History of Flight
On December 25, 2009, about 1300 central standard time, a single-engine Bell 407 helicopter, registration N600CE, was substantially damaged during a hard landing following a loss of engine power shortly after takeoff from the Wise Regional Health System Helipad in Decatur, Texas. The commercial pilot and flight medic sustained serious injuries, while the flight nurse sustained minor injuries. The helicopter was registered to and operated by Air Evac EMS Inc., of West Plains, Missouri. Visual meteorological conditions prevailed, and a company flight plan was filed for the 14 Code of Federal Regulations Part 91 positioning flight to Wichita Falls, Texas, to pick up a patient.
The pilot reported that on December 24, rain turned to moderate blowing snow with winds of 15 to 25 knots around 0900-1000. He performed a 5-minute engine ground run around 1100-1130, noting everything operated well and using anti-ice due to blowing snow. That afternoon, he inspected the engine intake and exhaust for snow buildup and found none. He then plugged the engine intakes and covered the exhaust with a plastic cover. The helicopter was not flown that night due to weather, including snow and ice accumulation on rotor blades and horizontal stabilizer.
On the morning of December 25, clear and cold conditions prevailed, but the helicopter had enough snow and ice to prevent taking calls. Around 0900, the pilot performed a walk-around, removed engine covers, and waited for ice to melt. By 1130, all ice was gone from the surfaces, and the temperature was 39 degrees Fahrenheit. At approximately 1249, the crew received a transfer request to Wichita Falls. The pilot did a walk-around, started the engine, and the medical crew arrived a few minutes later, also performing a walk-around before boarding. The helicopter ran for 7-8 minutes before takeoff.
With all systems normal, the pilot lifted off from the north helipad, hovered about 15 feet south, pointed into the southwest wind, pulled rotor pitch, and began climbing. At approximately 50-60 feet above ground level, two warning horns sounded, and the helicopter yawed 90 degrees left. The pilot reduced collective to preserve rotor rpm and maneuvered back to the south helipad. At about 5-8 feet above ground, he pulled collective pitch, but the helicopter descended rapidly and landed hard, spreading the landing skids and contacting the fuselage with the ground. The helicopter came to rest upright on the helipad.
The flight nurse stated that he did not notice any ice on the helicopter, but the helipad was covered with 1/2 to 1 inch of ice. He reported hearing a sound he recognized as the engine flaming out at about 50-100 feet. The helicopter fell and experienced a hard ground impact; during the sequence, it sounded like the engine tried to restart.
Video Surveillance Evidence
The helipad was equipped with a video surveillance system. A review by an FAA inspector revealed that on December 24, after the engine run, snow began at 1200 and worsened. At 1650, intake plugs were installed; at 1700, an exhaust boot was installed, but blew off at 1717 and was reinstalled at 1722. No visible activity occurred overnight. On December 25, at 0705 and 0718, individuals looked at the helicopter. At 0951, someone removed intake plugs and exhaust boot, looked at the main rotor mast, and rubbed hand on airframe areas. At 0955, an individual manually turned the tail rotor. At about 1253, the pilot walked to the helicopter, appeared to talk on a cell phone, and boarded within about 33 seconds. The helicopter started around 1255; the medical crew arrived about 2 minutes later. About 3 minutes 20 seconds later, the helicopter lifted off, performed a slight pedal turn, and climbed out of camera view. Seconds later, a cloud of smoke appeared, followed by a fast descent to ground impact. The inspector noted that no one looked in the exhaust stack, right side engine intake, or opened any access panels before the flight.
Meteorological Information
The NTSB reviewed weather data from the Decatur Municipal Airport automated system, 2.5 nautical miles north of the accident site. From 1206 on December 24 to 1246 on December 25, temperatures ranged from 16°F to 34°F, and winds from 4 to 28 knots. Precipitation (light to heavy snow) was recorded from 1206 to 1906 on December 24; no precipitation was recorded thereafter until the accident.
Engine and Airframe Examination
Fuel samples showed no abnormalities. The Engine Control Unit data from the accident flight revealed a momentary flameout followed by a successful relight. Although engine power was increasing, the helicopter was too close to the ground for the pilot to recover main rotor rpm before impact. The engine was removed and tested at Rolls-Royce Corporation; the test run met production test standards, with satisfactory start, run, and shutdown. The engine examination, ECU data, and test run revealed no evidence of a condition that would prevent normal operation. No airframe anomalies were found that would have contributed to the loss of engine power.
Additional Information
The operator's manual included cold weather procedures requiring, when possible, hangaring the aircraft at temperatures ≤40°F, running the aircraft at operating rpm for 20 minutes every 6 hours if not hangared, and ensuring removal of ice, snow, and frost from critical areas. The Bell 407 Rotorcraft Flight Manual required the cabin roof, transmission cowling, and engine inlet area to be cleaned of accumulated snow and ice. The Rolls-Royce engine manual included a warning that snow or ice slugs can cause engine flameout.