Transponders: They make the whole system work

They make the whole system work By Jim Sparks Air Traffic Control (ATC) has jokingly been called "an organization funded by the railroads to discourage travel by air." However, considering the total number of aircraft operations daily and the...


Many of the systems being produced and installed today use digital technology and include self-test capabilities. When associated with a digital control head and a digital air data computer, the entire system can be self-monitored and theoretically when any connection is broken the self-test should be able to verify system integrity. I asked my local Airworthiness Inspector about using the self-test to satisfy the FAR 91.413 requirement to verify no correspondence error; his comment was, "There is nothing like physically seeing it operate." This is a philosophy that is consistent with the nature of our industry.

What the future holds
Next up, for new aircraft delivered after March 31, 2004 upgraded Mode-S transponders with flight identification will be required for all aircraft regardless of weight for all IFR, and VFR flights within Europe. In service aircraft compliance is slated for March 31, 2005.

Reduced Vertical Separation Minimums (RVSM) is an issue that will impact many of us working with aircraft that routinely operate above Flight Level 290 (29,000 feet). This will go into effect in January 2005 for the continental United States and even though TCAS is not a requirement for RVSM operation, any aircraft incorporating collision avoidance will have to upgrade to TCAS version 7. Prior to this an alert would be issued if an aircraft were perceived to be within 1,250 feet of a TCAS equipped machine. With reduced vertical separation TCAS version 7 will provide the alert at 850 feet.

The transponder is an essential contributor to aviation safety and it is our responsibility as technicians to ensure continued proper operation. This will continue to maintain the well-being of passengers, crew, and the aircraft. After all I don't think most of us would look good carrying oil cans, or lubricating wheels on a train.

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