Flight crew experienced localizer oscillations during ILS 17 approach to mpv. After landing a large ...

Attributes
ACN	837437
Time
Date	200905
Local Time Of Day	0601-1200
Place
Locale Reference	MPV.Airport
State Reference	VT
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	Small Transport Low Wing 2 Turboprop Eng
Operating Under FAR Part	Part 91
Flight Phase	Final Approach
Route In Use	Other ILS17\(full\)
Flight Plan	IFR
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Flight Instructor Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 60 Flight Crew Total 8000 Flight Crew Type 3500
Events
Anomaly	Other ILS Signal

Narrative:

In short; we observed what appeared to be spurious and random oscillations in the localizer on the ILS runway 17 approach to the barre-montpelier; vt; airport (mpv). Our aircraft's FMS (GPS) data indicated we were consistently aligned with the final approach course. However from approximately 15NM out; the aircraft's localizer course deviation indicator (NAV1) scalloped left and right approximately half-scale; 4 to 5 times during the approach. After landing; we observed a large tractor-style mower cutting grass at the far end of the runway in the vicinity of the localizer antenna array in what might have been delineated an ILS critical area of a larger facility. We surmised that the movement of the mower through this area might have accounted for the erratic behavior of the localizer signal during our approach.

Original NASA ASRS Text

Title: Flight crew experienced localizer oscillations during ILS 17 approach to MPV. After landing a large mower is observed operating in the area of the localizer antenna. MPV is an uncontrolled airport.

Narrative: In short; we observed what appeared to be spurious and random oscillations in the localizer on the ILS Runway 17 approach to the Barre-Montpelier; VT; airport (MPV). Our aircraft's FMS (GPS) data indicated we were consistently aligned with the final approach course. However from approximately 15NM out; the aircraft's localizer course deviation indicator (NAV1) scalloped left and right approximately half-scale; 4 to 5 times during the approach. After landing; we observed a large tractor-style mower cutting grass at the far end of the runway in the vicinity of the localizer antenna array in what might have been delineated an ILS Critical Area of a larger facility. We surmised that the movement of the mower through this area might have accounted for the erratic behavior of the localizer signal during our approach.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Flight crew experienced localizer oscillations during ILS 17 approach to mpv. After landing a large mower is observed operating in the area of the localizer antenna. Mpv is an uncontrolled airport.