AV8 - GPS killed EARLE! Traditional Cache

This cache will take you to a location that is known by only a few (namely aviators) but is hardly ever seen in person. This location is known by local pilots as EARLE. This location is what was an NDB (non-directional radio beacon) in other words, it is an AM radio broadcast tower. This is however not a repeater of 890 WLS-AM from Chicago, it does however provide an important role in the local air traffic arriving into the Grater Lafayette area at the Purdue University Airport. This AM radio tower used to transmit an AM radio signal on 401 AM or 401 kHz. The sole transmission of 401 AM is a beeping morose code transmission of the letters "L" and "A" (the two letter identifier for EARLE) which pilots would listen to repeatedly as verification they were tracking the right signal - hence the subtitle (.-.. .-) SEE THE MAP SECTION BELOW

This omni-directional signal was used for tracking to or bearing from certain locations - namely the airport. In fact there was an approach based off of the EARLE NDB as the sole reference of navigation. This was called the Lafayette NDB (runway) 10 approach.

This was one of the approaches used by pilots as a way of descending through the clouds on a bad weather day (when the ground was not visible at altitude) in order to breakout of the clouds and see the runway visually for landings in less than questionable weather. NDB's had only marginal accuracy that got even worse when strong wind pushed the aircraft trying to track the NDB signal. EARLE has yet another function which will be discussed later…..

Speaking of EARLE, the name is literally the five letter identifier given to the navigation station when it was commissioned by the FAA (Federal Aviation Administration) or its predecessor the CAB (Civil Aviation Bureau). See you thought it was the pilots need to constantly personify their tools of the trade.

Okay, so why exactly did "GPS kill EARLE"? Starting with Y2K when accurate GPS was available to the masses (and geocaching as we know it today first began) aviation was also given a boost into the 21st century. Though GPS had already been previously available in the cockpit, it was not terribly accurate enough for navigation, just used only as a second or third reference to pilots. Nowadays, GPS is commonplace in the cockpits of even the smallest planes giving pilots accuracy of up to .03' while on approach. Wind is also taken into account and the track is adjusted for the wind conditions the aircraft is experiencing. The need for NDB as a navigational aid has gone the way of the old DC-3’s. Literally, "GPS DID kill EARLE !" As of July 7, 2005 EARLE NDB was officially decommissioned by the FAA, no longer able to be used for navigation.

SO……Why is EARLE still here ??????? The answer is quite simple EARLE served also as what’s called a Compass Locater (LOM) or Outer Marker for yet another approach to the same runway 10 at Purdue Airport. This approach is called the ILS 10 and is another lecture for another pilot ground school classroom; however, what is important is that EARLE serves as notification to the pilot that he/she is exactly 4.7 miles from the end of the runway.


This serves as the location that the landing gear and flaps are lowered for landing, and pilot begins to make to final decent to 200 feet above the ground to look for the runway. Day in and day out pilots can be heard calling out “EARLE inbound…” or “EARLE outbound…” to the Lafayette Air Traffic Control Tower over the radio when flying over this location.

THE CACHE...... is NOT located within the fence and does not require you to go over the fence or remove anything from within the fence! Heed the warnings of the sign posted by the FAA

Cache is a micro container and contains a log in a waterproof bag - but no pen BYOP! Cache IS on public property and does NOT require you to trespass! Parking is available roadside, but please be careful of traffic.

Congratulations to tbaker2500 for the FTF on this one!