduced Total Ownership Cost Office contracted with Total Quality Systems Inc., of Roy, to design and build two Intermittent Fault Detection and Isolation Systems.

Total Quality Systems had previously developed an IFDIS prototype with Universal Synaptics Corp., of Ogden, resulting in a temperature and vibration stimulus test system with Interface Test Adapters and testing profiles for MLPRF testing.

"The result of this type of testing is that intermittent events can readily be detected by the IFD," said Ken Anderson, vice president of sales and marketing for Universal Synaptics. "Our sensitive analog technology detects high speed (nanosecond) impedance changes."

After the Radio Frequency Shop and the manufacturer worked together to test the equipment and make revisions, and test some of the worst boxes in storage, Total Quality Systems and Universal Synaptics delivered the IFDIS to the 523rd in February 2009.

Located in Building 5 in an area the size of a large closet, the IFDIS includes a main computer to display the faults; an integrated neurological system, called a multimeter, that does a point to point test; a second computer that records and sends commands and controls through the environmental chamber; and the environmental chamber that uses temperature controls and vibrations to test the boxes.

"The machine replicates the environment -- the temperature and vibration, the vibration shock, the temperatures that the box goes through from 110 degrees on the tarmac in the desert to being 30,000 feet in the air," said Tatro, who operates the IFDIS along with Dave Brown. "The box is placed in the chamber and cables are attached to it. The computer does a diagnostic, similar to diagnostic machines that analyze car engines."

If every box-related test is made on the IFDIS, it takes about two hours.

"A printout labels everything that is wrong with the box and it also annotates the temperature and the environment that the fault was found in," Tatro said. "All that information is recorded and sent back to the technicians, who fix the problem according to what it takes to fix it, then run it on their machine or return it to us for further testing to see if the faults have been corrected."

Tatro considers the IFDIS a lifesaver for the Radio Frequency Shop.

"Before, technicians shotgunned the back and re-soldered every point, then tried to go through and find a better connection. They'd test it, and sometimes it didn't solve the problem at all," he said. "There was no real way of troubleshooting these boxes until the machine arrived. Now that we are testing the boxes and repairing them and sending them out, few are coming back. It's doing so well, it's almost putting itself out of business."

The shop is harvesting previously condemned boxes and is building a data base to determine cost savings and common problem sources.

"By early November, 171 MLPRF chassis have been tested, 131 of which had been considered un-repairable; 86 have been repaired and put back into service while the remaining IFDIS diagnosed LRUs are awaiting repair parts," Mansour said. "The value of an MLPRF is over $307,000 each, so the 86 already recovered and returned to service represents a return of over $26 million on the $2.2 million reduced total ownership cost investment.

"Collaboration has paid off for the war-fighter too. While diagnosing existing no-fault-found problems, the IFDIS caught developing problems -- early stage, extremely short intermittence, that was not yet causing a problem -- resulting in failure avoidance, and allowing the IFDIS to also function as a preventative maintenance tool."

As a result, mean operating time between depot repairs for IFDIS-tested units has increased from 315 hours to 731 hours, a significant increase in support to the war-fighter directly attributable to the proactive depot actions.

"The speed of detection is impressive, but also, the fact that this is not just product-specific to the F-16 MLPRF chassis is appealing," explains Bryan Steadman, Total Quality Systems program manager. "Essentially, anything that has complex wiring could have these intermittent issues, and an IFDIS can quickly identify, isolate and deliver the information to the technicians and that enables them to fix the problems."

The IFDIS can be adapted to study similar components on other aircraft.

"It's fun to operate and to run," Tatro said. "It gives me a sense of pride because it helps me help my fellow co-workers and tell them, 'You do this and it will be fixed.' There are some things that we just can't see and just can't do without this machine. It gives us X-ray vision in a sense."