LORAN C

[Guest Sabadin]

Hi all, I was wondering if anybody has information on how to fly using LORAN C and how the receiver works, been combing the web for days and it is proving to be a very elusive topic hehe. Any help would be greatly appreciated.

[Guest fame]

Loran-C determines present position from the intersection of lines of position (LOPs), just as VOR and NDB determine present position from the intersection of LOPs based on radials and bearings. Loren-C is deferent from VOR and NDB: a Loren-C LOP is not a straight line. A Loren-C is a curved line, a hyperbolic curve, or hyperbola, for short.Loren-C requires a network, chain, of at least three stations to determine a fix, one of which is designated the master station, while the others (a minimum of two) carry a secondary station designation. The master sends out a continuous string of pulses in the low frequency band (100kHz), which in turn triggers the secondaries to send out similar signals.The Loren-C receiver decodes all the signals, separates master and secondaries based upon coded differences that identify each station, corrects for the amount of time it took the secondaries to be triggered, and then subtracts the difference between receipt of the master signal and each of the secondaries.In just a few short years, Loren-C has grown from obscurity to perhaps the most significant new system of air navigation for general aviation since the VOR system. Loren-C approaches are just now beginning to replace and supplement less accurate and more difficult to fly VOR and NDB approaches in the US, and more are planned.Despite their increased accuracy, Loren-C approaches are still nonprecision approaches (No glide slope), and as with all nonprecision approaches are limited to minimums no lower than 400 feet agl and 3/4 mile visibility, but the ability to achieve those minimums with Loren-C is significantly increased. Loren-C approaches will not require the purchase or installation of additional ground facilities, it will only be necessary to design and flight test the approach procedure based upon signals from existing Loren-C facilities. If Loren-C were used for nothing more than to retire the existing NDB approaches and lower the minimums for many VOR approaches that alone would justify the system for most pilots.For all these reasons, it appears that Loren-C's future is very bright, especially if the system can be expanded to include more of the rest of the world, which isn't bad for a system that was never intended to be used for air navigation in the first place.Tom G, Sr.

[Guest jrewing]

You might find the information in the Aeronautical Information Manual useful. Check out http://www2.faa.gov/atpubs/aim/Chap1/aim0101.html#1-1-15I don't agree with the previous poster's comment about the future of Loran looking bright. I think GPS (with WAAS) is the where things are headed.John

[Guest Sabadin]

The reason LORAN C has a bright future is that it is most likely going to become the official backup in the event that GPS should ever be inserviceable for any reason. Now if only there was info on the net on how to actually use the blasted thing as a pilot lol.

[Guest fame]

Hi:How can you say that... in light of the detailed information that I supplied?Tom G, Sr.

[Guest jrewing]

I'm not saying that LORAN is/was a bad system, but for better worse, it's being supplanted by GPS.Quoting from an address made by Edward M. Bolen, President of the General Aviation Manufacturers Association to the US House of Representatives Committee on Transportation and Infrastructure back in June of 2000,"... First, there are few IFR en route receivers in the general aviation fleet. Very few, if any, LORAN receivers are installed in commercial aircraft. No IFR terminal/approach receivers were ever manufactured. And no LORAN instrument approach procedures were ever developed."It is important to note that a manufacturer tried 'non-precision approach' certification over ten years ago. Millions of dollars were spent to certify a LORAN approach receiver, without success. The manufacturer concluded that even with better antenna technology, LORAN signal availability and integrity were not adequate for instrument approaches. As GAO points out, LORAN could never provide vertical guidance. "I'm a CFII and I've had a GPS RAIM failure in actual conditions. I found that VORs, NDBs, and marker beacons make nice backups. John

[woodreau 0]

For the most part you use a LORAN-C receiver the same way you would use a GPS receiver. (Extreme simplification as explained below.)Both are RNAV navigation systems and both use a database. The difference is where each system receives its position information. LORAN-C via the ground stations, GPS via satellites.With a Loran-C receiver, you can enter a flight plan into the receiver and it will provide you with course guidance on the LCD screen - via a stylized OBS, and deflection needle. Center the needle, you're on course, and it could tell you how far away you were from the waypoint. You can also tell the receiver to fly direct-to a point, just like a GPS.Early GPS receivers looked like LORAN receivers, two lines of info, 18 characters each, LCD screen. But GPS receivers have progressed and incorporated things like a moving map (which made displaying that course info on the OBS on that two line screen obsolete), integration with VHF comm radios, VNAV, etc. I haven't seen a Loran-C receiver that gives you a moving map.Originally LORAN was developed for maritime use several decades ago. Only recently in the 1980's was it adapted for aeronautical use. The commerical maritime industry has switched exclusively to MDGPS (maritime differential GPS) for navigational info, and with the proliferation of inexpensive GPS receivers, LORAN C use in recreational boating I believe has pretty much disappeared as well.I do remember (in the 1980's) having to plot my position (sailboat) on a chart by interpolating the TD's from the LORAN receiver and then reading my lat/long from the chart. But that was using an old maritime LORAN receiver. Newer maritime and aeronautical LORAN receivers do the conversion from TD's to lat/long for you.Anyways getting back to the topic, there is no such thing as an approach dedicated to LORAN, and I don't think LORAN was ever meant to be used for approach, instead it was to be used for enroute navigation, after which you switch to ILS.But if there is a approach certified LORAN, you'd have to have an up-to-date navigation database for it, and you would have to use the RNAV(GPS) approach plates to fly the approach. The reason why the FAA renamed the approaches from GPS to RNAV(GPS) was to allow the airline industry with the FMS equipped aircraft to fly the GPS approaches. And FMS's are just another RNAV navigation system.Anyways, enough rambling from me. I never thought I'd see the day where I'd have a "I remember when we used to...." do things the old-fashioned way and have to explain.... Since I still consider myself young.Cheers :()Woodreau / KMVL