History of Flight
On February 4, 2015, at approximately 2109 central standard time, a Cessna 441 (Conquest II) twin turbo-prop airplane, registration N441TG, was substantially damaged when it struck terrain following a loss of control during an instrument approach to Denton Municipal Airport (DTO) in Denton, Texas. The commercial pilot was fatally injured. The airplane was registered to Del Air Enterprises II, LLC and operated by the pilot under 14 Code of Federal Regulations Part 91 on an instrument flight rules (IFR) flight plan. The cross-country flight departed Willmar Municipal Airport (BDH) in Willmar, Minnesota, around 1828. Night instrument meteorological conditions prevailed.
According to Federal Aviation Administration (FAA) air traffic control data, at 2050:46, the pilot contacted Dallas-Fort Worth Terminal Radar Approach Control and reported level at 4,000 ft mean sea level (msl). Radar data showed the flight about 35 miles northwest of DTO on a southbound course. The approach controller provided current weather at DTO and advised the pilot to expect the GPS runway 36 approach. At 2052:54, the controller instructed the pilot to fly direct to WOBOS, an intermediate fix for the approach. The flight turned south-southeast toward WOBOS. At 2059:35, the flight was cleared to descend to 3,000 ft msl, which the pilot acknowledged.
At 2101:24, the DTO tower controller informed the approach controller that a Cessna 172 had just landed and that its pilot reported light-to-moderate turbulence and in-flight visibility of about 1.5 miles. The approach controller relayed this to the accident pilot. At 2103:08, the flight was cleared to descend to 2,500 ft msl, and the pilot acknowledged. At 2103:24, the controller instructed a south heading; the pilot acknowledged and turned southbound. Radar data showed the airplane descended below 2,500 ft msl at 2104:09. At 2104:27, the controller instructed an east heading; the pilot acknowledged but did not initiate the turn. The airplane continued descending southbound to 2,100 ft msl at 2104:46, then began to climb. At 2104:59, noticing no turn, the controller instructed a heading of 080°, which the pilot acknowledged; radar data showed a climbing left turn toward the east.
At 2105:39, with the flight 8 miles from the final approach fix NULUX, the controller instructed a heading of 030° to intercept the final approach course, maintain 2,500 ft msl until established, and cleared the flight for the GPS runway 36 approach. The pilot responded, "Okay, 030 maintain 2.5 until established on the approach." Radar data showed the flight turned north instead of 030°.
At 2106:16, the controller told the pilot to contact DTO tower; the pilot acknowledged. The flight continued north until 2106:38, when it turned to 030° and descended through 2,500 ft msl at 2107:01. At 2107:16, the pilot contacted the tower controller, who reported surface wind 360° at 19 knots gusting 25 knots and cleared the flight to land on runway 36. The controller also asked about the pilot report (PIREP) from the preceding Cessna 172; the pilot confirmed receipt. Radar data showed the airplane descending as it intercepted the final approach course and continued north toward NULUX.
At 2108:44, the automated air traffic control system issued a low altitude alert for the accident flight, displayed on both tower and approach radar displays. At that time, radar data showed the airplane at about 1,500 ft msl. At 2108:47, the tower controller told the pilot to "check your altitude, you are still a couple of miles from the marker [NULUX], and uh believe your altitude should be about 2,100 there." At 2108:54, the pilot replied, "Okay, going back to (unintelligible)." Radar data showed the airplane continued descending until the final radar return at 2109:11, about 2.5 miles south of NULUX at 1,000 ft msl (about 300 ft above ground). At 2109:12, the tower controller transmitted again that the airplane was lower than the minimum altitude (2,000 ft msl) for that segment. No response was received from the pilot.
A security video camera located about half a mile southeast of the accident site captured the flight path. The camera, facing west, recorded the airplane's wingtip navigation and strobe lights as it crossed from left to right in the upper portion of the field of view. The airplane entered the camera's view at 2108:48 in a wings-level descent. At 2109:00, the descent angle increased substantially before the airplane entered a near-vertical spiraling descent. The lights were not visible after 2109:09.
Several 911 callers reported hearing an airplane at low altitude followed by a loud impact. One witness, about 1 mile from the site, saw navigation lights and a rotating beacon as the airplane flew north below an overcast ceiling toward DTO. The witness stated the airplane abruptly transitioned from straight-and-level flight to a nose-down, steep left bank, vertical descent. The witness also heard a momentary increase and then decrease in engine power before the descent, and lost sight of the airplane behind trees before hearing an impact sound.
Personnel Information
The 52-year-old pilot held a commercial pilot certificate with single-engine land, multi-engine land, and instrument airplane ratings. His last aviation medical examination was on January 13, 2014, when he was issued a second-class medical certificate with a limitation for corrective lenses. On that application, he reported 3,900 total flight hours, with 120 hours in the previous 6 months. FAA records showed no previous accidents, incidents, or enforcement actions.
A comprehensive pilot logbook was not found. A pilot journal recovered from the accident airplane contained a final entry for simulator training on a Socata TBM 700, completed on an unspecified date in 2014. That entry showed a total of 4,935 hours, with 4,899 as pilot-in-command, 4,834 hours in single-engine airplanes, and 101 hours in multiengine airplanes. The journal also included a flight instructor's endorsement for a flight review and instrument proficiency check dated August 13, 2013. An airplane utilization spreadsheet provided by the pilot's estate showed 56 hours in the previous 6 months, 23.6 hours in the previous 90 days, and 9.7 hours in the previous 30 days. The pilot's first flight in the accident airplane was on January 23, 2015, and as of the final spreadsheet entry on January 25, 2015, he had flown it 9.7 hours.
The pilot completed simulator-based training for the Cessna 441 on March 27, 2014, at SimCom Training Centers in Grapevine, Texas, and additional Cessna 441 training on January 4, 2015, at Executive Flight Training in Beaufort, South Carolina.
Aircraft Information
The accident airplane was a 1981 Cessna 441 (Conquest II), serial number 441-0200, powered by two Honeywell TPE331-10N-512S turbine engines driving constant-speed, full-feathering, four-blade McCauley propellers. It was a low-wing, conventional aluminum airplane with retractable tricycle landing gear and a pressurized cabin seating seven. It was approved for night and instrument meteorological conditions and for flight in known icing. The airplane received a standard airworthiness certificate and registration number on April 5, 1984, after being imported from France. The pilot purchased the airplane on January 22, 2015.
According to the weight-and-balance record dated January 3, 2011, the empty weight was 5,855 lbs, maximum takeoff weight 9,850 lbs, and useful load 3,995 lbs. Total fuel capacity was 481.5 gallons (475 usable). Fueling documentation indicated a full fuel load of Jet-A premixed with icing inhibitor at departure.
The airplane was maintained under an approved manufacturer inspection program. The Hobbs meter read 2,070.2 hours at the accident site; total airframe time was 3,830.2 hours since new. The last phase inspection was completed on August 22, 2014, at 3,767.8 total airframe hours, with 62.4 hours since then. The engines had 35.4 hours since their last 100-hour inspections on October 22, 2014. Engine serial numbers were P-77413 and P-77421, with total service time 3,830.2 hours since new and 2,303.5 hours since overhaul. Propeller serial numbers 972373 and 972370 had 2,303.5 hours since new and 284.6 hours since overhaul. A postaccident review found no unresolved airworthiness issues.
Meteorological Information
At 2103, the DTO automated surface observing system reported wind 350° at 17 knots gusting 25 knots, an overcast ceiling at 900 ft above ground level, 2 miles surface visibility with light rain and mist, temperature 3°C, dew point 3°C, and altimeter setting 30.26 inches of mercury.
The pilot of a Cessna 172 that landed about 8 minutes before the accident reported light-to-moderate turbulence and in-flight visibility of 1.5 miles during approach.
Sunset and end of civil twilight at the accident site were at 1803 and 1829, respectively. The moon was in a waxing gibbous phase with 99% illumination, but likely obscured by the overcast ceiling.
Wreckage and Impact Information
The wreckage was found in a grass-covered industrial storage yard about 6.4 nautical miles south of the runway 36 threshold, approximately 400 ft northeast of the final radar return and 207 ft right of the final approach course. The main wreckage consisted of the entire airplane, oriented on a west-northwest heading; elevation 679 ft msl. The wreckage was upright with no debris path and no evidence of inflight or postimpact fire. Structural separations were consistent with impact. The lower fuselage was crushed upward, indicating a vertical impact with a near-level pitch attitude. The tail section was partially separated aft of the pressure bulkhead; vertical stabilizer, rudder, horizontal stabilizers, and elevators were relatively undamaged. Wing leading edges, propeller spinners, and radome showed no evidence of ground impact.
Aileron control cable continuity was established through an overstress separation of the aileron sector drive cable in the mid-cabin area and a balance cable separation near the right wing root. Other flight control cables were continuous. Elevator trim actuators measured 1.6 inches (elevator trim tab trailing edge up about 5°). Aileron trim measured 1.1 inches (trailing edge down about 5°). Rudder trim measured 2.4 inches (trailing edge right about 5°). Landing gear were extended. Flap actuator measured 5.7 inches, consistent with 10° flaps. Stall warning horn and landing gear warning horn produced aural tones when powered. Left-side altimeter Kollsman window was set to 30.24 inches of mercury; right-side to 30.09 inches.
Both engines remained attached; first stage compressor impellers exhibited blade tip bends opposite rotation and scoring from contact with shrouds. Third axial turbine stages had re-solidified metallic splatter on stator vanes and blades, consistent with operation at impact. Both propeller assemblies remained attached; two 12-inch-deep holes were observed aside and slightly behind the engines where rotating propellers dug into soil. Propeller blades had significant bending opposite rotation, leading edge gouges, chordwise scratches, and burnishing. No anomalies were found that would have precluded normal operation.
Additional Information
First responders from the Argyle Fire Department reported no ice or frost on the fuselage, wings, or tail at the accident site. There was a substantial smell of Jet-A fuel but no evidence of explosion or postimpact fire. The pilot was seated in the left seat, secured by a lap belt; the available shoulder harness did not appear to have been used.
Medical and Pathological Information
The Tarrant County Medical Examiner's Office attributed the cause of death to multiple blunt-force injuries. FAA toxicology tests were negative for carbon monoxide, ethanol, and all tested drugs and medications.
The pilot had monocular vision following a childhood injury that resulted in very limited vision in his left eye. On June 18, 1991, after an ophthalmologist review and a medical flight test, he was issued a Statement of Demonstrated Ability (SODA) for a third-class medical certificate. On June 24, 1995, an updated SODA authorized a second-class medical certificate. He continued to receive second-class medical certificates with a limitation for corrective lenses.
Tests and Research
The airplane was equipped with a Honeywell KMH-820 Multi-Hazard Awareness System. Non-volatile memory data identified two alerts during the accident flight. The first was an obstacle pull-up alert when the airplane came near a tower during the final seconds: GPS altitude 1,030 ft (about 330 ft agl) and groundspeed 46.7 knots, about 361 ft south of the accident site and 700 ft west of the tower. The second alert was for excessive sink rate, but no further data was recorded before power loss.
Recovered electronic devices (Apple iPhone, iPad, and Appareo Stratus II) were examined. No data related to the accident flight was found on the iPhone or iPad. The Stratus II, an ADS-B device with GPS, contained flight parameter data for the accident flight. Using the Stratus II data and ATC radar track data, a performance study was developed.
According to the study, at 2106:38 during the approach, the pilot made an engine power reduction resulting in a 1,500 ft per minute descent and a 25 knot per minute airspeed deceleration. Between 2106:38 and 2109:00, airspeed decreased from 162 to 75 knots calibrated airspeed (KCAS), and angle of attack increased from 2.7° to 14°. At 2108:52, five seconds after the tower controller told the pilot to check altitude, the pilot made an abrupt elevator-up input, increasing airspeed deceleration to 168 knots per minute. At 2109:00, the airplane entered an aerodynamic stall after decelerating to 75 KCAS.
Aids to Navigation
The published inbound course for the GPS runway 36 approach was 357° magnetic; crossing altitude for NULUX was 2,000 ft msl; distance from NULUX to runway threshold was 4.2 nautical miles. After NULUX, LNAV-equipped aircraft descend to 1,300 ft msl until the stepdown fix SHIEV (2 nm from the runway end), then to the minimum descent altitude.