What happened
On June 4, 1996, a Learjet 25C, registration PT-KBC, was performing a flight check involving pilot proficiency evaluations. The flight originated in São Paulo, with scheduled stops in Uberaba and Ribeirão Preto. During the approach to Ribeirão Preto, the crew executed a go-around procedure. During this maneuver, the left engine throttle lever became stuck in the idle position, preventing the necessary acceleration.
The pilot flying, the co-pilot, was unable to advance the lever. The commander took control of the aircraft to attempt to complete the go-around. However, the aircraft failed to maintain sufficient lift and descended 92 meters beyond the end of the runway. As the aircraft moved off the airfield, the commander attempted another rotation to avoid a fence, but the aircraft lost control and struck a fence, a parked truck, and a tree. The impact caused the aircraft to catch fire, resulting in a total loss of the airframe.
The investigation
CENIPA investigators examined the mechanical state of the throttle assembly and the Fuel Control Units (FCU). While the mechanism appeared free during initial inspection, technical analysis suggested that the throttle jam might have been caused by broken fibers within the control cable housing, which could cause the cable to bind. This hypothesis was supported by reports that the same throttle had exhibited difficulty during taxiing in Uberaba and during a previous approach in Guarully the week prior.
The investigation also reviewed the operational environment, noting that the runway at Ribeirão Preto was partially closed for construction, reducing the available landing distance. The investigation also looked into the crew's training, the operator's safety programs, and the psychological factors present during the flight, including the crew's anxiety regarding a subsequent unscheduled mission to transport a critically ill infant.
Findings
- The left engine throttle lever jammed in the idle position during the go-around.
- The crew exhibited complacency regarding a previously reported throttle malfunction that had not been properly addressed by maintenance.
- There was a lack of effective Crew Resource Management (CRM), evidenced by the failure to perform takeoff and landing briefings and poor coordination during the emergency.
- The operator lacked an updated crew training program, specifically lacking simulator training and CRM training.
- The crew's situational awareness was compromised by a lack of coordination and the distraction of the commander focusing on flap settings during the transition of control.
- The aircraft struck a third-party vehicle and a tree, resulting in one fatality among the crew, one fatality of a person in the truck, and one serious injury to an inspector on board.