<< >> NASA ASRS Report 430173, March 1999

A DC9-30 on approach at 3000 ft had a 'slat disagree' warning light. Flaps were recycled and all annunciator lights were out.

Attributes
ACN	430173
Time
Date	199903
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : pit.airport
State Reference	PA
Altitude	agl single value : 3000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : pit.tracon
Operator	common carrier : air carrier
Make Model Name	DC-9 30
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : approach
Route In Use	arrival : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : multi engine pilot : instrument pilot : commercial
Experience	flight time last 90 days : 210 flight time total : 15000 flight time type : 210
ASRS Report	430173
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : slat position indicator
Resolutory Action	aircraft : equipment problem dissipated controller : provided flight assist flight crew : took precautionary avoidance action
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

During partial flap extension on approach, the 'slat disagreement' annunciator light illuminated and stayed on. We requested vectors to hold. No other indication of any sort of asymmetry was found. We cycled the flaps up and the annunciator light extinguished. At some point during our vectors, approach control advised us that he might take us below the class B airspace for a short time and that he observed no traffic in that area. I am not sure whether we actually exited the class B airspace or not. We extended the flaps again. All annunciator lights remained extinguished throughout the normal approach and landing. I entered the discrepancy into the aircraft maintenance log. We suspected a dirty microswitch in the slat mechanism. Callback conversation with reporter revealed the following information: the reporter stated maintenance replaced a slat extend switch to correct the intermittent slat disagree warning.

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Original NASA ASRS Text

Title: A DC9-30 ON APCH AT 3000 FT HAD A 'SLAT DISAGREE' WARNING LIGHT. FLAPS WERE RECYCLED AND ALL ANNUNCIATOR LIGHTS WERE OUT.

Narrative: DURING PARTIAL FLAP EXTENSION ON APCH, THE 'SLAT DISAGREEMENT' ANNUNCIATOR LIGHT ILLUMINATED AND STAYED ON. WE REQUESTED VECTORS TO HOLD. NO OTHER INDICATION OF ANY SORT OF ASYMMETRY WAS FOUND. WE CYCLED THE FLAPS UP AND THE ANNUNCIATOR LIGHT EXTINGUISHED. AT SOME POINT DURING OUR VECTORS, APCH CTL ADVISED US THAT HE MIGHT TAKE US BELOW THE CLASS B AIRSPACE FOR A SHORT TIME AND THAT HE OBSERVED NO TFC IN THAT AREA. I AM NOT SURE WHETHER WE ACTUALLY EXITED THE CLASS B AIRSPACE OR NOT. WE EXTENDED THE FLAPS AGAIN. ALL ANNUNCIATOR LIGHTS REMAINED EXTINGUISHED THROUGHOUT THE NORMAL APCH AND LNDG. I ENTERED THE DISCREPANCY INTO THE ACFT MAINT LOG. WE SUSPECTED A DIRTY MICROSWITCH IN THE SLAT MECHANISM. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED MAINT REPLACED A SLAT EXTEND SWITCH TO CORRECT THE INTERMITTENT SLAT DISAGREE WARNING.

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.