What happened
On December 6, 2025, a Boeing 727-227 cargo aircraft, registration HK5216, was performing a commercial flight from Bogotá, Colombia, to Maiquetía, Venezuela. During the takeoff roll at El Dorado International Airport, the aircraft reached rotation speed when the flight engineer reported a "Loss of all generators." Because the failure occurred after reaching V1, the crew continued the takeoff.
During the initial climb, the aircraft suffered a total loss of electrical generation. The crew was forced to rely solely on emergency instruments, including the standby altimeter, horizon, airspeed indicator, and compass. Critical flight information, such as flap and landing gear indications, was lost. The aircraft was operating exclusively on battery power, which the crew estimated had only 20 to 30 minutes of remaining autonomy.
After attempting to restore the generators by reducing electrical loads without success, the crew declared a MAYDAY emergency. Due to intermittent communications and the need to maintain visual separation from other traffic, the crew climbed to 13,000 feet and remained within the control zone to preserve visual references to the runway. The crew performed the approach at approximately 160 knots—higher than the standard Vref of 140 knots—because the flap position was unknown. The aircraft landed safely on runway 14L. The aircraft eventually stopped on taxiway Juliet 2 after the battery power was exhausted. All 4 occupants were unharmed.
The investigation
The investigation examined the aircraft's electrical system and maintenance records. Investigators confirmed that generator number 2 was operating under a deferred maintenance item (MEL category B), which allowed for continued operation for up to three days. Physical inspections of the electrical bus bars revealed sulfation at the connection points, which created additional resistance, leading to voltage drops and overheating. Additionally, sulfation was found on the contacts of the Bus Tie Breakers (BTB), which likely prevented proper interconnection and limited the ability to transfer electrical loads between generators.