What happened
On July 1, 2022, at 17:10 UTC, a Learjet 35A, registration LV-BPA, was performing a non-scheduled medical transport flight from Río Grande International Airport in Tierra del Fuego, Argentina. The flight crew, which included a doctor and a nurse, was attempting to return to San Fernando.
Following takeoff from runway 26, the aircraft experienced a significant roll to the left. While the aircraft momentarily leveled, it subsequently rolled to the left again, leading to a localized loss of lift on the left wing. The aircraft lost altitude and impacted the terrain approximately 1,870 meters from the runway threshold and 3/0 meters left of the centerline. The impact and subsequent fire resulted in the destruction of the aircraft and 4 fatalities.
The investigation
The investigation conducted by the JST focused on the mechanical state of the flight controls and the maintenance history of the aircraft. Investigators examined the aircraft's maintenance records, which showed that the aileron interconnect cable had been replaced in 2016 and tension checks had been performed in 2020.
Technical analysis of the flight controls revealed that the aileron interconnect cable was disconnected at the time of the accident. This disconnection caused a loss of synchronization between the left and right control columns, allowing only right-hand turns from the left yoke and left-hand turns from the right yoke. This asymmetry made the aircraft nearly impossible to control during the critical climb phase.
Findings
- The primary cause of the accident was the disconnection of the aileron interconnect cable.
- The disconnection likely occurred because the locking clips were not installed on the cable tensioners, allowing the tensioner to gradually unscrew under dynamic flight loads.
- Maintenance procedures for both the cable replacement and the tension verification tasks lacked explicit instructions regarding the installation and removal of these essential locking clips.
- Deficiencies were identified in the training of maintenance personnel and the oversight provided by the maintenance organization (TAR Air Delta S.R.L.) regarding the application of critical procedures.
Safety action
Following the investigation, the JST issued an Early Safety Recommendation to Bombardier Inc. requesting that the aircraft maintenance manuals be updated to include unambiguous instructions for the installation and removal of locking clips on aileron control cable tensioners. Bombardier Inc. responded by revising the maintenance manuals in August 2024 to clarify these procedures for the aileron, rudder, and elevator control systems.