Flight Crew Last 90 Days 240; Flight Crew Total 15000; Flight Crew Type 5900
Confusion; Troubleshooting
Aircraft Equipment Problem Critical
Flight Crew Landed in Emergency Condition; Flight Crew Diverted; General Declared Emergency
Aircraft
Our flight had been in the air for 1+30 when we heard the autopilot kick off; bottom screen only EICAS had numerous messages; overhead panel had many inoperative items. Because First Officer was already the pilot flying I told him to fly airplane. I scrolled thru EICAS to what I thought was the first message of BUS ISOL. [We] looked at its QRH procedure which really wasn't a procedure. It just mentioned not to cycle the ISOL switch. I also started APU in hopes this would be a shortcut to restoring power; but then read that only way to get power back to left AC was via an engine generator. So APU was turned off. We then discovered that L GEN OFF was actually the first EICAS message. Its procedure allows one reset of GEN. We did this and power was restored for 1-2 seconds; but then reverted back to L AC Bus being isolated. We then tried to contact company via VHF. This process took many tries (about 10 minutes); but contact was eventually made to Maintenance. About the only thing we hadn't done to that point was making sure all Circuit Breakers on First Officer's lower right side were in. Hoping maybe a generator field relay were open. When that didn't happen decision was made to divert where a normal approach and landing were made. CFR was asked to remain with us to gate because we still had EQP OHT on EICAS and overhead. As far as declaring emergency; we did this after the R GEN reset had failed and it became quite certain we would not get it back. The reason I was persistent about getting in touch with maintenance had several factors. In no particular order; the weather was clear and a million; there was not any better suitable alternate; and we still had time to get a fix from Maintenance before having to totally commit to diverting.
B757 Captain experiences a left AC Bus failure at FL350. The QRH is consulted and a generator reset is attempted without success. Flight diverts to a suitable airport.