A modern avionics system has thousands of internal and external circuit paths. These systems are subjected to hostile operating environments and will likely fail intermittently long before they fail permanently. Intermittence occurs randomly in time, place, amplitude and duration. Electromechanical devices go into a long and frustrating period of low-level intermittency as their mechanical tolerances change. It only takes one undetected and hence unrepaired intermittent circuit in an electronic box to cause it to randomly malfunction. The replacement of these assemblies is a major contributor to an annual intermittence faults cost of $2 Billion within the DoD. It is therefore very important that all intermittent circuits that are present in these boxes be detected, isolated and repaired. With the proper test equipment it is now possible to detect and repair these intermittent circuits. This virtual technology forum will provide examples of intermittence testing currently in use within the military Services, discuss the benefits and challenges of each, and talk about new technology being developed and demonstrated.
Intermittence Testing Agenda
1300-1309: Welcome and Overview – Greg Kilchenstein (OSD-MPP)
1309-1310: Administrative Notes – Debbie Lilu (NCMS)
1310-1335: Army Intermittence Testing – Tom Sullivan (160th SOAR)/CTMA
1335-1400: NAVAIR Intermittence Testing – Brett Gardner (COMFRC/FRC-SW)
1400-1425: USAF Intermittence Testing – Les Stone / Ken Anderson (Hill AFB)
1425-1450: MILPRF Overview – John Garrett (NAVAIR)
1450-1500: Wrap-up and JTEG Principals Comments
JTEG Forum Minutes
Event: On 27 October, 2015, the Joint Technology Exchange Group (JTEG), in coordination with the National Center for Manufacturing Sciences (NCMS), hosted a virtual forum on “Intermittence Testing”.
Purpose: The purpose of the forum was to provide information and exchange ideas on intermittence testing projects and techniques, the challenges, and the tools and processes being employed by DoD maintenance activities and supporting activities.
Welcome: Greg Kilchenstein (OSD-Maintenance), welcomed everyone to the forum and emphasized the importance of intermittence testing in identifying faults in systems where legacy test equipment is currently not capable of recognizing the faults. This is a big problem in the avionics community and has a significant readiness and financial impact. JTEG technology forums are held on the last Tuesday of each month and focus on a specific technological capability.
Administrative: This was an open forum. The presentations, along with questions and answers, were conducted through Defense Collaboration Services (DCS) and an audio line. Approximately 45 participants from across DoD and industry joined in the forum. Questions were sent through DCS and answered by the presenters during the forum.
Army Intermittence Testing – Thom Sullivan (160th SOAR(A)) provided a brief on “On-wing Wire Diagnostic Practices”. He described intermittent symptoms and the challenges in diagnosing them, then detailed electrical wiring interface system (EWIS) degradation, wire failure modes, and troubleshooting steps. He then described the pros and cons of the automatic wire test set (AWTS) and finished with some recent findings.
NAVAIR Intermittence Testing – Brett Gardner (FRC-SW) described NAVAIR’s experience with their first Intermittent Fault Detection and Isolation System (IFDIS). He detailed the test demonstration results, provided the interim and current solutions, and stated the main issues and concerns with the current technology.
USAF Intermittence Testing: – Ken Anderson (US Synaptics) presented what he called “the Intermittent Testing Void”, detailing the “no-fault found” problem, the conventional approaches used to deal with the problem, and the operational impact. He then described the IFDIS capabilities, solutions, and candidates. Les Stone (523rd EMXS, Hill AFB) described the limitations of conventional testers, and the USAF experience using IFDIS to successfully test for intermittent faults in the F-16 modular low power radio frequency (MLPRF).
MILPRF Overview – John Garrett (NAVAIR) briefed the MILPRF 32516 and the Joint Intermittence Team’s (JIT’s) process used to develop the document. He detailed the scope of the MILPRF to include fault classifications and provided a detailed description of the intermittent fault emulator (IFE) used to evaluate the performance of intermittent fault detection diagnostic equipment.
Closing Comments: Greg Kilchenstein thanked the presenters and the audience for their active participation in the Q&A, and noted the importance of collaboration amongst the military Services and agencies.
Presentation Slides and Questions & Answers: These meeting minutes, the Q&A, and those briefing slides approved for public release, will be posted on the JTEG website at http://jteg.ncms.org/ .
Next JTEG Meeting: The next JTEG virtual forum is 15 December 2015, 1:00 – 3:00 pm EST. The topic is Composite Material Repair.
POC this action is Ray Langlais, firstname.lastname@example.org , (571) 633-8019
JTEG Forum – 27 October 2015
US Army Intermittence Testing: Thom Sullivan (160th SOAR)
Answered Questions (7)
Q1. Is any subsequent analysis carried out to quantify the proportion of each cause type vs incorrect LRU replacements (ie what % pilot error, next test level, wiring, etc.)?
A1. Yes, there is. There are flight safety considerations. We look at all the data and update with fault isolation information.
Q2. Have you been able to verify that the intermittent faults indicated by the AWTS were caused by specific mechanical failures in the LRU, or are you looking primarily at the wiring harnesses?
A2. We are in checking in the LRU, but with respect to the switches, yes, the switches were damaged. It appears moisture was present in the connectors. With respect to the harnesses, we could not identify a defective condition, though there was mechanical wear.
Q3. How many black boxes do you normally replace in a year prior to AWTS wiring testing?
A3. Going back 10 years. The box would be first. They were high rates 70-80%
Q4. What did maintainers find when they repaired the “bad harnesses” found by AWTS testing?
A4. The harnesses are not repairable right now. We are recommending that the harnesses could be repaired. The program manager has it under consideration.
Q5. Have you had to retest any harnesses that were tested using the AWTS and the “amped up” test protocol? Do the harnesses remain reliable?
A5. Yes, they remain reliable. We have conducted a 2nd pass on two.
Q6. How long does it take to evaluate and make a definitive decision on the harness’ condition using this protocol?
A6. 30 minutes for set-up, 10 minutes to conduct the test, 2-3 minutes for final determination.
Q7. What threshold do you use to determine if a harness needs removal and repair?
A7. We start at 1 ohm, reduce to 250-270 milliohms.
NAVAIR Intermittence Testing: Brett Gardner (FRC-SW)
Answered Questions (8)
Q1. What is the estimated total cost to setup this shown capability at FRC-SW?
A1. $3.5M with 3 separate GCU IDs. ($3M for 2,000 test points, $400-500K for 3ea GCU ID. A GCU ID is required for each WRA)
Q2. What is your projected ROI for using IFDIS on the GCU?
A2. Currently we get 150 hours time-on-wing. We are hoping to increase that significantly – up to 75% are intermittent faults that are currently not being repaired. We are hoping for the time on wing to almost double.
Q3. What other LRUs or WRAs is FRC looking at doing IFDIS testing on?
A3. APG-65 & 75 for the F-18. Also looking at the E2C2 and talking to other depots.
Q4. ECP 6421 is supposed to correct under power and power factor issues of the GCU. Do you think that because the GCU is underpowered it is causing some of the intermittent faults if the wiring and connectors are not designed to accommodate the higher power?
A4. Good question. Probably, legacy GCUs are so old and have been repaired so many times over the years. We believe the majority of faults are at the connectors.
Q5. Does FRC have a process to determine where IFDIS testing may be beneficial?
A5. We believe the maximum benefit should be where the box is first brought in for testing.
Q6. Why is the shape of the wave form important?
A6. Because we are not only measuring the duration of the fault but the intensity. Waveforms are a measure of instability. Additionally, we are using the waveforms in the database being built.
Q7. If IFDIS can detect 99% of intermittent faults, why would you still need to add High voltage test functionality?
A7. Many things can cause intermittence. We are only using vibration and temperature, which we estimate are 99% of intermittent faults, but other factors such as load could also potentially cause intermittence.
Q8. How will the unit be logistically supported?
A8. We are recommending a repair contract be put in place. We did buy some repair capability and spare parts as back-up.
USAF Intermittence Testing: Ken Anderson / Les Stone (Hill AFB)
Answered Questions (4)
Q1. Ken, has the IFDIS system been adopted by the large commercial OEMS and MRO executors?
A1. Some MROs, not so much by the OEMs. Intermittence is a $2B annual problem for DoD, the money is going somewhere. The OEMs have new models, upgrades, etc. Increasing the time on wing translates to fewer new sales.
Q2. Les, Does Hill AFB have a prioritized list of the next IFDIS LRU/WRA applications? Has IFDIS been applied outside the F-16 community?
A2. We do, but I don’t remember the items. Yes, the C-17 power supply. Also, outside of Hill AFB IFDIS has been applied on numerous other aircraft platforms and on the M1 tank.
Q3. From a design perspective, is the MLPRF vastly different than other radar components…or is it fairly representative?
A3. Most are representative of what we see.
Q4. Has the Hill squadron been able to use the AWTS equipment in conjunction with the IFDIS to get best value of test capability?
A4. AWTS equipment has a scan capability and is located at the intermediate maintenance site. The depot only has the IFDIS, which has fault identification. AWTS uses higher electrical current levels. There may be value in using in conjunction, especially if there was a common connector for both systems.
MILPRF Overview: John Garrett (NAVAIR)
Answered Questions (3)
Q1. John, has the Navy established a requirement for intermittence test equipment?
A1. Yes, we are working on a requirement.
Q2. Industry Event a Lakehurst – how do we publish the results on what can meet the MILPRF?
A2. I’ll have to give that some thought.
Q3. The IFE appears to only locate the timing type failures similar to what the IFDIS is designed for and not the types of failures that Mr. Thom Sullivan was experiencing on aircraft testing. Is there a plan to adjust the MIL-PRF for load types of failures?
A3. That is not typically what we are testing for. The engineers would need to look at that.