Abrupt control movements — which “highly likely” resulted when a 5-year-old girl moved from her father’s lap and inadvertently stepped on the collective — were the probable cause of the Feb. 14, 2010, fatal crash of a Eurocopter EC135 in Cave Creek, Arizona, U.S., the U.S. National Transportation Safety Board (NTSB) says.
The NTSB cited as a contributing factor the “absence of proper cockpit discipline from the pilot.”
The pilot and all four passengers were killed in the crash, which occurred in visual meteorological conditions around 1505 local time during a planned flight from Whispering Pines Ranch near Parks, Arizona, to Scottsdale Airport, about 150 mi (241 km) to the south.
In the final accident report approved in November 2012, the NTSB said its investigation revealed that a rotor blade had struck the left horizontal endplate and the tail rotor drive shaft, resulting in the loss of control that preceded the crash.
“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,” the report said. “A helicopter pilot would not intentionally make such control movements.”
The report quoted the ranch foreman as telling NTSB investigators that, on the day of the accident, the pilot loaded the helicopter and conducted the preflight inspection before climbing into the right front cockpit seat and starting the engines. Two adult passengers and two dogs were boarded before the foreman observed the owner and his daughter, whose weight was estimated at 42 lb (19 kg), board through the left forward cockpit door.
The owner and his daughter both sat in the left front cockpit seat, “with the small girl positioned on her father’s lap,” the report said. “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.”
Witnesses near the crash site, about 14 nm (26 km) north of Scottsdale Airport, said they heard popping or banging sounds before the helicopter descended and crashed into the ground. Some said they saw parts of the helicopter separate in the final seconds of flight, before it “circled and dove to the ground,” the report said. The helicopter struck the ground in a river wash area and was consumed by fire.
11,000 Flight Hours
The 63-year-old helicopter pilot had about 11,000 flight hours, including 824 hours in the EC135 T1 and 13 hours in the 90 days before the accident, according to flight operations personnel at Services Group of America (SGA), which owned the helicopter. He also had a second-class medical certificate. Investigators did not obtain the pilot’s logbook and found no record of military flight time, but SGA personnel said the pilot had flown U.S. Army helicopters during the Vietnam War.
His initial training in the EC135 T1 was completed in 2002, with recurrent ground and flight training in 2003, 2004, 2006 and 2008. All training records indicated that the pilot had performed satisfactorily and noted no deficiencies.
Eurocopter EC135 T1
The T1, first delivered to a U.S. customer in 1996, is the Turbomeca engine version. The accident helicopter was equipped with two TM USA Arrius 2B1 turboshaft engines.The EC135 is a twin-turbine light helicopter first flown in 1988 with two Allison 250-C20R engines.
The helicopter can be equipped to seat up to eight people. It has a maximum normal takeoff weight of 5,997 lb (2,720 kg), maximum cruising speed at sea level of 139 kt and a maximum range at sea level with standard fuel of 402 nm (745 km).
Source: Jane’s All the World’s Aircraft, U.S. National Transportation Safety Board Accident Report No. WPR10FA133
The owner of SGA was 64 and held a private pilot certificate for single-engine airplanes, issued in 1967. A review of FAA records revealed no indication that he held a medical certificate and little other information about his aviation background.
The owner did not have a helicopter rating, but in post-accident comments to accident investigators, the SGA chief pilot said that the owner “liked to fly” and that it was common for him to take the controls. The report said that investigators could not determine which man was flying at the time of the accident.
The report said that two American Eurocopter instructor pilots told accident investigators that, during training sessions, the accident pilot spoke of the pressure he felt in his job.
One instructor said the accident pilot “displayed an abnormally high degree of perceived pressure to accomplish flights from the owner of the helicopter” and was “visibly shaken when discussing the amount of pressure he received.”
The instructor said that, during initial transition ground school training in 2002, the accident pilot had told him “that it would not be uncommon to fly the helicopter’s owner from Seattle to his home of Vashon Island when the weather conditions at night were so poor that they would follow the ferryboat lights to navigate across the bay under foggy conditions.”
The other instructor said that, during a 2008 training session, the accident pilot had commented “about the owner dominating the cockpit duties prior to a flight.
“I emphasized the importance of following the checklist and always performing the hydraulic check. He commented that when the owner flies, he gets in the cockpit and ‘flips switches and goes.’ I felt [the accident pilot] was intimidated by the owner and would not insist proper aircraft procedures be followed.”
In information submitted by SGA for the accident investigation, the company’s chief pilot questioned the instructors’ accounts. He wrote that he considered the accident pilot as “not a pilot who would be intimidated” and “a conscientious and professional pilot, in every sense of the word.”
Noting that the instructors had “inferred that [the accident pilot] feared for his job if he did not perform his trips regardless of risk,” the chief pilot said, “After 24 years of service with Services Group of America, there could be nothing further from the truth. I do not believe that an individual could stay at any company that long if they felt such pressure from their employer.” The accident pilot had left SGA in the late 1990s but returned three years later and remained with the company until his death, the chief pilot said.
The accident helicopter was manufactured in 1999, was purchased by SGA from its original owner in 2002 and had accumulated 1,116 operating hours. It had been maintained in accordance with the manufacturer’s recommendations, and its most recent annual inspection had been conducted Oct. 30, 2009.
The helicopter had two Turbomeca USA Arrius 2B1 turboshaft engines. At the time of the October 2009 inspection, the left engine had recorded 1,103 hours total time since new, and the right engine, 227 hours.
The helicopter had been involved in three incidents before the crash, the report said.
In the first incident, in May 2003, the helicopter’s owner was at the controls when the left seat — reportedly “not in the proper detent position” — slid aft, the report said.
“The helicopter dropped about 50 ft but was recovered by a quick collective input,” the report said. “In an incident report submitted by American Eurocopter, it was reported that a loud bang was heard, followed by the touchdown of the helicopter.”
The impact damaged the horizontal stabilizer, and pieces of the engine were found on the ground. The helicopter was repaired and returned to service in August 2003.
The second incident, with the accident pilot flying, involved a January 2004 hard landing at a grassy heliport on Vashon Island, Washington, U.S. After repairs, the helicopter was returned to service in April 2004.
In September 2007, an engine chip light illumination occurred, followed by a yaw, an engine shutdown and a single-engine landing; the engine was replaced in January 2008.
In addition, one of the helicopter’s main rotor blades was removed in November 2009 because maintenance personnel could not balance it correctly, and a temporary replacement blade was installed. The replacement was still in place when the accident occurred.
Visual meteorological conditions prevailed at the time of the accident, with clear skies, 10 mi (16 km) visibility and no wind.
Air traffic control facilities had no contact with the pilot on the day of the accident. Radar showed the helicopter flying south toward Scottsdale from Whispering Pines Ranch; the last radar return was recorded at 1503:37, about two minutes before impact. An NTSB radar study said the helicopter’s last known position was about 14 nm (26 km) north of Scottsdale Airport, above the accident site at 3,700 ft above mean sea level.
The NTSB investigation found that a single impact of one of the main rotor blades had damaged the tail rotor drive shaft.
“No pre-impact failures or material anomalies were found in the wreckage and component examinations that could explain the divergence of the … blade from the plane of main rotor rotation,” the report said.
The most likely explanation, the report added, 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.”
The report said investigators had conducted a biomechanical study that showed that “it was feasible that the child passenger … could fully depress the left-side collective control by stepping on it with her left foot” to stand up from her place in her father’s lap.
“It is highly likely that the child inadvertently stepped on the collective with her left foot and displaced it to the full down position,” the report said. “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.”
This article is based on NTSB accident report no. WPR10FA133 and accompanying docket information.
- The collective pitch control is the part of a helicopter’s flight control system that simultaneously changes the pitch angle of all main rotor blades. In the EC135, and in most other helicopters, the collective is on the left side of each pilot’s seat. The cyclic, located in the EC135 between the pilot’s legs at the center of each pilot’s seat, changes the pitch of the rotor blades one at a time, as each blade rotates past the same point in the rotor disk.