Time Domain Vs  Frequency Domain Reflectometers in Aviation Operations

Time Domain Vs Frequency Domain Reflectometers in Aviation Operations

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.

How to use a Frequency Domain Reflectometer in Aviation?

How to use a Frequency Domain Reflectometer in Aviation?

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 the Frequency Domain Reflectometer  with Boeing App Works?

How the Frequency Domain Reflectometer with Boeing App Works?

 Barfield Inc., in partnership with Bird, has developed the FlightHawk ( formerly known as SiteHawk-AV), a Frequency Domain Reflectometer (FDR), designed for aviation. It is aim at reducing aircraft downtime when troubleshooting any RF cable and antenna in an aircraft. The new Boeing App creates a layer of support simplifying testing of any navigation unit.

The FLightHawk connects from the end of the coaxial cable, testing if damages exist by identify the Distance to Fault (DTF) and capable of performing a frequency sweep to the antenna.

The latest App, allows for any technician to quickly diagnose problems with the navigation system by splitting the problem with certainty between the LRU and the connection to the antenna.

This video shows how the Automatic App made for Boeing works. Currently it is available with Boeing 737,767 and 787 coax and antenna configurations. 

The Automatic App allows to:  

  • Select an aircraft model.
  • Select the RF system.
  • It will automatically calibrate, select the cable type and the distance to the antenna for that specific system in that specific aircraft.
  • It will give you  a PASS or FAIL
  • If FAIL it will take you to the Manual mode to do the VSWR ( Voltage Standing Wave Ratio ) and DTF (Distance to Fault) analysis.

The simplicity of the App allows for any technician with some experience in avionics to run a test of any navigation unit. Qualifying the event facilitates the job for technical support, as many times expert avionics technician are not available right onsite. 

After running the test, the unit is capable of sending the information to an avionics manager, located remotely and transfer a picture of the signal via Bluetooth to a phone.  More Boeing configurations will follow.

How Airlines Are Testing Aircraft to Bring Them Back to Service

How Airlines Are Testing Aircraft to Bring Them Back to Service

A few months ago  we had shared a document of How Airlines Were Speeding Up Aircraft Turnaround Time. We are bringing back this topic back  as airlines are using the Frequency Domain Reflectometer called the FlightHawk to test antennas and coax cables to bring aircraft back to service. 

We published this document highlighting 3 easy steps:

3 Easy Steps - Barfield

1. Select Mode Automatic or Manual

Frequency Domain Reflectometer - Boeing App Step1 - Barfield

2. Pick Aircraft Type and Navigation System

Frequency Domain Reflectometer - Boeing App Step2 - Barfield

3. Test: Pass or Fail

Frequency Domain Reflectometer - Boeing App Step3 - Barfield