Wichita Falls, TX, USA
N335AE
BELL HELICOPTER TEXTRON 206L 1
The pilot reported that he was making an approach to a hospital helipad into light wind at night when he chose to go around because he felt that the approach was too high and fast. The pilot lowered the helicopter's nose, added power, and raised the collective, and the helicopter then entered a rapid, "violent" right spin. A review of the last 43 seconds of the helicopter's flight track data revealed that, as the helicopter approached the helipad, it descended from 202 to 152 ft and decelerated from a ground speed of about 9 to 5 knots before it turned right. The pilot attempted to recover from the uncommanded spin by applying left antitorque pedal and cyclic, but he was unable to recover, and the helicopter then spun several times before impacting power lines/terrain. Postaccident examination of the helicopter and the engine revealed no mechanical anomalies that would have caused the helicopter's uncommanded right spin. The helicopter was under its maximum allowable gross weight at the time of the accident, and the wind was less than 4 knots. Federal Aviation Administration guidance states that the loss of tail rotor effectiveness could result in an uncommanded rapid yaw, which, if not corrected, could result in the loss of aircraft control. The guidance further indicates that, at airspeeds below translational lift, the tail rotor is required to produce nearly 100 percent of the directional control and that, if the required amount of tail rotor thrust is not available, the aircraft will yaw right. Therefore, it is likely that that the pilot did not adequately account for the helicopter's low airspeed when he applied power to go around, which resulted in a sudden, uncommanded right yaw due to a loss of tail rotor effectiveness.
HISTORY OF FLIGHT On October 4, 2014, about 0155 central daylight time, N335AE, a Bell 206L1+ helicopter, was destroyed by post-impact fire after it impacted terrain while on approach to the United Regional Hospital helipad, in Wichita Falls, Texas. The commercial pilot was seriously injured and the flight nurse, paramedic, and patient died. The helicopter was registered to and operated by Air Evac EMS, Inc, O'Fallon, Missouri. A company visual flight rules flight plan was filed for the patient transfer flight that departed Jackson County Hospital, near Waurika, Oklahoma, about 0133. Visual meteorological conditions prevailed for the air medical flight conducted under the provisions of 14 Code of Federal Regulations Part 135. A witness, who was a photojournalist for NBC News 3 in Wichita Falls, TX, was driving southbound on the central freeway and was passing over Maurine Street when he first saw the helicopter. He said it appeared to be flying toward the "north" and its spotlight was turned on. As the witness continued to drive south toward downtown Wichita Falls, he realized the helicopter was hovering over 10th and Grace Streets and he thought it was odd that the helicopter had not landed yet and maybe he was waiting for someone to clear off the helipad. The witness said the helicopter was hovering at a height that was equal to the height of the top of the hospital, about 100-120 feet. The witness said that when he reached 9th Street, he saw the helicopter begin to spin to the right and move from its position over 10th and Grace Streets south toward the helipad. He said the helicopter entered the spin slowly and began to descend as soon as it started to spin. Initially, the witness thought the helicopter was going to land, but it continued to spin and descend. The helicopter then disappeared from his view behind a building. Shortly after it disappeared from his view, the witness saw sparks. He called 911 and drove the scene. Once he arrived on-scene the police and first responders were already there. According to the pilot, he and his Duncan, Oklahoma, based medical crew had just returned from a flight to Oklahoma City, Oklahoma, when he received a call from company dispatch to pick-up a patient in Waurika and transport him to United Regional Hospital in Wichita Falls. The pilot accepted the flight, but told dispatch that they needed 15 minutes on the ground to prepare for the flight since they had just landed. The pilot stated that he, along with the paramedic and flight nurse, re-boarded the helicopter, performed the necessary checklists, called dispatch and filed a flight plan. The flight to Waurika was uneventful. After landing, the pilot stayed in the helicopter for about 20 minutes with the engine running while the patient was prepped and loaded. The pilot and medical crew then departed for Wichita Falls. The weather was clear and the wind was three knots or less. The pilot said he used night-vision-goggles (NVGs) while en route, but flipped them up as he approached the hospital due to intense ground lighting. Upon arriving in Wichita Falls, the pilot said he performed a "high recon" of United Regional Hospital's helipad and called out his intentions to land. He performed the pre-landing checklists, and started the approach to the helipad from the northwest at an altitude of 700 feet above ground level (agl). Both of the hospital's lighted windsocks were "limp" but were positioned so they were pointing toward the northwest. The pilot, who said he had landed at this helipad on numerous occasions, said the approach was normal until he got closer to the helipad. He said he felt fast "about 12-15 knots" and a "little high," so he decided to abort the approach. At this point, with about ¼ to ½ -inch of left anti-torque pedal applied, he added power, "tipped the nose over to get airspeed," and "pulled collective." The pilot said that as soon as he brought the collective up, the helicopter entered a rapid right spin. He described the spin as "violent" and that it was the fastest he had ever "spun" in a helicopter. The pilot told the crew to hold on and that he was "going to try and fly out of it." The pilot said he tried hard to get control of the helicopter by applying cyclic and initially "some" left anti-torque pedal "but nothing happened." The pilot said he added more left anti-torque pedal, but not full left anti-torque pedal as the helicopter continued to spin and he was still unable to regain control. He also said the engine had plenty of power and was operating fine. The pilot recalled the helicopter spinning at least five times before impacting the ground inverted. He said smoke quickly filled the inside of the helicopter, so he unbuckled his seatbelt assembly, took off his helmet, punched out the windshield and exited the burning helicopter. The pilot also said that he did not hear any unusual noises prior to the "tail coming out from underneath them" and he did not recall hearing any warning horns or seeing any warning/caution lights. When asked what he thought caused the helicopter to spin to the right so quickly, he replied, "I don't know." The helicopter was equipped with a handheld Garmin GPS 396 and Sky Trac ISAT-100 flight-tracking software. The SkyTrac system recorded position every 5 seconds versus the GPS that recorded position every 60 seconds. Data was successfully downloaded from each unit. The data between the two units was fairly consistent and revealed that after the helicopter departed Waurika, it flew on a south-westerly heading until it crossed Highway 447 in Wichita Falls. It then flew on a westerly heading until it reached Highway 287, where it then turned on a north westerly heading. As it proceeded to the northwest, the helicopter flew past United Regional Hospital to the east before it made a left, 180 degree turn about 1 to 1.5 miles north of the hospital. The helicopter then proceeded directly to the helipad on a south-easterly heading. A review of the last 43 seconds of the recorded Sky Trac data revealed that as the helicopter approached the helipad, it descended from an altitude of 202 feet to 152 feet and decelerated from a ground-speed of about 9 knots to about 5 knots before it turned to the right. Over the next 10 seconds, the helicopter traveled back toward the northwest as it descended to an altitude of 54 feet and increased to a ground-speed of about 17 knots before the data ended at 0155:14. The location of the last recorded data point was consistent with where the helicopter impacted the ground. A portion of the accident flight and impact were captured on one of the hospital's surveillance cameras. A review of the surveillance tape revealed the helicopter approached the helipad from the north with the spotlight turned on (the pilot said that he used the spotlight during the approach). The helicopter then climbed and went out of frame before it reappeared in a descending right hand turn then hit the ground. The time of impact was recorded at 0154:56. About 6 seconds later, there was a large explosion. Another Air Evac flight crew (pilot, paramedic, and a flight nurse) was based at United Regional Hospital, and were in their quarters near the helipad when the hospital-based pilot heard the helicopter. The crew was preparing to assist the inbound crew with the patient transfer. The hospital-based pilot stated that when he opened the door to their quarters, he heard the helicopter arriving from the north. As the helicopter got closer, he heard "a change in rotor noise" followed by the sound of a "snap then bang then silence." The hospital-based pilot yelled to his crew that the helicopter may have crashed. All three immediately responded to the accident site where they found the helicopter upside down, facing west, and on-fire. The hospital-based pilot said the flight nurse, who was seated in the rear right seat, was lying about 6-feet away from the helicopter. She was on fire and most of her Nomex flight suit had burned away. The hospital-based pilot also saw the paramedic, who was seated in the rear, left seat, crawling out of the wreckage and the pilot was crawling out of the front of the wreckage. Due to the intense fire, there was no way to assist the patient. The hospital-based paramedic stated that he was asleep when he was alerted of the inbound flight. He heard the helicopter approaching "then nothing." The lights in their crew-quarters then flickered for about 10 seconds. The hospital-based pilot then came in and said the helicopter had crashed. The hospital-based paramedic said that when he got to the accident site, the flight nurse was lying on her back on the sidewalk. The paramedic was on fire and about 10 feet away from the helicopter in the street. A bystander was using his shirt to put out the flames on the paramedic. The hospital-based paramedic then ran over to the injured paramedic. He said the paramedic was alert and was aware that he was involved in an accident. The hospital-based paramedic said he picked the injured paramedic up, placed him on a gurney and took him to the emergency room. He did not talk to the flight nurse or pilot. The hospital-based flight nurse stated he was in bed, but had not fallen asleep. He heard the hospital-based pilot say that a company helicopter was inbound and he could hear it approaching the helipad. The flight nurse said he was putting on his jumpsuit when he heard the helicopter "power-up" followed by silence then the sound of a "crash." He and the two others immediately responded to the accident site. When the hospital-based flight nurse arrived on scene, he saw the flight nurse and thought she was deceased until she started screaming for help. The pilot was crawling through the front windshield and his foot was stuck. There was a "winding noise" coming from the helicopter so he helped him get out and away from the burning helicopter. He asked the pilot if he was ok, and he responded, "I don't know." The hospital-based flight nurse then saw the hospital-based paramedic dragging the injured paramedic away from the helicopter. He immediately realized the injured paramedic was a good friend and his flight partner. The hospital based flight nurse immediately went over to him and found the injured paramedic was alert. The injured paramedic said they were on final approach to the helipad when the helicopter started to spin, but he wasn't sure why. The hospital-based flight nurse later asked the pilot what happened, and the pilot said "he wasn't sure." When he told the pilot that the paramedic said that the helicopter had spun, the pilot responded, "yeah." The patient died in the accident but the flight nurse and the paramedic survived and were treated for severe burns. However, they both succumbed to their injuries within a month after the accident. PERSONNEL INFORMATION The pilot held a commercial pilot certificate for rotorcraft-helicopter, and instrument rotorcraft-helicopter. The operator reported his total flight time as 1,810 hours. About 1,584 of those hours were in helicopters, of which, 214 hours were in the Bell 206 series helicopter. His last Federal Aviation Administration (FAA) second class medical was issued on May 13, 2014, without limitations or waivers. The pilot was also a chief warrant officer with the United States Army. He attended Army flight school and was trained in the CH47D Chinook helicopters. According to time-on-duty records provided by the operator, the pilot came on duty October 2, 2014, at 1810. This was the start of his first shift after having the previous 6 days off. He had only made one flight prior to the accident flight. The pilot was hired by the operator on June 9, 2014. At that time, he reported a total of 1,755.6 total hours, of which, 159.1 hours were in the Bell 206 model helicopter. A review of his training records revealed he started initial/new-hire training on June 10, 2014, and satisfactorily completed ground school and 10.9 hours of flight training. The training included normal and emergency procedures, including loss of tail rotor effectiveness. On June 22, 2014, the pilot passed a flight crew-member competency/proficiency check- Federal Aviation Regulation (FAR) Part 135/NVG check ride. The pilot also completed "Initial Orientation-Flight" training at his assigned base in Duncan, Oklahoma. The training involved 5 flight hours and included cross country flights to the local area hospitals and landmarks; 2 hours of night flying for the same purpose; day and night approaches to hospital and elevated helipads; familiarization with all hazards, terrain and man-made, identified on the Duncan, Oklahoma base hazard map. This training was completed on July 8, 2014. METEOROLOGICAL INFORMATION Weather at Sheppard Air Force Base/Wichita Falls Municipal Airport (SPS), about 5 miles north of the accident site, at 0152, was wind from 140 degrees at 3 knots, visibility 10 miles, clear skies, temperature 51 degrees F, dewpoint 33 degrees F, and a barometric pressure setting of 30.24 in HG. HELIPAD INFORMATION The United Regional Hospital's ground-level helipad was located directly across the street from the hospital's emergency room entrance. The final approach/take-off area (FATO) was 60-foot-wide by 60-foot-long and was privately owned and operated by United Regional Health Care System. At the time of the accident, the hospital based flight crew's helicopter was in the hangar and the helipad was clear of obstacles. AIRCRAFT INFORMATION The single-engine, seven-place helicopter was manufactured in 1981 and equipped with a Rolls-Royce C-250-30P turbo shaft engine. It was configured for air medical transport; one pilot, two medical crew, and one patient. The operator reported that at the time of the accident, the airframe had about 18,378.6 hours total time and the engine had about 3,546.2 hours total time. The helicopter was retrofitted with Van Horn Aviation (VHA) after-market composite tail rotor blades (Supplemental Type Certificate No. SR02249LA). According to VHA's website, this install helps reduce overall aircraft noise and produce more tail rotor authority. The estimated gross weight of the helicopter at the time of the accident was 4,274 pounds, or about 176 pounds below the maximum gross weight of 4,450 pounds. WRECKAGE AND IMPACT INFORMATION An on-scene examination of the helicopter was conducted on October 4-5, 2014, under the supervision of the National Transportation Safety Board Investigator-in-Charge (NTSB IIC). The helicopter collided with power lines and came to rest inverted between two trees that lined a public sidewalk about one block northwest of the helipad. All major components of the helicopter were located at the main impact site. Small sections of the helicopter were found strewn within 100 feet of where the main wreckage came to rest. The helicopter was recovered and taken to a salvage facility where a layout examination was conducted on October 6, 2014. The above mentioned party members were in attendance for both the on-scene and salvage yard exams. The helicopter wreckage was extensively burned and fragmented into large and small sections. These sections were laid out in a manner that was consistent with how they would have been situated prior to the accident. The tail rotor and portion of the empennage sustained the least amount of impact and fire damage. The tailboom had separated from the main body of the helicopter just aft of where it attached to the fuselage. Both tail rotor blades exhibited minor leading edge damage and there was some de-bonding on the trailing edge. The pitch control tube to the gearbox to the 90-degree bend and forward to where the tail boom had separated from the fuselage was intact. The tail rotor gearbox magnetic plug was clean and there was no fluid observed the tail rotor gearbox sight-glass. The right horizontal fin remained attached to the tailboom and exhibited some thermal damage. The left horizontal fin was folded under and burned. The tail rotor driveshaft was relatively intact, but damage was noted to the Thomas couplings, which were splayed, and the hangar bearing between #1 and #2 was out of alignment. The aft short-shaft was separated and exhibited thermal d
The pilot’s failure to maintain yaw control when he applied power to execute a go-around at a low airspeed in dark, night conditions, which resulted in a rapid, uncommanded right yaw due to a loss of tail rotor effectiveness.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
