Mode C Intruder Alert Services - Merrill Field Airport

Anchorage, Alaska

MODE C INTRUDER ALERT is a function of certain air traffic control automated systems designed to alert radar controllers to existing or pending situations between a tracked target (known IFR or VFR aircraft) and an untracked target (an unknown IFR or VFR aircraft equipped with an operating Mode C transponder) that requires immediate attention/action.

Mode C Intruder Alert provides an aural and associated visual alert that produces enlarged and blinking alphanumeric data blocks displayed on the controller’s radar display. Due to the close proximity of aircraft, the enlarged and blinking data blocks overlap and may make the radar unusable during periods of high air traffic activity. Additionally, the associated aural alarm may distract the controller from performing air traffic control duties.

The Mode C Intruder Alert base altitude has been adjusted from 643 feet above Mean Sea Level to 1,201 feet above Mean Sea Level within that portion of the Merrill Class D Surface Area that overlies land southeast of the south shore of Knik Arm. This action eliminates Mode C Intruder Alerts in the Merrill Field traffic pattern, while continuing to provide alerts in the areas over the Knik Arm, east of Muldoon Road and South of Tudor Road.

Graphic depitcting the portion of Merrill Segment designated as MCI Inhibit Region

(AAL-530, 8/7/01)