A DC9-30 returned to the field immediately after takeoff due to unable to pressurize the cabin caused by a failed nose gear ground sensing switch and connector pin.

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Attributes
ACN	402346
Time
Date	199805
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : stl
State Reference	MO
Altitude	agl bound lower : 0 agl bound upper : 1000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : stl tower : stl
Operator	common carrier : air carrier
Make Model Name	DC-9 30
Operating Under FAR Part	Part 121
Flight Phase	climbout : initial climbout : takeoff other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 150 flight time total : 10900 flight time type : 5500
ASRS Report	402346
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa
Resolutory Action	other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Automatic pressurization inoperative after takeoff. Returned to stl. After maintenance action and logbook sign-off, took off again with same result. Returned to stl. After maintenance action and logbook sign-off, took off again -- pressurization operated normally. Callback conversation with reporter revealed the following information: the reporter stated the aircraft was a DC9-30 and the corrective action was a right nose gear squat switch replacement and a squat switch connector pin replacement in the ground sensing circuit. The reporter said the ground sensing failure caused the outflow valves to remain open when in-flight.

Original NASA ASRS Text

Title: A DC9-30 RETURNED TO THE FIELD IMMEDIATELY AFTER TKOF DUE TO UNABLE TO PRESSURIZE THE CABIN CAUSED BY A FAILED NOSE GEAR GND SENSING SWITCH AND CONNECTOR PIN.

Narrative: AUTOMATIC PRESSURIZATION INOP AFTER TKOF. RETURNED TO STL. AFTER MAINT ACTION AND LOGBOOK SIGN-OFF, TOOK OFF AGAIN WITH SAME RESULT. RETURNED TO STL. AFTER MAINT ACTION AND LOGBOOK SIGN-OFF, TOOK OFF AGAIN -- PRESSURIZATION OPERATED NORMALLY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT WAS A DC9-30 AND THE CORRECTIVE ACTION WAS A R NOSE GEAR SQUAT SWITCH REPLACEMENT AND A SQUAT SWITCH CONNECTOR PIN REPLACEMENT IN THE GND SENSING CIRCUIT. THE RPTR SAID THE GND SENSING FAILURE CAUSED THE OUTFLOW VALVES TO REMAIN OPEN WHEN INFLT.

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.