B737-400 captain experiences numerous anomalies during climb including loss of cabin pressurization;...

Narrative:

On climbout; autothrottle failed at approximately 10;000 ft. While running checklist; ATC notified us of no transponder being received. Received ACARS from dispatch saying our times where erroneous. While checking that; ground proximity fail light illuminated. Decided to stop climb at FL280 to remain clear of rvsm airspace. While continuing checklists; cabin altitude warning horn went off at cabin altitude of about 10;000 ft (10;500 ft cabin altitude was the maximum we got to and no masks deployed). Ran cabin altitude warning QRH and were unable to control cabin altitude in stby and switched to manual. Commenced descent to 10;000 ft after declaring an emergency. Engine master caution illuminated (low idle) on descent. Contacted dispatch and coordinated for a divert. Remained in continuous contact with ATC throughout flight. Landed uneventfully at our divert airport with no assistance required. No passengers required assistance upon landing. Maintenance discovered plastic bags and insulation in the pressurization outflow valve after shutdown. Malfunction could not be duplicated. Possible air/ground sensor. Still being reviewed by maintenance.

Original NASA ASRS Text

Title: B737-400 Captain experiences numerous anomalies during climb including loss of cabin pressurization; possibly caused by a faulty ground/air sensor. Plastic bags were found in the outflow valve on post flight.

Narrative: On climbout; autothrottle failed at approximately 10;000 FT. While running checklist; ATC notified us of no transponder being received. Received ACARS from Dispatch saying our times where erroneous. While checking that; GND PROX Fail light illuminated. Decided to stop climb at FL280 to remain clear of RVSM airspace. While continuing checklists; Cabin Altitude Warning Horn went off at cabin altitude of about 10;000 FT (10;500 FT cabin altitude was the maximum we got to and no masks deployed). Ran CABIN ALT WARNING QRH and were unable to control cabin altitude in STBY and switched to manual. Commenced descent to 10;000 FT after declaring an emergency. ENG Master Caution illuminated (LOW IDLE) on descent. Contacted Dispatch and coordinated for a divert. Remained in continuous contact with ATC throughout flight. Landed uneventfully at our divert airport with no assistance required. No passengers required assistance upon landing. Maintenance discovered plastic bags and insulation in the Pressurization Outflow Valve after shutdown. Malfunction could not be duplicated. Possible Air/Ground Sensor. Still being reviewed by Maintenance.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	1028877
Time
Date	201208
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.Airport
State Reference	US
Aircraft 1
Make Model Name	B737-400
Operating Under FAR Part	Part 121
Flight Phase	Climb
Flight Plan	IFR
Component
Aircraft Component	Squat Switch
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical

B737-400 captain experiences numerous anomalies during climb including loss of cabin pressurization; possibly caused by a faulty ground/air sensor. Plastic bags were found in the outflow valve on post flight.