What happened
On 27 March 2021, a P-68 Observer 2 aircraft, registration VT-TAA, operated by M/s Pinnacle Air Pvt. Ltd, was conducting a non-scheduled flight from Bhopal to Guna. Shortly after climbing to 4,000 feet, the crew heard an unusual noise originating from the left engine. This was accompanied by a drop in oil pressure and a rise in oil temperature.
While returning to Bhopal, the crew shut down the left engine. However, the aircraft was unable to maintain altitude on the remaining right engine. The crew initially requested to land on a disused runway/taxiway, but when denied by Air Traffic Control, they notified ATC of an impending forced landing. The aircraft subsequently performed a forced landing in an agricultural field approximately 3NM from Bhopal Airport. The pilot in command sustained serious injuries, while the co-pilot and one passenger sustained minor injuries. The aircraft suffered substantial damage.
The investigation
AAIB India investigators examined the wreckage and engine components, discovering oil splash marks on the left wing and engine cowling. A strip examination of the left engine revealed that only one liter of oil remained in the sump. The investigation established that an oil leak caused the engine's frictional components to run without adequate lubrication. This led to the failure of the number 4 piston connecting rod bearing, which broke into pieces and blocked the oil suction screen with metal debris.
Investigators also reviewed the aircraft's maintenance history and organizational practices. They noted that while the aircraft was airworthy, there were undocumented maintenance activities involving fuel and oil replenishment on the day of the accident. Furthermore, the investigation looked into the communication between the crew and ATC during the emergency.
Findings
- An oil leak from the left engine caused a significant drop in oil pressure and a rise in temperature.
- The lack of lubrication caused the number 4 piston connecting rod bearing to disintegrate, leading to metal particles circulating through the lubrication system.
- The crew failed to declare an emergency to ATC or communicate the true nature of the engine malfunction, instead attributing the return to wind and turbulence.
- The crew's decision to attempt landing on a taxiway was unsuccessful, and the lack of situational awareness regarding the engine failure hindered effective emergency management.
- There were indications of poor safety culture and lack of coordination within the operator's organization regarding maintenance and documentation.