A320 flight crew experiences localizer deflection on approach to runway 28R at sfo.

Attributes
ACN	445543
Time
Date	199908
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : sfo.airport
State Reference	CA
Altitude	msl single value : 1000
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : o90.tracon
Operator	common carrier : air carrier
Make Model Name	A320
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer & glide slope : 28r other
Flight Phase	descent : approach
Route In Use	approach : instrument non precision
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 150 flight time total : 18000 flight time type : 800
ASRS Report	445543
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : multi engine
Events
Anomaly	aircraft equipment problem : critical other spatial deviation
Independent Detector	aircraft equipment other aircraft equipment : loc indicator other flight crewa other flight crewb
Resolutory Action	none taken : detected after the fact
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Airport Flight Crew Human Performance Aircraft
Primary Problem	Ambiguous

Narrative:

On ILS approach to runway 28R at sfo at 1000 ft MSL (IMC), got full localizer deflection to both sides several times. Disconnected autoplt after 30 degree angle of bank turns from flight director following localizer. Hand-flew approach and broke out VMC shortly thereafter. VMC at approximately 700-800 ft. Landed normally. Local supervisor (ATC) said he thought it was due to taxiing aircraft in ILS critical area, however I've never seen this much deflection. As a result of this distraction, we landed without a clearance, or so we thought. The supervisor said that one was issued, so they were ok with it, but they failed to switch us to tower, and we missed it. This much deflection of the localizer is clearly unsafe.

Original NASA ASRS Text

Title: A320 FLC EXPERIENCES LOC DEFLECTION ON APCH TO RWY 28R AT SFO.

Narrative: ON ILS APCH TO RWY 28R AT SFO AT 1000 FT MSL (IMC), GOT FULL LOC DEFLECTION TO BOTH SIDES SEVERAL TIMES. DISCONNECTED AUTOPLT AFTER 30 DEG ANGLE OF BANK TURNS FROM FLT DIRECTOR FOLLOWING LOC. HAND-FLEW APCH AND BROKE OUT VMC SHORTLY THEREAFTER. VMC AT APPROX 700-800 FT. LANDED NORMALLY. LCL SUPVR (ATC) SAID HE THOUGHT IT WAS DUE TO TAXIING ACFT IN ILS CRITICAL AREA, HOWEVER I'VE NEVER SEEN THIS MUCH DEFLECTION. AS A RESULT OF THIS DISTR, WE LANDED WITHOUT A CLRNC, OR SO WE THOUGHT. THE SUPVR SAID THAT ONE WAS ISSUED, SO THEY WERE OK WITH IT, BUT THEY FAILED TO SWITCH US TO TWR, AND WE MISSED IT. THIS MUCH DEFLECTION OF THE LOC IS CLRLY UNSAFE.

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.