I noted that the localiser (LLZ) and the glide path (GP) can have different frequencies. For example, at Heathrow the AIP gives the LLZ frequency for Rwy 09L as 110.3 MHz (used in FS) and for the GP as 335.0 MHz. This difference in frequency appears at other UK airports, with LLZ being in the 1xx.x MHz range and the GP in 3xx.x MHz range.What happens in real life? Is there a need to select both, or are they linked in some way so that selecting the LLZ also tunes the GP?

The frequencies are paired. Not sure why the AIP shows the G/S freq, as I have never ever seen an ILS receiver with a separately tunable G/S receiver.RegardsBob ScottATP IMEL Gulfstream II-III-IV-V L-300Santiago de Chile

The FAA Instrument Flight Handbook says:"VHF Localiser provides horizontal guidance 108.10 - 111.95 MHz...UHF glideslope transmitter provides vertical guidance 329.3 - 335.0 MHz"The relationship between the frequencies appears to be a sawtooth one. Anyone know what it is, and are they automatically linked in the real world?

Found this explanation at:http://www.ntsb.gov/events/KAL801/Exhibits/Ex_9E.pdfAs for VOR or LLZ, "the [frequency] control selects a VHF localizer frequency which automatically selects the paired UHF glideslope frequency using a 2-of-5 binary, bridge tuning, or serial data word format." (so now we know.... :-roll )regards,Jeff

Thanks.

Similar to DME. DME's also have their own frequency. But they are paired with a VOR frequency.

And another little-known trivia tidbit, is that all TACAN stations have integrated DME...the freq is paired with the TACAN channel. The channel pairings can be found in the military Flight Information Handbook (FIH). It's still available on the NGA website until it goes behind the .mil/.gov firewall this year.AFAIK, FS doesn't do TACANs though. A shame, that.Bob ScottATP IMEL Gulfstream II-III-IV-V L-300Santiago de Chile

I've always wondered on TACAN, what makes it different from VOR/DME? I've heard something about the fact that it eliminates slant-range or something. Any truth to that?----------------------------------------------------------------John MorganReal World: KGEG, UND Aerospace Spokane Satillite, Private ASEL 141.2 hrs, 314 landings, 46 inst. apprs.Virtual: MSFS 2004"There is a feeling about an airport that no other piece of ground can have. No matter what the name of the country on whose land it lies, an airport is a place you can see and touch that leads to a reality that can only be thought and felt." - The Bridge Across Forever: A Love Story by Richard Bach

Nope, the DME signal off a TACAN station is exactly the same as what you get from a VOR-DME, VORTAC, or ILS-DME. Slant range and all. And TACAN has this nasty error mode called 40-degree lock-on error, which I've only seen once...but then you only need to see it once to be very wary.TACAN uses UHF frequencies (instead of VHF) to transmit the radial information, making the antenna size requirements much smaller, and thus making portable ops possible. A TACAN antenna is a cylinder about the same size/shape as a 100 gal water heater.CheersBob ScottATP IMEL Gulfstream II-III-IV-V L-300Santiago de Chile

>The FAA Instrument Flight Handbook says:>>"VHF Localiser provides horizontal guidance 108.10 - 111.95>MHz...UHF glideslope transmitter provides vertical guidance>329.3 - 335.0 MHz"And to add to this, Localiser frequencies are only on the odd tenths in that range. Example being 108.20 and 110.85 are VOR and not ILS frequencies whereas 108.50 and 110.35 are LOC/GS frequencies. And yes, the GS frequencies are paired up with the LOC frequencies inside the VHF/NAV receiver. Tuning a LOC automatically tunes the GS.Cheers,JohnBoeing 727/737 & Lockheed C-130/L-100 Mechanichttp://www.sstsim.com/images/team/JR.jpg

Ah. I just remember reading something about elimination of slant range for military aircraft that had the equipment but I wasn't sure the credibility of the information. I knew the DME information for us Civies was the same as civilian DME.----------------------------------------------------------------John MorganReal World: KGEG, UND Aerospace Spokane Satillite, Private ASEL 141.2 hrs, 314 landings, 46 inst. apprs.Virtual: MSFS 2004"There is a feeling about an airport that no other piece of ground can have. No matter what the name of the country on whose land it lies, an airport is a place you can see and touch that leads to a reality that can only be thought and felt." - The Bridge Across Forever: A Love Story by Richard Bach