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N3971X accident description

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Tail numberN3971X
Accident dateOctober 26, 2007
Aircraft typePiper PA-28R-200
LocationCedar City, UT
Near 37.429167 N, -112.913333 W
Additional details: None

NTSB description

HISTORY OF FLIGHT

On October 26, 2007, about 2006 mountain daylight time, a Piper PA-28R-200, N3971X, experienced an in-flight breakup while in an uncontrolled descent over mountainous terrain about 21 miles southeast of Cedar City, Utah. The airplane was destroyed during the breakup and post impact ground fire. The private pilot, who co-owned the airplane, and the passenger were killed. Dark nighttime visual meteorological conditions prevailed at the time. No flight plan had been filed for the business flight that was performed under the provisions of 14 Code of Federal Regulations Part 91. The flight originated from Bountiful, Utah, about 1815.

The elevation of Bountiful's Skypark Airport is 4,234 feet msl. Skypark is located about 5 miles north of the Salt Lake City International Airport.

At 1816 the pilot contacted the Salt Lake City Terminal Radar Approach Control Facility. The pilot reported that he had departed Bountiful and was at 4,800 feet mean sea level (msl). The pilot indicated that he planned to fly in a southerly direction. (Family members subsequently reported to the National Transportation Safety Board investigator that the pilot intended to fly south, passed the accident site, to an airport in Arizona.) The air traffic controller identified the airplane on radar and provided flight following service as the airplane climbed. At 1842 the airplane was at 9,500 feet, as indicated by the airplane's Mode C altitude encoding transponder, and the southbound airplane departed Salt Lake City airspace. Federal Aviation Administration (FAA) controllers had no further communications with the airplane pilot, and no additional radar flight following or other services were provided.

A review of recorded FAA radar data for the area between Bountiful and the vicinity of the accident site, about 21 miles southeast of Cedar City, revealed one target having a flight path consistent with that of the accident airplane. A review of the target airplane's radar track revealed that it continued climbing while proceeding in a southerly direction.

The pilot's wife reported to the Safety Board investigator that about 1930 she received a cellular phone call from her husband, who was flying home with his brother. The pilot indicated that their departure had been delayed, but they were currently en route home. Based upon information from the airplane's global positioning satellite receiver, their ground speed was 120 knots. They anticipated landing at 2021. The pilot's wife had no further communications with her husband.

Between 1958:06 and 2005:04, the southbound airplane descended from about 12,600 feet to 11,100 feet. Thereafter, the radar data indicated that the airplane commenced a clockwise turn while continuing to descend. The airplane was last recorded on radar while on a northwesterly track at 2005:34, and seconds earlier had descended through 10,800 feet.

The airplane's fuselage, wings, empennage, and other non-structural components were found scattered over a mountainside. The main wreckage was located about 1/3-mile from the last recorded radar position.

No person reported to the Safety Board investigator having observed the accident airplane descend or impact the mountainous terrain. No homes, lights, or roadways exist in the vicinity of the accident site.

PERSONNEL INFORMATION

The pilot, age 29, held a private pilot certificate and was rated to fly single engine land airplanes. According to data contained in an insurance application dated July 2007, the pilot's total flight time was about 200 hours. He had about 40 hours experience flying in the accident model of airplane.

FAA records indicated that on the pilot's May 2007 application for a third-class aviation medical certificate, he reported having 200 hours of flying experience. The pilot also reported having flown 6 hours during the preceding 6 months.

AIRPLANE INFORMATION

The airplane was manufactured in 1975. The airplane's logbooks were not provided to the Safety Board investigator for examination, and they reportedly may have been in the airplane, which was consumed in the post impact fire.

The mechanic who had been hired by the airplane owners to perform maintenance provided the Safety Board investigator with copies of logbook entries he had kept. In pertinent part, the records indicated that the airplane received an annual inspection in June 2007. The most recent 100-hour inspection was performed in August 2007, at an airplane total time of 3,370.5 hours.

METEOROLOGICAL INFORMATION

A review of the meteorological conditions in the vicinity of the accident did not reveal reports or forecasts of adverse convective activity. No evidence was found of conditions that would preclude flight under visual flight rules.

The closest aviation weather observation station to the accident site is located at Cedar City, Utah (CDC), about 19 miles northwest of the accident site. At 1953, CDC reported the following weather: sky clear, visibility 10 miles, wind from 190 degrees at 4 knots, temperature 13 degrees Celsius, dew point -6 degrees Celsius, and altimeter 30.17 inches of Mercury.

The United States Naval Observatory reported that on the accident day, the end of civil twilight occurred in Cedar City at 1908. The moon's disk was 99 percent illuminated, and the nearly full moon rose in the east at 1849.

About 30 miles east of the 6,400 foot mean sea level accident site, the elevation of the mountaintops was between 8,000 and 9,400 feet msl. At the time of the accident, the moon would appear near the mountaintops. As the airplane turned westward, the moon would not have been visible from the airplane's cockpit.

Within a few days preceding the accident, numerous forest fires were prevalent in California mountains south of the accident site. The smoke layer drifted into Utah. According to a Civil Air Patrol pilot who searched for the accident airplane, the layer of smoke from the fires impaired horizontal flight visibility. The pilot opined that the flight visibility in the accident site area would have been very bad at night.

COMMUNICATION

According to the FAA, no communications occurred with the accident airplane pilot following termination of radar flight following service.

WRECKAGE AND IMPACT INFORMATION

An examination of the accident site and airplane wreckage revealed that the airplane experienced an in-flight breakup. All of the airplane's structural components were located. Airframe components were found scattered over an estimated 950 foot long by 350 foot wide oval shaped area, and within a radius of 550 feet of the main wreckage. The long axis of the wreckage distribution path was oriented on a magnetic track of about 030 degrees.

The main wreckage consisted of the fuselage with attached cockpit and engine assembly. The main wreckage was found upside down and pointed about 010 degrees, magnetic.

Components south and west of the main wreckage principally consisted of the right wing, right aileron, and the vertical stabilizer. The remainder of the airplane, including the separated left wing (outboard section), left stabilator, and various skin panels, were located northwest to north of the main wreckage.

Also, several localized areas of fire were noted in native shrub vegetation surrounding the wreckage area. The majority of the fuselage was consumed by fire.

MEDICAL AND PATHOLOGICAL INFORMATION

On October 27, 2007, an autopsy was performed on the pilot by the Office of the Medical Examiner, Utah Department of Health, Salt Lake City, Utah. The autopsy findings indicated that the pilot died from "massive deceleration injuries." Forensic toxicology was performed on specimens from the pilot. The Medical Examiner found no evidence of volatiles, marijuana or drugs.

The FAA's Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, also examined specimens from the pilot. The FAA reported no evidence of drugs. The FAA laboratory reported finding 15 and 22 mg/dL of ethanol in liver and muscle samples, respectively. Also, 1 and 2 mg/dL of N-Propanol was found in liver and muscle samples, respectively. The laboratory's manager noted that the samples exhibited evidence of putrefaction.

TESTS AND RESEARCH

Fuel Information

A lineperson at the pilot's departure airport reported completely filling the airplane's fuel tanks just prior to the accident flight. The lineperson indicated it appeared the pilot was in a hurry to become airborne. During the on scene examination of the ground surrounding the fuselage, the Safety Board investigator noted the odor of fuel upon excavating several inches of soil, between 2 and 5 yards south of the wreckage.

Airframe Examination

The wreckage was recovered from its mountainside location and additionally examined. Although the majority of the airframe was destroyed by fire, all structural components were located. Airframe sections that were found separated from the fuselage consisted of the outboard portions of both wings, the vertical stabilizer with attached rudder, and the stabilator with attached antiservo tab. The area where the left and right wing fuel tanks were situated was heavily fire damaged. The entire instrument panel, cockpit, and cabin were consumed by fire. The inboard portions of both wings were partially melted. Fire-damaged sections of both wing flaps were found with the wreckage.

The baggage door was found with the main wreckage. The internal locking mechanism components were not found. The door and fuselage skin surrounding the door were fire damaged.

Wing Separation and Bending Signatures

The right wing spar's attachment bolts were found intact and were secure in the wing spar. The outboard 6 foot long span of the right wing was found separated from the inboard wing section where the wing spar's production splice is located. The lower surface of the spar's web was found bent in a downward direction. Rivets attaching the splice to the main spar's lower surface were pulled out of the main spar in a downward direction. The outboard portion of the right wing's lower surface was found with diagonal wrinkles in the skin panels. The direction of the wrinkles in the panels was consistent with the wing having been subjected to torsional twisting in a leading edge downward direction.

The left wing's attachment bolts were not located. The left wing's spar was partially melted in the area where the attachment bolts would have been located. The outboard 6 foot long span of the left wing was found separated from the inboard wing section at approximately the same location that separation occurred in the right wing. The area of the wing where the production splice existed at the spar was bent in a downward direction. The lower and upper surfaces of the spar splice were found with rivets pulled out in a downward direction. No evidence of diagonal skin buckles was present on the separated outboard portion of the wing. The spar, at the production splice, showed evidence of compressive buckling in a downward direction. The upper portion of the spar web was bent in a downward direction, and it was twisted in a leading edge downward direction. The associated spar on the separated outboard wing span was found bent downward and twisted in a leading edge downward direction.

Stabilator Separation and Bending Signatures

The right and left halves of the stabilator were found separated from each other, and from the attachment location at the center spar box in the airplane's tail. The antiservo tab was found attached to the stabilator.

The upper and lower surfaces of the right side of the stabilator's spar were observed bent in a downward direction. The upper skin of the right side of the stabilator was also buckled in a downward direction.

The upper and lower surfaces of the left side of the stabilator's spar web were found bent in a downward direction. The spar was twisted in a leading edge downward direction, and the entire span of the stabilator was bowed in a downward direction.

Vertical Stabilizer, Control Cables and Flight Controls

The entire vertical stabilizer and the attached rudder were found separated from the tail. No evidence of airborne-related impact deformation was noted. Both structures appeared straight.

The aileron cables and bellcrank attachment fittings were found connected in the wings. The top and bottom stabilator control cables were found routed over their respective pulleys in the tail, and the cables were connected to the counter weight bar. The rudder cables were observed connected to the rudder horn in the tail of the airplane.

The hinge areas and travel limit stops of all separated control surfaces were examined. None of the flight control surfaces or stops exhibited overtravel or impact signatures indicative of flutter.

Fracture Surfaces

All of the fracture surfaces in locations where spars had broken were examined, unless they had been subjected to obvious heat distortion or melting. All examined surfaces exhibited either uniform appearing granular characteristics or had angular sheer lips consistent with bending overload or compressive buckling signatures. Skin sections adjacent to separated spars were found distorted in the direction of the principal axis of spar separation.

Propeller

Two of the three propeller blades were found attached to the engine, and the third blade was found about 15 feet away. The blades were torsionally twisted. The leading edges of all the blades were nicked and gouged. Numerous scratches in a chordwise direction were noted on the blade surfaces.

Engine

Under the supervision of the Safety Board investigator, the Lycoming Engine participant examined the engine. The engine was ground impact and fire damaged, and it came to rest inverted. The flow divider was destroyed. The crankshaft could not be rotated. The accessories, including the magnetos, were destroyed by fire. The spark plugs exhibited wear signatures consistent with mid-life usage when compared with the Champion Spark Plug wear guide, according to the Lycoming Engine participant. The participant examined the cylinders using a borescope, and he reported finding no evidence of preimpact defects. No contaminants were observed in the oil suction screen. At the conclusion of the examination, the engine participant indicated that no evidence of any preimpact mechanical failure was found.

(c) 2009-2011 Lee C. Baker. For informational purposes only.