MD-82
Flight Crew Air Transport Pilot (ATP)
Workload; Troubleshooting; Distraction; Confusion; Human-Machine Interface
Aircraft Equipment Problem Critical
Flight Crew FLC complied w / Automation / Advisory; Flight Crew Took Evasive Action; Flight Crew Returned To Departure Airport
Procedure; Chart Or Publication; Aircraft; Manuals
While climbing through FL200 we experienced an electrical malfunction which clicked off the autopilot (A/P) and autothrust (A/T); followed by loud chattering noises and all aural and visual warnings going off continually with constant chimes and all annunciator lights flashing. At the time of the failure the First Officer was flying in day VFR conditions. We requested a return back to the departure airport. He continued to fly the aircraft using the stand-by instruments and outside horizon. Most of the equipment and systems on the aircraft were giving false readings; the only flight instruments available to us were the stand-by. The procedure; 'Intermittent AC Power Interruptions'; was attempted with no real changes to the electrical systems. Due to the fact that all the annunciators were flashing; we had a difficult time determining which ones were really on. Next was RT GEN OFF which again was difficult to proceed to completion due to all annunciators flashing. We did as much as possible to gain enough systems and flight instruments to safely conduct an approach and landing. The RT GEN OFF; procedure was followed but without many changes. Since all communication systems were very difficult to use with the loud chattering and chiming; I opened the cockpit door and briefed the #1 Flight Attendant. We also tested the PA system to make sure it worked so I could brief the passenger; which I did. When I returned my attention to the cockpit my First Officer informed me that now my side was working and I took control of the aircraft while he reviewed the QRH procedure again prior to setting up for the approach and landing. When we received the aircraft at the start of the flight; the RT GEN OFF annunciator light was placarded inoperative; and was on continually. There was a history of the light coming on but normal GEN operation. When trying to work through both QRH procedures; we could not proceed beyond the first notes pertaining to lights being on because ALL the annunciator lights were flashing. I suggest more guidance for flight crews when encountering this problem in the future.
During preflight the Crew reviewed the RT GEN OFF MEL because the light had been written up previously and the aircraft released because the generator was apparently functioning normally. The Reporter understands that the GEN OFF light annunciation is the result of a two stage Generator Control Unit process where an abnormal condition is sensed and then the generator removed from the bus. Because it was apparently operating normally they accepted the faulty indication conclusion. The event began during climb after the Reporter conducted a system check and saw the right generator load meter fluctuating from its normal low load state to the maximum load. He pointed it out to the First Officer and very shortly thereafter the rapid annunciator lights flashing; aural warnings and very loud relay tripping began. The Reporter estimated that the relays were switching three times per second and conditions were so loud from this point all the way to landing that they had to shout into the microphone to communicate with ATC. They were able to contact ATC only intermittently and did declare an emergency and start a return to the departure airport. The Reporter stated that only flight instruments operating normally were the Standby and they were difficult to see because of the location. The First Officer; a very experienced pilot; used the visual horizon and normal thrust setting knowledge to maintain airspeed. The QRH has a procedure for a rapid relay switching anomaly but it could not be used because the AC CROSSTIE LOCKOUT light was flashing along with all other aural warning annunciations and lights so the crew was asking themselves 'Where to we go.' APU started; but would not come on line.  The flap overspeed and overspeed warnings were also alerting along with the other indications and added greatly to the confusion. About ten minutes after the event began; the Captain's instruments returned to normal so he began flying while the First Officer again attempted to find a QRH procedure to address the situation. They felt helpless in this situation and were fortunate that VMC conditions existed because had it been IMC the situation would have been 'dicey.'  At one point they turned the Right Generator OFF during troubleshooting inflight; although that action was not called for in any procedure; because they felt the Right Generator was the problem having the previous load spiking. After landing the Right Generator Switch was turned OFF and the relay switching and other annunciations ceased. The Reporter has not heard from maintenance what the problem was.
While [we were] climbing through approximately FL200; A/P and A/T disconnected followed by the majority of the aircraft's warning systems activating. As pilot flying; I continued to fly; started a level off and return to our departure airport. Concurrently; the Captian (pilot not flying) determined the situation was under control and began working on the checklist. Initially; the type of malfunction was difficult to determine due to conflicting indications. 'Don't Stall' was followed by 'Overspeed'; three different altitude and airspeed indications were present; engine instruments were fluctuating and most warning and caution lights were flashing. Additionally; communications were difficult due to the loud and distracting warnings. The Captain was able to determine the type of electrical problem and ran the appropriate checklist while informing the flight attendants and passengers of the plans. The Captain's side seemed to have the reliable instruments; so we traded duties; and he finished up [with] an uneventful approach and landing.
A MD82's electrical system malfunction caused continuous false visual and aural system warnings as well as inaccurate flight instrument displays. Flight returned to the departure airport.