Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy
General Flight Cancelled / Delayed; General Maintenance Action
Aircraft; Company Policy; MEL; Procedure
We currently operate the Legacy 450/500 electrical system differently than it was designed and intended to be operated. We do this during ground operations and in flight until we accomplish our after takeoff checklist at 3000 ft MSL. During our after start checklist; we place the Bus Tie #2 Knob in the 'Open' position and leave it there until the after takeoff checklist is completed. This is done to prevent a cascade electrical fault caused by the failure of a DC electrical Hydraulic Pump that has in the past; transferred over to and completely disabled both the #1 and #2 electrical systems. Not a good situation in any airplane; especially one with a fly-by-wire flight control system. Embraer recommended opening the Bus Tie Knob as a temporary fix until new and improved DC Hydraulic pumps could be installed. The problem in this instance is that when you have the #2 Engine Generator deferred; the APU generator will not power the #2 Electrical system when the Bus Tie #2 Knob is open. Operating the aircraft on the ground; during takeoff and climb with the Bus Tie #2 Knob in 'Auto' is the only solution but is not I/A/W (in Accordance With) our current operating procedures. Operating in this manner opens us up to the possible situation described above. Opened the Bus Tie #2 Knob as per the [company] Legacy 450 After Start Normal Checklist and the entire #2 electrical system became unpowered.Utilizing an MEL listed procedure (24-XX-XX-XX) that does not take into account the abnormal electrical switch position (Bus Tie #2 Knob) OPEN vs. AUTO.Placed the #2 Bus Tie Knob to the Auto position; the #2 electrical system regained power but numerous nuisance CAS (Crew Alerting System) messages remained posted which required a complete aircraft shutdown of at least 15 minutes. Maintenance was then contacted.Do not allow the deferring of the #2 DC Generator per MEL # 24-XX-XX-XX on ALL Legacy 450/500 aircraft until Embraer and [the company] have addressed the underlying non-normal operation of the aircraft electrical system. The normal operating checklists; procedures will have to be updated as well as all crew members must be informed and trained on the new procedures.
EMB-545 Captain reported experiencing an electrical system failure after engine start.