LOM - Low frequency Outer Marker

This is an outer marker with a co-located NDB (non directional beacon).
Most larger airports have a OM & LOM co-located so you can see where the OM is as you fly around.

As you fly around the traffic pattern, you will notice the needle always points to the LOM. This is why it's called a "bird dog" because it just points TO the station. The needle gives you relative bearing to the station. If the needle is in a RMI (Radio Magnetic Indicator) as it is in the 707 & 727, then the needle gives you a magnetic bearing to the station. This RMI makes it easier because you don't have to try to figure the relative bearing and apply your compass heading to make it a magnetic bearing.

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http://www.fltplan.com/AwDisplayAppChart.exe?CRN10=1&CARRYUNAME=PILOT&DEPTARPT=KMDT&ARRARPT=XPTG&TYPECHART=00188IL13.PDF&END=END&WINDOW=YES

This link takes you to an approach plate for the Harrisburg airport. The ILS for RW-13 has a LOM co-located with the OM. The LOM is named ENOLA. The frequency is 204 and the ID is MD. As you fly the pattern with ENOLA tuned in, place the small switch on the RMI to ADF. You can display either ADF or VOR in the RMI. This is the basic tool for flying the non glass planes and keeping track of where you are.

As you fly downwind keep an eye on the needle in the RMI. As you fly abeam the OM the needle will point 90 degrees to your heading - no wind. This will tell you where you are in the traffic pattern. Fly a few miles past the OM and start you turn back to intercept the LOC. The LOM needle is still pointing to the OM so you can see your magnetic bearing to the OM and thus the position of the LOC. As you approach the intercept for the LOC the needle will show how far you are from the LOC. When you intercept the LOC the needle will point to the inbound course - no wind. As you pass the LOM the needle will swing and you use the tail of the needle to track the inbound LOC.

If Bruce Scott lived near-by I would get together with him and produce a video to show how this works.  8-)

Lou