Arden Hills, MN, USA
N119SP
BELL 206
The purpose of the flight was to simulate elevated close-quarter operations with firemen mounting and dismounting the helicopter skids following a pinnacle approach and landing to a shipping container at a training facility. The pilot stated that he made a “stable” straight-in approach to the shipping container and that, shortly after landing, he heard a “bang” and a “thunk.” The pilot stated that the helicopter “felt loose” and that he was having difficulty keeping it in position on top of the shipping container, so he decided to abort the landing and climb away from the shipping container. He increased collective to establish a climb, but quickly realized that the helicopter was not climbing as intended. The pilot briefly lowered collective to gain main rotor rpm, then increased the collective to reduce the helicopter’s rate of descent before a hard landing between shipping containers. The pilot remembered hearing an engine-out warning and possibly a low rotor speed alarm in the cockpit, but he could not recall exactly when he heard the warning and/or alarm. He also did not recall seeing any master warning indicator lights, but he stated that his attention was focused outside of the helicopter during the final moments of the flight. A review of video footage from a camera mounted to one of the firefighter’s helmets indicated that, after the pilot aborted the landing on the shipping container, the helicopter rotated slightly left as it climbed about 10 to 15 ft before it rotated about 90° to the right and descended to a dirt road between three shipping containers. As the helicopter descended, there was an audible decrease in engine speed and main rotor speed. The helicopter landed hard upright, which deflected the landing skids and fractured the tail boom aft of the fuselage. The helicopter sustained substantial damage to the lower fuselage, tail boom, and the tail rotor driveshaft during the hard landing. Postaccident examination and testing of the engine did not reveal any anomalies that would have precluded normal operation. The engine successfully ran at ground idle, flight idle, takeoff power, and maximum continuous power. Additionally, the engine was rapidly cycled between flight idle and maximum power numerous times with no observed hesitation or surging in engine operation. The engine exceeded the expected power output for a new-production engine at low cruise, normal cruise, and maximum takeoff power settings. Functional testing of the fuel control unit and power turbine governor revealed no anomalies that would have precluded normal engine operation. Additionally, the helicopter had ample fuel available at the time of the accident. The reason for the loss of engine power could not be determined based on the available information.
On April 18, 2016, about 1224 central daylight time, Bell 206-L4 helicopter, N119SP, was substantially damaged when it was involved in an accident near Arden Hills, Minnesota. The pilot sustained minor injuries. The helicopter, registered to the Minnesota Department of Public Safety, was operated as a public aircraft. According to the operator, the accident occurred during a Minnesota Aviation Rescue Team training mission that included the St. Paul Fire Department and Minnesota State Patrol personnel. The purpose of the training was to practice having the firemen mount and dismount the helicopter skids following a pinnacle approach and landing. The pinnacle landings were made to several Conex shipping containers located within the training site. One of the firefighters had a helmet camera that partially captured the accident sequence-of-events. The firefighter was positioned on top of a shipping container and was preparing to mount the helicopter when the accident occurred. His helmet camera footage showed the helicopter approach and land on the shipping container. However, before he and his partner were able to mount the helicopter skids, the helicopter lifted off and moved forward away from the shipping container. The helicopter then descended and impacted terrain between shipping containers. The pilot reported that, earlier in the morning, he had completed an uneventful flight from St. Paul, Minnesota, to the training facility located in Arden Hills, Minnesota. After landing, he shut down the helicopter and participated in the pretraining briefing with the firefighters. Following the briefing, he boarded the helicopter and completed an uneventful engine startup. He then repositioned four teams of two firefighters each into position before beginning the elevated close-quarter loading training. The pilot stated that the accident occurred during his seventh approach-and-pickup of firefighters from various shipping containers in the training area. The pilot stated that he made a “stable” straight-in approach to the shipping container while he kept visual contact with the firefighter on his right side, who gave him a “thumbs-up” to continue with the landing and firefighter pickup. The pilot noted that he lost visual contact with the firefighter shortly before the helicopter settled onto the shipping container. He stated that he then heard or felt a “bang,” which he initially thought was the helicopter’s tail contacting the shipping container; however, a tail strike at that point was not possible due to the helicopter’s attitude and position on top of the container. The pilot also noted that the audible “thunk” that he heard was different from when the landing skids normally touch down on the shipping container. He stated that the helicopter “felt loose” and that he had difficulty keeping it in position on top of the shipping container, so he decided to abort the landing and climb away from the shipping container. The pilot stated that he increased collective to establish a climb but quickly realized that the helicopter was not climbing as intended. There was another shipping container ahead of the helicopter, so he maneuvered the helicopter to the right where a hard landing was completed between shipping containers. The pilot remembered hearing an engine-out warning and possibly a low rotor speed alarm in the cockpit, but he could not recall exactly when he heard the warning and/or alarm. The pilot also did not recall seeing any master warning indicator lights, but he stated that his attention was focused outside of the helicopter during the final moments of the flight. The pilot reported that as the helicopter descended, he briefly lowered collective to gain main rotor rpm, then increased the collective to reduce the helicopter’s rate of descent before it landed hard between shipping containers. After the accident, the pilot shutoff the fuel and battery switch before he exited the helicopter. The helicopter sustained substantial damage to the lower fuselage, tail boom, and the tail rotor driveshaft. Further review of the video footage from the camera mounted to one of the firefighter’s helmets indicated that after the pilot aborted the landing on the shipping container the helicopter rotated slightly left as it climbed about 10-15 ft before it rotated about 90° to the right and descended to a dirt road between three shipping containers. As the helicopter descended, there was an audible decrease in engine speed and main rotor speed. The helicopter landed hard upright, which deflected the landing skids and fractured the tail boom aft of the fuselage. The main rotor blades struck the adjacent shipping container, which caused the separation of 8-10 ft of one of the rotor blades. A postaccident examination revealed that the engine, a Rolls Royce 250-C30P, serial number CAE 895853, remained within the engine compartment and the engine mounts appeared to be undamaged. A visual examination of the engine exterior did not reveal any evidence of impact-related damage, fire, or internal engine failure. Engine control continuity was established between the collective twist grip to the engine, with no unusual resistance or excessive travel noted as the controls were moved by hand. All engine B-nut fittings were confirmed to be at least hand-tight and were marked with torque paint. Both the N1 and N2 rotors rotated by hand with no anomalies, and continuity was established between the power turbine and the power output and tail rotor output shafts. The compressor inlet exhibited no evidence of damage to the inlet guide vanes or the impeller. Continuity was confirmed throughout the N1 rotor system from the impeller to the starter-generator cooling fan. The 4th stage turbine blades and exhaust plenum appeared undamaged when examined with a mirror. The upper and lower magnetic chip detectors were removed and did not exhibit any evidence of metallic debris. The fuel cutoff control in the cockpit and the fuel cutoff valve at the engine were in the closed position. No anomalies were noted with the fuel cutoff valve when cycled by hand. The cockpit fuel gauge indicated there was about 575 lbs (90 gallons) of fuel remaining. The inlet line to the fuel pump contained fuel, and the collected fuel sample did not exhibit any contamination. After the initial engine examination, the engine was removed from the helicopter and shipped to the manufacturer where an engine test run could be completed. The engine was mounted in a test stand at the manufacturer’s factory in Indianapolis, Indiana, where it demonstrated the ability to develop maximum horsepower with no anomalies that would have precluded normal operation. The engine successfully started, ran, and shut down a total of 5 times. The engine successfully ran at ground idle, flight idle, takeoff power, and maximum continuous power. Additionally, the engine was rapidly cycled between flight idle and maximum power numerous times with no observed hesitation or surging in engine operation. No excessive vibrations were noted during the test runs. When corrected for standard atmospheric conditions, the engine exceeded the expected power output for a new-production engine at low cruise, normal cruise, and maximum takeoff power settings. The engine’s fuel control unit (FCU) and power turbine governor (PTG) were removed from the engine following the test runs and were bench-tested at the manufacturer. Functional testing of the FCU and PTG revealed no conditions that would have precluded normal engine operation.
A partial loss of engine power for reasons that could not be determined based on the available evidence
Source: NTSB Aviation Accident Database
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