A super MD80 flight crew reported a false GS on approach to runway 27L at ord.

Attributes
ACN	443810
Time
Date	199907
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : ord.airport
State Reference	IL
Altitude	msl bound lower : 3500 msl bound upper : 5000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : c90.tracon
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 27l
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	443810
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial
Events
Anomaly	other anomaly
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : overrode automation
Supplementary
Problem Areas	Aircraft Navigational Facility
Primary Problem	Ambiguous

Narrative:

At 5000 ft we were cleared for the ILS runway 27L approach with an intercept heading of 300 degrees. GS and localizer were alive when we came out of the turn on a 300 degree heading. I lined up with the runway and started down on the GS. When clear of clouds, it was obvious that we were not on the appropriate GS. I leveled off at about 3500 ft MSL and observed the GS climb to a full scale fly-up. We intercepted that GS and it checked correct at the OM. Landing was uneventful. We advised approach of the false GS and said they were wondering where we were going. A check of the cabin found no electronic devices in use.

Original NASA ASRS Text

Title: A SUPER MD80 FLC RPTED A FALSE GS ON APCH TO RWY 27L AT ORD.

Narrative: AT 5000 FT WE WERE CLRED FOR THE ILS RWY 27L APCH WITH AN INTERCEPT HDG OF 300 DEGS. GS AND LOC WERE ALIVE WHEN WE CAME OUT OF THE TURN ON A 300 DEG HDG. I LINED UP WITH THE RWY AND STARTED DOWN ON THE GS. WHEN CLR OF CLOUDS, IT WAS OBVIOUS THAT WE WERE NOT ON THE APPROPRIATE GS. I LEVELED OFF AT ABOUT 3500 FT MSL AND OBSERVED THE GS CLB TO A FULL SCALE FLY-UP. WE INTERCEPTED THAT GS AND IT CHKED CORRECT AT THE OM. LNDG WAS UNEVENTFUL. WE ADVISED APCH OF THE FALSE GS AND SAID THEY WERE WONDERING WHERE WE WERE GOING. A CHK OF THE CABIN FOUND NO ELECTRONIC DEVICES IN USE.

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.