LAX98FA098

Witnesses reported hearing the aircraft fly overhead, then a 'schwap' sound, followed by silence. They looked up and saw the helicopter falling vertically to the ground. Postaccident investigation revealed that one main rotor blade had entered the cockpit through the left windshield half and cut the cabin floor aft to the left seat. The location of an indentation in the cyclic control crosstube, made by the rotor blade, corresponded to the cyclic control having been about in the full left control position. There was no evidence of a mechanical malfunction prior to the rotor divergence. A report of meteorological conditions by the Safety Board showed conditions conducive to mountain wave turbulence, and there were pilot reports of moderate to severe turbulence in the area of the accident. An AIRMET was in effect, calling for occasional moderate turbulence. The pilot did not receive a preflight weather briefing. The Aircraft Flight Manual instructed the pilot to 'minimize cyclic control inputs in turbulence; do not overcontrol' and to land the aircraft 'as soon as practical.' A manufacturer's Safety Notice regarding flight in high winds or turbulence advised pilots 'Do not overcontrol. Avoid large or abrupt control movements. Allow the aircraft to go with the turbulence, then restore level flight with smooth, gentle control inputs.'

History of flight

On February 26, 1998, at 1318 hours Pacific standard time, a Robinson R22, N8457J, impacted terrain in a ravine near Littlerock, California. The aircraft was destroyed and the commercial pilot/owner, the sole occupant, suffered fatal injuries. Visual meteorological conditions prevailed at the time of the accident and no flight plan was filed. The aircraft was being operated under 14 CFR Part 91 as a personal flight, and originated from a private airport at Adelanto, California, at 1300.

The right-hand cockpit door of the helicopter and pieces of the windshield Plexiglas were found in a debris field approximately 1/4 mile east of the main wreckage. Witnesses reported that winds at the time of the accident were westerly at 20 to 25 knots. One witness reported he heard a loud "schwapp-like" noise followed shortly by engine silence, and then saw the helicopter disappear from view in a near vertical descent.

The pilot of a sheriff's department helicopter located the wreckage, landed nearby, and was the first person on scene. He reported that the surface winds were from the west at 20 -25 knots and that it was "bumpy and turbulent" in the area when he arrived. He also said that there was the smell of fuel in proximity of the fuel tank and he noted that the cap from the fuel tank had been ejected and was laying on the ground opposite the tank, about 15 feet upslope. The citizen who had called in the report of the accident arrived at the scene and said he had seen the aircraft roll to the left and fall.

A friend of the pilot, who is a student helicopter pilot, reported that on the day of the accident, the pilot flew the accident helicopter from Whiteman to the friend's hangar at Adelanto private airport and back. He did not refuel. They were going to fly the friend's Rotorway helicopter; however, the friend said that the wind was blowing about 15 knots and he was experiencing translational lift in hover which made him uneasy so he landed and put the helicopter away. They then got in the car and drove around the airport for 3 or 4 hours before the pilot departed for home. The friend said that he had frequently flown in the R22 with the pilot and that he cruised at 21 inches manifold pressure, which gave about an 80-knot indicated airspeed. The pilot also had told him to slow down in turbulence but not below 60 knots.

Another friend, also a helicopter rated pilot, characterized the pilot as a "very conservative, better than average" pilot whom "always wanted to learn more." He had "good ability for a man his age." The two men had attended a CFI renewal conference at the HAI convention in February (1998) where low-g flight and mast bumping were discussed. The friend said "he was well aware of it."

This friend recalled two instances when they had encountered turbulence while flying up to the desert from Whiteman in the R22. He said he was alarmed by the amount of [acoustic] blade slap in the turbulence. They turned around and went home. When asked about airspeeds flown, the friend recalled that the pilot was always "very conservative in cruise setting, a little below recommended."

Personnel information

The pilot's wife reported that he maintained two logbooks, one for fixed wing flight hours and another for rotary wing flight hours. After the accident only the rotary wing logbook was located. The pilot's wife said, however, that he had flown rotary wing aircraft exclusively for at least the last 2 years. On November 8, 1994, when the pilot applied for his airplane, single engine sea rating checkride, he reported having 1,450 fixed wing hours.

According to the aircraft manufacturer, the pilot completed the factory pilot training course in the aircraft in 1994, 1995, and in February 1997. In the 1995 and 1997 training, the company records indicate that the pilot's proficiency was rated "below average."

Aircraft information

Robinson Helicopter Company recommends that the R22 helicopter is overhauled (engine and airframe) at 2,000-flight hours or 10-year intervals, whichever comes first. The accident aircraft was last overhauled at the Robinson factory in December 1987, and had accumulated 907 flight hours since overhaul.

According to the aircraft maintenance records, main rotor blades (serial numbers 3011 and 3017) were installed during the 1987 overhaul and were new at that time. They have a 2,000-hour service life.

Radar data

A replay of recorded radar data at High Desert TRACON showed a VFR aircraft (transponder code 1200) flying from east to west at 3,800 feet (msl) which disappeared from radar at the accident location at 13:11:42 hours. High Desert TRACON has a REHOST radar system that does not output recorded data. On March 6, 1998, a Safety Board investigator viewed a replay of the data on a display at the High Desert facility and manually recorded the data (attached). According to system specialists at TRACON, the scan rate of the antenna results in a target return (update) approximately every 4.5 seconds and ground speeds displayed are rounded to the nearest 10 knots using conventional arithmetic rounding (e.g. 75 to 84 knots is displayed as 80 knots). The ground speed displayed is determined from the distance traveled and elapsed time since the last radar return.

At 13:06:23, an arbitrary start time, the radar displayed the aircraft approximately 7 miles east of the accident location at 3,800 feet msl, tracking 255 degrees magnetic, at 80 knots ground speed. In the next 5 minutes the target continued westbound on approximately a 255-degree magnetic course at displayed ground speed of 80 knots, or occasionally 90 knots, at altitudes of 3,700, 3,800, or 3,900 feet. At 13:11:13, the aircraft was 0.7 miles east of the accident site at 3,900 feet with ground speed of 90 knots. At 13:11:17, while still at 3,900 feet, the ground speed increased to 130 knots. In the two subsequent returns, while remaining at 3,900 feet, the ground speeds displayed were 140 and 120 knots. At 13:11:31, the altitude increased to 4,000 feet and the ground speed decreased to 100 knots and then, at 13:11:36, slowed to 80 knots. At 13:11:40, the radar return indicates that the aircraft reached 4,100 feet at 70 knots ground speed, and this is the last return from the aircraft. A tabulation of the radar data is attached to this report.

A systems performance specialist at TRACON speculated that the ground speed increase at 13:11:17 might have been due to an anomaly in the REHOST display software. The display is comprised of a mosaic of radar maps and the aircraft was crossing a boundary from one map to another at that time. Several replays of the data showed the aircraft westbound with equal distance traveled between radar returns. At 13:11:13 the target moved an inordinate distance west, and then at 13:11:17, moved back eastward near the prior return. The specialist was otherwise unable to explain this return. The reference barometric pressure, used to decode the aircraft's mode C return, was 29.92 for the east map and 29.93 for the west map.

Meteorological information

According to the Quality Assurance Office at the Federal Aviation Administration (FAA) Western Region headquarters, there was no record of any weather briefing given to the pilot.

A meteorology factual report prepared by the Safety Board staff meteorologist is attached. The meteorologist reported that surface observations near the time of the accident from surrounding stations reported westerly to northwesterly surface winds at 10 to 30 knots. Winds aloft from the accident elevation to 10,000 feet were northwesterly from 6 knots increasing to 40 knots, and several pilots reported moderate to severe turbulence below 8,000 feet with winds aloft of up to 50 knots and updrafts and downdrafts near the mountains.

AIRMET TANGO 3 was valid at the time of the accident for occasional moderate turbulence belo