Intermittent failures in electronics wiring drastically reduce Mean Time Between Failure (MTBF) and cause repeated No Fault Found (NFF) test results. Traditional test equipment that is inadequate to detect this failure mode. The Voyager is an advanced engineering diagnostic tool specifically engineered to supplement traditional test equipment and address the issue of intermittent failures.

  • The Voyager uses state of the art patented technology that is able to monitor all wiring paths in a UUT simultaneously and continuously for intermittent failures. The Voyager detects intermittent failures in continuity as short as 50 nanoseconds.
  • The Voyager provides the ability to detect and isolate intermittent failures so that they can be repaired.
  • Millions of maintenance dollars have been saved by employing this technology in both the defence and private industry.

Intermittents

Intermittents are the result of interconnections within electronic systems.

Intermittent Fault Detection: The Problem

No Fault Found (NFF), Re-Test Okay (RTOK), and Can Not Duplicate (CND) are just a few terms used to describe a maintenance phenomenon that plagues electronic equipment and costs billions of dollars every year. An NFF occurs when an electronics unit fails in operation but during subsequent testing and troubleshooting, no problem can be identified. Typically, the unit is verified as fully functional then the unit is placed back into service. The cycle of operational failures and NFF test results then repeats.

Cracked Solder JointThis NFF problem is largely due to intermittent failures in the wiring that interconnects the components and sub-assemblies within an electronics unit, or between electronic units. An intermittent failure, as related to electronics wiring, can be defined as a momentary interruption or anomaly in the flow of current through a circuit. A few common causes of this type of failure are: cracked solder joints, loose wire wraps, loose crimp connections, broken wire strands, corrosion on connector contacts, etc. These types of problems occur in new electronics too, but become more frequent and severe in aging electronics as the integrity of the wiring degrades with age and wear.

Loose Wire WrapA permanent or “hard failure,” such as an open or short, is usually not difficult for test equipment to detect. Intermittent failures can be unpredictable, extremely short in duration, of varying amplitude (from slightly higher resistance to completely open), and may only occur during specific environmental conditions (such as temperature change and/or vibration). Intermittent faults are a very common failure mode and the inability to detect them is a major testing void in standard test equipment.

Why ATE is Ineffective in Detecting Intermittent Failures

  1. Standard test equipment has a huge testing “blind-spot.” Standard test equipment scans through a Unit Under Test’s (UUT’s) circuitry, meaning that the circuits or functions are tested and measured one at a time.

    SyncronizationAn intermittent fault may occur on any circuit, at any time, and for only a very short duration. Many UUTs have hundreds or even thousands of circuits, and each circuit has the potential for intermittent failures. While a conventional tester is measuring only one circuit, a momentary intermittent fault can occur on any of the other hundreds or thousands of circuits not being measured, resulting in the failure being completely undetected.

  2. Standard tests are usually performed at room temperature in a benign test facility. An intermittent failure occurs when a circuit momentarily changes its state from “closed” to “open” (or momentarily increases resistance). When a UUT is at room temperature and sitting completely still, there is no physical reason for a circuit to change from its current state. Certain types of physical stimuli can cause a momentary change in a circuit’s state to occur. For example, a loose wire wrap may be making good electrical contact when a UUT is at room temperature; however, when the UUT is heated and cooled, the expanding and contracting that takes place may cause the wire-wrap connection to loosen enough that the circuit momentarily opens. Vibration can also have the same effect of causing an intermittent event to manifest.

    Test results have shown that certain intermittent failures occur only at a particular temperature and/or when subjected to a certain frequency and magnitude of vibration. If a UUT is not tested under these specific conditions, the intermittent fault may not occur and thus the problem may not be detected.

  3. Standard test equipment uses “digital precision. However, digital measurement is counterproductive and has a very negative effect when attempting to detect intermittent failures. This is because digital measurements are made by taking a sample of readings and averaging the results to give a stable and accurate reading. The problem with digital equipment is that intermittent failures are missed due to the sampling process or are masked due to data averaging.

  4. Most maintenance philosophies are geared towards testing for component failure (IC chips, transistors, diodes, resisters and other discrete components), not wiring problems. The typical maintenance philosophy prevalent today is to identify the electronic component that caused the system to fail so that it may be removed and replaced, while assuming the wiring that interconnects the components is “good.”

Intermittent Fault Detection: The Solution

Intermittent failures in wiring, solder joints, connectors, etc. are generally very easy to repair once the fault has been detected an isolated. This is the very reason that the Voyager was developed.

The Voyager injects a small programmed Direct Current (DC) stimulus through each circuit of the UUT and the analog neural network monitors every circuit for slight changes or anomalies in current flow. When a change of even just a few ohms is detected, the fault decoding elements pinpoint and display the failing circuit.

Intermittents

Testing of Line Replaceable Unit for Intermittents


Case Study 1 – NAVAIR – F/A-18 Generator Convertor Unit (GCU)

A Technology Demonstration Project of Voyager diagnostics capability has taken place with the cooperation and support of the NAVAIR Fleet Readiness Center South West (FRC SW). An F/A-18 Generator Convertor Unit (GCU) was selected as the test candidate. All of the GCUs tested had passed FRC SWs testing protocols and had been certified “Ready for Issue” (RFI) before Voyager testing.

Voyager testing found intermittent circuits which had previously gone undetected in 80% of the GCUs.


Case Study 2 – USAF – F-16 Modular Low Power Radio Frequency unit (MLPRF)

Testing was developed for the F-16 AN/APG-68 Radar System MLPRF Line Replaceable Units (LRUs). Intermittence testing of the MLPRF has provided valuable insight on the need for this type of testing. Because the intermittent circuit problems within the LRU chassis are precisely detected and isolated, they are easily repaired.

There were 138 MLPRFs that were considered to be “un-repairable” because they had intermittent, open and/or shorted circuits in the chassis that could not be isolated by traditional test equipment.

Through Voyager testing the chassis circuit faults were diagnosed and repaired, enabling these LRUs to be returned to service. These 138 MLPRFs represent over $42 million in recovered assets, and are now some of the most reliable MLPRFs in the USAF inventory.

Over 400 MLPRFs tested showed:

  • 60% had intermittent circuits which went undetected utilizing conventional ATE
  • Mean Time Between Repair more than tripled
  • 138 “un-repairable” MLPRFs – worth $42M – successfully recovered
  • $14M in MLPRF maintenance saving and growing
  • Removed from the Mission Capable (MICAP) impact list after sitting at or near the top of the list for over a decade
  • Over $150M projected through-life savings.

Case Study 3 – NAVAIR – EA-6B Audio Intercommunication System (AIC-45)

A Technology Demonstration Project of Voyager diagnostics capability has taken place with the cooperation and support of the NAVAIR Fleet Readiness Center South East (FRC SE). An EA-6B Audio Intercommunication System (AIC-45) was selected as the test candidate. Conventional test equipment has been unable to identify intermittent issues or improve AIC-45 availability.

Voyager testing found intermittent circuits which had previously gone undetected utilizing conventional ATE in 83% of the AIC-45s.


Case Study 4 – Royal Air Force (RAF) – CH-47 Chinook Helicopter

A Technology Demonstration Project of Voyager diagnostics capability has taken place with the cooperation and support of the United Kingdom, Ministry of Defense and Royal Air Force. CH-47 Chinook high NFF wiring harnesses were selected as the test candidates. Conventional test equipment has been unable to identify intermittent issues or improve these high NFF wiring harness issues, reduce No Fault Found (NFF) or improve availability.

Voyager testing detected and isolated intermittent wiring issues that cause NFF.


Case Study 5 – Boeing 757 – Auxiliary Power Unit / Engine Controller Unit (APU/ECU)

A Technology Demonstration Project of Voyager diagnostics capability has taken place with the cooperation and support of one of the world’s largest commercial freight and shipping companies. A Boeing 757 Auxiliary Power Unit / Engine Controller Unit (APU/ECU) was selected as the test candidate. Conventional test equipment has been unable to identify intermittent issues, reduce NFF, reduce Aircraft on Ground (AOG) or improve dispatch reliability and APU/ECU availability.

Voyager testing detected and isolated nine intermittent circuits in the APU/ECU. The APU/ECU selected for Voyager testing had been returned “Fully Serviceable” from the OEM prior to Voyager testing. Since Voyager testing the APU/ECU has remained on wing for 255 consecutive days with 2,295 consecutive operational hours and growing.

For cable testing, harness testing and other automated product testing solutions, customers rely on DIT-MCO wiring analyzers.

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