SEA00FA014

History of flight

On November 2, 1999, at 1532 Pacific standard time, an Enstrom F28C helicopter, N635H, was destroyed when it sustained a tail rotor blade strike during a solo instructional flight at Pendleton airport, Pendleton, Oregon. The airline transport pilot, who was preparing for a commercial rotorcraft-helicopter rating, was fatally injured. The helicopter was registered to Charlie Inc., an entity of which the pilot was a principal. Visual meteorological conditions prevailed at the time of the flight. No flight plan was filed. There was a post-impact fire. No ELT was installed in the aircraft.

According to the pilot's flight instructor, he had accumulated approximately 66.5 hours of helicopter instruction, and was scheduled for an add-on commercial rating on the day following the accident. The instructor had flown once with the pilot for 1.7 hours the morning of the flight. The pilot had then flown again for approximately an hour in an additional flight before the accident flight. On the accident flight, the pilot was on his second left-hand circuit of the pattern for runway 34. According to the tower controller, the pilot had been cleared for the option on runway 34 on his first circuit . He had made three touchdowns along the length of runway 34, at the threshold, mid-length, and at the departure end of the runway, then had continued his circuit. On the second circuit, the tower controller had again cleared the pilot for the option. The tower controller observed similar touchdowns at the threshold, and at mid-field. He stated that he was looking away at the time of the crash; however he heard a very garbled transmission, looked in the direction of the helicopter, saw dirt flying, and activated the siren and dispatched rescue vehicles. He then saw smoke and flames.

Ground strikes consistent with tail rotor blade strikes were found near the wreckage. Both tail rotor blades separated from the tail rotor hub, and the tail rotor gearbox also separated from the tailcone. The pilot was at least partially ejected from the helicopter's cockpit and was partially beneath the fuselage when rescuers arrived. Rescuers lifted the fuselage and pulled him from the burning wreckage.

Wreckage and impact information

The wreckage was located along the east edge of runway 34, a few hundred feet from the departure end of the runway. Two groups or sets of surface scars were found on the asphalt runway surface. The first set included a gouge estimated to be about 1/4 inch deep and one inch in diameter, with a 4-5 inch scratch or metal and paint transfer. A few inches away were three other scrapes or gouges. This set of marks was to the right of the runway centerline. The second surface scar location was about 20 yards closer to the departure end of the runway, and on the left side of the runway centerline, consisting of another similar crater, with an associated 4-5 inch scratch mark. In both instances, flecks of paint and material similar to that used for tail-rotor bonding were found in the vicinity.

One tail rotor blade, including the grip, was found a few yards from the first surface scars, closer to the approach end of the runway. The tail rotor gearbox was found about twenty yards north of the second surface scar, also on the left side of the runway centerline. The second tail rotor blade was found beyond the gearbox, again to the left of the runway centerline.

The tail rotor blade nearest the approach end of the runway exhibited large radius bending, and two separate areas of compression folds on the trailing edge. The other tail rotor blade exhibited trailing edge folding, large radius bending from about mid-span, and leading edge crushing and impact signatures.

The tail rotor gearbox exhibited a broken casting, and the two associated control cables exhibited signatures similar to tensile overload. One blade grip remained attached to the spindle; the other blade grip remained with the other rotor blade.

The fuselage was found laying on its left side, with the tailboom separated from the fuselage aft of the engine. The upper fuselage and cockpit area exhibited fire damage, as did both the upper and lower area aft of the passenger compartment bulkhead. The belly exhibited arcing scratches in the paint and crushing. The left skid was folded beneath the fuselage. The right skid was bent forward of the front attachment point; the forward portion of that skid exhibited abrasion and scratches at an angle to the skid tube's longitudinal axis.

The tail rotor hoop had separated into two main pieces, which were located separately in the wreckage distribution. No evidence of scratches, scoring, or paint transfer was observed on the outer surface of the hoop.

Control continuity was established from the cyclic and collective controls to the swash plate. Pedal cables were, as earlier described separated.

All three main rotor blades exhibited tip damage and delamination consistent with blade strikes. No pre-impact mechanical anomalies were noted during the on-scene investigation.

The helicopter was equipped with seat belts. No evidence of installed shoulder harnesses was found. The pilot's seat belt buckle remained buckled when observed at the accident scene. The belt was found outside the aircraft. Its right-side attachment point remained clasped on its attachment point; however the attachment point had separated from the airframe. The other end of the belt exhibited melting and separation.

Medical and pathological information

An autopsy of the pilot was performed November 3, 1999 by Dr. James B. Sawyer of Blue Mountain Pathology, Inc., in Pendleton, Oregon. Toxicological testing was conducted by the FAA laboratory, with negative results for carbon monoxide, cyanide, and ethanol.

Fire

The tower controller activated the siren and dispatched fire/rescue personnel after observing the crash. Vehicles were en route to the accident scene within 4 minutes of notification. The fire was suppressed using foam.

Additional information

The wreckage was released to the insurance adjuster, as owner's representative, on November 4, 1999, after inspection by investigators. At the time of release the wreckage was located at the General Aircraft Services, Inc., facility in Pendleton, Oregon.