B737-300 crew encountered air-ground logic system failure.

Attributes
ACN	551561
Time
Date	200206
Day	Wed
Local Time Of Day	0601 To 1200
Place
State Reference	IA
Altitude	msl single value : 23000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zmp.artcc
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 210
ASRS Report	551561
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial
Experience	flight time type : 1369
ASRS Report	551562
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : numerous warnings other flight crewa other flight crewb
Resolutory Action	controller : provided flight assist controller : issued new clearance flight crew : landed in emergency condition flight crew : declared emergency none taken : detected after the fact other
Consequence	faa : reviewed incident with flight crew other other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

Day VFR flight, captain flying. Crew encountered continuing and multiple problems from liftoff to FL230. Autothrottles disengaged (no warning light), vertical navigation would not engage, lateral navigation would not engage, transponder was intermittent. Both captain's and first officer's eadi and ehsi began to flicker. The electronic equipment supply fan failed (switched to alternate). Approximately 80 mi west of FOD, the cabin altitude warning horn came on and the cabin altitude indicated just over 10000 ft. Qrc for cabin depressurization did not control pressurization. An emergency descent was initiated with the qrc. Declared emergency and descended to 10000 ft. Flight attendants indicated no injuries or passenger distress. Coordination with dispatch and maintenance controller. Fuel was not a factor and the aircraft was in good shape other than pressurization and previously noted problems. Aircraft continued to ord with assumed malfunctioning air-ground logic. Flight completed to ord at 10000 ft. Normal landing completed. No further incident. No passenger injuries or complaints. Crew was being administered an FAA line evaluation. At the time, debrief at completion of flight, FAA indicated the crew did an excellent job. Debriefed flight manager and union. Supplemental information from acn 551562: requested emergency vehicles to be available upon landing. Subsequently landed the aircraft without further incident. I believe there was a failure in the air-ground logic system.

Original NASA ASRS Text

Title: B737-300 CREW ENCOUNTERED AIR-GND LOGIC SYS FAILURE.

Narrative: DAY VFR FLT, CAPT FLYING. CREW ENCOUNTERED CONTINUING AND MULTIPLE PROBS FROM LIFTOFF TO FL230. AUTOTHROTTLES DISENGAGED (NO WARNING LIGHT), VERT NAV WOULD NOT ENGAGE, LATERAL NAV WOULD NOT ENGAGE, XPONDER WAS INTERMITTENT. BOTH CAPT'S AND FO'S EADI AND EHSI BEGAN TO FLICKER. THE ELECTRONIC EQUIP SUPPLY FAN FAILED (SWITCHED TO ALTERNATE). APPROX 80 MI W OF FOD, THE CABIN ALT WARNING HORN CAME ON AND THE CABIN ALT INDICATED JUST OVER 10000 FT. QRC FOR CABIN DEPRESSURIZATION DID NOT CTL PRESSURIZATION. AN EMER DSCNT WAS INITIATED WITH THE QRC. DECLARED EMER AND DSNDED TO 10000 FT. FLT ATTENDANTS INDICATED NO INJURIES OR PAX DISTRESS. COORD WITH DISPATCH AND MAINT CTLR. FUEL WAS NOT A FACTOR AND THE ACFT WAS IN GOOD SHAPE OTHER THAN PRESSURIZATION AND PREVIOUSLY NOTED PROBS. ACFT CONTINUED TO ORD WITH ASSUMED MALFUNCTIONING AIR-GND LOGIC. FLT COMPLETED TO ORD AT 10000 FT. NORMAL LNDG COMPLETED. NO FURTHER INCIDENT. NO PAX INJURIES OR COMPLAINTS. CREW WAS BEING ADMINISTERED AN FAA LINE EVALUATION. AT THE TIME, DEBRIEF AT COMPLETION OF FLT, FAA INDICATED THE CREW DID AN EXCELLENT JOB. DEBRIEFED FLT MGR AND UNION. SUPPLEMENTAL INFO FROM ACN 551562: REQUESTED EMER VEHICLES TO BE AVAILABLE UPON LNDG. SUBSEQUENTLY LANDED THE ACFT WITHOUT FURTHER INCIDENT. I BELIEVE THERE WAS A FAILURE IN THE AIR-GND LOGIC SYS.

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.