Talk:Transponder Landing System

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What? "Variations - There is a similar truck mounted system for military usage." I've been flying military aircraft for 17 years and have never heard of TLS. Dr1819 20:39, 30 June 2006 (UTC)

Firefly truck mounted TLS system. It wasn't around 17 years ago. --Dual Freq 21:23, 30 June 2006 (UTC)

It appears they're using different terminology. DME equipment is transponder-based, not the normal transponder aboard the aircraft, but the plane interrogates the DME and the DME responds. The variance in time is calculated to produce DME readout. Used with a VOR or a localizer signal it can provide non-precision approaches. But the picture can't be an ILS because ILS requires a third, physically separate structure to produce the glideslope. Dr1819 16:50, 14 July 2006 (UTC)

The picture is a TLS system, I took the photo. I believe it is the first of one of the first commissioned in the US. There are no Localizer or Glideslope Array like you would see on a normal ILS. It only has a single antenna for each frequency. --Dual Freq 02:32, 15 July 2006 (UTC)

TLS does not use a glideslope or localizer facility, but the ground based equipment transmits on the ILS frequencies. There is an antenna for the GS frequency and one for the Loc signal. The system does not use or require DME. But it can be set up to transmit marker signals from the TLS station. It uses the aircraft transponder like secondary radar, or beacon or IFF whatever you want to call it. You tune your transponder to the facility specific code, the TLS interrogates your transponder, when it replies the TLS calculates the location of your aircraft using direction finding type antennas that calculate the time of arrival of the signal and it figures out where your plane is in the air. The TLS then transmits the appropriate ILS type signals to you using the correct frequencies so you use a standard ILS receiver. The problem is, only one plane can use it at a time. If your aircraft is left of course, it tells you to fly right until you get to center line, unfortunately it tells everyone to fly right even if a second plane is to the right of course they see the signal meant for you. Everyone sees the same signal because the transmitted signal is only for the aircraft interrogated. This is unlike ILS where two complex antenna arrays set up a pattern and your plane sees the correct signal at the correct time. TLS transmits the signal you need based on where you are. I thought this was fairly clear in the article, but maybe I need to look over the sources and clarify that. See also Mfr. TLS Tech page. --Dual Freq 02:32, 15 July 2006 (UTC)