WPR10FA133

The sudden and inadvertent lowering of the collective to near the lower stop, followed by a simultaneous movement of the collective back up and the cyclic control to a nearly full-aft position, which resulted in the main rotor disc diverging from its normal plane of rotation and striking the tail rotor drive shaft and culminated in a loss of control and subsequent impact with terrain. Contributing to the accident was absence of proper cockpit discipline from the pilot.

A ranch foreman who observed the flight preparations saw the helicopter owner board the helicopter through the left forward cockpit door and occupy the left front cockpit seat. The helicopter owner's 5-year old daughter also boarded the helicopter through the left forward cockpit door and sat on her father's lap. The pilot, who had accumulated 11,045 hours of total flight time, all in rotorcraft-helicopters, 824 hours of which were in the EC135 T1, was already seated in the right front cockpit seat. Both the left and right front cockpit seats were equipped with dual flight controls. Operator personnel revealed that the helicopter owner's daughter had sat on her father's lap occasionally during flights, that the owner liked to fly the helicopter, and that it was common for him to fly. Although the owner held a certificate for airplane single-engine land, he was not a rated helicopter pilot. However, it could not be determined who was flying the helicopter at the time of the accident. About 35 minutes after departing the ranch, the helicopter approached an area about 1 nautical mile (nm) north of the accident site. Radar data revealed that the helicopter was about 2,000 feet above ground level (agl). Witnesses on the ground stated that they heard unusual popping or banging noises. Several witnesses also stated that they saw parts separate from the helicopter before it circled and dove to the ground. The helicopter impacted a river wash area north of the destination airport in a slightly nose-down and slightly left-bank attitude. The helicopter was subsequently consumed by a postcrash fire. The accident was not survivable. A postaccident examination of the helicopter revealed that the yellow blade had impacted the left horizontal endplate and the tail rotor drive shaft in the area of the sixth hangar bearing, which resulted in the loss of control and subsequent impact with terrain. All of the damage at the aft end of the steel section of the tail rotor drive shaft was consistent with a single impact from the yellow main rotor blade. No preimpact failures or material anomalies were found in the wreckage and component examinations that could explain the divergence of the yellow blade from the plane of main rotor rotation. The most probable scenario to explain what caused the yellow blade to be in a position to strike the tail rotor drive shaft was that all of the main rotor blades were following a path that would have intersected the tail rotor drive shaft as a result of an abrupt and unusual control input. Further, witness marks that were on the tops of the blade cuffs likely occurred during the accident flight. Flight simulation indicated that the only way that this condition could have occurred was as a result of a sudden lowering of the collective to near the lower stop, followed by a simultaneous reaction of nearly full-up collective and near full-aft cyclic control inputs. A helicopter pilot would not intentionally make such control movements. A biomechanical study determined that it was feasible that the child passenger was seated on the helicopter owner's lap in the left front cockpit seat during the flight and that the child could fully depress the left-side collective control by stepping on it with her left foot. The child was estimated to weigh about 42 pounds at the time of the accident. The collective has a breakout force of between 2.2 and 3.1 pounds and would only need a maximum force of 5 pounds to fully move the control. Thus, the force to displace the collective fully was a maximum of 8.1 pounds, which is much less than the child's total weight and less than she would exert with her left foot if pushing to stand up from a seated position. The biomechanical study also found that the collective lever's full range of motion was 9.5 inches from full up to full down and that the spacing between the left edge of the seat, the collective, and the door are sufficient such that a child's foot could rest on the collective and depress it. The study noted that the cyclic control could be moved to the full-aft position even with a small child of this size seated on the lap of an adult male in various positions. Because the spacing between the upper partition, which separated the cockpit from the aft cabin compartment, and the ceiling was about 5 inches, it is unlikely that the child could shift from the left front cockpit seat to one of the rear seats during the flight. Considering that the child was sitting on the owner's lap in the left front cockpit seat, it is highly likely that the child inadvertently stepped on the collective with her left foot and displaced it to the full down position. This condition would have then resulted in either the pilot or the helicopter owner raising the collective, followed by a full-aft input pull of the cyclic control and the subsequent main rotor departing the normal plane of rotation and striking the left endplate and the aft end of the tail rotor drive shaft. During its investigation of this accident, the NTSB found that the pilot was involved in two incidents (in May 2003 and January 2004) while operating the accident helicopter; neither incident was reported to the Federal Aviation Administration. Of note, on May 8, 2003, the helicopter owner was operating the aircraft, and his seat slid aft while on final approach to landing. The helicopter dropped about 50 feet before impacting terrain, resulting in damage to the horizontal stabilizer. In this incident, the pilot failed to use proper cockpit discipline when he allowed the helicopter owner, who did not have a helicopter rating, to operate the helicopter's controls, particularly during a critical phase of flight. Further, an instructor pilot who conducted recurrent training for the accident pilot, reported that, during a conversation, the accident pilot commented to him about how the owner would dominate the cockpit duties, as he would get in the helicopter, flip the switches, and go. Although it could not be determined who was flying the helicopter at the time of the accident (and it is not relevant to the cause of this accident), the previous incidents, the statement by the pilot that the helicopter owner dominated cockpit duties, and the pilot allowing the owner’s daughter to sit on his lap during flight together indicate that the pilot did not maintain strong cockpit discipline.

HISTORY OF FLIGHT On February 14, 2010, about 1505 mountain standard time, a Eurocopter Deutschland GmbH EC135 T1 twin-engine turbine-powered helicopter, N127TS, lost control and impacted terrain near Cave Creek, Arizona. The pilot and four passengers were fatally injured. The helicopter was substantially damaged. The helicopter was registered to Services Group of America Inc. (SGA), of Scottsdale, Arizona, and was operated under the provisions of 14 Code of Federal Regulations Part 91 as a personal cross-country flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed. The flight departed the Whispering Pines Ranch, Parks, Arizona, about 1430 and was destined for Scottsdale Airport (SDL), Scottsdale, Arizona. SGA personnel reported during postaccident interviews that the helicopter made frequent trips between SDL and the Whispering Pines Ranch and that the helicopter had arrived at the ranch on February 12, 2010. In a statement submitted to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), the ranch foreman indicated that he had spoken to the helicopter owner while the helicopter was en route to the ranch on February 12. He was not present when the helicopter arrived and did not know who was on the helicopter when it arrived other than the pilot and owner, but he recalled helping the pilot put the helicopter in the hangar after its arrival. In a postaccident interview with the IIC, the ranch foreman reported that the helicopter was scheduled to return to SDL on the day of the accident. The foreman stated that, on the morning of the accident, the pilot, four passengers, and two dogs arrived at the helicopter hangar for the flight to SDL. The foreman revealed that he placed the passenger’s personal items on the ground outside of the baggage compartment, which was located at the rear of the helicopter; he said that the pilot always loaded the baggage compartment himself. The foreman reported that after the pilot had completed loading the helicopter and doing his preflight inspection, he entered the helicopter, sat in the right front cockpit seat, and started both engines. The foreman added that he then assisted the adult female into the rear cabin area, where she occupied the left rear aft-facing seat. Subsequently, a male passenger boarded the helicopter and sat in the right rear forward facing seat. This was followed by a small dog that occupied the left rear forward-facing seat directly across from the female passenger and a larger dog that was positioned on the floor between the left rear aft-facing and forward-facing seats. The foreman reported that after the male and female passengers and the two dogs were on board, he closed the right passenger door and ensured that it was locked. The foremen further reported that he moved forward to a position that was immediately outside of the right front pilot's position. He observed the helicopter owner and his 5-year-old, 42-pound daughter walk around in front of the helicopter and board the helicopter from the left forward cockpit door where they both occupied the left front cockpit seat, with the small girl positioned on her father’s lap. When asked how frequently the child occupied the left front cockpit seat with her father, the ranch foreman replied "occasionally." The foreman stated that he could not tell if either the helicopter owner or the child were secured and restrained in the helicopter. The foreman revealed that on previous flights, the helicopter owner had strapped his daughter in on top of him. He said that after everyone was on board, he closed the right passenger door and ensured that it was locked and secured. He said he then went forward to the right front cockpit window area, looked at the pilot, who had his shoulder harness and seatbelt on, and motioned to him that the right passenger door was secured and the helicopter was ready for departure. The foreman indicated that he then proceeded away from the helicopter to his pickup truck, which was positioned about 90 degrees to the right (west) of the helicopter, which was oriented to the south. The foreman said that from his truck, he watched the helicopter lift off, ascend to about 100 to 150 feet, then make a 180 degree turn to the north and begin forward flight, after which the helicopter departed to the northwest. Several witnesses to the accident were either interviewed by or submitted written statements to the IIC. Witness #1, who was located on the helicopter's flightpath and was about 1,385 feet north of the accident site, reported that while facing east, he heard two pops. The witness stated that he subsequently looked to the southeast where he estimated the helicopter was about 300 feet above ground level (agl); at the same time, he observed blade debris separate from the rear of the helicopter. The witness added that the helicopter then turned to the west before going inverted and appeared to go straight down. The witness added that the main rotor blade was making a loud clapping sound. Witness #2, who was located about 500 feet west of the helicopter's flightpath and was about 2,000 feet north-northwest of the accident site, reported that he heard the helicopter approaching from the north and that the engine was cutting out; he described it as popping a couple of times. The witness stated that he observed the helicopter in a rotation but could not indicate in which direction. He further stated that it went around in a circle two times and then suddenly went down in a steep angle of about 30 degrees while cork screwing. The witness added that he did not observe any debris separate from the helicopter. Witness #3, who was in line with the helicopter's flightpath and was about 2,350 feet due north of the accident site, stated that he initially saw the accident helicopter when it was about 1 mile north of his position and that it sounded perfect when he first sighted it. The witness reported that, about 10 seconds later, he heard what sounded like two small pops, followed by the helicopter making roaring noises. He said he then observed two flashes on the top of the main rotor. The witness stated that the helicopter started spinning and losing altitude and that it spun at least three times; he indicated that he then heard the engine cut out and make a big pop. The witness added that the tail of the helicopter went down, the nose went up, and then the aircraft fell tail first. In a follow-up interview, the witness reported seeing the helicopter spiral in a circular motion towards the ground and then rapidly gain altitude before it flipped upside down and spiraled nose first into the ground. Witness #4, who was inside of his home and was about 1,250 feet east southeast of the accident site, reported that he heard a loud and unusual sound. The witness stated that he then went outside and observed the helicopter go straight down from about 200 feet before it went out of view. Witness #5, who was about 500 feet west of the helicopter's flightpath and was initially in his house about 1,000 feet north-northwest of the accident site, stated that he first heard a rotor noise but that the noise changed, and then he heard a pop, followed by popping and banging sounds for a few seconds. The witness reported that he then went outside and observed the helicopter go down. He described the descent as a nose dive, estimated to be at about an 80 degree nose-down attitude before it went out of sight. Witness #6, who was about 650 feet east of the helicopter's flightpath and was about 2,000 feet north-northeast of the accident site, reported that he heard a popping sound. The witness stated that he observed the helicopter when it was about 400 feet agl moving to the south and that he heard it making popping sounds about every 15 to 20 seconds. The witness stated that he observed the helicopter make four circles in a level, clockwi