CASE STUDY #1
Tornado GR4 Fighter Aircraft
The Tornado is the UK’s leading ground attack aircraft. It has been constantly deployed on operations in recent years. The portable Voyager Intermittent Fault Detector™ (VIFD™) has been used on 2 Tornado projects: an industry demonstration project and a fault investigation project.
The nose-wheel steering system is susceptible to intermittent faults that are difficult to diagnose during flight line maintenance, which often leads to speculative replacement of other components. A 2009 pilot project was conducted which successfully demonstrated the ability of the VIFD to detect hard and intermittent faults that conventional equipment were unable to detect. Unserviceable harnesses were confirmed to have intermittency and continuity faults; brand-new harnesses were confirmed as being both intermittency-free and continuity fault-free; and life-expired harnesses were found with intermittent faults even though they passed continuity testing.
In another example, one specific Tornado aircraft had suffered an intermittent fault within the secondary power system since 2006. An analysis of the fault-maintenance history was conducted, along with an intermittent fault diagnosis of the system. As most of the system LRUs had already been replaced it was agreed that the condition of the wiring should be tested. The system’s wiring integrity was tested with an VIFD and this found that 12% of the cables tested had intermittency/noise/continuity issues.
These cables were repaired by the RAF and then re-tested the system wiring with the VIFD, which confirmed that the system’s wiring integrity had been fully restored. Once the aircraft was rebuilt for flight testing it transpired that the intermittent fault’s symptoms were unchanged, enabling the RAF to now rule both the LRUs and the wiring out of the diagnosis. An external influence was suspected and this was traced to a faulty circuit-breaker (CB), which was outside the scope of the wiring tested by the VIFD. Since the CB was replaced, the fault has not recurred. Overall, the intermittent fault analysis and VIFD testing vastly accelerated the timeframe for isolating the fault, hence a ‘No Fault Found ‘ which had persisted for years was ultimately resolved in a matter of weeks.
CASE STUDY #2
Helicopter Radio Backplane
A Transmitter/Receiver LRU from a helicopter radio system, as used in several UK military helicopter fleets, suffers significant levels of No Fault Found (NFF). The client responsible for depth support of these assets to assess the LRU design and identify how best to test them to isolate root causes of intermittent faults.
Analysis of the design resulted in the decision to focus on testing the ribbon-cable back-plane, owing to the fact that this type of component is chronically susceptible to intermittent faults. The ribbon-cables were tested using the portable VIFD and it was quickly discovered that the vast majority of the ribbon-cables yielded intermittent faults, even though they had been removed from LRUs that were passing in-depth conventional ATE testing.
The faults detected were easily repairable, with further VIFD testing confirming that their full system integrity had been restored.
CASE STUDY #3
Sentinel R1 Airborne Stand-Off Radar (ASTOR)
The ASTOR (Airborne Stand-Off Radar), in the pretext of the Sentinel R1 aircraft, provides long-range, battlefield-intelligence, target-imaging and tracking radar for the RAF and the Army and has surveillance applications in peacetime, wartime and in crisis operations.
The Sentinel fleet has been on active operational service over the last two years and the need to maintain the capability of its mission sensors is paramount.