Destin, FL, USA
N444WT
ROBINSON HELICOPTER R44
The helicopter reached about 200 feet above ground level in the initial climb when the pilot noticed that the engine needle in the dual tachometer (engine/main rotor rpm) had "spiked" and then remained "at the top of the gauge." The pilot turned the helicopter around to return to the airport, and, during the turn, the low rotor rpm warning alarm sounded. The pilot responded by lowering the collective control and increasing throttle but then determined that an airport landing could not be completed because the helicopter had already lost altitude. The pilot selected a forced landing area in a sand pit and responded to another low rotor rpm alarm by again lowering the collective. She attempted to cushion the landing with the available rotor rpm, but the helicopter landed hard, and the main rotor blades severed the tailboom. Examination of the helicopter revealed that the engine had a stuck (open) number 5 exhaust valve caused by buildup of oil carbon deposits. This is an issue with the Robinson Helicopters if the engine is not cooled down properly after flight. Air tour operations seem to be prone to carbon buildup mainly due to quick multiple shutdowns. The operator has established a postflight cool down procedure to prevent further problems. On January 19, 1988, Textron Lycoming published Service Letter No. L197A, Recommendations to Avoid Valve Sticking. The guidance offered included, "Rapid engine cool down from low power altitude changes, low power landing approach and/or engine shutdown too soon after landing or ground runs should be avoided."
On May 19, 2012, about 1540 central daylight time, a Robinson R44 helicopter, N444WT, was substantially damaged during a forced landing after takeoff from Destin-Fort Walton Beach Airport (DTS), Destin, Florida. The certificated commercial pilot and two passengers were not injured. Visual meteorological conditions prevailed, and a company flight plan was filed for the flight. The local sightseeing flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. According to the pilot, the helicopter had reached approximately 200 feet above ground level (agl) in the initial climb when she noticed that the engine needle in the dual tachometer (engine/main rotor rpm) had "spiked" and then remained "at the top of the gauge." She turned that helicopter to return to the airport, and during the turn, the low rotor rpm warning horn sounded. The pilot responded by lowering the collective control and increasing throttle, but then determined that an airport landing could not be completed due to the resultant loss of altitude. The pilot selected a forced landing area in a sand pit, and responded to another low rotor rpm alarm by again lowering the collective. She attempted to cushion the landing with the available rotor rpm, but the helicopter landed hard, and the main rotor blades severed the tailboom. The helicopter came to rest upright, and the occupants egressed without injury. In interviews and written statements provided to the local sheriff's department, the passengers each stated that the helicopter was "leaning to the right" during the takeoff, and that the helicopter "beeped and descended" twice before it landed hard in the sand. The helicopter was removed from the site, and a detailed examination of the wreckage was scheduled. According to Federal Aviation Administration (FAA) and operator records, the helicopter was manufactured in 2000 and had accrued 1,668 total aircraft hours as of the date of the accident. Its most recent annual inspection was completed April 12, 2012. The pilot held an FAA commercial pilot certificate with ratings for rotorcraft-helicopter and instrument helicopter. She also held a flight instructor certificate with ratings for rotorcraft-helicopter and instrument helicopter. Her most recent FAA second class medical certificate was issued March 16, 2012. The pilot reported 433 total hours of flight experience, of which 143 hours were in the accident helicopter make and model. The helicopter was examined on June 6 and 7, 2012 by FAA inspectors, and the results of that examination were summarized in an email from one of the inspectors who stated, "The engine had a stuck (open) number #5 exhaust valve caused by buildup of oil carbon deposits. This is an issue with the Robinson Helicopters if the engine is not cooled down properly after flight. Air tour operations seem to be prone to carbon buildup mainly due to quick multiple shutdowns. The operator has established a post flight cool down procedure to prevent further problems." On January 19, 1988, Textron Lycoming published Service Letter No. L197A, Recommendations to Avoid Valve Sticking. The guidance offered included, "Rapid engine cool down from low power altitude changes, low power landing approach and/or engine shutdown too soon after landing or ground runs should be avoided."
The partial loss of engine power due to a stuck (open) exhaust valve in the No. 5 cylinder. Contributing to the accident was the operator’s failure to follow the engine manufacturer’s directives concerning cooling of the engine after flight.
Source: NTSB Aviation Accident Database
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