Oklahoma City, OK, USA
N917EM
EUROCOPTER AS 350 B2
The emergency medical services helicopter departed a hospital helipad in dark night visual flight rules conditions and proceeded on its mission. Satellite data showed that, after takeoff, the helicopter began a gradual climb toward its planned destination. The data stopped about 3 minutes and 30 seconds into the flight. No distress calls were heard from the pilot. Fixed video surveillance cameras located near the accident site showed the last few seconds of the helicopter descending toward the ground. The helicopter impacted a parking lot, and a postimpact fire occurred. Examination of the wreckage revealed that three of the engine's first-stage axial compressor blades exhibited deformation consistent with soft body foreign object damage. The remainder of the engine and airframe exhibited no evidence of malfunction that would have contributed to an in-flight loss of engine power. The helicopter's air intake design, which had been modified to accommodate a different engine than that originally supplied by the helicopter's manufacturer, incorporated a blanking plate attached to the top side of the engine cowling that covered a portion of the air inlet screen. A gap in the area where the blanking plate and the screen overlapped made it possible, in certain meteorological conditions, for water or snow to pass through the screen, accumulate on the blanking plate, and freeze into ice. Ice accumulation in this area, if left undetected, could result in the ice detaching from the blanking plate and entering the engine during operation, causing soft body foreign object damage and a loss of engine power. Precipitation and outside temperatures ranging from 35 to 19 degrees F occurred during the 12-hour period preceding the accident. The combination of these meteorological conditions was conducive to the formation and accumulation of ice in the area between the air inlet screen and the blanking plate. Although the helicopter's flight manual supplement for cold weather operations recommended installation of an air inlet cover after the last flight of the day, during the day and night before the flight, the helicopter was parked outside on the helipad without an air inlet cover installed. According to the helicopter's mechanic, he inspected the helicopter on the afternoon before the flight and noted that some snow had accumulated on it. It is likely that the lack of an engine air inlet cover allowed precipitation to accumulate in the vicinity of the engine air intake. The helicopter's flight manual cold weather operations supplement also contained instructions for the pilot to perform a visual and manual (tactile) inspection of the air intake duct up to the first-stage compressor for evidence of snow and ice. Furthermore, the manufacturer and the Federal Aviation Administration had previously released information notices regarding inflight loss of engine power due to snow or ice ingestion caused by inadequate inspection or removal of snow or ice from the engine air inlet. These notices recommended a thorough inspection in and around the engine inlet area in order to detect and remove any snow or ice accumulation before flight. The initial on-scene examination found no remnants of ice or snow on these components because exposure to the postcrash fire would have melted such evidence. Surveillance video of the helipad showed that most of the helipad lights were off at the time of the pilot's preflight inspection immediately before the flight, making it difficult for him to detect any ice or snow accumulation in the area of the engine air intake. Thus, the ice accumulation between the air inlet screen and the blanking plate remained undetected, and shortly after takeoff, the ice detached from the blanking plate, slid into the air inlet, and was subsequently ingested by the engine, resulting in an in-flight loss of engine power. .
HISTORY OF FLIGHTOn February 22, 2013, approximately 0542 central standard time, an Eurocopter AS350B2 emergency medical service (EMS) configured helicopter, N917EM, registered to Wells Fargo Equipment Finance Inc., care of EagleMed LLC, of Wichita Kansas, impacted in the parking lot of St. Ann's Retirement Home located in Oklahoma City, Oklahoma. The flight was being conducted under the provisions of 14 CFR Part 91 as a repositioning flight. The intent of the flight was a prescribed inter-hospital transfer of a cardiac patient from the Watonga Municipal Hospital to the University of Oklahoma Medical Center. Of the three crewmembers onboard, the commercial pilot and flight nurse sustained fatal injuries and the paramedic sustained serious injuries. Dark night visual meteorological conditions prevailed in the vicinity along the route of flight and accident site and a company flight plan was filed with EagleMed flight dispatch control. The flight originated from the Integris Baptist Hospital (OK19) helipad at 0538 and its intended destination was Watonga, Oklahoma. SkyConnect satellite data showed that the helicopter departed OK19 and began a gradual climb on a northwest bearing toward Watonga. The data stopped approximately 3 minutes and 30 seconds into the flight. Fixed video surveillance cameras located on a building adjacent to the parking lot showed the last few seconds of the helicopter descending toward the ground. The video showed that the helicopter burst into flames upon impact. From the initial impact point, the debris path was approximately 75 feet in length, on a heading of 065 degrees magnetic. All of the impact signatures were consistent with a right side low (approximate 40 degree) attitude, with a high rate of descent. Using the geometry of impact signatures and adjacent structures clearance, the helicopter's angle of descent was approximately 25 degrees. Witness Statement Summaries Witness 1 was a person who was driving in the vicinity of the accident site reported that he distinctly observed a "flash" in the sky in front of him. After the flash, he saw the helicopter in an increasingly rapid descent before it disappeared behind buildings. He then drove toward an area where smoke was emanating and saw that the helicopter was on fire in the parking lot of St. Ann's. He immediately assisted others (St. Ann's employees) in pulling the surviving paramedic away from the burning aircraft. Witness 2 was a resident of St. Ann's and her apartment was on the third floor. The window from which she observed the helicopter impact area faced in an approximate south-easterly direction. She was awake in her bedroom when she heard the helicopter come over, followed by the sound of the crash-impact. She said it sounded like the helicopter came over her building from the north and that it sounded like a very loud motor-type sound. It was a constant sound, not cutting in and out up to the time of the impact. When she heard the impact, she ran to her window and saw the helicopter on fire and people running out to assist. She said after the initial impact, there were two more explosions. One of the two explosions blew out her next door neighbor's window. It was dark outside at the time. Witness 3 arrived at St. Ann's for work about 0540. She was parking her car and saw the helicopter flying nose down but appeared to be normal. The helicopter seemed to hover as if looking for a place to land. I thought it was a normal landing, then, the helicopter started to angle down as if trying to land. Then the helicopter touched down and the impact wasn't violent but a fire started. She went inside, pulled the alarm and announced "fire" and grabbed an extinguisher and ran back out. She made eye contact with one of the persons in the wreckage and tried to pull him out, then, another St. Ann's employee came and pulled him out. Another man came up and helped and there was another explosion as the St. Ann's employees were trying to pull persons from the wreckage. The Fire Department showed up and took over. Witness 4 was sitting in her car when she saw the helicopter "fall." The helicopter was heading toward her car when it hit the ground and skidded into an embankment. All of this happened in a few seconds. There was a fire immediately upon impact. She heard a "screech" sound that lasted a few seconds prior to impact. Witness 5 was in his home preparing to go on duty with the Oklahoma County Sheriff's Office. He heard what sounded like the EagleMed helicopter approaching from the southeast. He stated that this indicated a recent lift off from Integris Baptist or possibly one of the other Oklahoma City hospitals located in that general direction. He said that the particular type of aircraft used by EagleMed makes a very distinct sound and it is not hard to distinguish from other helicopters. As the helicopter flew over his house, the engine of the helicopter very suddenly powered down so quickly that the engine noise became silent. He was not certain as to what altitude the aircraft was at, but before the engine went silent, it sounded as though it was maybe 500 to 600 feet above the house. This estimation was made from having lived in the Wiley Post Airport (PWA) flight path for several years and observing different aircraft. He stated that he was inside his home at the time and did not physically see the helicopter. When he heard the engine go silent, he glanced at the clock and noted that it showed 0542. In the ensuing few moments after glancing at the clock, he wondered what was going on. It was then that an explosion shook the walls and windows of every home in the area. NOTE: Additional and Complete Witness Statements are Included in the Docket Summary of Interview with EagleMed Integris Hospital Base Pilot (Prior Shift) The prior shift pilot stated that she had spoken with the EagleMed base mechanic at the Integris Hospital crew quarters on the afternoon of February 21st. They talked about the weather and the mechanic told her that he was concerned about precipitation melting in the tail area and re-freezing. She stated that the accident pilot arrived for his night shift on the evening of the 21st between 1840 and 1845, which was about 20 minutes later than he normally arrived, due to traffic. She stated that when inclement weather was coming in, they would normally fly the helicopter to a nearby company hangar. About 2200, several hours after she went off shift, she sent a message to the accident pilot to warn him that it was icing over outside due to the cold weather and asked him not to fly. Summary of Interview with EagleMed Base Mechanic The base mechanic last saw the accident helicopter parked on the Integris Hospital helipad on February 21st, about 1430. The helicopter had been out of service due to inclement weather. He knew that there was a hard freeze coming and went to check on the helipad to clear off any snow/ice that had accumulated on and around the helicopter. He took a shovel with him and cleared slush and snow off the sidewalk, the area around the helicopter, and the drain nearby. At that time he also generally inspected the condition of the helicopter. During this general inspection, he looked up on the top of main rotor, the engine inlet, canopy, exhaust duct, and horizontal stabilizer for snow/ice accumulation. He noted that engine inlet plugs, pitot plugs, or covers were not installed. Early in the interview, he stated that there was a little bit of residual accumulation in the engine inlet, and there was some accumulation in the exhaust duct which he cleaned out. Later in the interview, he stated there was no accumulation in the engine inlet. He said there was some snow/slush on the horizontal stabilizer which he removed with a brush. He also checked fluid levels, pitch links, and the tail rotor, which seemed fine. He looked around the pad for leaking fluids and noted none. At that time, it was drizzling and wet outside. The temperature was above freezing, and the accumulation was melting. He stated that he was generally concerned about removing any moisture because of the freeze warning. When the mechanic went inside to visit with the crew, he talked with the pilot (prior shift pilot) about the weather. They walked outside under a covered area and discussed that it wasn't clear enough to fly at that time. He said the pilot said she had been checking the weather every hour and that it wasn't looking good. The mechanic further commented that when he was out on the helipad with the helicopter he did not open the cabin doors, but he noticed that the aircraft cabin heater was plugged in. He also added that the windows were polished recently to help prevent moisture accumulation. When asked whether any plugs or covers were normally installed over the engine inlet or pitot tube when it was parked, he said no. When the mechanic was asked whether he or the crew perceived any pressure from the hospital when the aircraft was out of service due to weather, he said no. When asked whether he perceived that the aircraft would remain out of service for the foreseeable future due to weather, he said yes. When asked when he expected that the daily inspection would be accomplished, he said he expected that the pilot on duty (the accident pilot) would perform the daily inspection later that evening. NOTE: Complete Statements of the Prior Shift Pilot and Base Mechanic are Included in the Docket PERSONNEL INFORMATIONThe pilot was employed with EagleMed since February, 2011. He held a valid Commercial Helicopter Pilot Certificate with an Instrument Helicopter rating. His most recent FAA medical certificate, Second Class, was dated January 1, 2013, with no limitations or waivers. The pilot's total flight time was 4,960 hours (3,702 hours Pilot-in-Command), all of which were in helicopters. His total time in the AS350B2 helicopter was 202 hours. His most recent annual training was completed on January 15, 2013, which included practice autorotations and simulated engine failure scenarios. The EagleMed chief pilot reported that the pilot was in good health, had a great sense of professional conduct, and did not have any extraordinary events in the previous 72 hours prior to the accident. He worked his normal shifts and seemed to be well rested. AIRCRAFT INFORMATIONThe Eurocopter AS350 B2 helicopter, also known as the "AStar", was originally equipped with a single Turbomeca Arriel 1D1 turboshaft engine, mounted behind the main transmission, which provides power to the main and tail rotor systems. On the accident helicopter, the operator had replaced the Turbomeca engine with a Honeywell (formerly Lycoming) LTS101-700D-2 turboshaft engine under Soloy Aviation Solutions supplemental type certificate (STC) No. SR01647SE on July 30, 2008. The airframe-supplied engine air intake system was modified to accommodate the Honeywell LTS101 engine under the same STC. An optional inlet air filter kit, manufactured by Aerospace Filtration Systems (AFS), was offered as part of STC No. SR01647SE if installed at the time of the LTS101 engine conversion, or under STC No. SR02393CH if installed after the LTS101 engine conversion was performed; the inlet air filter kits under both STCs are identical in design. Neither of the inlet air filter kits was installed on the accident helicopter. According to soloy, the design of the air intake system for STC SR01647SE is virtually identical to the design of the Airbus Helicopters AS350D equipped with a LTS 101-600A2 engine. The LTS101-700D-2 engine installed on the helicopter at the time of the accident was serial number (S/N) LE-46036C, which was installed on the accident helicopter on June 8, 2012. According to the engine data plate, the date of manufacture for engine S/N LE-46036C was September 1983. Prior to the accident flight, the engine had accumulated a total time of 8,568.1 hours since new (TSN) and the helicopter accumulated a total (Hobbs) time of 6,473.6 hours. Refer to the Maintenance Group Chairman's Factual Report for more information on the maintenance history of engine S/N LE-46036C. The Honeywell LTS101-700D-2 engine is a dual-spool turboshaft that features a single-stage axial compressor and a single-stage centrifugal compressor, a reverse flow annular combustor, a single stage turbine rotor that drives the compressor, an accessory gearbox, and a power turbine rotor that drives the helicopter's main and tail rotors. The LTS101-700D-2 engine's maximum takeoff power rating is 732 shaft horsepower (shp) and a maximum continuous power rating of 650 shp, both of which are flat-rated to 72 Degrees F. NOTE: The Maintenance Group Chairman's Report is available in this Report's Public Docket. METEOROLOGICAL INFORMATIONOn the morning of the accident, at 0453, an automated weather reporting facility at the Wiley Post Airport (PWA), Oklahoma City, Oklahoma, reported wind from 340 degrees at 10 knots, visibility 10 statute miles, temperature 19 degrees Fahrenheit (F), dew point 12 degrees F, and a barometric pressure of 30.02 inches of mercury. The day prior to the accident, on February 21, 2013, METAR data from PWA reported 0.07 inches of precipitation in the last 6 hours at 1153 while METAR data from Will Rogers World Airport (OKC) reported 0.14 inches of precipitation in the last 6 hours at 1152 CST. METAR data from WPA and OKC reported trace precipitation from 1553 CST to 1752 CST with temperatures around 35°F. The Integris Hospital Helipad (OK19) is about 3 miles east of PWA and about 8 miles north of OKC. METAR data from PWA reported that temperatures fell consistently from a high of 35°F (recorded at 1753 on February 21, 2013) to a low of 19°F (recorded at 0753 on February 22, 2013). WRECKAGE AND IMPACT INFORMATION (On Site) Airframe The majority of the helicopter structure was thermally damaged consistent with a post-impact fire, and fragmented from impact forces localized in the area of its final resting location. The majority of the burned structure debris indicated the aircraft came to rest in the upright position. The energy debris path was approximately 75 feet in length and on a heading of 065 degrees. All the impact signatures were consistent with a right side low (approximately 40 degrees) attitude, with a forward movement from a high rate of descent. The fuselage was broken open (both doors were separated from the fuselage and found near the main wreckage and damaged from the impact and post-impact fire), the medical litter, the pilot's seat and rear seats remained inside the aircraft. The pilot's seat was a conventional bucket type seat; the seat was burned away from the floor and leaning forward. A 4-point seat restraint buckle was found clasped together in the ash of the wreckage. The 4 steel frames of the aft medical service seats remained mounted to the aft bulkhead. The 'Starflex' remained in the center of the rotor hub; however, all of the star arms and sleeves were thermally damaged. All three of the main rotor blades remained attached to the rotor head and mast. The leading edges of each blade exhibited light impact damage; the tips of each blade were bent up. One of the MRB tips was missing its tracking finger and static and dynamic balance weights. Ground scars consistent to low rotor RPM from the main rotor blades were found near the final wreckage resting place. The tail section (which includes the tail-boom, tail-rotor gear box, rotor blades, drive shaft and pitch change system) was separated from the main fuselage at the forward tail cone attach point from thermal distress. The right horizontal stabilizer was damaged from impact forces, bending up approximately 50 degrees. Almost no damage was observed to the left horizontal stabilizer. The tail ventral fin and stinger were bent up and aft, consistent with a forward flight path at impact. The tail rotor blades were damaged at the hub consistent with lateral impact forces. Both blade tips had dirt debris consistent with rotation at ground contact, and ground scars were present matching the tail rotor blade tips. The ventral fin and tail skid had correlated ground impact signatures in the same area as the tail rotor, consistent with a 40-degree a
The loss of engine power due to engine ice ingestion during initial climb after takeoff in dark night light conditions. Contributing to the accident were the lack of an installed engine air inlet cover while the helicopter was parked outside, exposed to precipitation and freezing temperatures before the accident, and the pilot’s inadequate preflight inspection that failed to detect ice accumulation in the area of the air inlet.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
