EMB ERJ 145 ER/LR
Flight Crew Commercial
Confusion; Troubleshooting; Workload; Communication Breakdown
Aircraft Equipment Problem Critical
Flight Crew FLC complied w / Automation / Advisory; Flight Crew Landed in Emergency Condition; General Declared Emergency
Aircraft
While in cruise flight at night in VMC the EICAS message 'AHRS 1 ON BATT' appeared.  I was the Pilot Not Flying and ran the appropriate QRH checklist which only stated that the AHRS would be available for another 40 minutes.  The Captain and I began to discuss the situation when he mentioned that the lighting on his side of the instrument panel was very low.  The Captain then noticed that his RMU screen was blank.  I used the Copilot RMU to verify the frequency and attempted to establish contact with Center.  After several radio calls with no response it was determined that COMM 1 was inoperative.  At this point the Captain lost all electrical power on his side of the instrument panel.  The Captain then handed the flight controls to me.  I re-engaged the autopilot and the autopilot seemed to hold altitude.  I had already attempted to contact Center on 121.5 with no success.  Then conducted a radio check on 121.5 which was responded by someone else.  So it seemed that COMM 2 was still operational.  I again tried to contact Center multiple times with no luck and started to get out the Low-altitude enroute charts to determine the local low-sector Center frequency.  I then asked the Captain to look up the frequency since I was task saturated.  At this point I also determined that we were about 200 FT below altitude and attempted to start a climb using the autopilot.  The aircraft did not seem to respond properly and I elected to turn off the autopilot and hand-fly the aircraft.  The Captain found the frequency and entered it into the RMU.  I again tried to call Center and there was no response.  I verified the frequency with the Captain and tried again.  Finally we got a response and advised the Controller of our location (by now were getting past the under cast and I could see the lights of the city below us) at FL340 and needed the frequency of the high sector Controller; which we received.  At this point we were not certain if the moving map display was working properly and elected to fly direct to the our destination VOR.  We had also discussed landing short at a divert airport; but we could now see the lights of our destination and the weather was better there.  I established contact with the proper Controller and declared an emergency; and advised them that we only have on VOR receiver for navigation.  They cleared us direct to the VOR and we started our descent.  By this time the EICAS message screen was completely full and the Captain was running through various checklists.  We did not have intercom within the cockpit or with the flight attendant.  The Captain advised me that we had an Essential Bus 1 failure and that we could expect a degraded landing; that we may have problems with the landing gear; flaps; brakes; and potentially flight controls.  I told him that we would lower the landing gear earlier than normal and to be ready to enter the speeds for a Flaps 0 landing.  We also received continual aural warning messages since the aircraft systems believed that the aircraft was sitting on the ground and not in-flight.  The Captain also reviewed the emergency evacuation procedures.  At about 5;000 feet and 20 miles from the airport we lowered the landing gear but did not receive a down indication for the nosewheel.  The Captain then completed the emergency landing gear extension procedure and I advised Approach Control that we are not getting and down nose wheel indication.  After multiple attempts the Captain was still not able to get a good indication and advised me that he wanted to abandon the approach to troubleshoot the problem.  I advised Tower that we wanted to go-around and troubleshoot this problem.  We received a vector for our climb and the Captain continued to attempt to lower the landing gear.  We were unable to get a nose wheel indication and eventually requested to land on Runway 28 since this is the longest runway; and to definitely have equipment standing by.  The approach was relatively uneventful and we were able to get full flaps.  Upon settling on the main landing gear I slowly de-rotated the aircraft to determine if in fact we did or did not have a nosewheel extended.  If it would seem that we did not I would then try to keep the nose up for as long as possible.  However; we got a normal nose touchdown and finished the landing roll-out.  A fire truck inspected the nose landing gear and advised us that it looked normal.  The Captain then slowly taxied the aircraft to the gate.
A EMB-145 lost the Essential DC Bus 1 in flight; so the crew declared an emergency and continued to the filed destination with multiple avionics and equipment failures.