B737-400
Flight Crew Air Transport Pilot (ATP)
Time Pressure; Troubleshooting; Training / Qualification; Situational Awareness; Workload
Aircraft Equipment Problem Critical
Flight Crew Diverted; Flight Crew FLC complied w / Automation / Advisory; General Maintenance Action; General Declared Emergency
Aircraft
FL310. Autothrottles stopped working; but did not shut off. As we were troubleshooting autothrottles; cabin altitude horn sounded. Cabin altitude was 10;000 FT and climbing. Donned O2 masks and established communication. Declared emergency and began descent to FL240. Reiterated need for lower and were cleared to 10;000 FT. Advised flight attendants to sit down and don O2. Didn't appear we could catch cabin but were able using high flow packs to keep the cabin just below 14;000 FT. We were unable to send diversion message to Dispatch because ACARS thought we were on the ground. Called a nearby Station Operations and had them advise Dispatch. When aircraft and cabin were at 10;000 FT; advised (using jumpseat rider) passengers and flight attendants of the situation. Called flight attendants on interphone and determined they were OK and passengers were ready for landing. Since cabin altitude never reached 14;000 FT; passenger O2 masks were never deployed automatically or manually. Landed at a divert airport. [We] wrote up autothrottles and pressurization. Verbally discussed the fact that the aircraft seemed to think we were on the ground. [We] told them about the diversion message on the ACARS. Aircraft systems were operating as if the aircraft was on the ground. Cannot recommend maintenance since they still do not know what happened.
See callback narrative in ACN 1070645. Nose gear air ground squat switch partially failed in this first of two failures.
A B737-400 Cabin Altitude Warning sounded and the autothrottles stopped working at FL310 because the nose gear air/ground sensor partially failed so an emergency was declared and the flight diverted to a nearby airport.