Aircraft equipment problem malfunction goes unnoticed until the LOM in approach procedure.

Attributes
ACN	242633
Time
Date	199305
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : ord
State Reference	IL
Altitude	msl bound lower : 3000 msl bound upper : 14000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ord artcc : zse
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent : approach descent other landing other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : flight engineer pilot : cfi pilot : atp
Experience	flight time last 90 days : 150 flight time total : 6000 flight time type : 2000
ASRS Report	242633
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical non adherence : published procedure
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

On descent into ord while still south of oxi on the kokomo arrival ATC slowed us to 190 KTS. The first officer was flying and called for 2 degrees flaps. The inboard flaps extended properly, however, the outboard flaps remained up thus locking all leading edge devices in the up position. The aircraft continued to fly normally and the problem went unnoticed. Later we were slowed to 170 KTS. 5 degrees flaps were called for and the inboard flaps continued to extend normally while the outboards remained up along with all led's. The problem continued to go unnoticed and the aircraft continued to handle normally. This scenario continued throughout the approach phase of the flight until the 'final approach checklist' was called for at the OM. Since the aircraft was still handling 'normally' we added the prescribed extra airspeed per the abnormal checklist and landed uneventfully. Prevention: we as a crew were so used to the aircraft system working normally that without a sudden change in aircraft handling the flap/led problem went unnoticed. A good and vigilant scan is still vital even when all appears normal. Also, the approach should have been discontinued and the full abnormal procedure completed even though there were no 'handling' problems.

Original NASA ASRS Text

Title: ACFT EQUIP PROB MALFUNCTION GOES UNNOTICED UNTIL THE LOM IN APCH PROC.

Narrative: ON DSCNT INTO ORD WHILE STILL S OF OXI ON THE KOKOMO ARR ATC SLOWED US TO 190 KTS. THE FO WAS FLYING AND CALLED FOR 2 DEGS FLAPS. THE INBOARD FLAPS EXTENDED PROPERLY, HOWEVER, THE OUTBOARD FLAPS REMAINED UP THUS LOCKING ALL LEADING EDGE DEVICES IN THE UP POS. THE ACFT CONTINUED TO FLY NORMALLY AND THE PROB WENT UNNOTICED. LATER WE WERE SLOWED TO 170 KTS. 5 DEGS FLAPS WERE CALLED FOR AND THE INBOARD FLAPS CONTINUED TO EXTEND NORMALLY WHILE THE OUTBOARDS REMAINED UP ALONG WITH ALL LED'S. THE PROB CONTINUED TO GO UNNOTICED AND THE ACFT CONTINUED TO HANDLE NORMALLY. THIS SCENARIO CONTINUED THROUGHOUT THE APCH PHASE OF THE FLT UNTIL THE 'FINAL APCH CHKLIST' WAS CALLED FOR AT THE OM. SINCE THE ACFT WAS STILL HANDLING 'NORMALLY' WE ADDED THE PRESCRIBED EXTRA AIRSPD PER THE ABNORMAL CHKLIST AND LANDED UNEVENTFULLY. PREVENTION: WE AS A CREW WERE SO USED TO THE ACFT SYS WORKING NORMALLY THAT WITHOUT A SUDDEN CHANGE IN ACFT HANDLING THE FLAP/LED PROB WENT UNNOTICED. A GOOD AND VIGILANT SCAN IS STILL VITAL EVEN WHEN ALL APPEARS NORMAL. ALSO, THE APCH SHOULD HAVE BEEN DISCONTINUED AND THE FULL ABNORMAL PROC COMPLETED EVEN THOUGH THERE WERE NO 'HANDLING' PROBS.

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.