Autoplt erratic during visual approach. Passenger cellular phone use suspected.

Attributes
ACN	277118
Time
Date	199407
Day	Wed
Place
Locale Reference	airport : ord
State Reference	IL
Altitude	msl bound lower : 4000 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ord
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	277118
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : critical other anomaly other anomaly other other spatial deviation
Independent Detector	other flight crewa
Resolutory Action	flight crew : regained aircraft control flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

On approach to ord -- VFR conditions -- we were at 4000 ft heading 090 degrees and cleared to intercept runway 4R localizer. Autoplt was armed for intercept. As the course came off the wall the autoplt smoothly started to intercept. Abruptly, the airplane entered a 30 degree bank and started to turn away from the localizer. Using heading select, we turned the plane back towards the localizer and rearmed the autoplt for localizer intercept. Again, the airplane started to intercept the course and then abruptly turned to the right, away from the localizer course. This happened again a third time. Autoplt was disconnected and uneventful visual landing made. Both captain and first officer flight directors were correctly tuned to the runway 4R localizer frequency and the airplane had no maintenance history of autoplt problems. We had a full load of passenger but, due to the phase of flight, we did not have time to investigate the cabin for electronic devices. After debriefing the flight attendants at the gate they informed me the passenger in 28D had a large cellular telephone that they suspect he was using. They had repeatedly told him to discontinue its use during the descent. This incident matches other published reports of electronic interference -- autoplt banking uncommanded away from localizer course.

Original NASA ASRS Text

Title: AUTOPLT ERRATIC DURING VISUAL APCH. PAX CELLULAR PHONE USE SUSPECTED.

Narrative: ON APCH TO ORD -- VFR CONDITIONS -- WE WERE AT 4000 FT HDG 090 DEGS AND CLRED TO INTERCEPT RWY 4R LOC. AUTOPLT WAS ARMED FOR INTERCEPT. AS THE COURSE CAME OFF THE WALL THE AUTOPLT SMOOTHLY STARTED TO INTERCEPT. ABRUPTLY, THE AIRPLANE ENTERED A 30 DEG BANK AND STARTED TO TURN AWAY FROM THE LOC. USING HDG SELECT, WE TURNED THE PLANE BACK TOWARDS THE LOC AND REARMED THE AUTOPLT FOR LOC INTERCEPT. AGAIN, THE AIRPLANE STARTED TO INTERCEPT THE COURSE AND THEN ABRUPTLY TURNED TO THE R, AWAY FROM THE LOC COURSE. THIS HAPPENED AGAIN A THIRD TIME. AUTOPLT WAS DISCONNECTED AND UNEVENTFUL VISUAL LNDG MADE. BOTH CAPT AND FO FLT DIRECTORS WERE CORRECTLY TUNED TO THE RWY 4R LOC FREQ AND THE AIRPLANE HAD NO MAINT HISTORY OF AUTOPLT PROBS. WE HAD A FULL LOAD OF PAX BUT, DUE TO THE PHASE OF FLT, WE DID NOT HAVE TIME TO INVESTIGATE THE CABIN FOR ELECTRONIC DEVICES. AFTER DEBRIEFING THE FLT ATTENDANTS AT THE GATE THEY INFORMED ME THE PAX IN 28D HAD A LARGE CELLULAR TELEPHONE THAT THEY SUSPECT HE WAS USING. THEY HAD REPEATEDLY TOLD HIM TO DISCONTINUE ITS USE DURING THE DSCNT. THIS INCIDENT MATCHES OTHER PUBLISHED RPTS OF ELECTRONIC INTERFERENCE -- AUTOPLT BANKING UNCOMMANDED AWAY FROM LOC COURSE.

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.