Failure to obtain green gear safe lights traced to open air/ground relay circuit breaker by B737-400...

Attributes
ACN	811692
Time
Date	200811
Local Time Of Day	0001 To 0600
Place
Locale Reference	airport : zzz.airport
State Reference	CA
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	tracon : zzz.tracon tower : zzz.tower
Operator	common carrier : air carrier
Make Model Name	B737-400
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 : 220 flight time type : 1300
ASRS Report	811692
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	aircraft equipment other aircraft equipment : gear safe lights
Resolutory Action	flight crew : overcame equipment problem
Consequence	other other
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Aircraft

Narrative:

Autobrake disarm light remained illuminated after selection of autobrakes 2 at cruise for landing at ZZZ. Completed automatic-brake disarm QRH resulting in 'off.' made maintenance log entry and sent ACARS message to maintenance prior to initiating descent. Nose gear red light illuminated intermittently in descent. We discussed options and chose to extend gear early on high downwind near ZZZ as a system check and safety precaution. No green lights. Sound and flight characteristics seemed to indicate a gear down condition but this could not be confirmed. Ran the manual gear extension QRH. No green lights! Declared an emergency and requested a low pass for a visual gear check by the tower. They see 3 gear. Checked cockpit nose gear periscope; verified nose gear down and locked; went to cabin to do same. Upon return to cockpit; conversation with captain and maintenance revealed an open circuit breaker C18 air/ground relay. Agreed to close breaker; gear indications returned to normal; 3 green lights confirmed gear down. Landed uneventfully. Entered tripped breaker in maintenance log; had numerous conversations with maintenance; station and emergency personnel.

Original NASA ASRS Text

Title: FAILURE TO OBTAIN GREEN GEAR SAFE LIGHTS TRACED TO OPEN AIR/GROUND RELAY CIRCUIT BREAKER BY B737-400 FLIGHT CREW.

Narrative: AUTOBRAKE DISARM LIGHT REMAINED ILLUMINATED AFTER SELECTION OF AUTOBRAKES 2 AT CRUISE FOR LNDG AT ZZZ. COMPLETED AUTO-BRAKE DISARM QRH RESULTING IN 'OFF.' MADE MAINT LOG ENTRY AND SENT ACARS MESSAGE TO MAINT PRIOR TO INITIATING DSCNT. NOSE GEAR RED LIGHT ILLUMINATED INTERMITTENTLY IN DSCNT. WE DISCUSSED OPTIONS AND CHOSE TO EXTEND GEAR EARLY ON HIGH DOWNWIND NEAR ZZZ AS A SYSTEM CHK AND SAFETY PRECAUTION. NO GREEN LIGHTS. SOUND AND FLT CHARACTERISTICS SEEMED TO INDICATE A GEAR DOWN CONDITION BUT THIS COULD NOT BE CONFIRMED. RAN THE MANUAL GEAR EXTENSION QRH. NO GREEN LIGHTS! DECLARED AN EMER AND REQUESTED A LOW PASS FOR A VISUAL GEAR CHK BY THE TWR. THEY SEE 3 GEAR. CHKED COCKPIT NOSE GEAR PERISCOPE; VERIFIED NOSE GEAR DOWN AND LOCKED; WENT TO CABIN TO DO SAME. UPON RETURN TO COCKPIT; CONVERSATION WITH CAPT AND MAINT REVEALED AN OPEN CIRCUIT BREAKER C18 AIR/GND RELAY. AGREED TO CLOSE BREAKER; GEAR INDICATIONS RETURNED TO NORMAL; 3 GREEN LIGHTS CONFIRMED GEAR DOWN. LANDED UNEVENTFULLY. ENTERED TRIPPED BREAKER IN MAINT LOG; HAD NUMEROUS CONVERSATIONS WITH MAINT; STATION AND EMER PERSONNEL.

Data retrieved from NASA's ASRS site as of May 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.

Failure to obtain green gear safe lights traced to open air/ground relay circuit breaker by B737-400 flight crew.