Flight crew of B757-200 experience flap slat control unit failure on descent for landing.

Attributes
ACN	645006
Time
Date	200501
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : zzz.airport
State Reference	FO
Altitude	msl single value : 1700
Environment
Flight Conditions	VMC
Aircraft 1
Controlling Facilities	tower : zzz.tower
Operator	common carrier : air carrier
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 210 flight time total : 11700 flight time type : 1000
ASRS Report	645006
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 150 flight time total : 18250 flight time type : 2400
ASRS Report	645007
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	aircraft equipment other aircraft equipment : eicas 'te flap assym' other flight crewa other flight crewb
Resolutory Action	flight crew : declared emergency flight crew : overcame equipment problem flight crew : landed in emergency condition flight crew : executed go around
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Flap slat control unit #1 failure. Intercepting extended final runway 19L. I was hand flying and asked the captain to select flaps 20 degrees from flaps 5 degrees. Speed was 180 KTS; but nonetheless we had EICAS messages pop up indicating overspd and flap load relief. Neither of these should have occurred. Those EICAS messages cleared to be replaced with a 'trailing edge flap asymmetry' message. After concurring with the flaps were stuck at 20; we performed a go around with ATC. The 'te flap assym' checklist was completed. We declared an emergency with ATC as a precautionary measure and performed a flaps 20 degree landing on runway 19L with no further difficulties. Talked to maintenance this morning and he said the flap slat control computer #1 had a fault. They had to replace it to fix the problem. Supplemental information from acn 645007: declared emergency. Glad we added fuel or the real emergency would have been low fuel after getting everything done.

Original NASA ASRS Text

Title: FLT CREW OF B757-200 EXPERIENCE FLAP SLAT CTL UNIT FAILURE ON DSCNT FOR LNDG.

Narrative: FLAP SLAT CTL UNIT #1 FAILURE. INTERCEPTING EXTENDED FINAL RWY 19L. I WAS HAND FLYING AND ASKED THE CAPT TO SELECT FLAPS 20 DEGS FROM FLAPS 5 DEGS. SPD WAS 180 KTS; BUT NONETHELESS WE HAD EICAS MESSAGES POP UP INDICATING OVERSPD AND FLAP LOAD RELIEF. NEITHER OF THESE SHOULD HAVE OCCURRED. THOSE EICAS MESSAGES CLRED TO BE REPLACED WITH A 'TRAILING EDGE FLAP ASYMMETRY' MESSAGE. AFTER CONCURRING WITH THE FLAPS WERE STUCK AT 20; WE PERFORMED A GAR WITH ATC. THE 'TE FLAP ASSYM' CHKLIST WAS COMPLETED. WE DECLARED AN EMER WITH ATC AS A PRECAUTIONARY MEASURE AND PERFORMED A FLAPS 20 DEG LNDG ON RWY 19L WITH NO FURTHER DIFFICULTIES. TALKED TO MAINT THIS MORNING AND HE SAID THE FLAP SLAT CTL COMPUTER #1 HAD A FAULT. THEY HAD TO REPLACE IT TO FIX THE PROB. SUPPLEMENTAL INFO FROM ACN 645007: DECLARED EMER. GLAD WE ADDED FUEL OR THE REAL EMER WOULD HAVE BEEN LOW FUEL AFTER GETTING EVERYTHING DONE.

Data retrieved from NASA's ASRS site as of January 2009 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.