outer marker

[′au̇d·ər ′mär·kər]

(navigation)

That instrument landing system (ILS) marker farthest from the approach end of the instrument runway; the marker is located 4.5 miles ± 1000 feet (7240 ± 305 meters) from the end of the runway and not more than 250 feet (75 meters) from the extended center line of the runway.

outer marker

An ILS (instrument landing system) navigational facility in the terminal area navigation system located at 4 to 7 miles (6 to 11 km) from the runway edge on the extended centerline. It transmits a 75-MHz fan-shaped radiation pattern, modulated at 400 Hz (fan markers and station markers radiate at 3000 Hz, whereas middle markers do so at 1300 Hz), keyed at two dashes per second, and received by compatible airborne equipment. It indicates to the pilot, both aurally and visually, that he or she is passing over the facility and can begin the final approach. See instrument landing system.

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References in periodicals archive

Pilots responded significantly slower to the onset when it occurred outside the outer marker (6.8 s) than when it occurred at (4.9 s) or inside (4.6 s) the outer marker, t(403) = 3.37, p < .001, and t(403) = 3.49, p < .00 1, respectively.

Supporting decision making and action selection under time pressure and uncertainty: The case of in-flight icing

DUNNS sports a Localizer Outer Marker (LOM) with both a marker beacon and an NDB transmitter.

Capital line items

The Aeronautical Information Manual does indeed make the recommendation laid out in your sidebar, "What the FAA Says," to broadcast your intentions, including "the type of approach being executed, your position, and when over the final approach fix inbound (non-precision approach) or when over the outer marker or fix used in lieu of the outer marker inbound (precision approach." But most of this information merely clogs up the frequency and is meaningless to the VFR pilots you are trying to avoid.

Missing the point

With the physical outer marker they couldn't do that, but now they can since the OM was decommissioned.

Why the change?

Radar data associated with the accident aircraft shows it crossed the final approach course from the west between the initial approach fix and the outer marker. The airplane's track overshoots the final approach course to the east and then corrects back so that it is on course at the outer marker.

More likely is that putting the published missed at WATON (a localizer outer marker at a nearby airport) was an ATC request to place the hold at a fix already in use for this busy airspace near Seattle.

Read beside the lines

* Failure to identify outer marker: Use DME, a cross radial or time.

Five ILS gotchas: flying the ILS isn't rocket science, but there are a few mistakes pilots regularly make. Knowing what they are and how to prevent them can keep you out of the weeds

Me: "PDK tower, Bonanza 12345, 3000 feet, ILS 20L inbound." At this point I was 1.5 miles from the outer marker, which is where well-trained Bonanza pilots put down the gear and start riding the ILS rails down to terra firma at 115 knots.

Seduced