Narrative:

[Flight was] was delayed due to an APU failing prior to pushback.the captain coordinated with dispatch; maintenance; and operations to have a gpu and ground cart brought to the aircraft. A gpu was delivered to power the aircraft. Unfortunately; the gpu did not meet the aircraft manual voltage limitations and we could not use it to power the aircraft. Due to the extended delay; with no quick resolution available; the captain made the decision to deplane the passengers. After the passengers deplaned a total of three gpus were brought to the aircraft; the aircraft showed the first gpu voltage at 22 volts and the second gpu showed 31 volts and the last gpu (the one that we accepted) was 28.8 volts (which was within the aircraft manual limitations of 28 +1/-2 volts).per the MEL specifications and in coordination with maintenance personnel; a test of the engine generators was to be made to determine the operation of the engine driven generators. A ground cart was used to start engines at idle thrust which confirmed that the four engine generators were operating normally and that the APU could be deferred per the MEL specifications/limitations. The APU circuit breaker(s) were pulled; deactivated placards posted; and the logbook entries completed per standard policies and MEL specifications.the passengers were boarded and the cabin door closed. An engine start was performed at the gate using the ground cart and then a cross-bleed start performed during taxi out. For the engine ground start; cross bleed start; after start; before takeoff; and climb normal procedures and checklist were completed and the aircraft operated normally.I was the pilot designated for flying for this leg of the trip. As we passed through 10;000 ft.; the emergency lights cycled on then off rapidly. Additionally; an EICAS message and master caution lights repeated cycled on and off. I called for 'identify and cancel' however the associated EICAS messages did not stay illuminated for more than a very brief moment which made identification of the exact issue difficult. I suggested that we check the electrical system page for abnormality; but the generator loads and voltages appeared normal. Unfortunately; the issue/abnormality continued to occur repeatedly and the captain advised that we were going to turn back to the field.I agreed with the captain's decision to return to the field and believed the decision was the best course of action. We were very near the departure airport; VMC; and at night. The decision to turn back seemed to be the safest course of action given that we had EICAS messages and master cautions lights erratically blinking on and off; the sound of electrical relays were clicking on and off behind our heads; and lights blinking on and off. Additionally; I had concern the issue could become more serious at any time if the electrical issue resulted in substantial electrical power loss or electrical fire.the captain [advised ATC]. He notified the flight attendant to prepare the cabin with no brace required. We followed ATC instructions and setup for the descent; approach; and landing. So that I could brief the approach; the controls were transferred to the captain and he assumed flying the aircraft. At this time; the captain advised me that due to the landing being overweight he was going to pilot the approach and landing. ATC gave us vectors to provide time enough to complete our standard descent; approach; and landing checklist. On final approach; two EICAS master caution messages illuminated and stayed on. The messages were identified as 'emergency lights not armed' and 'electrical emergency abnormal'. The approach was normal and stabilized and the captain performed the touchdown as smoothly as possible given the state of the overweight aircraft. Once we landed; we exercised caution with deceleration and made a smooth taxi off on a high speed exit per ATC request. At that time; the parking brake was set and emergency vehicles and personnel approached the aircraft for physical inspection. Due to the close proximity of ground personnel the captain had me hold on performing the after landing check. After the ground personnel completed their inspection; we were cleared to taxi to the ramp. After taxing had commenced; I started the performance of the after landing check. During this time; the captain did make an incorrect turn (we turned right onto the taxiway when we should have turned left). Immediately upon recognition of the error; the aircraft was stopped and ATC advised. We received amended taxi instructions; a taxied to the ramp without further difficulty.after the aircraft was parked at the ramp/gate location; we had one last difficulty. As the APU was meled; we needed ground power before we could shut down the number 2 engine and deplane the passengers. We advised the passengers of the delay and reason for holding off deplaning until ground power could be supplied to the aircraft and both engines shutdown. During this time and after the passengers deplaned the captain made his best effort to inform all stakeholders of the situation including dispatch; maintenance control; local maintenance; gate agents; and passengers.no passengers were injured to my knowledge nor any customer upset beyond what would be expected considering the inconvenience. I believe the captain and myself made the best use of all available resources; used sound judgment and good decision making given the situation and tried to follow all company procedures; fars; and other policies to the best of our abilities. Additionally; to my knowledge the flight attendant followed all policy and procedures correctly and adequately prepared and informed the passengers for the situation.

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Original NASA ASRS Text

Title: EMB-145 flight crew reported receiving flashing EICAS messages that were impossible to distinguish. Upon returning to the departure airport 'EMERGENCY LIGHTS NOT ARMED' and 'ELECTRICAL EMERGENCY ABNORMAL' EICAS messages illuminated.

Narrative: [Flight was] was delayed due to an APU failing prior to pushback.The Captain coordinated with dispatch; maintenance; and operations to have a GPU and ground cart brought to the aircraft. A GPU was delivered to power the aircraft. Unfortunately; the GPU did not meet the Aircraft Manual voltage limitations and we could not use it to power the aircraft. Due to the extended delay; with no quick resolution available; the Captain made the decision to deplane the passengers. After the passengers deplaned a total of three GPUs were brought to the aircraft; the aircraft showed the first GPU voltage at 22 volts and the second GPU showed 31 volts and the last GPU (the one that we accepted) was 28.8 volts (which was within the Aircraft Manual limitations of 28 +1/-2 volts).Per the MEL specifications and in coordination with maintenance personnel; a test of the engine generators was to be made to determine the operation of the engine driven generators. A ground cart was used to start engines at idle thrust which confirmed that the four engine generators were operating normally and that the APU could be deferred per the MEL specifications/limitations. The APU circuit breaker(s) were pulled; deactivated placards posted; and the logbook entries completed per standard policies and MEL specifications.The passengers were boarded and the cabin door closed. An engine start was performed at the gate using the ground cart and then a cross-bleed start performed during taxi out. For the engine ground start; cross bleed start; after start; before takeoff; and climb normal procedures and checklist were completed and the aircraft operated normally.I was the pilot designated for flying for this leg of the trip. As we passed through 10;000 ft.; the emergency lights cycled on then off rapidly. Additionally; an EICAS message and master caution lights repeated cycled on and off. I called for 'Identify and Cancel' however the associated EICAS messages did not stay illuminated for more than a very brief moment which made identification of the exact issue difficult. I suggested that we check the electrical system page for abnormality; but the generator loads and voltages appeared normal. Unfortunately; the issue/abnormality continued to occur repeatedly and the Captain advised that we were going to turn back to the field.I agreed with the Captain's decision to return to the field and believed the decision was the best course of action. We were very near the departure airport; VMC; and at night. The decision to turn back seemed to be the safest course of action given that we had EICAS messages and master cautions lights erratically blinking on and off; the sound of electrical relays were clicking on and off behind our heads; and lights blinking on and off. Additionally; I had concern the issue could become more serious at any time if the electrical issue resulted in substantial electrical power loss or electrical fire.The Captain [advised ATC]. He notified the flight attendant to prepare the cabin with no brace required. We followed ATC instructions and setup for the descent; approach; and landing. So that I could brief the approach; the controls were transferred to the Captain and he assumed flying the aircraft. At this time; the Captain advised me that due to the landing being overweight he was going to pilot the approach and landing. ATC gave us vectors to provide time enough to complete our standard descent; approach; and landing checklist. On final approach; two EICAS master caution messages illuminated and stayed on. The messages were identified as 'EMERGENCY LIGHTS NOT ARMED' and 'ELECTRICAL EMERGENCY ABNORMAL'. The approach was normal and stabilized and the captain performed the touchdown as smoothly as possible given the state of the overweight aircraft. Once we landed; we exercised caution with deceleration and made a smooth taxi off on a high speed exit per ATC request. At that time; the parking brake was set and emergency vehicles and personnel approached the aircraft for physical inspection. Due to the close proximity of ground personnel the Captain had me hold on performing the after landing check. After the ground personnel completed their inspection; we were cleared to taxi to the ramp. After taxing had commenced; I started the performance of the after landing check. During this time; the Captain did make an incorrect turn (we turned right onto the taxiway when we should have turned left). Immediately upon recognition of the error; the aircraft was stopped and ATC advised. We received amended taxi instructions; a taxied to the ramp without further difficulty.After the aircraft was parked at the ramp/gate location; we had one last difficulty. As the APU was MELed; we needed ground power before we could shut down the number 2 engine and deplane the passengers. We advised the passengers of the delay and reason for holding off deplaning until ground power could be supplied to the aircraft and both engines shutdown. During this time and after the passengers deplaned the Captain made his best effort to inform all stakeholders of the situation including dispatch; maintenance control; local maintenance; gate agents; and passengers.No passengers were injured to my knowledge nor any customer upset beyond what would be expected considering the inconvenience. I believe the Captain and myself made the best use of all available resources; used sound judgment and good decision making given the situation and tried to follow all company procedures; FARs; and other policies to the best of our abilities. Additionally; to my knowledge the flight attendant followed all policy and procedures correctly and adequately prepared and informed the passengers for the situation.

Data retrieved from NASA's ASRS site 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.