NTSB Identification: ERA09FA537
14 CFR Part 91: General Aviation
Accident occurred Friday, September 25, 2009 in Georgetown, SC
Probable Cause Approval Date: 01/19/2012
Aircraft: EUROCOPTER AS-350, registration: N417AE
Injuries: 3 Fatal.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
After conducting an interfacility patient transfer, the pilot refueled and then requested flight-following services from air traffic control, departing in visual meteorological conditions (VMC) for the return flight to his base. During the return flight, the pilot encountered instrument meteorological conditions (IMC). A review of Sky Connect data for the accident flight revealed that the helicopter was cruising at varying altitudes and never reached a steady state cruise altitude for any significant period of time. The majority of the flight was flown at altitudes below 1,000 feet with the greater part of the last 8-minute segment of the flight being operated below 800 feet. (The lowest altitude recorded during the last cruise segment of flight was 627 feet.) Witnesses who observed the helicopter before the accident described it as flying about 1,000 feet above ground level (agl), with its searchlight turning on and off, in moderate to heavy rain. A subsequent loss of control occurred, and the helicopter impacted terrain about 1.92 nautical miles (nm) southwest of Georgetown County Airport (GGE).
Postaccident examination of the main wreckage revealed no evidence of any preimpact failures or malfunctions of the engine, drive train, main rotor, tail rotor, or structure of the helicopter. Additionally, there was no indication of an in-flight fire.
During the first legs of his flight, the pilot experienced and observed VMC conditions along his route. However, postaccident witness reports and in-flight statements from the accident pilot indicated that the weather in the area had deteriorated since his southbound flight 2 hours prior. According to Omniflight’s Savannah, Georgia, base manager, who was also a pilot operating in the area on the night of the accident, the weather that night was deteriorating but was forecast to remain well above minimums for his flight from Savannah to Greenville, South Carolina, and then to the Medical University of South Carolina (MUSC) in Charleston. However, while he was refueling at the Greenville airport, the pilot of the accident helicopter contacted him by radio and advised him to double check the weather before returning to MUSC. The accident pilot stated that “bad thunderstorms” were in the GGE area and that he did not know if he would be able to return to his base that night. The Savannah base manager then advised the accident pilot that he could stay at the Charleston base that night. However, the accident pilot decided to return to his base at Conway-Horry County Airport (HYW), Conway, South Carolina.
Review of radar data and weather observations provided by the National Oceanic and Atmospheric Administration revealed that, after departing, the helicopter entered an area of convective activity and precipitation. The University Corporation for Atmospheric Research regional radar mosaic chart for 2333 also depicted a large area of echoes north of the frontal boundary, with several defined thunderstorms and rain showers extended over South Carolina and over the accident helicopter’s flight route. Additionally, correlation of the radar data to the location of the accident site revealed that several defined cells surrounded the site at the time of the accident.
The terminal aerodrome forecast (TAF) for Myrtle Beach International Airport, Myrtle Beach, South Carolina, which was located 29 nm northeast of the accident site, was issued about 1928 and indicated expected marginal visual flight rules conditions through 0100 on September 26. From 2000 through 2130, variable winds to 15 knots with visibility of 4 miles in thunderstorms, moderate rain, and a broken ceiling of 3,500 feet agl in cumulonimbus clouds were expected. From 2130 to 0100, the wind was expected to be from 040 degrees at 12 knots with a visibility of 6 miles in light rain showers and mist and a broken ceiling at 2,000 feet agl. About 2207, the National Weather Service issued an amended TAF that expected instrument flight rules (IFR) conditions to prevail during the period with a broken ceiling at 700 feet agl and light drizzle and mist after midnight.
The pilot had previously flown helicopters in IMC but was not current in instrument ratings at the time of the accident. The accident helicopter was not certificated for flight in IMC but had sufficient instrumentation to operate in the event of an inadvertent encounter with IMC. On the pilot’s last Part 135 airman competency/proficiency check, which occurred on December 12, 2008, he satisfactorily demonstrated inadvertent IMC loss of control recovery.
Although the pilot encountered an area of deteriorating weather and IMC, this did not have to occur as the pilot did not have to enter the weather and could have returned to Charleston Air Force Base/International Airport or landed at an alternate location. The pilot, however, chose to enter the area of weather, despite the availability of safer options. Based on the pilot’s statement to the Savannah-based pilot regarding bad thunderstorms in the area, he was aware of the weather and still chose to fly into it. In addition, the pilot’s inability to maintain a steady state cruise altitude during the flight and the declining altitude throughout the flight likely reflected his attempt to stay below the cloud level. These cues should have indicated to the pilot that it was not safe to continue flight into IMC. This decision-making error played an important causal role in this accident.
In the absence of evidence indicating a mechanical malfunction, severe turbulence, or some other factor that would explain the accident pilot’s apparent loss of control of the helicopter, spatial disorientation is a likely explanation, as it has contributed to many accidents involving loss of control. In many cases, loss of control follows a pilot’s inappropriate control inputs resulting from confusion about the aircraft’s attitude. Two major situational risk factors for spatial disorientation were present in this accident, including high workload and transitions between VMC and IMC that require shifting visual attention between external visual references and cockpit flight instruments. Attempts to continue visual flight into IMC are even more problematic for helicopter pilots than for pilots of fixed-wing aircraft because helicopters are inherently less stable and require near-continuous control inputs from the pilot. Helicopters, like the accident helicopter, that are not equipped for IFR flight and do not have control stabilization or an autopilot impose high perceptual and motor demands on the pilot. This can make it very challenging for pilots to maintain stable flight by referring to flight instruments alone. When the accident pilot attempted to continue visual flight into IMC, he would have been subjected to a high workload to maintain control of the helicopter. The extent of the weather and the duration of the flight also suggest that the pilot’s encounter with IMC was prolonged. This would have further complicated the pilot’s workload and increased the potential for spatial disorientation resulting from hazardous illusions, thereby increasing the potential for inappropriate control input responses.
According to Omniflight’s 135 Operations Manual, the pilot-in-command was responsible for obtaining weather information before beginning a series of flights. During interviews with National Transportation Safety Board (NTSB) investigators, Omniflight pilots indicated that, at the beginning of each shift, they would obtain weather information from a base computer and would advise the Omniflight Operational Control Center (OCC) of weather conditions in the operating area throughout the period of their flight. Before any launch, the OCC must approve the flight. If the OCC knew of adverse weather, it would contact the pilot to evaluate the weather. Based on launch approval and actual weather conditions encountered and reported by the pilot, the weather at takeoff and along the flight route was VMC. About 2242, an MUSC communications center specialist spoke with an Omniflight OCC operations coordinator and indicated that the helicopter would be returning to HYW as soon as the patient transfer was complete. The operations coordinator then advised the MUSC specialist that if the pilot called before takeoff, they would review the weather with him for his return flight. However, the pilot never called the OCC, and the OCC did not contact the pilot. While the OCC was not required to contact the pilot and review the weather, if the OCC had contacted the pilot before takeoff, the OCC could have advised the pilot about the adverse weather, given him the updated TAF information issued about 2207 with IMC, and noted the potential risks involved with the flight. On February 7, 2006, the NTSB issued Safety Recommendation A-06-14, which asked the Federal Aviation Administration (FAA) to “require emergency medical services operators to use formalized dispatch and flight-following procedures that include up-to-date weather information and assistance in flight risk assessment decisions.” On February 18, 2010, based on the FAA’s pending notice of proposed rulemaking concerning helicopter operations and pending timely issuance of a final rule mandating formalized dispatch and flight-following procedures that include up-to-date weather information and assistance in flight risk assessment decisions, the NTSB classified this recommendation “Open—Acceptable Response.”
The accident helicopter was not equipped with an autopilot. On September 24, 2009, the NTSB issued Safety Recommendation A-09-96, which asked the FAA to “require helicopters that are used in emergency medical services transportation to be equipped with autopilots and that the pilots be trained to use the autopilot if a second pilot is not available.” On December 23, 2009, the FAA stated that it would conduct a study of the feasibility and safety consequences of requiring a second pilot or operable autopilot. On October 7, 2010, pending the NTSB’s review of the results of this study, Safety Recommendation A-09-96 was classified “Open—Acceptable Response.”
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot’s decision to continue the visual flight rules flight into an area of instrument meteorological conditions, which resulted in the pilot’s spatial disorientation and a loss of control of the helicopter. Contributing to the accident was the inadequate oversight of the flight by Omniflight’s Operational Control Center. Full narrative available
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