Narrative:

Departed ZZZ1 on day 3 of operational experience flight with a new hire first officer. Autothrottles were MEL'ed in ZZZ1 due write up on aircraft arrival. When I spoke with maintenance control to complete the en route MEL for the autothrottles; I expressed my concern about the write-up's mention of the ACARS 'resetting' and sending a false on time while in flight. I said that I was concerned about two unrelated systems having simultaneous malfunctions. He responded with something to the effect that there was nothing he could do about that. On departure ZZZ1; LNAV momentarily engaged; then disconnected. VNAV would not engage. ATC reported our transponder not received. Tried second transponder; also not received. FMC displayed 'verify position' message. FMC 'N1' page displayed the takeoff power settings; not the in-flight power settings. FMC takeoff page did not change to climb page. I commented to the first officer that the airplane still thinks it is on the ground. First officer checked for tripped circuit breaker's and looked for an air/ground sensing checklist. Pressurization showed normal differential and slowly climbing cabin. Climbed to FL260. Several minutes after leveloff; approximately 30 miles north of ZZZ; cabin altitude warning horn sounded. Declared emergency; accompanied emergency descent and diverted to ZZZ. Normal landing. Post flight found mach trim circuit breaker was tripped. After landing in ZZZ a review of MEL 22-4A showed that the maintenance procedure to pull the autothrottle circuit breaker's was not accomplished. I did not catch this on the ground in ZZZ1 and maintenance control did not direct me to pull these circuit breakers. Recommendations: we were faced with multiple unrelated system malfunctions that; as a group; we had not seen before and that no checklist addressed. The only checklist that addresses air/ground sensing is the 'landing gear lever will not move up after takeoff' checklist. We did not have any of the symptoms described in that checklist. I recommended that air/ground sensing failures be researched and the results of the research be provided to our crews through the QRH or training materials.

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Original NASA ASRS Text

Title: A B737-400 EXPERIENCED A GND/AIR SENSE SWITCH FAILURE AND SUBSEQUENTLY RECEIVED MULTIPLE SYSTEMS MALFUNCTION INDICATIONS WITH A FAILURE TO PRESSURIZE. AN EMER WAS DECLARED.

Narrative: DEPARTED ZZZ1 ON DAY 3 OF OPERATIONAL EXPERIENCE FLT WITH A NEW HIRE FO. AUTOTHROTTLES WERE MEL'ED IN ZZZ1 DUE WRITE UP ON ACFT ARR. WHEN I SPOKE WITH MAINT CTL TO COMPLETE THE ENRTE MEL FOR THE AUTOTHROTTLES; I EXPRESSED MY CONCERN ABOUT THE WRITE-UP'S MENTION OF THE ACARS 'RESETTING' AND SENDING A FALSE ON TIME WHILE IN FLT. I SAID THAT I WAS CONCERNED ABOUT TWO UNRELATED SYSTEMS HAVING SIMULTANEOUS MALFUNCTIONS. HE RESPONDED WITH SOMETHING TO THE EFFECT THAT THERE WAS NOTHING HE COULD DO ABOUT THAT. ON DEP ZZZ1; LNAV MOMENTARILY ENGAGED; THEN DISCONNECTED. VNAV WOULD NOT ENGAGE. ATC RPTED OUR XPONDER NOT RECEIVED. TRIED SECOND XPONDER; ALSO NOT RECEIVED. FMC DISPLAYED 'VERIFY POSITION' MESSAGE. FMC 'N1' PAGE DISPLAYED THE TKOF POWER SETTINGS; NOT THE INFLT POWER SETTINGS. FMC TAKEOFF PAGE DID NOT CHANGE TO CLB PAGE. I COMMENTED TO THE FO THAT THE AIRPLANE STILL THINKS IT IS ON THE GND. FO CHKED FOR TRIPPED CB'S AND LOOKED FOR AN AIR/GND SENSING CHKLIST. PRESSURIZATION SHOWED NORMAL DIFFERENTIAL AND SLOWLY CLBING CABIN. CLBED TO FL260. SEVERAL MINUTES AFTER LEVELOFF; APPROX 30 MILES N OF ZZZ; CABIN ALT WARNING HORN SOUNDED. DECLARED EMER; ACCOMPANIED EMER DSCNT AND DIVERTED TO ZZZ. NORMAL LNDG. POST FLT FOUND MACH TRIM CB WAS TRIPPED. AFTER LNDG IN ZZZ A REVIEW OF MEL 22-4A SHOWED THAT THE MAINT PROC TO PULL THE AUTOTHROTTLE CB'S WAS NOT ACCOMPLISHED. I DID NOT CATCH THIS ON THE GND IN ZZZ1 AND MAINT CTL DID NOT DIRECT ME TO PULL THESE CIRCUIT BREAKERS. RECOMMENDATIONS: WE WERE FACED WITH MULTIPLE UNRELATED SYSTEM MALFUNCTIONS THAT; AS A GROUP; WE HAD NOT SEEN BEFORE AND THAT NO CHKLIST ADDRESSED. THE ONLY CHKLIST THAT ADDRESSES AIR/GND SENSING IS THE 'LNDG GEAR LEVER WILL NOT MOVE UP AFTER TKOF' CHKLIST. WE DID NOT HAVE ANY OF THE SYMPTOMS DESCRIBED IN THAT CHKLIST. I RECOMMENDED THAT AIR/GND SENSING FAILURES BE RESEARCHED AND THE RESULTS OF THE RESEARCH BE PROVIDED TO OUR CREWS THROUGH THE QRH OR TRAINING MATERIALS.

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