Emj flight crew experiences an ILS GS malfunction during a visual approach to ord.

Attributes
ACN	592045
Time
Date	200308
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : ord.airport
State Reference	IL
Altitude	msl single value : 4000
Aircraft 1
Controlling Facilities	tracon : c90.tracon
Operator	common carrier : air carrier
Make Model Name	Embraer Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 22r
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	592045
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : ils/flt director other flight crewa other flight crewb
Resolutory Action	flight crew : overcame equipment problem
Consequence	other
Supplementary
Problem Areas	Navigational Facility Aircraft
Primary Problem	Ambiguous

Narrative:

We were established inbound on the runway 22R localizer at ord in VMC at 240 KTS, flaps 9 degrees, when we received our ILS runway 22R approach clearance. The first officer was the PF. We suddenly experienced a split GS with left side fly-up and right side fly-down commands. There were no flags displayed. The autoplt which was coupled to the left side pitched the aircraft down significantly, my first officer disconnected the autoplt and initiated the recovery during which the aircraft exceeded 250 KTS, flaps 9 degrees speed. A visual approach clearance was obtained and an uneventful landing followed. The left GS flag appeared below 500 ft. Altitude of incident was approximately 4000 ft. Maintenance was notified of GS problem and flap overspd. Maintenance entry was made.

Original NASA ASRS Text

Title: EMJ FLT CREW EXPERIENCES AN ILS GS MALFUNCTION DURING A VISUAL APCH TO ORD.

Narrative: WE WERE ESTABLISHED INBOUND ON THE RWY 22R LOC AT ORD IN VMC AT 240 KTS, FLAPS 9 DEGS, WHEN WE RECEIVED OUR ILS RWY 22R APCH CLRNC. THE FO WAS THE PF. WE SUDDENLY EXPERIENCED A SPLIT GS WITH L SIDE FLY-UP AND R SIDE FLY-DOWN COMMANDS. THERE WERE NO FLAGS DISPLAYED. THE AUTOPLT WHICH WAS COUPLED TO THE L SIDE PITCHED THE ACFT DOWN SIGNIFICANTLY, MY FO DISCONNECTED THE AUTOPLT AND INITIATED THE RECOVERY DURING WHICH THE ACFT EXCEEDED 250 KTS, FLAPS 9 DEGS SPD. A VISUAL APCH CLRNC WAS OBTAINED AND AN UNEVENTFUL LNDG FOLLOWED. THE L GS FLAG APPEARED BELOW 500 FT. ALT OF INCIDENT WAS APPROX 4000 FT. MAINT WAS NOTIFIED OF GS PROB AND FLAP OVERSPD. MAINT ENTRY WAS MADE.

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.