Embraer Legacy 450/500
Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 100; Flight Crew Total 4800; Flight Crew Type 900
Troubleshooting; Workload; Confusion
Aircraft Equipment Problem Critical
Flight Crew Overcame Equipment Problem; General Declared Emergency
Human Factors; Aircraft
At FL450 we noticed the battery 1 indication on the MFD was amber and increasing. When I first noticed it was around 29.5V but rising quickly. The Captain grabbed the QRH but within a few seconds the voltage had reached about 31v and still rising. About this time the amber 'Batt Exceedence' CAS message appeared. We both agreed (per the QRH checklist) we should turn the BATT 1 switch off; which we did. By that time we had pulled up the Electrical System page on the MFD. We noticed that GEN 1 was putting out very high voltage and the amperage appeared fluctuating. If I recall correctly; we started the process of now looking up the QRH for a GEN 1 failure; but within the next 10-15 seconds the CAS lit up with about 20 messages simultaneously (enough they couldn't all be displayed at once). At the same time; numerous indications failed. The IHSI went away. The autopilot disconnected and the cabin began to climb (we think both PRSOV's closed). We both remember there was no 'golden' CAS message. We never received a 'GEN 1 fAIL' CAS message.At this point we donned O2 masks; began an emergency descent; and declared an emergency. However; we couldn't get any additional drag on the plane as the spoilers and landing gear were both failed (flaps as well). What resulted was a bit of a tug of war between knowing we needed to get to a safe altitude and trying not to overspeed the plane; or not to overspeed it too much. The overspeed we had was only in the higher altitudes as a Mach overspeed (Mmo) once down to thicker air; we were able to find an acceptable rate of descent by keeping it way below the Vmo speed. Some time (perhaps 45-60 seconds into the event); as the cabin was climbing through around 10;000 FT; we decided to manually deploy the O2 masks for our passengers as well. There were several more system failures on the way down including all fuel indications 'Xs' over all items on the fuel synoptic (strangely enough; I seem to remember the right fuel gauge started working again somewhere on the way down); and a few other ones we can't remember but just know more messages appeared. We are not sure exactly all of the items that had failed but in retrospect; it is possible that items on both the number 1 and 2 side had failed due to the #1 GEN dragging down the system voltage. On the way down our transponder was also malfunctioning. It was apparently 'stuck' at some altitude. Also; at some point (not sure exactly when or at exactly what altitude) we had an RA with another aircraft. I saw the plane 3 to 5 miles away and had already turned away; but we got the RA anyway. Sometime after this ATC had us turn the transponder either OFF or just ON; without an ALT squawk. We got clearance to descend all the way to 10;000 FT. Once there; and stabilized; we removed our oxygen masks and began a more in-depth review of what happened. It was obvious to us that GEN 1 was malfunctioning; though not obvious why it was still showing green in the electrical system (though only putting out around 14V and a few amps). We could not find any electrical emergency or abnormal procedure that encompassed our current situation in the checklist. We decided since the generator was obviously not acting normal; and we definitely could not harm the system any more by doing so; that we would start by turning it off. Once we put the switch in the OFF position; systems immediately started working again. The number of CAS messages began to reduce; until we eventually were able to eliminate most all of them except for GEN 1 OFF; SHED BUS OFF (normal for that condition) and BLEED 2 OFF. The right PSROV never opened again. We considered flipping the switch off and back on; but the aircraft was fine and we wanted to leave well enough alone. With the aircraft mostly restored to normal operation; we decided to divert with the assumption maintenance would be more readily available and services would be available to our passengers. The weather conditions were solid VFR and everything was stabilized system wise. In terms of recommendations; it may be useful for the manufacturer to consider adding a generator over-voltage procedure to the QRH. The first indication of a problem (Batt exceedance) led us to a QRH procedure that; had it been fully completed; would have probably made the situation worse. From a decision-making standpoint; we prioritized aircraft control and the descent over immediate troubleshooting; and I can't think of any reason we should have done that differently. From a human performance standpoint; there was so much information coming at us so quickly (multiple failures; hand flying; ATC communication; collision avoidance; passenger considerations) that it was difficult to do much more than execute the basic mission of flying the aircraft and descending safely until we reached a safe altitude. Even though the resolution in the end was essentially one switch; it wasn't immediately obvious that this was the correct action - no QRH guidance pointed us there and no system information displayed made that obvious (the low voltage on the generator wasn't hard to see but it was still green; no 'GEN FAIL; GEN OVERVOLT; etc' message was displayed; no red 'X's' on the electrical system page). We were very aware in the descent that we didn't want to make the situation worse by guessing at what action to take with the electrical system. That was at the heart of our decision to get the aircraft to a safe altitude and remain in VMC before additional troubleshooting.
EMB-505 First Officer reported multiple electrical system failures apparently stemming from failure of Number 1 Generator.