<< >> NASA ASRS Report 420555, November 1998

A B727-200 flight crew on final approach at 1500 ft found inboard trailing edge flaps failed at 25 units instead of the selected 30 units. This was caused by a faulty flap indicator internal asymmetry switch.

Attributes
ACN	420555
Time
Date	199811
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : syr
State Reference	NY
Altitude	agl bound lower : 1500 agl bound upper : 1500
Environment
Flight Conditions	Mixed
Light	Dusk
Aircraft 1
Controlling Facilities	tower : syr
Operator	common carrier : air carrier
Make Model Name	B727-200
Flight Phase	descent : approach landing other
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 : 130 flight time total : 10500 flight time type : 3500
ASRS Report	420555
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

While performing checklist (before landing) PNF and so discovered right inboard flap had remained at 25 degree setting when flaps 30 degrees was selected. Noting no control difficulty, increased approach speed by 20 KIAS and landed. Troubleshooting by maintenance revealed temporary malfunction of indicator. Reseat of cannon plug freed up right inboard flap needle. Numerous ground extensions and retraction of flaps revealed no further discrepancy. Callback conversation with reporter revealed the following information: the reporter stated the inboard flap indicator had a slight needle split which triggered the asymmetry switch shutting off the flaps at 25 units. The reporter said maintenance reseated the indicator electrical connector and jiggled the indicator and everything worked ok.

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Original NASA ASRS Text

Title: A B727-200 FLC ON FINAL APCH AT 1500 FT FOUND INBOARD TRAILING EDGE FLAPS FAILED AT 25 UNITS INSTEAD OF THE SELECTED 30 UNITS. THIS WAS CAUSED BY A FAULTY FLAP INDICATOR INTERNAL ASYMMETRY SWITCH.

Narrative: WHILE PERFORMING CHKLIST (BEFORE LNDG) PNF AND SO DISCOVERED R INBOARD FLAP HAD REMAINED AT 25 DEG SETTING WHEN FLAPS 30 DEGS WAS SELECTED. NOTING NO CTL DIFFICULTY, INCREASED APCH SPD BY 20 KIAS AND LANDED. TROUBLESHOOTING BY MAINT REVEALED TEMPORARY MALFUNCTION OF INDICATOR. RESEAT OF CANNON PLUG FREED UP R INBOARD FLAP NEEDLE. NUMEROUS GND EXTENSIONS AND RETRACTION OF FLAPS REVEALED NO FURTHER DISCREPANCY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE INBOARD FLAP INDICATOR HAD A SLIGHT NEEDLE SPLIT WHICH TRIGGERED THE ASYMMETRY SWITCH SHUTTING OFF THE FLAPS AT 25 UNITS. THE RPTR SAID MAINT RESEATED THE INDICATOR ELECTRICAL CONNECTOR AND JIGGLED THE INDICATOR AND EVERYTHING WORKED OK.

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.