Time Domain Vs Frequency Domain Reflectometers in Aviation Operations

Time Domain Vs Frequency Domain Reflectometers in Aviation Operations

Ground Support Test Equipment

Distance To Fault (DTF) measurements of coaxial cables and testing of antennas are typically performed by independent analyzers. Historically, aviation technicians have used Time Domain Reflectometers (TDR) to perform DTF measurements. A TDR sends a pulse of Direct Current (DC) of half sine wave into the coax cable copper pair and digitizes the return response of the reflected pulse in time domain. The difference in velocity of propagation (Vp) estimates the potential location of the problem. TDRs are limited as no information regarding the performance problems at actual operating radio frequency (RF) is determined.

 

What does an FDR do?

DC pulse vs Frequency Sweep reflectometer

Image Source: https://www.anritsu.com/en-us/test-measurement/solutions/en-us/distance-to-fault

Frequency Domain Reflectometers performs a sweep of frequencies of the transmission line input, and then using Inverse Fast Fourier Transform (IFFT) on the reflected signals, convert them back to time domain. The analyzer not only performs the calculations of the DTF from the Vp received, but in addition receives all the reflected signals from the faults in the frequency spectrum that provides characteristics of the type of fault found. Therefore, users could create a characterization of the type of damage, i.e.: corrosion or bad shielding etc. It is also important when doing FDR test to consider the characteristics of the cable to compensate for any losses during the transmission. 

An FDR could create characterizations of the type of fault found, not capable when using a TDR.

TDRs are not capable of troubleshooting antennas. Typically, operators will have to bring a more sophisticated equipment, such as a spectrum analyzer, if available, or swap antennas, as best way to discard possible problems with navigation systems. This process is time consuming, and costly to the operators, in particular if the no fault is found (NFF) with the antenna.

 

What technology is available approved for aviation?

FlightHawk_Barfield

The FDR analyzer such as FlightHawk P/N 7003A001-4, is capable of performing both tasks in one analyzer: DTF and antenna frequency sweep. The FlightHawk sweeps in a frequency range of 1MHz to 6GHz, capable of connecting to any navigation system such as VHF, DME, TCAS etc. It contains a friendly user interface for the testing of coaxial cables and antennas with measurements in feet or meters for DTF and dB or Voltage Standing Wave Ratios (VSWR) for frequency sweeps. It is capable of integrating a power sensor to measure power output from the source.   

The FDR analyzer such as FlightHawk P/N 7003A001-4, is capable of performing both tasks in one analyzer.

Finally, it uses an android base operating system that provides flexibility to store images of any measurement, downloadable via USB drive, Bluetooth or WIFI. This is particularly useful when line maintenance technicians require additional support from avionics techs or engineers remotely located.

Barfield contribution to this equipment to make it suitable for aviation, was identifying and including the library of commonly used coaxial cable part numbers with their characteristics. The versatility of the equipment and the ease of use, are part of the reasons that have been included in the Boeing Aircraft Maintenance Manual (AMM). 

TDR could provide DTF measurements, but FDRs such as the FlightHawk is a more comprehensive, fast troubleshooting tool for line maintenance, helping avoid no fault founds.  

Other articles:

  1. How the Boeing Frequency Domain Reflectometer Works?
  2. How Airlines Are Testing Aircraft to Bring Them Back to Service?
  3. How to use a Frequency Domain Reflectometer in Aviation?

Barfield Inc., in partnership with Bird continue supportting operators to help diagnose avionics problems.

If you still have more questions or want to learn more about this technology, please fill out the form below.

Frequently Asked Questions About Barfield GSTE Products

Frequently Asked Questions About Barfield GSTE Products

Ground Support Test Equipment

Having all your questions about Barfield products answered for a better experience, is one of our main objectives. Our customer support and engineering teams have compiled an extensive list of Frequently Asked Questions to save you time.  

Where can I find the Barfield App on my mobile device to use with my DPS1000 and/or 1811NG? 

Connect your mobile device to the Internet via local Wi-Fi network or phone provider data plan, visit the Apple App or Google Play, search and download the “Barfield ADTS” app.  

Here are the links: 

Apple App Store 

Google Play 

How do I connect my DPS1000 and 1811NG to a mobile device? 

Find the detailed process in this article published on our blog: How to connect the DPS1000 and 1811NG to a Tablet 

What is the password to connect Barfield ADTS app to the DPS1000 and 1811NG ? 

Refer to the link: How to connect the DPS1000 and 1811NG to a Tablet 

Does my mobile device Wi-Fi need to be connected to a local network to connect and work with my DPS1000 and/or 1811NG? 

No, the test set is equipped with Wi-Fi Direct which works pier-to-pier, it connects and communicates directly between the mobile device through the Barfield ADTS App to the DPS1000 or 1811NG.  

How can I get my latest software update on my DPS1000 and 1811NG? 

Through your mobile device: Having the Barfield ADTS App up to date on the mobile device will ensure that your test equipment runs with the latest software (HUIM and PCM) installed.  The App detects the equipment’s current firmware and triggers a message with the need to run the software update.  The customer can choose to run the update or do it later, but the App won’t run the Test Equipment until the sotfware is updated. 

Visiting Barfield’s website: Barfield GSTE website

How can I register my Barfield product? 

You can register any of your Barfield products including the products distributed by Barfield by clicking on the following link: Warranty Registration 

What is the warranty on my Barfield product?  

All warranties are 1 year 

Exception:  The  DPS1000 and 1811NG  have a 2 year warranty.  

What is the calibration interval of my Barfield product? 

All DPS1000 and 1811NG have a 1-year calibration cycle. 

Analog instruments may require calibration every 6 months. Refer to the specific Instruction Manual for more information.  

Where can I find the latest manuals and information letters? 

The information on the latest manuals and information letters can be found on the GSTE page here 

What is the difference between calibration vs bench check? 

An inspection/verification from a third-party, non-Barfield authorized repair station, is not considered recertification of the Test Equipment. It determines, at best, if the Test Equipment’s performance meets Barfield’s published specifications.  It is important to clarify that Recertification does NOT result in any adjustments to the measurement system. 

The process of Calibration requires the Unit Under Test (UUT) be compared to Certified Traceable Standards.  Adjustments are made to the UUT during calibration in order to align the UUT to the exact values of the Standards so that the errors at all required test points are zeroed out. 

A true Calibration results in the equipment operating at its optimum accuracy and performance levels, which ensures the instrument will maintain its performance specification for another year until the next annual calibration recertification is due.    

In summary, the recertification (calibration) is normally required to be performed every year; “inspection-verification” is NOT recertification. 

Where can I send my Barfield equipment for calibration and repair? 

Barfield Test Equipment can be sent to Barfield Headquarters. Please, contact our customer support at gste.service@barfieldinc.com   

For Barfield authorize repair station contact gsesales@barfieldinc.com 

If you have any more questions about Barfield products fill out the form below 

 

How to Troubleshoot No Fault Founds in Complex Wire Harnesses?

How to Troubleshoot No Fault Founds in Complex Wire Harnesses?

Ground Support Test Equipment

Intermittence fault is a known problem in aircraft due to a large number of electrical wire and complex systems that make an aircraft. Newer aircraft have more computer-based system which has even more wiring than legacy aircraft.

 

Why aircraft intermittences are so difficult to detect?

Small-Engine_CFM56-5B_CDG (5)

Finding a problem in a bundle of wire-harness is a complex challenge. Sporadic intermittences that appear in mid-air are detected and reported by pilots. Once the aircraft is back on the ground these intermittences are difficult, if not impossible for technicians to replicate. Aircraft vibration can not easily be replicated, and many times the intermittences happen in fractions of milliseconds.

Therefore,  problems observed in mid-air can not easily be replicated on the ground. Technicians rely on ohmmeters to run conductivity testing, selecting line by line, looking for the problem. The tool of choice, a multimeter, is set up to find transients with millisecond accuracy. There are two challenges with this approach:

 

  1. Harnesses are interconnected systems of multiple wires, and a multimeter is only capable of testing one wire at a time.
  2. It is possible that the transients occur in less than a millisecond, undetectable by the multimeter.

Problems observed in mid-air can not easily be replicated on the ground.

Hence, the multimeter works to detect open circuits, which is considered hard or semy hard intermittences. But not accurate enough to detect random sporadic intermittences at low-level noise or micro-breaks.

 

New Technology

IFD - 256 Voyager - Barfield Inc - Universal Synaptics-min - Intermittence Analyzer

New technology has emerged. It takes into consideration all electrical lines by testing each line simultaneously with a nanosecond accuracy in a closed-loop environment. This technology uses a hardware version of a neural network, in which signals are sent to each node combining all feedback back to the analyzer. Then, the system could be checked as a whole, and not each line separately, creating the necessary environment to detect any fault.

New technology has emerged. It takes into consideration all electrical lines by testing each line simultaneously with a nanosecond accuracy in a closed-loop environment.

The United States Department of Defense is one of the early adopters of this technology that tests LRU, by extending the mission capability of their fleet and reducing operating costs.

GE-90 Wire Harness Case Study

We have identified by Boeing 777 operators that the  GE-90 115B engine typically shows intermittency problems in the wire harness. Our engineer group along with the team at Universal Synaptics developed an interface, to connect the bundle of wires into the IFD (portable).

 

GE 90 complex cables IFD Universal Synaptics

The complexity of this task can only be solved by sending simultaneous pulses at a nanosecond speed through all cables simultaneously. The IFD (portable) connects in series with the wire harness and detects any possible anomaly.  

This report shows the results of the test. GE 90 complex cables IFD Universal Synaptics

Lockheed Martin with F-16

Lockheed Martin currently uses the versions of the IFD on their different platforms. Check video below:

Several case studies have come to light recently and a selected group can be downloaded here:

Selected Aircraft Case Studies:

  1. F-16 Nose Landing Gear Harness.
  2. Boeing 777 GE90 Engine Harness
  3. Total Air Temperature Probes .
  4. Pratt & Whitney V2500 Engine Harness
  5. AH-64 Apache EWIS Testing 
  6. Elevator and Aileron Computer (ELAC)

Barfield Inc., in partnership with Universal Synaptics, is bringing this technology to operators of commercial and business aircraft.

If you still have more questions or want to learn more about this technology, please fill out the form below.

How to use a Frequency Domain Reflectometer in Aviation?

How to use a Frequency Domain Reflectometer in Aviation?

All Posts, Ground Support Test Equipment

Barfield Inc., in partnership with Bird, collaborated in the development of the FlightHawk ( formerly known as SiteHawk-AV).  This is a Frequency Domain Reflectometer (FDR), commonly used in the telecommunication industry, modified to be used in aviation operations. It can usually be found under Part Number: 7003A001-5 in many manuals.

Training on how to use the FlightHawk:

The FlightHawk is a Frequency Domain Reflectometer that connects from the end of the coaxial cable, testing if damages exist by identifying the Distance to Fault (DTF) and capable of performing a frequency sweep to the antenna.

The following videos provide instructions that allow the testing of any type of antenna and coaxial cables with this Frequency Domain Reflectometer, in any navigation systems of any aircraft. 

  1. Introduction to FlightHawk ( formerly known SiteHawk-AV).
  2. Antenna and Cable Health Checks: Boeing Use case.
  3. How to Calibrate the FlightHawk.
  4. VSWR and return loss sweep with the FlightHawk.
  5. Distance to Fault Test Using FlightHawk.
  6. Sending files from the FlightHawk to an Android phone.
  7. Save files from FlightHawk to a USB Drive.

1. Introduction to the FlightHawk

This video is an introduction of the FlightHawk. It explains what it consists of and what features are included.

2. Antenna and cable health checks: Boeing use case 

This video is a presentation from Boeing, showing details of the use of the FlightHawk in an aircraft.

3. How to calibrate the FlightHawk

This video shows the process of how to calibrate the Frequency Domain Reflectometer.

4. VSWR and return loss sweep with the FlightHawk

This video shows how to do a Voltages Standing Wave Ratio (VSWR) and return loss frequency sweep.

5. Distance to fault test using the FlightHawk

This video shows the Distance To Fault (DTF) test procedure.

6. Sending files from the FlightHawk to an Android phone

This video shows how to send files from the Frequency Domain Reflectometer to an Android phone. It is a great tool for saving images and results from tests performed.

7. Save files from FlightHawk to a USB drive

This video is about how to save files from the FlightHawk to a USB drive. It is also, a great tool for saving images and results from tests performed.

We hope with these videos, to give you an overall understanding of the FlightHawk Frequency Domain Reflectometer (FDR). The videos showed how to perform Distance to Fault (DTF) and VSWR testing. For Boeing operators, there is an additional option, a Boeing App, that can be installed on your device.

If you still have more questions or want to send us a quote, please fill out the form below.

How to set the limits of the DPS1000 and 1811NG?

How to set the limits of the DPS1000 and 1811NG?

All Posts, Ground Support Test Equipment

Using incorrect limits can cause damage to sensitive components and aircraft systems. 

For that reason, it is very important to ALWAYS verify and ensure the limits selected are appropriate for the aircraft and/or the instruments that are going to be tested. 

The DPS1000/1811NG Test Sets come with two (2) pre-defined sets of operating limits – the default limits profile and the max limits profile. These limits are available for each of the of the three (3) operating modes – Aeronautical, Pressure units and EPR. 

Both DPS1000 and 1811NG Test Sets include a setting that allows creating and saving custom limits. With this feature, the customer can easily access and use the custom limits again in the future.

The values for both limits profiles are stored in an R/O, “read only”, file. The Test Set will first power up and initialize with the default limits profile. As a result, if the customer changes the limits to the max or custom limits profile, the Test Set will power up using the last profile selected.  

The Test Set limits must be configured with the appropriate values to protect the aircraft system or instrument(s) about to be tested. 

“…it is very important to ALWAYS verify and ensure the limits selected are appropriate for the aircraft and/or the instruments that are going to be tested.“

How to set up the limits 

 

NOTE: Before creating new limits refer to the appropriate AMM (Aircraft Maintenance Manual) or CMM (Component Maintenance Manual) for the actual minimum and maximum values to be applied. 

 A. If the limits don’t exist:  

Go to Setup 2 and create the limit file following these steps: 

  1. From Main Menu display, press “Page 2” button.  
  2. Screen is displayed with four options (Setup 1, Setup 2, Setup 3 and Change User Pin#). Select Setup 2.  
  3. From keypad screen, input user PIN (manufacturing default PIN: 123456– unless already changed by the user).  
  4. Select Limits Create/Edit/Delete.  
  5. Select Create Custom Limits – enter the parameter values for ALT, ROC, CAS, RtCAS, MACH, and ALR (Auto Leak Recovery). Note: You can select each parameter by touching the parameter or cycle through each parameter using the “Enter” key.  

Note: It’s recommended to Save the Limits with the aircraft name. 

The limits profile currently in use is displayed on the right upper quadrant of the screen (Figure 1). 

DPS1000 Front Screen Image

B. Selecting limits: 

If the operating limits exist because they were already created go to Setup 1 and select the limit file following these steps: 

  1. From Main Menu, press “Page 2” button.  
  2. Screen is displayed with four options (Setup 1, Setup 2, Setup 3 and Change User Pin#). Select Setup 1. 
  3. Touch “Limits View/Select” key. 
  4. Touch “Select Limits” 
  5. Select applicable limit from the list displayed. 
  6. Click OK. 

NOTE: The tables showing the default and max limits profile values included in the DPS1000/1811NG Test Sets can be found in the corresponding user instruction manuals under “Appendix B: Operating Limits”. 

Viewers of this article also were interested on How to Connect the DPS1000 and 1811NG to a Tablet 

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How to interface a TT1000A and TT1200A with an Aircraft?

How to interface a TT1000A and TT1200A with an Aircraft?

All Posts, Ground Support Test Equipment

This is a brief description of some of the concerns regarding the proper point for interfacing the Barfield TT1000A and TT1200A test sets into the aircraft Turbine Temperature Indicating System. 

Where to break into the aircraft engine temperature indicating system to perform Indicator tests?   

Break at the engine terminal block

If the aircraft indicator is a servo, digital, or glass, it is recommended breaking into the system at the engine terminal block.

Test at the indicator

Note that if the indicator does not use aircraft power and has only 2 posts for the electrical connections then it is NOT recommended to break into the terminal block.

This type of system is powered solely by the millivoltage from the thermocouples and must be tested at the indicator.

The indicator is calibrated to measure K type thermocouple millivoltage with a specific in-line resistance, typically 8.00 ohms.

If the Test Set is configured to simulate the 8.00 ohms and interfaced at the terminal block, then the indicator will see the simulated 8 ohms plus the combined resistance of the Chromel and Alumel wire lengths between the terminal block and the indicator.

The result will be that the indicator will read lower than the Test Set display.

TT1000 Schematic Barfield

Where to find the manuals?

To learn more about the proper usage and interfacing of the test sets, please refer to the appropriate Instruction Manuals, availble on our website barfieldinc.com:  56-101-00901  or 56-101-00930  

TT1000 Temperature Tester - Barfield
TT100A