F100 crew had stable localizer and GS signals on runway 4R at ord.

Attributes
ACN	519051
Time
Date	200107
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : ord.airport
State Reference	IL
Altitude	msl single value : 8000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : c90.tracon tower : zzz.tower
Operator	common carrier : air carrier
Make Model Name	Fokker 100
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : approach
Route In Use	approach : instrument precision
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	519051
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : ldc & gs needles other flight crewa other flight crewb
Resolutory Action	none taken : anomaly accepted
Consequence	other
Supplementary
Problem Areas	Navigational Facility FAA
Primary Problem	Navigational Facility

Narrative:

GS and localizer needle fluctuations. Shot 2 approachs to runway 4R ord. On both approachs, experienced constant GS and localizer fluctuations in rhythm, and from 8000 ft to ground. Aircraft flight guidance also was following fluctuations, did also have several larger fluctuations that displaced localizer up to 1/4 DOT and GS about 1/8 of a DOT. Experienced those larger fluctuations inside the FAF as well as outside the FAF.

Original NASA ASRS Text

Title: F100 CREW HAD STABLE LOC AND GS SIGNALS ON RWY 4R AT ORD.

Narrative: GS AND LOC NEEDLE FLUCTUATIONS. SHOT 2 APCHS TO RWY 4R ORD. ON BOTH APCHS, EXPERIENCED CONSTANT GS AND LOC FLUCTUATIONS IN RHYTHM, AND FROM 8000 FT TO GND. ACFT FLT GUIDANCE ALSO WAS FOLLOWING FLUCTUATIONS, DID ALSO HAVE SEVERAL LARGER FLUCTUATIONS THAT DISPLACED LOC UP TO 1/4 DOT AND GS ABOUT 1/8 OF A DOT. EXPERIENCED THOSE LARGER FLUCTUATIONS INSIDE THE FAF AS WELL AS OUTSIDE THE FAF.

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.