Thursday, January 7, 2010

End of the Line for LORAN?

Before there was GPS, there was LORAN (LOng RAnge Navigation).

The Piper Archer II with which I was associated before N631S joined our family had a Northstar M1 LORAN-C receiver in its panel - a very nice and very useful piece of kit.

The LORAN didn't have a moving map, and it wouldn't tell you your position with a Circular Error Probability of 15 feet (more like a couple 10ths of a mile). But it was a wonderful aid to situational awareness under both VFR and IFR rules. I liked it very much.

Now, it is being reported that the LORAN signals will be turned off beginning in February, with termination to be completed in the Fall. According to the US Coast Guard:

In accordance with the DHS Appropriations Act, the U.S. Coast Guard will terminate the transmission of all U.S. LORAN-C signals effective 2000Z 08 Feb 2010. At that time, the U.S. LORAN-C signal will be unusable and permanently discontinued.

In the last couple of years there has been much discussion about the potential that an enhanced LORAN system (the so-called "eLORAN") would have as a backup to GPS. There are worries about the ability of the Air Force to keep the GPS satellite constellation fully populated, and the FAA is very desirous of shutting down most (or all) of those expensive-to-maintain VOR's. But the Coast Guard is taking the position that:

If a single, domestic national system to back up GPS is identified as being necessary, the Department of Homeland Security will complete an analysis of potential backups to GPS. The continued active operation of Loran-C is not necessary to advance this evaluation.

I'm sure that the old LORAN-C equipment has become devilishly difficult and costly to maintain, and that there is a very good rationale for pulling the plug on it. But that does leave us with a lot of our eggs in the GPS basket. We had better watch that basket really closely. And I expect that as long as N631S and I are flying together I'll be dialing in VOR frequencies as backup to GPS navigation.

So let us bid a fond farewell to the faithful LORAN-C system. It had a good run and, who knows? Someday we might see the technology resurrected in modernized form.


Dr.ATP said...

My father used LORAN as a navigator in WW2; that's a long run for an engineering solution! Still, I hate to see any navigation system shut down. While WAAS has made a large improvement in GPS reliability, the system is not perfectly reliable. As a later edition of Nathaniel Bowditch's American Practical Navigator wrote, "A wise navigator never relies on any 'black box.'"

What this means is that flight crews in remote areas (oceanic or otherwise) should keep more detailed navigation logs, but of course they won't. You'll still see turbine airplanes flying 1500NM "direct" with no sense of what's happening in between takeoff and touchdown.

The last CONSOLAN station (on Nantucket) was active within my memory. I guess I can say the same of LORAN.

Frank Van Haste said...


Thanks for stopping by. Agreed, it's sad to see a reliable nav system just "turned off". And I'd really like to see a good backup for GPS.

Although, LORAN had its issues too. I recall one time while flying with my instructor soon after I got my instrument ticket, we penetrated some HEAVY precip. And the LORAN hated it...the ground speed readout went down to something like 30 knots (the speed shown on the DME never budged). As soon as we flew out of the rain the LORAN recovered to normal. Made for an interesting lesson.

We DO need a backup to GPS. The VOR array is fine for now, but that technology is getting elderly, too. I like the idea of an inertial navigation system with occasional position updates from GPS. Think we can do that for <$1,000?

Stay well,


Rich Van Haste said...

Speaking of legacy navigation systems…


Frank Van Haste said...


Good one. Thanks!