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On December 20, 2011, about 0145 central standard time, a Cessna 172R airplane, N987BT, impacted terrain while flying the Instrument Landing System (ILS) approach to runway 18 at the Denton Municipal Airport (KDTO), Denton, Texas. The commercial pilot was fatally injured and the certificated flight instructor (CFI) and student pilot-rated observer/passenger were both seriously injured. The airplane was registered to and operated by US Aviation Group, LLC under the provisions of 14 Code of Federal Regulations as a personal flight. Instrument meteorological conditions prevailed for the flight, which was being operated on an instrument flight rules flight plan. The flight originated from San Antonio International Airport (KSAT), San Antonio, Texas, at 2323, and was destined to KDTO.
A review of a transcript of the pilots' transmissions with air traffic control (ATC) revealed that at 0057, the pilots were informed by ATC that the weather at KDTO reported 1/2 mile visibility and an indefinite ceiling at 100 feet. The pilots then requested an approach into the Fort Worth Alliance airport (KAFW) where weather was reported to be 3 miles visibility with few clouds at 100 feet. At 0128 the pilots reported to have obtained current weather at KDTO and requested the ILS at KDTO since the weather was being reported at 1/2 mile visbility and two hundred feet.
According to the observer, the flight was uneventful until the airplane started the ILS to runway 18 at KDTO. The observer reported that the airplane then entered a fog bank, while on the approach. The observer added that he saw the airport lighting system to the left of the airplane, and the airplane began a left turn before it impacted terrain.
During interviews with the observer, he stated that during the approach the commercial pilot called out an altitude, possibly the decision height altitude, at which time the instructor pilot is said to have stated, "Descend a little more." The observer recalled seeing either taxiway light or runway lights to his left and the crew realized that they were not aligned with runway 18. Rather than perform the previously issued missed approach procedures, one of the pilot’s decided to attempt a circle to land on runway 36. The observer said that the airplane climbed during the circling maneuver and then attempted to land on runway 36; the pilots judged that they did not have sufficient runway to land and decided to go missed approach. As the airplane departed towards the north, one of the pilots initiated a turn to the south, and the airplane then impacted terrain. The flight instructor sustained head injuries and did not recall details from the accident flight.
The purpose of the flight was to build flight time for the commercial pilot. Flight school policy required the CFI to be on-board the airplane.
The commercial pilot, age 30, held a commercial pilot certificate with airplane multi-engine land and instrument airplane ratings. In addition, the pilot held a private pilot certificate for airplane single engine land. The pilot’s log book was not made available during the investigation, and the pilot’s complete flight history is not known. On January 28, 2011, the pilot was issued a first class medical certificate without restrictions. The pilot’s sleep and awake times could not be determined.
The CFI, age 22, held an instructor certificate with ratings for airplane single engine land and instrument airplane. In addition, the CFI held a commercial pilot certificate with ratings for airplane single engine land, multi-engine land, and instrument airplane. The CFI’s log book was not made available during the investigation, and the CFI’s complete flight history is not known. On July 13, 2011, the CFI was issued a first class medical certificate without restrictions. The CFI’s sleep and wake times could not be determined.
The single engine, high wing, fixed gear Cessna 172R airplane, serial number 17280452, was manufactured in 1998. It was powered by a 180-horsepower Lycoming IO-360-L2A engine, serial number L-30965-51A, driving a McCauley two-bladed, fixed pitch, metal propeller. The airplane’s last inspection was an annual type that occurred on January 20, 2011, at a total airframe time of 7,904 hours. The airplane’s total airframe time at the time of the accident was 8,833.9 hours.
At 0125, the automated weather observation facility located at DTO reported wind from 150 degrees at 7 knots, 1/2 mile visibility with fog, 200 feet vertical visibility, temperature 10 degrees Celsius (C), dew point 10 C, and a barometric pressure of 29.85 inches of Mercury.
At 0153, the automated weather observation facility located at DTO reported wind from 170 degrees at 7 knots, 3/4 mile visibility with mist, 200 feet vertical visibility, temperature 11 degrees Celsius (C), dew point 11 degrees C, and a barometric pressure of 29.85 inches of Mercury.
A weather review conducted by an NTSB meteorological specialist noted that air sounding conducted in the area indicated the potential for clouds between the surface and 1,300 feet without the potential for icing. In addition, there was a potential for low-level wind shear between the surface and 2,000 feet. Infrared imagery detected a layer of low-clouds and stratus was recorded over the accident area. The height of the clouds tops were estimated at 1,500 feet.
AIDS TO NAVIGATION
A copy of the ILS 18 approach procedure listed minimum weather for the ILS approach as a 200 foot ceiling and 1/2 mile visibility with a decision height of 839 feet mean sea level (msl). The circling weather for their category of airplane was listed as a 600 foot ceiling and 1 mile visibility with a circling altitude of 1,160 feet msl. The inbound course is 177 degrees.
Denton Municipal Airport (KDTO) has a single runway 36/18 that is a 7,002 foot long, 150 foot wide asphalt runway. A control tower is staffed daily from 0600 to 2200. Four instrument approaches service the runway, the most precise approach being the ILS 18.
WRECKAGE AND IMPACT INFORMATION
The accident site was located about 700 yards northwest of runway 18. Tree damage and impact signatures were consistent with the airplane in a left turn. Both wings were torn and broken in multiple places. The left wing sustained more damage than the right wing, with the left wing nearly separated from the fuselage. The left wing, outboard of the flap, was separated from the rest of the wing. Both propeller blades showed leading edge polishing and gouging. One blade was bent rearward about 90 degrees near the mid-span. The cockpit instrumentation was impact damaged. The vertical speed indicator read a 1,800 foot per minute descent. The altimeter was set to 29.82 inches of Mercury. The course deviation indicator was set to an inbound course of about 177. The flaps were set to 10 degrees. Engine continuity and thumb compression was obtained. Both magnetos produced sparks at their individual leads when rotated. The postaccident examination of the airplane and engine did not reveal any preimpact anomalies which would have precluded normal operation.
MEDICAL AND PATHOLOGICAL INFORMATION
An autopsy was performed on the commercial pilot by the Tarrant County Medical Examiner. The cause of death was due to blunt force injuries. Forensic toxicology was performed on specimens from the pilot by the FAA Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma. Toxicology testing was negative for the presence of carbon monoxide, cyanide, ethanol, or drugs.
Search and Rescue
Since the airplane’s instrument flight plan was not closed out as expected, the Dallas/Fort Worth Terminal Radar Approach Control (TRACON) D10 supervisor coordinated with the Denton Police Department (DPD) to search for the airplane at KDTO. About 0300, responding officers encountered a survivor who had extricated himself from the airplane. The survivor relayed that the airplane had crashed with another survivor trapped inside. DPD then requested the assistance from the sheriff, state police, and the Denton Fire Department to search the area for the missing airplane. The D10 supervisor was then advised that a survivor had been located, later relaying that information to the Fort Worth Center operations manager. The D10 Front Line Manager then notified Fort Worth Center and requested that Center issue an Alert Notice (ALNOT) formally declaring the airplane missing. According to the Air Force Rescue Coordination Center (AFRCC) mission log, the ALNOT was received at 0308 and search and rescue procedures were initiated. A member of the DPD, contacted the D10 supervisor on duty via cellphone, and received information from the supervisor that the last known position of the airplane was about 1.25 to 1.5 miles directly north of the airport. First responders then concentrated their search in this area.
At 0343, the AFRCC received a call from the Fort Worth Center operations manager relaying the information that a survivor had been found, and incorrectly advised the AFRCC mission controller that there was no further need for search and rescue. The AFRCC terminated their search activities.
DPD requested helicopter assistance from the Fort Worth police. The helicopter arrived in the area about 0410, and received the last known position of the airplane from D10; so the helicopter began searching 1.5 miles north of the airport. At 0433, D10 provided DPD with a revised location for the airplane, a point southwest of the original last known position. About 0545, a sheriff’s deputy using a smartphone was able to “ping” a cellular telephone belonging to the survivor trapped on the airplane and obtain a latitude/longitude position. The new location information was relayed to the search helicopter, which left the airport at 0546 after refueling. The airplane was located at 0548, and the first ground assistance arrived at 0550. The pilot was deceased, and the remaining survivor remained trapped in the airplane. Additional details on local search and rescue activities following the accident are contained in Denton Police Department dispatch logs incorporated in the docket for this case.
Radar usage to determine the airplane’s last position
D10 used two ASR-9 radar sites located at DFW airport (DFW-E and DFW-W), and two additional ASR-9 sites located at Azle, Texas, and Sachse, Texas. Coverage of the Denton area was best from the DFW-W site, with good coverage also provided by the DFW-E site. While the airplane was on approach to Denton, the controller was using the DFW-E radar site. Post-accident review of radar data showed that the DFW W site provided additional targets not seen by the DFW-E radar. In particular, the DFW-W site detected five targets in the vicinity of the airport, including four targets that tracked toward the crash site. The last DFW-W radar target detected for the airplane was 259 yards from the crash site. None of the data from the DFW-W site was provided to the search teams following the accident.