20190415002849A

On April 15, 2019 at approximately 0345, N395AE, a Bell 206-L1+ helicopter conducting a part 135 flight, was involved in an accident at coordinates 32°29?45 north, 82°55?35 west. On board the aircraft at the time of the accident were the pilot, medic and nurse who reported to have no injuries as a result.

Pilot stated that before take-off, a crew walk around was performed and pre-start checklist was completed with no issues noted. The engine started normally with no indications of any problems and a pre-takeoff checklist was completed. The pilot proceeded to apply power to come to a hover and make a right hand turn into a 6 to 8 mph westerly wind to perform an engine power check. At approximately 50 feet, while using an estimated 86% torque to accelerate airspeed , a loud bang was heard by all three on board which was followed by a clicking sound coming from the engine bay. The pilot did not recall seeing any warnings or indications during this time but N395AE began losing power and immediately started to descend. Security video showed that with the nose of the aircraft slightly pitch up, the aircraft collided with the ground hitting the aft section of the skids and tail section first. The force of the initial impact resulted in N395AE bouncing to the right and landing upright on the aircraft?s skids. Damage to the aircraft included separation of tail vertical stabilizer from the tail boom. The bottom of the tail vertical stabilizer with the stinger was found approximately 150 feet from where the aircraft landed. There also appeared to be main rotor and tail rotor damage, along with the front right transparency broken and the skids spread apart. After the aircraft came to rest, the pilot rolled the throttle to idle to start an engine shutdown, shut off the fuel valve in case of a fire, applied the rotor brake and all onboard exited the aircraft safely.

Upon initial visual inspection of the engine at the scene, there were no obvious signs of any leaking fluids or lines disconnected. The engine inlet fairing was clean and no damage or debris could been seen at the introduction of the compressor section. An aircraft fuel sample was taken on scene and no visible debris or water was found. Other than the damage caused by the ground impact, no discrepancies were noted.

After discussing with the NTSB the aircraft crew?s statements and the FAA?s visual observations, the NTSB coordinated a more thorough inspection of the engine and N395AE was sent to a repair station in broussard, Louisiana. Representatives from the NTSB, FAA, engine manufacturer, air operator and repair station participated in the inspection. Samples were taken of the engine oil and fuel filter and rotation of the compressor, turbine and main drive shaft were accomplished without any discrepancies. The engine was then removed from the aircraft and placed in a test cell for run-up. The first engine start was aborted due to indications of an unusually high advancing turbine outlet temperature. After a second aborted start, the fuel nozzle spray pattern and installation depth were checked and found to be normal. A third start was performed and the throttle was advanced to idle. During this start, the turbine outlet temperature and compressor vibrations were both higher than normal. The throttle was then advanced to see if 100% could be achieved but at approximately 70-75% there was an increasingly loud deep buzzing noise with a significantly higher and out of limit compressor imbalance level. The engine was returned to idle and shut down. The compressor section was then removed and disassembled. During disassembly it was found that the diffuser assembly part number 23051119AL had failed with the front shield completely unbonded from the vanes of the assembly but no other signs of foreign object damage or failures were found.

Currently the compressor diffuser is being analyzed by the NTSB to identify a cause of the debonding failure.