On Wed, Jul 7, 2010 at 7:02 PM, Paul Hayward <pdh_at_mmcl.co.nz> wrote: > > So what is there in the SAR cockpit that says 'go left' or 'go back' as the > pilot homes in on a 121.5 MHz signal over a black ocean ? > That's a good question since technology has changed a lot over the past 10 years and I'm not familiar with all of the changes. However at one time an "IFR" cockpit would have had an Automatic Direction Finder (ADF) as part of its standard equipment. Many airports had nothing but ADF approaches (with the minimums raised). Today, with relatively inexpensive GPS units, and almost ubiquitous GPS approaches, I'm not sure that an ADF would be that usual. The ADF is a radio that can be tuned to the normal aviation channels and is coupled to an indicator that is basically an arrow (similar to a compass) that points toward the signal (or away from it - sometimes the trick is how to know which way to the source). One of the channels it can be tuned to is, of course, 121.5Mhz. However an ADF does not tell you how far away the "beacon" (or whatever signal it's tuned to) is from you and generally you only know you've gone over it when the needle suddenly swaps ends. One trick is to fly at right angles to the signal and see how quickly the bearing to the source changes. If it changes quickly you are close. A helicopter, with its ability to fly slowly, probably could home in on a beacon transmitting on 121.5. Joq probably has a better insight to this. Craig Jungers Moses Lake, WA www.nwkayaking.net *************************************************************************** PaddleWise Paddling Mailing List - Any opinions or suggestions expressed here are solely those of the writer(s). You must assume the entire responsibility for reliance upon them. All postings copyright the author. Submissions: PaddleWise_at_PaddleWise.net Subscriptions: PaddleWise-request_at_PaddleWise.net Website: http://www.paddlewise.net/ ***************************************************************************Received on Wed Jul 07 2010 - 20:04:40 PDT
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