Denton

After takeoff, the pilot proceeded about 30 miles and climbed to an altitude of about 2,200 ft mean sea level (msl). About 8 minutes after takeoff, the airplane entered a descending left turn that continued until impact. A witness observed a twin-engine airplane at a low altitude and in a descent. After the airplane descended below the tree line, a fireball emerged followed by some smoke; however, the smoke was thin and dissipated quickly. A second witness observed the airplane at a low altitude and in a slow, descending turn. The flight path was steady and the wings “never dipped.” Shortly after the airplane descended out of sight, he observed an explosion. Both engines were on fire when he arrived at the accident site, and there was a fuel leak from the right engine toward the cockpit area. He used a fire extinguisher to keep the fire off the fuselage until first responders arrived. The airplane impacted a utility pole and terrain. Burned vegetation was present over portions of the accident site. The left wing was separated outboard of the engine and was located near the utility pole. A postaccident examination revealed that the left main fuel tank was partially consumed by the postimpact fire; therefore, the amount of fuel in the tank could not be determined. The left engine nacelle was discolored consistent with the postimpact fire. The left nacelle fuel tank appeared intact, and no fuel was visible in the left nacelle fuel tank. However, the amount of fuel in the left nacelle fuel tank at the time of impact could not be determined. The right main fuel tank appeared intact, and about 1 gallon of fuel was drained from the tank during recovery of the airplane. While the postimpact fire was consistent with fuel present onboard the airplane at the time of the accident, the lack of an extensive and sustained ground fire suggested that a limited amount of fuel was present. The left and right engine cockpit fuel selectors were both positioned to the “RIGHT MAIN” fuel tank. The left fuel selector valve, located in the engine nacelle, was in the “OFF” position at the time of the exam. The right fuel selector was in the “RIGHT” fuel tank position. A teardown examination of the left engine did not reveal any anomalies consistent with a preimpact failure or malfunction. A teardown examination of the right engine revealed damage consistent with oil starvation throughout the engine. A teardown examination of the left propeller assembly revealed indications that the blades were at or near the feather pitch stop position during the impact sequence. A teardown examination of the right propeller assembly revealed indications that the blades were on or near the low pitch stop position during the impact sequence. The fuel flow indicator displayed the total fuel remaining as 8.3 gallons when powered up on a test bench. However, the fuel quantity indications are dependent on the pilot properly configuring the device when the airplane is refueled. The fuel flow indicator does not directly provide fuel quantity information. According to the airplane flight manual, the total unusable fuel for the airplane, with one engine nacelle fuel tank installed, was 7.8 gallons. Engine performance data recovered from the onboard engine monitor revealed a reduction in right engine power to near idle power. About 1 minute later, the airplane entered a descending left turn which continued until impact. About 3 minutes after the reduction in right engine power, the left engine completely lost power. Immediately afterward, right engine power increased to near full (takeoff) power. However, about 30 seconds later the right engine completely lost power. The airplane impacted the pole and the terrain a few seconds later. The pilot likely detected an impending failure of the right engine and intentionally reduced power. However, shortly afterward, the left engine lost power due to fuel starvation. At that time, the pilot likely set the left engine to crossfeed from the right main fuel tank to restore power. Unsuccessful, the pilot then decided to feather the left propeller and attempted to use any available power from the right engine, but the right engine immediately lost power as well. Whether the right engine lost power at that moment due to fuel starvation or oil starvation could not be determined. The pilot was obese and had hypertension, high cholesterol, and an enlarged heart with left ventricular thickening. While these cardiovascular conditions placed him at an increased risk for a sudden incapacitating cardiac event, the autopsy did not show any acute or remote myocardial infarction, and the flight path suggests intentional actions until the crash. Thus, the pilot’s cardiovascular disease was not a factor in this accident. Toxicology testing detected the muscle relaxant cyclobenzaprine and its active metabolite norcyclobenzaprine in the pilot’s femoral blood at low therapeutic levels. The sedative-hypnotic medication zolpidem was detected at subtherapeutic levels. While these substances are associated with side effects such as drowsiness and dizziness, the operational findings of this accident do not suggest performance issues related to fatigue. Thus, it is unlikely that the effects from the pilot’s use of cyclobenzaprine and zolpidem were factors in this accident.

The instrument-rated commercial pilot was approaching the destination airport after a cross country flight in night instrument meteorological conditions. According to radar track data and air traffic control communications, while receiving radar vectors to the final approach course, the pilot did not always immediately comply with assigned headings and, on several occasions, allowed the airplane to descend below assigned altitudes. According to airplane performance calculations based on radar track and GPS data, the pilot made an engine power reduction about 2.5 minutes before the accident as he maneuvered toward the final approach fix. Following the engine power reduction, the airplane's airspeed decreased from 162 to 75 knots calibrated airspeed, and the angle of attack increased from 2.7° to 14°. About 4 miles from the final approach fix, the airplane descended below the specified minimum altitude for that segment of the instrument approach. The tower controller subsequently alerted the pilot of the airplane's low altitude, and the pilot replied that he would climb. At the time of the altitude alert, the airplane was 500 ft below the specified minimum altitude of 2,000 ft mean sea level. According to airplane performance calculations, 5 seconds after the tower controller told the pilot to check his altitude, the pilot made an abrupt elevator-up input that further decreased airspeed, and the airplane entered an aerodynamic stall. A witness saw the airplane abruptly transition from a straight-and-level flight attitude to a nose-down, steep left bank, vertical descent toward the ground, consistent with the stall. Additionally, a review of security camera footage established that the airplane had transitioned from a wings-level descent to a near vertical spiraling descent. A post accident examination of the airplane did not reveal any anomalies that would have precluded normal operation during the accident flight. Although the pilot had monocular vision following a childhood injury that resulted in very limited vision in his left eye, he had passed a medical flight test and received a Statement of Demonstrated Ability. The pilot had flown for several decades with monocular vision and, as such, his lack of binocular depth perception likely did not impede his ability to monitor the cockpit instrumentation during the accident flight. The pilot had recently purchased the airplane, and records indicated that he had obtained make and model specific training about 1 month before the accident and had flown the airplane about 10 hours before the accident flight. The pilot's instrument proficiency and night currency could not be determined from the available records; therefore, it could not be determined whether a lack of recent instrument or night experience contributed to the pilot's difficulty in maintaining control of the airplane.

The twin-engine airplane impacted the ground during an uncontrolled descent while maneuvering in dark night instrument meteorological conditions in the vicinity of Lewisville, Texas. The commercial pilot contacted the approach controller and stated that his attitude indicator was "not helping" and needed "a little bit of help with trying to keep it straight." The pilot was instructed by approach control to maintain an altitude of 3,000 feet msl. The approach controller confirmed with the pilot that he could not fly headings, and instructed the pilot to turn right. Seconds afterwards, the pilot was instructed to turn left and the controller would tell him when to stop the turn. The pilot acknowledged. There were no further communications between the pilot and air traffic control. The airplane initially impacted in a near vertical attitude into a wooded area adjacent to a rural paved road, slid across the road, and impacted a residence. Radar data showed that the airplane's magnetic heading was erratic throughout the 5-minute flight. The gyro instruments found at the accident site were the copilot's direction gyro (vacuum), a turn and bank indicator (electric), and the pilot's attitude indicator (vacuum). The gyros were disassembled, and visually examined. The co-pilot's direction gyro examination revealed rotation signatures on the gyro and the gyro housing. The turn and bank indicator revealed a "faint" rotational signature on the gyro. The pilot's attitude indicator gyro had no rotational signatures, and exhibited blunt impressions corresponding to the gyro buckets on the inside of the gyro-housing wall. A maintenance repair data plate ("Functional Tested") was found on the attitude indicator's instrument housing dated 12/2/02. Due to the extent of the fire damage, no instrument readings could be obtained. Seven days prior to the accident flight, a company pilot who flew the accident airplane reported that the pilot's attitude indicator (part number 102-0041-04, serial number 92B0346) "rotated" and the flight was aborted. The next day, the attitude indicator was removed and bench checked, cleaned, and adjusted. The attitude indicator was reinstalled and an operational check on the ground was performed. Three days prior to the accident the pilot's attitude indicator was again removed for an overhaul. According to company maintenance personnel, the attitude indicator was reinstalled the night prior to the morning of the accident, and an operational check on the ground was performed. Radar data showed that the aircraft did not stabilize on a particular heading throughout the flight. Physical evidence showed that the pilot's attitude gyro was not "spooled" at the time of impact.