Narrative:

Departing in VMC; the first officer was PF. At approximately 70 KIAS I heard relays clicking behind me (in the main electrical power center); saw some flashing lights on the overhead and flashing messages on the overhead annunciator panel (oap) as well as a master caution light and the auto brake disconnect warning light on the glareshield. After a couple of transient messages disappeared the oap settled on two remaining messages 'left gen off' and 'left AC power fault' and the status cue light was illuminated; as we were still in the low speed regime (though accelerating rapidly) I decided to reject the takeoff per company policy below 80 KIAS. When the status cue button was pressed it revealed the oap message 'left elec system fail.' I assumed control of the aircraft and had no difficulty taxiing clear. I estimate peak speed was probably on the order of 90 KIAS before deceleration began. There was never any question about our ability to stop safely; and due to our low speed and the fact that the auto brakes disconnected with the power transient; I elected to use less than full braking power to clear the runway; and was given permission to clear on runway xx; which we did. The brakes were not hot; and we coordinated with ATC; the flight attendants and made an announcement to the passengers all in accordance with our SOP's. After determining that hot brakes weren't going to pose a problem we coordinated with our ramp control and returned to the gate. Where we were met by personnel from the ramp and maintenance. Several more PA's were made to keep the passengers informed and the first officer took over coordinating with the cabin while I called our dispatcher and maintenance controller on my cell phone. We got the duty pilot on the phone who also got a chief pilot on the phone to determine if we could continue the trip. The first officer and I discussed the situation before I called and we determined that it was unquestionably safe to do so; the chief pilot disagreed and removed us from the trip. Several lessons are to be had here; the first relating to the law of primacy so familiar to every CFI: first learned is best learned. I have flown the dc-9/ md-80/ md-90 series since 1988 and have instructed on it extensively. I consider myself to have better than average systems and procedural knowledge and understanding. On every dc-9/md-80 model except the md-90; a simple generator failure is annunciated by a single light or message 'left gen off' (or 'right gen off'). Only on the md-90 does a generator failure also give the messages; 'left AC power fault' and the status message 'left AC power fail.' in fact; when faults are discussed in the dc-9 world they are normally centered on bus faults which implies a major short circuit and fire hazard. I can never remember in my md-90 differences or recurrent training ever being told that the md-90 also gave these additional warnings; which are highly distracting to someone with a lot of dc-9/md-80 experience. Because it appeared there was a major electrical fault; I discontinued the takeoff; which was certainly the prudent things to do. In talking to the maintenance controller I learned about these additional messages that went with an md-90 generator failure; and also that this particular aircraft had a history on the left generator. If it had failed 10 seconds earlier or later it would have been completely inconsequential; but it failed (again) at the worst possible time. The crew worked very well together; and the first officer especially was invaluable. The event underscores the need for effective crew briefings for rejected takeoffs; we had accomplished a thorough briefing and did everything like we had previously discussed. It was a safe outcome; although it proved to be a major disruption in the airline's schedule.

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Original NASA ASRS Text

Title: An MD-90 Captain rejected the takeoff when he observed failure of the left generator.

Narrative: Departing in VMC; the F/O was PF. At approximately 70 KIAS I heard relays clicking behind me (in the main electrical power center); saw some flashing lights on the overhead and flashing messages on the Overhead Annunciator Panel (OAP) as well as a Master Caution light and the auto brake disconnect warning light on the glareshield. After a couple of transient messages disappeared the OAP settled on two remaining messages 'L GEN OFF' and 'L AC POWER FAULT' and the status cue light was illuminated; as we were still in the low speed regime (though accelerating rapidly) I decided to reject the takeoff per company policy below 80 KIAS. When the status cue button was pressed it revealed the OAP message 'L ELEC SYS FAIL.' I assumed control of the aircraft and had no difficulty taxiing clear. I estimate peak speed was probably on the order of 90 KIAS before deceleration began. There was never any question about our ability to stop safely; and due to our low speed and the fact that the auto brakes disconnected with the power transient; I elected to use less than full braking power to clear the Runway; and was given permission to clear on Runway XX; which we did. The brakes were not hot; and we coordinated with ATC; the flight attendants and made an announcement to the passengers all in accordance with our SOP's. After determining that hot brakes weren't going to pose a problem we coordinated with our ramp control and returned to the gate. Where we were met by personnel from the ramp and maintenance. Several more PA's were made to keep the passengers informed and the first officer took over coordinating with the cabin while I called our dispatcher and maintenance controller on my cell phone. We got the duty pilot on the phone who also got a chief pilot on the phone to determine if we could continue the trip. The FO and I discussed the situation before I called and we determined that it was unquestionably safe to do so; the chief pilot disagreed and removed us from the trip. Several lessons are to be had here; the first relating to the law of primacy so familiar to every CFI: First learned is best learned. I have flown the DC-9/ MD-80/ MD-90 series since 1988 and have instructed on it extensively. I consider myself to have better than average systems and procedural knowledge and understanding. On every DC-9/MD-80 model EXCEPT the MD-90; a simple generator failure is annunciated by a single light or message 'L GEN OFF' (or 'R GEN OFF'). Only on the MD-90 does a generator failure ALSO give the messages; 'L AC POWER FAULT' and the status message 'L AC POWER FAIL.' In fact; when faults are discussed in the DC-9 world they are normally centered on bus faults which implies a major short circuit and fire hazard. I can never remember in my MD-90 differences or recurrent training ever being told that the MD-90 also gave these additional warnings; which are HIGHLY distracting to someone with a lot of DC-9/MD-80 experience. Because it appeared there was a major electrical fault; I discontinued the takeoff; which was certainly the prudent things to do. In talking to the maintenance controller I learned about these additional messages that went with an MD-90 generator failure; and also that this particular aircraft had a history on the left generator. If it had failed 10 seconds earlier or later it would have been completely inconsequential; but it failed (again) at the worst possible time. The crew worked VERY well together; and the F/O especially was invaluable. The event underscores the need for effective crew briefings for Rejected Takeoffs; we had accomplished a thorough briefing and did everything like we had previously discussed. It was a safe outcome; although it proved to be a major disruption in the airline's schedule.

Data retrieved from NASA's ASRS site as of April 2012 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.