Lawton, OK, USA
N361SF
BELL 407
The commercial pilot of the helicopter was approaching to land on a helipad. It was his first landing to this helipad, though he had departed from the helipad the day before. Due to trees and transmission lines near the helipad, the pilot flew a slight right-turning, steep approach. When the helicopter was about 125 ft above the pad and 150 ft to the southwest of it, the pilot commanded left cyclic to stop the right turn. He estimated the helicopter to be 40 knots above effective transitional lift, and in a stable 500 ft per minute descent; there was a headwind. The helicopter did not respond to his control input, and the pilot announced to the crew his intention to go around. He increased left cyclic until the cyclic was against his left leg and the helicopter still did not respond. The pilot lost control of the helicopter and it landed hard, colliding with a wall. Data extracted from the engine control unit (ECU) was consistent with the engine producing the required power and responding to collective control inputs; however, the data indicated that the main rotor speed and torque were exceeded. These exceedances suggested that a large demand for power was commanded by the pilot, likely during the go-around. Examination of the helicopter did not reveal any mechanical anomalies that would have precluded normal operation. The helicopter was in a right bank with 3 crewmembers seated on the right side of the helicopter, one crewmember seated on the left side, and was carrying a near-full fuel load. The distribution of crew members and a high torque setting may have contributed to the pilot's inability to maintain helicopter control; however, the extent to which these factors may have contributed could not be determined.
On September 29, 2016, about 0600 central daylight time, N361SF, a Bell 407 helicopter, impacted terrain following a loss of control while attempting to land at the Comanche County Memorial Hospital Heliport (18OK), Lawton, Oklahoma. The pilot and 2 crew members had minor injuries. One crew member was seriously injured, and the helicopter was substantially damaged. The helicopter was owned and operated by Survival Flight under the provisions of 14 Code of Federal Regulations Part 135 as a positioning flight. Night visual meteorological conditions prevailed for the flight which operated on a company flight plan.The pilot reported that he approached the helipad from the southwest. It was his first landing to this helipad but had departed from the helipad on the day prior. Due to trees and transmission lines within 40-50 ft of the elevated helipad, the pilot flew a slight right-turning, steep approach. When the helicopter was approximately 125 ft above the pad and 150 ft to the southwest, the pilot commanded left cyclic to stop the right turn. He estimated the helicopter was below 40 knots, but above effective transitional life, with wind off the nose of the helicopter or slightly left, and a stable 500-ft per minute descent. The helicopter did not respond to his control input and the pilot announced his intension to the crew to go-around. He increased left cyclic until it was against his left leg and the helicopter still did not respond. The pilot lost control of the helicopter and it landed hard colliding with a wall. An inspector from the Federal Aviation Administration (FAA) examined the airframe with the assistance of a technical representative from Bell Helicopter. No preimpact anomalies were discovered with the wreckage. The engine control unit (ECU) was removed from the helicopter and sent to Triumph in West Hartford, Connecticut. With oversight from an FAA inspector, data from the unit was downloaded. The data extracted was consistent with the engine producing the required power and responding to collective control inputs. Exceedance information captured by the ECU recorded an exceedance of main rotor speed (Nr) and torque (Q). The unit recorded 10 lines of data with this exceedance which contained information consistent with the accident sequence. Prior to the accident there were 2 spikes in engine parameters. Without changes in collective inputs, demands of flight control inputs could impact a spike on engine demand. On the NTSB Form 6120, the pilot stated that the helicopter was loaded with 3 crew members on the right side of the helicopter, and a near full fuel load. Up to the accident landing, the helicopter had flown for 6 hours including 6 approaches and night landings at other hospitals without incident.
The pilot's loss of helicopter control during landing, which resulted in a hard landing and collision with a wall.
Source: NTSB Aviation Accident Database
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