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Commercial aircraft come with embedded position or proximity sensors to detect equipment failure. The sensors are placed in various strategic locations, such as forward wing slats/flaps, hatches and doors, landing gear, and engine thrust reversers, and are an important safety feature for monitoring the status of these aircraft components. However, these proximity sensors exhibit significant failure rates, causing unnecessary and costly aircraft turnbacks and delayed flights.  
Better Sensor Testing

To address this sensor failure problem, aviation consulting firm R.H. Caldwell & Associates looked at current automated test applications and determined that automated test techniques could be used to identify, predict and analyze the failures of these aircraft sensors. In cooperation with Geotest — Marvin Test Systems, Inc., the company designed an inexpensive PXI-based Automated Test Equipment (ATE) system that can be installed in existing aircraft during routine ground maintenance.

Changing the traditional process
Before the introduction of ATE for aircraft sensor testing, maintenance workers and technicians had to manually test the sensor's two wire pairs through an Aeronautical Radio, Incorporated (ARINC) connector. Workers had to locate the appropriate sensor pins on the connector and verify the health of the sensor by measuring DC resistance and inductance while placing the test component in various positions. These manual techniques slowed the process of identifying the faulty sensors or wiring and caused significant delays and expense in troubleshooting and replacing the sensors.

In an article for the March 1, 2010, issue of Test & Measurement magazine, Roger Caldwell, project consultant for R.H. Caldwell & Associates, said the new PXI-based test system conducts real-time tests on a variety of aircraft sensors. According to Caldwell, the system also provides the location of the failed sensor and gathers data for performance analysis and failure prediction.

The PXI system which is based on the GX7600, and includes a switching matrix, DMM and ATEasy application, offers many new features and functionality, including:
Quick installation and setup into aircraft line-replaceable unit (LRU) locations
An ATEasy based test program that provides automated access to the entire sensor network, with customizable measurement and control of all test system resources
The ability to process logged data so that operators can predict impending sensor or network failure
An intuitive User Interface providing easy control of the test system by maintenance personnel

Moving forward, there is great potential for using this technology for other aircraft test applications. Some examples of these applications include:
Modifying the proximity sensor test system to support other aircraft types beyond the B737 — Classic
Testing of aircraft fuel system components, such as wiring, pumps, and gauges
Adding Time Domain Reflectometry (TDR) technology to allow verification of coaxial cable and antenna components as well as locating faults in long cable runs throughout the airframe

Nearly any aircraft maintenance procedure that involves an electrical interface can benefit from the test system that Geotest helped create for R.H. Caldwell & Associates. Because the system's hardware and software is flexible and expandable, you can configure the ATE system for a variety of test interfaces and applications according to a user's specific needs and requirements.

To learn more about this PXI-based proximity sensor test solution, download the associated whitepaper. For additional ATE solutions, visit Geotest's website.

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Geotest-Marvin Test Systems, Inc.
1770 Kettering
Irvine, CA 92614
1-949-263-2222
1-888-837-8297

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