A BE55 crew, on an ILS to iad, noticed localizer needle deflections throughout the approach.

Attributes
ACN	545735
Time
Date	200204
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : iad.airport
State Reference	VA
Altitude	msl single value : 3000
Environment
Flight Conditions	IMC
Weather Elements	Turbulence Rain
Aircraft 1
Controlling Facilities	tracon : iad.tracon tracon : pbi.tracon
Operator	general aviation : personal
Make Model Name	Baron 55/Cochise
Navigation In Use	ils localizer only : il
Flight Phase	descent : approach
Route In Use	arrival : on vectors
Flight Plan	IFR
Person 1
Affiliation	other
Function	flight crew : captain oversight : pic
Qualification	pilot : multi engine pilot : flight engineer pilot : commercial pilot : atp
Experience	flight time last 90 days : 200 flight time total : 20000 flight time type : 4000
ASRS Report	545735
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical inflight encounter : turbulence inflight encounter : weather non adherence : clearance non adherence : published procedure other anomaly other other spatial deviation
Independent Detector	atc equipment other atc equipment : radar other controllera other flight crewa other flight crewb
Resolutory Action	controller : issued alert none taken : detected after the fact
Consequence	faa : reviewed incident with flight crew other
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance Weather
Primary Problem	Aircraft

Narrative:

Being vectored to join runway 1L localizer, moderate turbulence and rain. We would get on localizer indications and then off localizer to the left indications on both radio/navigation units. Approach several times asked if we were tuned to the correct localizer. Later found that a cable was loose on localizer antenna coupler. Suspect intermittent indications caused by cable/loose and turbulence. Not aware of any conflict with other traffic. We broke out of clouds and continued visually to runway 1L.

Original NASA ASRS Text

Title: A BE55 CREW, ON AN ILS TO IAD, NOTICED LOC NEEDLE DEFLECTIONS THROUGHOUT THE APCH.

Narrative: BEING VECTORED TO JOIN RWY 1L LOC, MODERATE TURB AND RAIN. WE WOULD GET ON LOC INDICATIONS AND THEN OFF LOC TO THE L INDICATIONS ON BOTH RADIO/NAV UNITS. APCH SEVERAL TIMES ASKED IF WE WERE TUNED TO THE CORRECT LOC. LATER FOUND THAT A CABLE WAS LOOSE ON LOC ANTENNA COUPLER. SUSPECT INTERMITTENT INDICATIONS CAUSED BY CABLE/LOOSE AND TURB. NOT AWARE OF ANY CONFLICT WITH OTHER TFC. WE BROKE OUT OF CLOUDS AND CONTINUED VISUALLY TO RWY 1L.

Data retrieved from NASA's ASRS site as of July 2007 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.