LAX99FA006

After completing a refueling stop at a nearby airport, the helicopter was next seen flying on a southeasterly heading at low altitude. Gusting winds at the accident site were opposite the direction of flight. The aircraft began a deceleration, the tailboom struck the ground and was severed by the main rotor blades as the aircraft pitched forward. As the nose pitched down, the main rotor blades struck the ground in front of the aircraft and the rotor head separated from the mast. The aircraft then rolled onto its right side with the engine running. A few seconds after impact, the aircraft burst into flames. The throttle was at idle and carburetor heat was applied. The stinger was broken from the empennage. Neither occupant wore fire-retardant apparel. The area of the accident site is commonly used for simulated emergency landings. Insufficient evidence existed to determine which pilot was manipulating the flight controls.

History of flight

On October 5, 1998, at 1405 hours Pacific daylight time, a Robinson R-22, N801EH, collided with terrain while maneuvering over an open meadow southeast of Lower Lake, California. The aircraft was destroyed during the impact sequence and postcrash fire. The flight instructor and his student both received fatal injuries, although the student succumbed on November 24, 1998. The aircraft was being operated as an instructional flight under 14 CFR Part 91 by Sacramento Executive Helicopters, Inc., when the accident occurred. The flight originated from Sacramento Executive Airport earlier in the day, and had last departed Lampson Field, Lakeport, California, after a refueling stop about 1350, en route back to Sacramento. Visual meteorological conditions prevailed at the time and a VFR flight plan was filed.

One witness near the accident site reported that he saw the aircraft fly over his home on a southeasterly heading. As he watched, the aircraft began a left turn toward a more easterly heading. He stated that the aircraft suddenly dove into the ground. He saw debris fly from the aircraft on impact. About 10 seconds after seeing and hearing the impact, he heard an explosion as he saw the aircraft burst into an orange and black fireball. He described the aircraft as having been flying "low" prior to the impact. He also reported that at the time of the accident the sky was clear with strong, gusting winds.

Another witness stated that the aircraft was southbound at about 200 feet above the trees. He said that it entered a steep, right-banked turn and then hit the ground. He described the winds at the time as very gusty.

The two persons who were the first to reach the aircraft after the crash reported that they heard the engine running. They also observed some mechanical movement in the burning wreckage. After walking around the aircraft they found that one of the occupants had climbed out of the wreckage.

Another pilot at Lampson Field said that he told the instructor that there was a lot turbulence to the east of the airport. At a 10-foot hover he said that winds were from the southeast at between 15 and 30 knots.

The operator reported that the Lower Lakes area is commonly used as a simulated emergency landing site by instructors en route to, or coming from, Lampson Field.

Personnel information

The instructor was a full-time employee of Petroleum Helicopters, Inc. (PHI). He worked a 7-day schedule with PHI and then worked Monday, Tuesday and Wednesday every other week as an instructor at Sacramento Executive Helicopters, Inc., and had worked this schedule since June 1998. A 14 CFR Part 141 standardization check was completed at the school in September 1998. He had obtained a private pilot certificate for airplane single-engine land on August 3, 1997. His pilot's logbook was not located after the accident and the flight time appearing on page 3 of this report, 500 total hours, was obtained from the pilot's declaration of flight time on his most recent Federal Aviation Administration (FAA) airman medical application. According to the operator's flight and payroll records, the pilot had flown the Robinson R-22 for 34 hours as a flight instructor during the preceding 90 days.

The student pilot received his private pilot certificate with a rotorcraft helicopter rating on May 18, 1998, with 73.4 flight hours. He returned to his home in Japan after getting his certificate and returned to the same flight school on September 6, 1998, to continue training for his commercial certificate. His recent flight training records reflected better than average grades on autorotations and forced landings. The only negative comment was that he was slow in picking up visual cues. The chief instructor at the school attributed this to a lack of currency after he had not flown for nearly 4 months. He was currently flying 3 times a week and had accumulated 19.5 hours since he resumed training on September 6, 1998. According to the instructor, he had always been prompt in relinquishing the controls during previous progress checks.

Aircraft information

The operator reported that the aircraft was on a 14 CFR Part 135 certificate at the time of the accident and had accrued a total of 6,672 total hours of operation. The most recent 100-hour inspection was completed 1 month prior to the accident. The engine underwent the unscheduled replacement of the front crankshaft seal on July 7, 1998, and a crankshaft plug on October 2, 1998.

The aircraft had a supplemental type certificate (STC) for auto fuel. The aircraft was last serviced with 14.1 gallons of 100-octane low lead aviation fuel at Lampson Field prior to its last departure.

The aircraft gross weight at the time of last departure was estimated as 1,372.45. The manufacturer's gross weight limitation is 1,370. The center of gravity (CG) was estimated as 96.8. The CG range is 96.5 to 100 at maximum authorized gross weight.

A review of the aircraft and engine logbooks by Safety Board investigators and FAA inspectors failed to disclose any discrepancies.

A witness at Lampson Field reported that he saw a trace of oil on the starboard side at the forward end of the cooling fan shroud.

Wreckage and impact information

The accident site was located at 38 degrees 50.460 minutes north longitude and 122 degrees 32.750 minutes west latitude across from 4794 Spruce Grove Road. The site was in an area of flat grassy terrain. Safety Board investigators estimated the elevation to be approximately 1,400 feet msl. The aircraft was found oriented on a bearing of 135 degrees. The median long axis of the debris field was also along the same bearing and extended about 500 feet.

The aircraft was burned from the nose aft to the attachment point for the tailboom. The landing lights were found in their normal position and were not broken. The remains of both doors locking bolts were found within the area of the cabin. There was no deformation visible on the skids or cross tubes. Control continuity could not be established from the cockpit to the main and tail rotors due excessive thermal damage to the control components.

The carburetor heat was found pulled open 2.7 inches (hot). The mixture was pulled 2 inches into idle cutoff. The throttle was at low idle. All were in their described positions both in the cockpit as well as on the air box and carburetor. The carburetor and induction system were examined and were found to be free of any obstructions. The fuel inlet screen was examined and was found to be free of contamination. The carburetor bowl contained no fuel. The metal floats were in place and exhibited no evidence of chaffing or binding. The airframe gascolator filter was destroyed.

The engine was found attached to the engine mounts. The entire engine compartment had been exposed to fire. The cooling fan and flywheel were removed in order to be able to examine the crankcase seal. The STD-1211 crankshaft expansion plug was in position and was partially coated with silicon sealant. The LW13792 crankshaft oil seal was in position. The oil cooler had ruptured in an area where it had contacted the ring gear. This was evidenced by rotational scoring signatures at the rupture site. The crankshaft was hand rotated through the cooling fan mounted on the crankshaft flange. Thumb compression was established in the proper order at all cylinders. The complete valve train was observed to operate in the proper order as well. Lift action was observed at each rocker assembly. Uncontaminated oil was visible within each rocker box. Mechanical continuity was visually established throughout the rotating group, valve train assembly, and accessory section. The cylinders were observed through the spark plug holes and appeared to be free of any internal damage. The gas path and combustion chamber were free of any debris or contamina