Air carrier PIC reports NAVAID problem on ILS 27L, atl.

Attributes
ACN	253369
Time
Date	199310
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : atl
State Reference	GA
Altitude	msl bound lower : 3500 msl bound upper : 3500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : atl
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other
Route In Use	approach : visual approach : straight in
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 175 flight time total : 15000 flight time type : 10000
ASRS Report	253369
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa
Resolutory Action	aircraft : equipment problem dissipated
Consequence	Other
Supplementary
Primary Problem	Navigational Facility
Air Traffic Incident	other
Situations
Airport	other physical facility

Narrative:

Cleared to 3500 ft VOR visual approach to runway 27L atl. Captain on ILS, first officer on VOR for DME reading. We were level at 3500 ft at 16 DME. GS indicated we were above GS 1/4 DOT with no flags from 16 DME to 10 DME. Once at proper distance/altitude ratio, GS centered and remained centered. We were getting unusable GS signals without the flag. A continued descent to 2500 ft would probably have given the sudden 'fly up' signal when closer to the airport. This is what happened in 1990 when I first reported this. This only seems to happen when capturing GS from below.

Original NASA ASRS Text

Title: ACR PIC RPTS NAVAID PROB ON ILS 27L, ATL.

Narrative: CLRED TO 3500 FT VOR VISUAL APCH TO RWY 27L ATL. CAPT ON ILS, FO ON VOR FOR DME READING. WE WERE LEVEL AT 3500 FT AT 16 DME. GS INDICATED WE WERE ABOVE GS 1/4 DOT WITH NO FLAGS FROM 16 DME TO 10 DME. ONCE AT PROPER DISTANCE/ALT RATIO, GS CTRED AND REMAINED CTRED. WE WERE GETTING UNUSABLE GS SIGNALS WITHOUT THE FLAG. A CONTINUED DSCNT TO 2500 FT WOULD PROBABLY HAVE GIVEN THE SUDDEN 'FLY UP' SIGNAL WHEN CLOSER TO THE ARPT. THIS IS WHAT HAPPENED IN 1990 WHEN I FIRST RPTED THIS. THIS ONLY SEEMS TO HAPPEN WHEN CAPTURING GS FROM BELOW.

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.