BFO94FA121

While in cruise flight at 10,000 feet MSL, the airplane deviated slightly below and above the assigned altitude, then it entered a rapid descent and broke apart in flight. An investigation revealed evidence of an in-flight fire, but the source of the fire was not verified. A post-crash fire consumed the forward fuselage. A substance identified as pvc-dop was found on the forward utility door and on the right horizontal stabilizer. Both of these had separated from the fuselage and were found with other pieces of wreckage that were scattered over a 1/2 mile area. The pvc-dop had been deposited in a 'molten state.' Analysis of the pvc-dop revealed that it had a melting point of 185 degrees celsius. Examination of the wreckage revealed that the horizontal stabilizer had failed in numerous pieces, and the wings had failed downward with separation occurring just outside the engine nacelles. Both wing spars exhibited downward deformation. No preaccident anomalies were found with the airframe or engines. Pathological examinations of the occupants revealed sooting in their trachea's.

History of flight

On June 29, 1994, at 0810 eastern daylight time, a Beech "Baron" BE-58TC, N333TK, departed its assigned cruising altitude of 10,000 feet mean sea level and descended in altitude, breaking apart in the air. The pilot and the two passengers were fatally injured. Visual meteorological conditions prevailed at the accident site. An instrument flight rules flight plan had been filed for the business flight. The flight departed Pittsburgh International Airport, Pittsburgh, Pennsylvania, at 0734 and was originally destined for Nashville, Tennessee. While enroute, the pilot amended the intended destination to Lebanon, Tennessee. The flight was conducted under 14 CFR Part 91.

Data recorded at the Indianapolis Air Route Traffic Control Center (ARTCC) indicated that between 0806:47 and 0809:59, N333TK maintained an altitude of about 9,900 feet msl and was on a southwesterly heading. At that time the airplane's airspeed fluctuated around 185 knots. The radar data indicated that between 0810:12 and 0811:36, the airplane's altitude radar returns fluctuated from 9,900 feet msl (0810:12), decreased to 9,600 feet msl (0810:48), increased to 10,300 feet msl (0811:12), and then decreased to 8,400 feet msl (0811:39).

Radar data indicated the airplane continued to descend on a southwesterly heading. The last two radar returns (0811:51 and 0812:03) showed N333TK in a right turn with an increasing true airspeed and descending through 2,800 feet msl.

A witness located near the accident site stated, "I was at the kitchen sink and heard a loud explosion. The explosion seemed to last for a few seconds. I ran to the back porch and looked up in the sky....I saw a wing of an airplane with what looked like wires hanging from the wing. The wing was in a triangle shape, going straight down."

Another witness located near the accident site stated, "At about 8:10 or 8:15 a.m., I heard this plane. It sounded normal at first. I couldn't see it because it was above the clouds. All at once, the sound died off. Then the sound came back up to a normal pitch. Then I heard the sound go up and down three or so times....I saw the plane come out of the clouds. I couldn't really see the outline of the plane, but I could see a ball of flame. It seemed to be staying in one place only blowing back and there was a considerable amount of a smoke. It dropped on down what appeared to be a considerable distance. Then it was followed out of the clouds by a flat object. Then the plane exploded in the air."

The accident occurred during the hours of daylight, at a latitude of 39 degrees 20 minutes and 57 seconds North and longitude of 81 degrees 08 minutes and 12 seconds West.

Personnel information

The pilot held an Airline Transport Pilot certificate with a multiengine land rating and had commercial pilot privileges for single engine land and sea. She also held a Flight Instructor certificate with single and multiengine land and instrument airplane ratings. She was a certificated ground instructor with advanced and instrument ratings. At the time of the accident she had accumulated about 4,676 hours of flight time, of which 984 hours were in a multiengine airplane.

Aircraft information

According to the airplane's log books, the airframe and engines were inspected in accordance with an annual inspection and were determined to be in airworthy condition on March 7, 1994.

Meteorological information

A visual satellite image with a nominal time of 0801 showed thunderstorms about 30 nautical miles east of the accident location.

The Parkersburg, West Virginia, Weather Observing Station located 15 nautical miles West from the accident site reported at 0750 the following:

Estimated ceiling of 2000 feet overcast, 7 miles visibility, temperature 67 degrees F, dew point 67 degrees F, winds from 100 degrees at 5 knots, altimeter setting of 29.83 inches of mercury.

According to a report issued by GDS National Lightning Detection Network located in Tucson, Arizona, there were no cloud to ground lightning strikes at the time and near the location of the accident. (See attached GDS Report).

Wreckage and impact information

The wreckage was examined at the accident site on June 29 and 30, 1994. The wreckage was scattered over mountainous terrain and covered a 1/2 square mile. The main wreckage included the nose section, instrument panel, fuselage, the inboard section of each wing, and the airplane's two engines. The empennage, both wing outboard sections, and various airplane parts were scattered throughout the 1/2 square mile (see attached Wreckage Distribution Chart for exact locations.) All control surfaces were located.

The main wreckage came to rest on heavily wooded sloping terrain. The cabin area and forward fuselage were consumed by fire. Instruments that were not consumed by the on ground fire were heat damaged and sooted on their fronts, but not aft of the instrument panel. All the instruments were destroyed. The forward cabin door was in the burned section of the cabin and was in the unlatched position. Its window was not present. The forward cabin door interior was burned and the exterior portion exhibited heat damage. The airplane's heater was examined and no evidence of fire damage was noted.

The forward utility door was found outside the main wreckage and exhibited fire damage. Its interior was burned and the exterior was intact. The aft utility door was not located.

The aft fuselage exhibited fire damage on its exterior and interior. The bottom skin of the aft fuselage was burned and brittle and portions of it were missing. The inside of the aft fuselage and the avionics it contained were burned. Black scrape marks and gouges, starting where the leading edge of the horizontal stabilizer attaches to the left side of the aft fuselage and extending downward toward the bottom of the fuselage, were noted. The fuselage skin in the area of the left horizontal stabilizer forward spar cutout was torn down in direction and aft.

The right engine remained with the main wreckage and was burned. The left engine was downhill from the fuselage. Both engines were removed from the accident site and examined. The examinations revealed no anomalies. All internal engine components were checked for signatures of electrical arcing and magnetism per TCM Service Bulletin M88-9. No signatures were found.

The outboard section of the right wing with the aileron attached exhibited heat damage. The bottom of the wing was covered with soot. The wing surface exhibited numerous areas of buckled and torn skin. The soot was deposited such that many areas adjacent to the buckled and torn skin exhibited soot concentrations which varied from the surrounding wing skin. The pneumatic de-ice boot which extends along the wing's outboard leading edge exhibited heat damage. The wing's spar was deformed in a downward direction. Separation of the wing occurred at the outboard side of the engine nacelle. The fuel tanks were ruptured and burned. A right main landing gear position was not determined.

The outboard section of the left wing with the aileron attached exhibited heat damage. The top of the wing was covered with soot. The wing surface exhibited areas of buckled and torn skin. The soot was deposited such that many areas adjacent to the buckled and torn skin were free of soot. A portion of the upper trailing edge surface inboard of the aileron was found folded up and forward, and was found lying flat against the upper wing surface. Thus, the upper surface covered with soot exhibited a lighter concentration of soot as compared to the surrounding area. The de-ice boot exhibited heat damage. An undetermined amount of fuel was found in the wing. The left wing spar was deformed in a downward direction. Separation of the wing occurred at the outboard side of the engine nacelle. The f