Showing posts with label OMNI. Show all posts
Showing posts with label OMNI. Show all posts

Friday, August 2, 2013

Old School Air Navigation


After sharing some early aviation history with old NFO, he suggested I do a blog entry.

One unchanging challenge in aviation is finding your way from one point to another without getting lost. For non pilots, this may be puzzling. Show me any pilot who claims he/she hasn’t been lost, and I will show you someone who’s veracity is suspect.

Today’s newer airliners and many General Aviation airplanes have “Glass Cockpits”. Using several different transmitted date sources, including GPS, and along with sophisticated autopilots, they will nearly fly themselves. In the case of some advanced drones, they will fly themselves. For those who want more information.


The early developer of air navigation systems was the U.S Postal Service in the 1920’s to support their airmail service. First came ground markers, large concrete arrows placed along routes. Some have survived.


Next came lighted beacons, lighted airports, and rudimentary aircraft lighting. Akin to the Pony Express way stations, if you will.


Some of these operated into the late 1950’s. I can remember seeing them in Wyoming as a child. Some were left at higher elevations to aid night flight terrain clearance.

The twin challenges of weight and reliability in equipping airplanes with radios started to come together in the 1930’s. This led to the development of radio ranges and radio beacons (Automatic Direction Finders – ADF). 


The range system was later refined into the Omni Directional Navigation System (OMNI) still used today. With the proper equipment, OMNI will give you the distance to the station. With ADF, you have an indicator pointing toward, or away, from the radio station. In general, you need bearings from two ADF transmitters to locate your position. You can do the same with two separate OMNI stations.

Another newer aid was LORAN, a system using two Low frequency transmitters many miles apart,  and timing the difference between the two transmissions reaching you. Considerable math is involved if you receiver can’t do it for you. LORAN will cover vast areas but is subject to things like sunspots and isn’t terrible precise. A version was used by the British in WWII to guide their bombers over Europe.

At airports (and on aircraft carriers) are aids to help the pilot’s approach. One, glide slope, provides vertical guidance as to the preferred descent profile. The other, the localizer, provides left/right guidance. Two other transmitters complete the system, the outer and middle markers. These help you judge your distance from the runway. This system allows approach to landing operations in poor visibility.
In all cases, the first pilot requirement is to fly the airplane. Asiana 214 is one example of what not to do. 


For all you professional pilots out there, the CFIs and those with  thousands of hours of PIC time, please remember I was a lowly Cessna/Piper driver before you pick the post apart.

 That said, I can beat any of you in a conventional gear spot landing contest. Oh yeah, still have the swagger!