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On August 7, 1994, at 0006 Pacific daylight time, a Piper PA-28R-200, N6959J, collided with power lines during an attempted night forced landing at San Luis Obispo, California. The aircraft was owned and operated by American Aviation, Inc., and was on a dual instructional flight. Visual meteorological conditions were prevalent at the time and no flight plan was filed for the operation. The aircraft was destroyed in the collision sequence.
The certificated flight instructor, the student pilot, and two passengers sustained fatal injuries. The flight originated from the San Luis Obispo airport at 0003 on the morning of the accident.
Witnesses near the scene of the accident reported seeing the aircraft flying between 50 and 100 feet agl, approximately 3 1/2 miles west of the airport. They described the aircraft as flying westbound and then entering a gradually descending southerly left turn over the 101 Freeway. Several witnesses stated that the aircraft's position lights and rotating beacon appeared illuminated. Two witnesses stated that the engine sounds were unusually loud and did not sound normal.
As the aircraft descended in a turn over the freeway and approached a section of overhead high-tension electrical lines that spanned the roadway, a brilliant flash was described by numerous witnesses. Almost simultaneously, the city of San Luis Obispo reported a major power outage occurring at 0006 on the morning of the accident.
The driver of a compact pickup truck, who was northbound on the 101 Freeway a few hundred feet south of the electrical lines, reported that his vehicle struck the accident aircraft as it slid toward him across several lanes of traffic in the opposite direction. Rubber smears corresponding to the right front tire of the pickup truck were observed on the left side of the fuselage between the main wing and horizontal stabilizer. The aircraft fuselage came to rest, inverted, in the emergency lane of the northbound 101 Freeway at the Prado Road exit.
Pacific Gas and Electric repairmen at the scene reported that the bottom two lines of the 6-line high-tension span which crossed the freeway had been broken. They stated that the normal height of the broken lines was 50 feet agl. There were no warning markers on any of the lines.
The engine had undergone a factory overhaul on May 13, 1992. Since that date, the aircraft had flown approximately 942 hours. A review of the aircraft and engine logbooks revealed that the aircraft had been maintained in accordance with all applicable directives.
An airport refueler reported that the aircraft had been refueled with 38 gallons of low-lead aviation fuel at 1700 on the afternoon prior to departure. The fuel capacity of both tanks totals 48 gallons.
Computations established that the aircraft had been loaded within the manufacturers applicable limitations.
There were no reported radio transmissions from the aircraft indicating an in-flight emergency.
WRECKAGE AND IMPACT INFORMATION
The axis of the wreckage distribution was along a 180-degree path. The heading of the aircraft, at rest, was 085 degrees. Flight control continuity was established for all control surfaces. The flap control handle was found in the first notch position which, according to the manufacturer, corresponds to 10 degrees of flaps.
The rudder trim was found in the neutral position. The elevator trim actuator was found with 13 threads exposed. According to the manufacturer, this corresponds to a 8- to 9-degree tab-down setting.
The aircraft propeller exhibited a midspan aft bend on the first blade and minor leading edge abrasions near the blade tip on the second blade. The spinner was crushed on one side at approximately a 30-degree angle relative to the longitudinal axis of the aircraft. There was no evidence of rotational scoring on the spinner or propeller blades. The propeller control lever was found in the full-decease position.
The aircraft propeller also exhibited indications of electrical arcing on both blades just outboard of the spinner. The aircraft skin on both wings exhibited additional random indications of arcing. The aircraft fuselage, in the position of the rotating beacon, and the upper leading edge portion of the vertical stabilizer, exhibited sooting.
The landing gear switch was in the down position and had sustained impact damage. The right main gear was down and locked. The left main gear was extended; however, the gear extension mechanism was fractured and the gear was not locked. The nose gear was partially extended and was not locked.
The upper surface of the right wing and the upper portion of the engine cowling exhibited evidence of sliding across an abrasive surface. The cabin roof separated from the aircraft from a point beginning at the windscreen and aft to a point midway between the main wing and the horizontal stabilizer. The exterior surface of the cabin roof also exhibited evidence of abrasion scoring. The two rear passenger seats were separated from the floor of the aircraft.
The right wing remained attached to the aircraft fuselage. The outboard portion of the wing exhibited an upward and aft deformation along with leading edge crush.
The left wing was found separated from the aircraft, nearer the initial point of impact. The outboard section of the wing exhibited evidence of overstress. The wing tip was separated from the main wing.
The empennage was found separated from the aircraft and exhibited evidence of overstress failure just forward of the horizontal stabilizers. The vertical stabilizer was separated from the empennage and was located toward the initial point of impact. There were slight indications of leading edge damage to the empennage flight surfaces.
The engine case exhibited fractures on the upper and lower sections in a location corresponding to the No. 4 cylinder.
The fractures resulted in a hole being opened in the lower section of the case. A further examination of the internal components revealed that the No. 4 rod end cap was separated. The threaded portions of both end cap bolts were fractured. The end cap was fractured and exhibited scoring and deformation. The connecting rod was also fractured and its surfaces were scored. The No. 4 journal exhibited rotational scoring. The No. 4 bearing and portions of the No. 4 connecting rod, rod end cap, and end cap bolts were not located.
The oil sump contained numerous metal fragments. The oil suction screen also contained numerous metal fragments.
The tachometer had recorded 5,052.79 hours. The Hobbs meter had recorded 1,193.6 hours.
The fuel selector switch was on the left main tank. Both main tanks, which were found inverted, were empty. The mixture control lever was found in the idle-cutoff position. The gascolator was empty; however, the engine had been sitting in an inverted position for over 6 hours prior to inspection. The electric fuel pump contained fuel as did the fuel lines from the pump to the engine. The fuel pump switch was in the "on" position. The ignition switch was in the "off" position.
MEDICAL AND PATHOLOGICAL INFORMATION
A review of the forensic toxicology fatal accident report provided by the Federal Aviation Administration (FAA) Civil Aeromedical Institute was negative with the exception that Acetaminophen was detected during the analysis conducted for the first pilot. Two Tylenol tablets were found in his personnel effects.
The San Luis Obispo County Coroner's office performed an autopsy on the aircraft occupants.
There was evidence of a fire confined to the engine compartment. Witnesses reported that some of the first people on the scene had been able to extinguish the fire by tossing dirt on it.
The occupiable space in the aircraft cabin had been reduced to the top of the instrument panel.
Evidence indicated that all four occupants were wearing seatbelts and that both front seat occupants were wearing shoulder harnesses.
TESTS AND RESEARCH
The connecting rod, rod end cap, and end cap bolts for the No. 4 cylinder were submitted to the Materials Laboratory Division of the National Transportation Safety Board for metallurgical analysis. Due to subsequent smearing of the fracture surfaces after the initial failure, the results of testing were inconclusive.
Fuel samples were collected from the fuel truck and fuel farm which had provided refueling services to the accident aircraft. The results of the testing indicated that the samples were aviation grade fuel with an octane rating which exceeded 105. No foreign contamination was reported.
The aircraft was recovered and stored at Santa Paula, California. The wreckage was subsequently released to a representative of the registered owner.