Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Engineer; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 15; Flight Crew Total 6386
Aircraft Equipment Problem Critical
Flight Crew Landed in Emergency Condition; Flight Crew Overcame Equipment Problem; General Declared Emergency
During a maintenance test flight the pilot's ESS BUS Circuit Breaker (CB) popped removing all essential power from the pilot's and copilot's flight instruments. I conducted the QRH ESSENTIAL BUS FAILURE - DC POWER LOSS Emergency Checklist which restored all DC Essential power. I declared an emergency for electrical power interruption; advising future communications may not be available; and of my intention of returning to our departure airport.I then configured the aircraft for landing early with Gear DOWN; flaps 20 [in anticipation of a possible recurrence]. Five to eight minutes later the ESS BUS CB popped again. Upon reaching the FAF I again reset the ESS BUS CB for landing and communications and landed without further failures.
While conducting a maintenance test flight the pilot of a Lear 35 suffered the loss of DC Essential bus electrical power. Although able to regain power through QRH procedures allowing the declaration of an emergency the bus failed again enroute back to the departure airport. Another reset of the offending Circuit Breaker (CB) permitted communications during the uneventful landing.