1999-12-15: HBIBX G4 enroute Savannah to Mulhouse experienced a total Electrical Failure. Requested divert to CYQX.
Landed at 0003z. TSB Case Closed A99A0163: The Jet Club operated Gulfstream Four SP was approximately 90 NM south west of Gander cruising at 41,000 feet when the aircraft lost electrical power to the (DC) essential bus. The crew decided to divert to Gander and began descent immediately. While in the descent, they tried to contact Gander ACC; however, the remaining battery power was insufficient. They then selected the transponder code to 7700 and were identified by Gander ACC. The crew heard the controller trying to make contact with the aircraft; after shedding most of the electrical load two-way communication was established. An attempt was made to start the APU in flight but battery power was insufficient to sustain the start sequence. The crew were provided vectors to Gander and landed uneventfully in at 2033 AST with emergency vehicles standing by. The G4 is equipped with a standby hydraulic operated generator which can provide emergency electrical power in the event of an (AC) or (DC) bus failure. It will begin to function when the circuit logic detects that the (AC) bus power has gone off line but it cannot detect a (DC) bus system failure. In this case the (AC) bus power was on line, but the (DC) bus dropped off line, including the charge function to the batteries. There is a procedure in the flight manual that will initiate the standby generator by pulling two circuit breakers for the (AC) power; the logic in the standby generator circuit senses a system failure thus activating the standby generator. The crew did not follow this procedure as they were close to Gander and were intent on getting the aircraft on the ground as soon as possible. There are two warning lamps located on the overhead panel to indicate a potential problem with the (DC) bus power but they are beyond the periphery of the crew's line of sight; consequently these indications are difficult to notice. As a result, the battery power depletion went undetected by the crew. A Ni-Cad battery will sustain power to the bus until it's capacity is almost completely used and then it will deplete rapidly leaving the crew with little time to detect and/or react to the situation. In this case the crew indicated they had less than two minutes from the time they noticed the lights in the cockpit dimming until most of the instrument display information began failing. The flight and engine instruments are powered predominantly by the (AC) bus, however, the input source for most of the information displayed is provided by units that are (DC) powered. Gulfstream has previously issued an Aircraft Service Change (ASC327
) which requires that the two indicator lights be moved to an annunciator on the instrument panel or, on later model aircraft, to the Engine Indicating and Crew Alert System (EICAS.) Compliance time is set at two years. The operator intends to incorporate (ASC327
) when the aircraft arrives at base. Gulfstream dispatched two technicians to Gander to troubleshoot the problem. The aircraft was started with a ground power unit and the problem did not reappear. As a precaution all of the associated wiring in the (DC) control circuit was tested and the following components were replaced: Both Batteries, Electronic Power Monitor Panel, (DC) Power Control Unit and the Run Distribution Box. The aircraft was ground run and returned to service. The removed components are undergoing tests at Gulfstream in an attempt to isolate the fault. TSB file # A99A0163