What happened
On 7 July 2019, a Gulfstream G6CO, registration EI-JSK, departed Shannon Airport for Farnborough, UK, carrying two pilots, a cabin attendant, and one passenger. During the climb through Flight Level 290, the crew observed an amber maintenance message regarding the left engine. Within seconds, the Electronic Engine Controller (EEC) triggered an automatic shutdown of the left-hand engine, displaying a red engine failure warning.
The sudden loss of the left engine also interrupted power to the aircraft's Air Data System, causing the right-hand engine to revert to an alternate control mode. The crew declared a PAN, which was later upgraded to a MAYDAY. The pilots opted to return to Shannon, choosing a gradual descent to manage power demands on the remaining engine. During the descent, the crew communicated with the manufacturer's technical team via radio, as the aircraft's satellite phone was unavailable due to the power loss. After a brief period of holding, the aircraft performed a second approach and landed safely with no injuries.
The investigation
The AAIU examined the engine's fault history and performed detailed inspections. While a borescope inspection of the left engine did not immediately reveal the source of the failure, subsequent strip and examination of the engine by the manufacturer identified the root issue. Post-occurrence torque checks on the VSV system showed that the left engine's torque levels remained excessively high even after lubrication attempts.
Findings
- The engine shutdown was triggered by the EEC identifying a VSV system track check fault, which occurs when there is a discrepancy between the commanded and actual position of the vanes.
- The underlying cause was corrosion within the bores of the VSV system, which compressed the bushings and created excessive friction at the vane actuating spindles.
- The loss of the left engine's generator caused a momentary loss of air data to the right engine, forcing it into alternate control mode.
- The aircraft's software logic at the time directed the engine to shut down entirely when this specific fault was detected, rather than simply issuing a maintenance alert.
- The crew successfully managed the emergency, though the loss of cabin power hindered direct communication with the manufacturer.