Frequently Asked Questions - All FAQs
The Ncompass-Voyager is a multi-purpose, multi-channel portable tester for troubleshooting and integrity testing/trending of electrical, avionics and electronic components and wiring. As well as being the market-leading Intermittent Fault Detection test set the Ncompass-Voyager has a comprehensive range of Point2Point and Neural test functions including: Continuity, LogScope, Shorts, Diode testing, AutoMap, sync with Environmental stimulus (option), Distance-to-Fault (option) and LCR characterising (option).
In addition to being a powerful troubleshooting tool its test results data can also be used prognostically for evidence-based decision-making on component maintenance and policy. The Ncompass-Voyager is available with 128, 256 or 512 test points. Technical specification details can be found here.The Ncompass-Voyager functionality is also available as a 19-inch rack-mount unit - the Intermittent Fault Detection & Isolation System (IFDIS) - which can be scaled up to over 16,000 test points.
The Intermittent Fault Detection & Isolation System (IFDIS) features the same patented IFD technology and test functionality used in the Ncompass-Voyager portable (see previous question). As well as being the market-leading Intermittent Fault Detection test technology the IFDIS has a comprehensive range of Point2Point and Neural test functions including: Continuity, LogScope, Shorts, Diode testing and AutoMap.
In addition to being a powerful troubleshooting tool its test results data can also be used prognostically for evidence-based decision-making on component maintenance and policy.
IFDIS uses the industry standard 19-inch rack-mount format and is available with multiple test points from 1280 to over 16,000. Specification details can be found here.
Ncompass-Voyager’s powerful range of test functions and user-oriented features mean that they can be used - in a rapid, repeatable and standardized fashion - to benefit an extensive range of production and maintenance scenarios.
Electrical and electronic integrity faults of down to 100 nanoseconds can be detected and isolated and the subsequent test results data can be used to characterize the fault in the following types of ‘Unit Under Test’ (UUT):
- EWIS components (CBs, relays)
- Wiring harness and connectors
- LRU external and chassis interconnections
- PCB connections
- Faults are rapidly detected and isolated, including distance-to-fault (option).
Test results data can also be used prognostically for evidence-based decision-making on component maintenance and policy.
IFD testers have been successfully used on the following aircraft and platforms:
- UK - CH-47 Chinook, C-130J Hercules, Tornado GR4, Sentinel R1, Train door & braking systems, Combat land vehicles
- Europe - Eurofighter, Regional Jet systems, Business Jet systems
- USA - F-16, F-18, UH-60, EA-6B, B757
The Test Program Sets (TPS) for Ncompass-Voyager & IFDIS testers comprise the Interface Adapters (IAs) and the Unit Under Test (UUT) configuration on the testers software user interface (called 'NODES'). There are a number of ways that the UUT configuration can be set up. Firstly, if the wiring diagram is available then the Ncompass MAP file can be constructed using NODES. Secondly, an AutoMap facility is available which will automatically construct the MAP file. This can be then imported into NODES and then, if required, it can be compared to the theoretical MAP file. Both these processes are easily carried out and seamless to the user.
We can either supply the tester pre-configured with customer-specified UUT set up on NODES and with IAs; or we can train the customer how to design and assemble their own TPS.
You don’t need to test everything, so do some analysis of which wiring harnesses/components cause the most pain in terms of NFF and repeat arisings and focus on them first. Or we can do that analysis for you. The analysis will show whether you have rogue LRUs (also known as LRIs or WRAs) to be tested, or whether the system EWIS (Electrical Wiring & Interconnection System) components/wiring need to be tested instead. This will then determine if you actually need a Special-To-Type (STT) Interface Adapter (IA) or not.
IA for EWIS Testing:
You may already have IA from other testers, from DIT-MCO or Eclypse for example, so where applicable you can connect to the Unit Under Test (UUT) using those. Or for one-off, simple tests there is a range of generic IA available to suit most applications eg with standard connector types or with standard pins on flying leads.
If an STT IA is needed they are simple to make, using the relevant aircraft connectors and readily available shielded D-sub cables; or we can supply them with the tester. Once you’ve got an STT IA you can then carry out rapid, repeatable and standardised testing as often as you like.
IA for LRU Testing:
IAs to test the internal interconnections of an LRU need to be built in such a way that they are as representative as possible of the connections within the chassis and so the number of test points involved does require a more sophisticated IA. Overall, the complexity and sophistication of the LRU/UUT will determine the complexity and sophistication of the IA. The complexity of the IA will be reflected in its cost and - more importantly - in the savings achieved from being able to routinely carry out IFD testing. Several case studies show huge Returns On Investment from, for example, IFD testing of LRUs - a case in point is the F-16 case study.
Yes - the Ncompass is only tester that is able to find early stages of intermittency on a databus. There are methods of testing that are designed to find intermittency on a databus by logging failures to transmit/receive, handshake and parity errors. However, these are limited methods given they are point in time, and in some cases, sample rates are not high enough to detect small glitches in the databus line; this is especially so when parts of the databuses are tested in isolation and therefore when they are not under load.
Ncompass-Voyager and IFDIS testers always test Units Under Test in a power-off condition because they are testing the integrity and not the functionality. Therefore PCBs can be tested and this means that all interconnects to the PCB are fully tested, although the power-off condition will mean that there are some dead zones on the PCB where continuity cannot be achieved and so not all of the PCB's circuits can be tested.
Yes. As long as all the windings of the transformer can be connected to the Ncompass or IFDIS tester via an array of test points, the transformer can be tested for intermittency, continuity, shorts and/or Log Scope
Not directly. Whilst Ncompass & IFDIS testers are not designed to test for insulation they can, however, find intermittent faults between test points or ground which might be a result of insulation breakdown.
No. Clearly it is important to understand the circuit dynamics and where the test points need to be connected to the Ncompass to ensure maximum test coverage. However, from experience it is more likely that intermittency is due to the mechanical interfaces ie the matting parts of the Unit Under Test such as the cables, chassis and connectors. Therefore, test points should be chosen to ensure these areas are exposed to the Ncompass testing regime. CTL can advise clients on any aspect of this FAQ.
Yes, the Ncompass or IFDIS tester needs to connect to both ends of the cable run. However, this can be achieved by having a fly-lead to connect to the other end of the cable run, or a shorting link at the other end of the cable harness could be used to provide a complete circuit. The latter solution is a better method for longer cable runs.
No. Unlike HiPot testers, the Ncompass-Voyager will not damage wiring or components because it generates extremely low current levels: less than 1 milli-Amp at the very most. We have successfully used it to test surface mount components on PCBs and never damaged anything.
No - it only finds faults if they are there! Our IFD testers have routinely tested items with several hundred test points and found the integrity of the vast majority are not in question. For example, on a RAF Tornado GR4 testing project only a handful of the approx 50 test points exhibited faults. If the tester was too sensitive far more ‘events’ would have been detected, but that wasn’t the case.
If there is concern about over-sensitivity then the test settings can be adjusted to reduce drive and sensitivity levels and then build them back up until an appropriate level is found.
For pure cable runs, with no in-built components, such as ballast resistors or protection diodes (although in the majority of cases these do not pose a problem either), the cable run length which can be tested effectively can exceed over 100m (330ft). This is more than the length of A380-800 or Boeing 747-8 and includes the return path for the test point ie 200m test length.
A limited self-test is needed to ensure that all the test points are still functioning but this is a very quick test to perform and it does not need to be sent away for this. As for calibration, there is no need to calibrate the Ncompass for Intermittency Testing or number of the other tests it can perform. Calibration is only needed on an annual basis if the Analyse test is used to compare ‘Gold’ items or compare a Unit Under Test against itself using a previous test results; this has to be carried out by your IFD supplier.
No. A product falls under ITAR if it meets one of the product definitions on the US Munitions List [http://www.ecfr.gov/cgi-bin/text-idx?node=pt22.1.121]. This includes products modified or adapted for military use. The Ncompass-Voyager and its integral Intermittent Fault Detection technology are not modified or adapted for military use and they have been employed in identical fashion on both civilian and military customer testing projects. Therefore this is dual use technology and hence is not subject to ITAR.
The training provided will be tailored to the needs of the Customer. Testers are delivered with a one-day Operators course as standard; additional days are added as required if the Customer is going to (a) make their own Interface Adapters and/or (b) set up their own Unit Under Test configurations on the software user interface ('NODES').
One-year's warranty is standard and Help-desk and extended warranty support is available - details on request.
Ncompass-Voyager and IFDIS are the ONLY testers that can detect and isolate random intermittent faults on multiple test points, down to nanoseconds, simultaneously and continuously. They are not intended to replace TME or ATE that test for isolation, accuracy in ohmic/capacitance etc, because they complements these testers with its revolutionary technology to detect intermittency.
In addition, to intermittency detection, the Ncompass can provide the user with continuity, shorts and scope testing; plus it provides the benefit of being able to connect to other 3rd party passive testers such as TDR, Oscilloscope or high end DMM.
Intermittency can be described as a temporary deviation from normal operating conditions of a circuit or device. It manifests itself as intermittent faults as the system or platform degrades through 100% availability to a ‘hard fault’ (ie permanent) state. Intermittency may last for as little as nanoseconds, causing intermittent symptoms.
Intermittency is caused by minute changes in a circuit’s characteristics such that they have repercussions on the operating parameters of the system in which they occur. These continuity 'micro changes' result from the degraded integrity of connections (ie in cables, connectors or chassis) and this can be caused by and/or exacerbated by fretting corrosion, vibration, maintenance damage, humidity and other environmental factors.
Digital systems and, in particular, databus circuits are more susceptible to intermittent faults, with micro-changes in continuity causing drops in voltage which then lead to data bits being dropped from the data-stream and thus causing parity errors.
These errors result in either the system locking out/shutting down/restarting, or data being transferred again and again until a hand-shake is satisfactory, with delays in data transfer.
A "No Fault Found" (NFF) is a reported fault for which the root cause cannot be found. The NFF phenomenon is usually encountered as a symptom that has been reported by the operator of a platform, system or piece of equipment and can not be reproduced or replicated. It is a chain of events that starts, chronologically, with the end user experiencing a fault symptom. The chain of events might progress from reporting the fault to the relevant technicians, through to diagnosis and rectification activity. If the diagnosis is a success then the genuine root cause of the fault is isolated and rectified and the equipment is signed off serviceable having been made fit-for-purpose and airworthy once more. However, if the root cause cannot be found – in other words, the activity has resulted in diagnostic failure– you are dealing with a NFF situation.
This topic is discussed in more detail here, in our blog.
A "No Fault Found" (NFF) occurrence occurs when a maintenance organisation cannot detect the cause of a reported fault. There are many reasons for this 'diagnostic failure' scenario, ranging from pilot error to maintainer experience to software to shortfalls in trouble-shooting manuals. However our research has shown that the aerospace industry considers intermittent faults to be the leading, major root cause of NFF problems. This is because intermittent faults are difficult to diagnose and isolate and so they result in incorrect repair solutions such as, for example, replacing Line Replaceable Units on spec when the fault actually lies undetected within a wiring connector.
No Fault Found has implications for safety and impacts heavily on support costs, availability and operational reliability/readiness. In some people's minds the root cause of an NFF occurrence perhaps becomes synonymous with the NFF end result.
The root cause and its in-flight effects can be a safety problem: whether by causing a crew distraction (such as a transient fault affecting flight deck display units), or by affecting a safety-critical system (such as an intermittent undercarriage retraction handle). So whilst most seem to agree that NFF-related maintenance activity itself is not the safety issue, it is fully recognised that a fault root cause could well have safety implications if left undiagnosed and unrectified. As for the other effects of NFF, the available data paints a compelling picture.
The USDOD incurs NFF costs of $2B to $10B per year and IATA has estimated the commercial aircraft sector cost impact to be over $0.2M/airliner/year. The UK MOD analysed 2012 NFF arisings and estimated their cost impact at £200M; however recent academic research identified that the total number of NFF events is in fact 3 times greater than the number of repair entries formally recorded as NFF. Combining these facts results in an MOD NFF cost of the order of £0.5B per year.
Despite these shocking figures our aerospace industry surveys revealed that over 60% of civil & military aerospace maintenance organisations do not know the cost of NFF to their enterprise, whilst 39% don’t know the impact on Availability of aircraft. This topic is discussed in more detail here, in our blog and a detailed description of the cost impact can be found here.
You need a strategy to deal with it - there is 'no one-size-fit-all method' and 'no silver bullet'. Your strategy needs 3 key elements: Data Analysis, Education (ie tailored NFF training and improved fault diagnosis manuals) and Intermittent Fault Detection. A detailed blog on the strategies needed to defeat NFF can be found here and you can assess the maturity of your organisation's NFF solutions here.