Accident Overview
On July 4, 2012, at approximately 0340 eastern daylight time, a Robinson R44 helicopter, registered as N561CH, was substantially damaged when it struck a lake while maneuvering near Tallahassee, Florida. The certificated private pilot, who was the sole occupant, was not injured. Night visual meteorological conditions prevailed at the time, and no flight plan had been filed for the personal flight conducted under 14 CFR Part 91.
Pilot and Flight Information
The pilot held a private pilot certificate with a rotorcraft-helicopter rating issued in March 2012. He reported 204 total flight hours, with 181 hours in the accident helicopter make and model, and 11 hours at night. His most recent FAA second-class medical certificate was issued in April 2012. The helicopter, manufactured in 2008, was equipped with a Lycoming O-540, 260 hp engine. Its most recent 100-hour inspection was completed on May 29, 2012, at a total time of 1298.6 hours; the helicopter had accumulated 1336 total hours at the time of the accident.
Accident Sequence
The pilot stated he had awakened at 0900 on July 3 and driven approximately six hours with another pilot to West Palm Beach, Florida, to pick up a helicopter and fly it back to Tallahassee Regional Airport (TLH). That flight occurred from about 2230 to 0200. Upon arrival at TLH, the pilot decided to take the accident helicopter on a short flight to build night flight time and conduct a landing to meet night proficiency requirements. After departing TLH at about 0330, he followed a road northeast at an altitude between 600-800 feet mean sea level for about 8 minutes before turning back toward TLH. The turn was conducted over his residence, which was next to a lake.
During the turn, the pilot observed the clutch actuator light illuminate and remain on for 9 seconds. He reached for the circuit breaker box under the passenger seat to pull the clutch circuit breaker. Immediately after, he felt "light in the seat" and the helicopter began descending rapidly. He increased collective pitch to arrest the descent, then heard the low rotor rpm horn sound. He saw the lake surface reflecting moonlight about 50 feet below as the helicopter continued descending. He increased collective pitch to soften the impact, and the helicopter came to rest in the lake. The pilot egressed and swam to shore.
Examination Findings
The helicopter was recovered from the lake on July 7, 2012, and moved to a secure location for examination. On August 17, 2012, control continuity was established from the cyclic and collective controls to the main rotor. Flight control and drive train continuity were confirmed from the anti-torque pedals to the tail rotor gearbox through a fracture of the tail boom. The four v-belts were in place on the sheave, taut and in good condition. The v-belts and clutch actuator were removed and sent to the manufacturer for examination on August 23, 2012. Visual inspection revealed no damage or unusual wear on any of the four v-belts. The clutch actuator was observed extended approximately one inch. After freeing the motor to rotate using hand pressure, the actuator was installed on a production test fixture and operated normally in both directions; the down-limit switch functioned correctly, and in the up direction both spring switches activated simultaneously as designed. The actuator was cycled an additional two times with no anomalies.
Weather and Night Conditions
The 0353 weather observation at TLH included winds from 190 degrees at 3 knots, 10 miles visibility, clear skies, temperature 23°C, dew point 21°C, and an altimeter setting of 30.00 inches of mercury. According to U.S. Naval Observatory data, the moon rose at 2042 on July 3 and set at 0735 on July 4, with a waning gibbous phase and 99% illumination.
Reference to Operating Handbook and Advisory Circular
The Robinson R44 Pilot's Operating Handbook notes that the clutch light indicates clutch actuator operation during engagement or disengagement. It states that the light may come on momentarily during run-up or flight to retension belts as they warm up and stretch, but if the light flickers or comes on and does not go out within 7 to 8 seconds, the pilot should pull the CLUTCH circuit breaker, reduce power, and land immediately, prepared to enter autorotation. FAA Advisory Circular AC120-100 discusses a window of circadian low typically occurring between 3 a.m. and 5 a.m., associated with low alertness and elevated operational risk.