N381MC

HISTORY OF FLIGHT

On November 8, 2007, approximately 1245 Pacific standard time, a Schweizer 269C helicopter, N381MC, impacted the terrain about one and one-half mile north of Baker City Municipal Airport, Baker City, Oregon. The private pilot, who was the sole occupant, was killed in the accident sequence, and the helicopter, which was owned and operated by Baker Aircraft, was substantially damaged. The 14 CFR Part 91 solo instructional/proficiency flight, which departed Baker City Municipal Airport about five minutes prior to the accident, was being operated in visual meteorological conditions. No flight plan had been filed.

According to witnesses, after departing Baker City Municipal Airport, the helicopter turned to the north, climbed to an altitude that was reported to be as low as 100 above ground level (agl) and as high as 800 feet agl. The helicopter then paralleled Interstate Highway 84 as it proceeded to the north. As it approached Chandler Lane (Highway 203), its tail reportedly lowered, it slowed, rotated or turned slightly to the east, and then descended rapidly toward the terrain. Witnesses reported that near the beginning of the descent, the main rotor blades either slowed their rotation significantly or "stopped turning." One witness stated that almost immediately after observing the change in rotation speed of the main rotor blades, "…the helicopter just dropped out of the sky."

PERSONNEL INFORMATION

The 59-year-old pilot held a commercial pilot certificate with an airplane single engine land (ASEL) rating and an instrument rating for airplanes. His last medical, a Second Class, was issued on March 1, 2007. He had accumulated about 2,050 hours of flight time, with about 62 hours in helicopters, 60 of which were accumulated in the 90 days prior to the accident. According to a representative of Baker Aircraft, the pilot was in the process of developing his proficiency for an upcoming flight check during which he hoped to qualify for a commercial helicopter rating.

According to the pilot’s logbook he flew five flights in N381MC on the day prior to the accident, for a total of 5.8 hours. Four of those flights were during daylight hours, and one, lasting 1.3 hours, was logged as night time. On the morning of the accident, the pilot flew a 1.5-hour dual instructional flight, which ended around 1000.

AIRCRAFT INFORMATION

The accident helicopter, a Schweizer 269C, serial number 1240, was manufactured in 1986. It was owned and operated by Elkhorn Aviation, Inc., doing business as Baker Aircraft. Its last 100-hour inspection was completed on October 28, 2007, and at the time of the accident, it had accumulated 4,324 hours. The helicopter had been flown on two prior flights on the day of the accident. The first was the training flight involving the deceased pilot, and the second was another training flight of 1.5 hours duration. The helicopter’s fuel system was then topped off with 16.65 gallons of aviation fuel prior to the accident flight.

METEOROLOGICAL INFORMATION

According to the 1253 automated aviation weather surface observation (METAR), the winds were from 230 degrees magnetic at four knots. The sky was clear, with a visibility of eight statute miles. The temperature was 13 degrees Celsius, and the dew point was two degrees Celsius. The altimeter setting was 30.03 inches of mercury. There were no reports of gusting winds or turbulence.

WRECKAGE AND IMPACT INFORMATION

The helicopter impacted flat level open terrain about one-tenth of a mile south of Chandler Lane/Highway 203, and about four-tenths of a mile east of Interstate Highway 84. The altitude of the site was approximately the same as that of the airport, 3,370 feet mean sea level (MSL). The initial ground impact scar consisted of two parallel indentations about 65 inches apart and about 50 inches long. The indentations, both of which were about one inch deep and two inches wide, ran on an east/west magnetic heading. The northerly indentation had created a ridge about one-half inch in height along its northern edge, and near its westerly end was found about the aft 18 inches of the left skid. This portion of the skid was still connected to its lateral support leg and diagonal brace, both of which had separated from the airframe. Lying alongside of the aft portion of the skid was the aft skid oleo/vertical support leg. Another section of the left skid, about 16 inches long, was lying about two feet northeast of the aforementioned section, and the forward oleo/vertical support leg was located about two feet further northeast. The primary wreckage came to rest about 20 feet north of the initial impact point. The only other readily identifiable object located at the initial impact point was the cylindrical body of the fuel gasculator unit, along with its associated wire screen filter.

The primary wreckage, which included the pilot/passenger compartment, right skid, engine/transmission section, and the main rotor shaft and blades, was lying on its right side facing to the east. The bottom of the helicopter’s structure, along with the engine induction and exhaust pipes, had been crushed directly upward into the structure above them. The forward portion of the left skid was found lying about three feet north of the primary wreckage. The Plexiglas pilot/passenger compartment enclosure/bubble had fractured into small pieces, and the instrument pedestal had been thrown forward out of the compartment, and remained only partially attached by its associated electrical wiring. The transmission and main rotor shaft were still attached to the primary structure, but the main rotor shaft housing had fractured just above the flange that attaches it to the transmission housing.

The shroud was removed from the drive belt/clutch pulley system, and it was determined that the arms that support the driven pulley and the tensioner/clutch pulley had fractured. All eight drive belts were still in their respective groves on all three pulleys, and there was no evidence of in-flight slippage of any of the belts. The electrically-driven jackscrew in the actuator that controls the engagement of the driven pulley, by causing the tensioner/clutch pulley to increase tension on the drive belts, was found in the fully retracted (driven pulley fully engaged) position. The clutch engagement toggle switch on the instrument console was found in its center "HOLD" position, with the switch guard open.

The scroll was removed from the induction fan, and circumferential rubbing/scaring was found along about 45 percent of the interior of the scroll structure. In addition, much of the area of the aft (non-attached) end of most of the fan blades had been burnished to a bright shine due to their rotational contact with the scroll.

All three main rotor blades were still attached to the rotor hub, and all three were still attached to their pitch change links. The drag-link dampeners attached to the root of the blades had been pulled out of their housings on two of the blades. The flight control torque tubes were traced from the rotor head to the point where they entered the crushed structure of the pilot/passenger compartment, and no evidence of malfunction, anomaly, or failure was evident in either the tubes or their interconnect ends. One main rotor blade, which suffered very little direct impact damage, was relatively straight along about two-thirds of its span. It then was bent downward about 10 degrees, before bending upward again about 10 degrees, and then continuing relatively straight to its tip. The second blade, which had been ripped open span-wise along its most outboard 18 inches by contact with the terrain, showed the upward curvature and upper skin compression creases consistent with coning along its entire span. The third blade, which had been bent downward about 45 degrees about one foot outboard of the hub by terrain contact, also showed signatures consistent with coning along its entire span.

The tail boom had been torn from the fuselage, and was located about 10 feet west of the primary wreckage. The two tail boom support arms had torn loose of the fittings that attach them to the undercarriage structure. The tail rotor drive shaft had separated from its junction just aft of the upper (driven) pulley assembly. The tail rotor gearbox remained attached to the aft end of the boom, but one of the tail rotor blades had separated from the tail rotor shaft at its root. The separated blade was found lying about 25 feet west of the primary wreckage. The tail rotor pitch change links showed no signs of malfunction or anomaly. The vertical stabilizer, which normally sticks straight down from the boom, had been crushed upward and folded up and around the right/starboard side of the boom structure by contact with the terrain. The horizontal stabilizer, which normally angles diagonally up and to the right, had flexed downward about 60 degrees. The tail rotor drive shaft had come in contact with the tail boom root internal structure. The drive shaft was dented inward, with no circumferential scaring of its surface. The impact damage to the drive shaft was consistent with the drive shaft contacting the boom structure after its rotation had been stopped by the tail rotor contact with the terrain.

An on-scene inspection of the engine determined that the fuel servo, fuel pump, and left magneto had broken loose from their mounts. Before removing the helicopter from the field, fuel was confirmed at the boost pump, and a borescope inspection was performed on all cylinders, with no anomalies noted. In addition, the top spark plug from each cylinder was examined, and no damage, unusual wear, or contamination was noted.

The helicopter, except for the fuel injection servo, was recovered to SP Aircraft, of Boise, Idaho, where, on December 13, 2007, it underwent a further teardown inspection directed by the Federal Aviation Administration (FAA). During that inspection the magne...