MD-82
Aircraft Equipment Problem Critical
Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; General Declared Emergency; General Maintenance Action
Aircraft; Human Factors; Weather
The airplane had been stuck for two days with heavy rain awaiting the ice storm in [the south] to clear up. I started both engines for taxi knowing the aircraft had not flown trying to' warm it up.' A normal taxi until near the end of the runway when the First Officer noted his Navigation Display (ND) had failed compass indications. The First Officer pulled out the QRH and I went for the MEL. Before we could find the references the issue cleared up. Shortly thereafter we took off; passing about 5;000 FT the ND indicated compass failure. The First Officer went to the QRH. In the mean time I reached over and turned the EFIS switch to both on one or two with no success. I then thought I would turn the autopilot and autothrottles back on to help ease the work load; but it would not re-engage. Unsure of my problem and with lousy weather in front of me and a VFR airport below me I elected to return as opposed to trouble shooting our issue. I asked the First Officer to start preparations for landing. He noted we were at 143;000 LBS; 13;000 over our Operations Manual landing weight so we declared an emergency. Un-eventful landing and taxi back. Maintenance Control felt the problem was the two day sit with rain and told the mechanic to use hot air to dry out the electronics bay. Thirty minutes later the flags were gone and we soon taxied back out. While turning on to the runway the First Officers compass red 'off' re-appeared and we decided to return it to the gate. Maintenance is there for a reason. There are no missions.
MD82 Captain reports the First Officer's compass failure during taxi out on a ferry flight after the aircraft had sat for two days in the rain. Before any remedial action can be taken the problem cleared and the flight departed. Passing 5;000 FT the problem returns and EFIS switching has no effect; and the flight returns to the departure airport. Maintenance attempts to dry out the avionics with hot air with apparent success; but on taxi out the problem returns again.