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    Re: Loran-C
    From: Tmstock
    Date: 2009 Mar 24, 08:09 -0400
    I should note that ADS-B uses GPS for positioning; it has it's own data link.

    Sent from my iPod

    On Mar 24, 2009, at 6:49, tmstock---.net wrote:

    Backup strategy for the National Airspace System is an evolving issue - particularly since the cornerstone for what is called the Next Generation Air Transportation System (NEXTGEN) is Automated Dependent Surveillance-Broadcast.  This technology uses GPS to allow aircraft to send their position and velocity information to the ground and to each other for situational awareness as well as applications which enhance efficiency and capacity.  The issue here is that with a GPS outage, both aircraft navigation and ground surveillance is lost, versus the current approach using primary and secondary radar for surveillance and distributed, ground-based aids for navigation. 

    The delemma facing NEXTGEN architects is whether to eliminate the thousands of ground based navigation aids and hundreds of radar installations in favor of technologies which depend on one easily-disrupted technology (aka, ignoring the problem), retain a mix of legacy (read expensive) systems to act as a backup for GPS and ADS-B, or adopt a new technology - eLoran - and convince 200,000+ aircraft owners to shell out anywhere between $5K and $150K per aircraft for what they see as a low probability event.

    As someone who has worked on teams examining the issue, eLoran appears to be the only good engineering  choice; however, the FAA must balance the best engineering solution with what is for the Agency the bad economics of appearing to be the primary user of an expensive technology...in other words, looking like they want their pocket picked to pay for it. 

    I would not worry too much about the issue for a bit.  Most airlines have been and will continue to be exceptionally conservative about new technology - generally adding systems such as GPS and ADS-B to their fleets through new aircraft equipage versus retrofit - so figure at least 20 years for big changes in the way things get done in the NAS, if not longer.  Twenty years is plenty of time to argue the pros and cons and develop a policy...and if we are lucky, it might even address the problem.




    On Tue, Mar 24, 2009 at 12:00 AM, Lu Abel wrote:

    > ... so I'm really
    surprised the FAA is accepting this call for eliminating e-Loran.



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