NYC98LA053

The pilot stated the helicopter was approximately 800 feet above ground level, climbing 300 feet-per-minute at 60 knots airspeed, when he heard the low rotor RPM warning horn and saw the corresponding low RPM warning light. The pilot said he entered autorotation '...with a nasty tailwind.' The pilot selected an open field for a forced landing site, determined he would overshoot, but continued straight ahead into trees. Prior to entering the trees that bordered the field, the pilot '...attempted to roll on throttle but got no response.' According to a manufacturer's Safety Notice: 'No matter what causes the low rotor RPM, the pilot must first roll on throttle and lower collective simultaneously to recover RPM before investigating the problem.' The pilot reported there were no mechanical deficiencies prior to the low RPM warning and the engine ran to manufacturer's specification after the accident. According to an icing probability chart published by the FAA, atmospheric conditions at the time of the accident were conducive to '...serious icing at cruise power.'

On December 26, 1997, at 1414 eastern standard time, a Robinson R-22 BETA, N8015V, was substantially damaged during a forced landing and collision with trees near the Danville Airport (8N8), Riverside, Pennsylvania. The certificated private pilot and a passenger sustained minor injuries. Visual meteorological conditions prevailed for the personal flight that originated at 8N8, at 1345. No flight plan had been filed for the flight conducted under 14 CFR Part 91.

In a telephone interview, the pilot stated he had flown, landed, and refueled the helicopter prior to the accident flight. He said approximately 30 minutes after takeoff during a climb, the helicopter experienced a loss of engine power.

The pilot stated the helicopter was approximately 800 feet above ground level, climbing 300 feet-per-minute at 60 knots airspeed, when he experienced a "...sharp nose left yaw." He then heard the low rotor RPM warning horn and saw the corresponding low RPM warning light. The pilot said he entered autorotation "...with a nasty tailwind."

According to the pilot, the wind was from 270 degrees at 14 knots and the helicopter was headed 070 degrees. He continued straight ahead to a cornfield selected for the forced landing. The pilot estimated the field was 300 yards long, with only the final 1/3 suitable for the forced landing. He said he maintained 60 knots throughout the descent but recovered only 90 percent rotor RPM, below the 97-104 percent operating range.

In a written statement, the pilot said, "The low rotor RPM light and horn sounded and I entered into an autorotation." The helicopter was established in the autorotation when the pilot determined he could not complete a safe landing on his current heading or by turning the helicopter 180 degrees into the wind. He said:

"We were closing in on the tree line and I told [the passenger] we were going into the trees. I attempted to roll on throttle but got no response."

The helicopter struck tree tops approximately 30 yards beyond the field's perimeter. The pilot stated, "I started my flare higher than recommended because I didn't want to continue into the woods, but the helicopter settled into the top of two big oaks."

The pilot reported there were no mechanical deficiencies prior to the low rotor RPM warning and that the "...helicopter responded fine..." throughout the autorotational descent.

On February 11, 1998, a test cell run of the helicopter's engine was performed at the Textron-Lycoming engine factory, Williamsport, Pennsylvania. The engine run was supervised by a Federal Aviation Administration Aviation Safety Inspector (Airworthiness). According to the Inspector's report:

"It was noted that two ignition leads on the left mag were cut through the insulation but the core wire was intact. This was believed to be accident related due to other marks and damage in the area. The leads were taped and the run up proceeded.

"In the test cell, the engine started easily and all parameters were within spec except at 1800 RPM the left mag was rough due to arcing of the leads at the cut areas. The engine was stopped and a slave harness installed. The run up was completed with no other abnormalities."

According to the Robinson Helicopter Company's Operator Handbook for the R-22, the first sentence in the emergency procedure for WARNING HORN & CAUTION LIGHT-LOW ROTOR RPM is:

"Immediately roll on throttle and lower collective."

According to Robinson Helicopter Company Safety Notice SN-10:

"No matter what causes the low rotor RPM, the pilot must first roll on throttle and lower collective simultaneously to recover RPM before investigating the problem."

At the time of the accident, the weather reported at Williamsport, Pennsylvania, 20 miles north of the accident site was: winds from 260 degrees at 10 knots. The temperature was 39 degrees and the dewpoint was 30 degrees.

According to an icing probability chart obtained from DOT/FAA/CT-82/44, atmospheric conditions were conducive to: "Serious icing at cruise power."

The pilot had approximately 136 hours of total flight experience, of which 87 hours were in helicopters, 85 in the Robinson R-22.