History of Flight
On September 6, 2023, about 1148 central daylight time, a Cessna 150K airplane, N6059G, was substantially damaged during an accident at Huntsville Municipal Airport (UTS) in Huntsville, Texas. The flight instructor and student pilot were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight.
According to ADS-B flight track data, at 1027 the airplane departed from runway 14 at North Houston Regional Airport (CXO), Conroe, Texas. It flew northeast about 6 nautical miles before turning northwest toward UTS. About 1050, the airplane entered the traffic pattern for runway 36 at UTS. It flew six traffic patterns consistent with touch-and-go landings on runway 36, descending below ADS-B coverage about 700 ft mean sea level (msl), or about 337 ft above airport elevation. About 1128, the airplane switched landing direction to use runway 18, flying three additional traffic patterns consistent with touch-and-go landings on runway 18. At 1146:54, the last ADS-B return was recorded about 830 ft msl as the airplane descended on the base leg for runway 18.
Two witnesses reported that the airplane was flying in the airport traffic pattern before the accident. They were on the ramp preparing for an instructional flight when they heard a sudden decrease in engine rpm. They turned and saw the airplane flying south over runway 18, about 500 ft above the runway, in a level pitch attitude with rocking wings. The airplane then entered a left turn toward east in a nose-down attitude. The flight instructor believed that the pilot of the airplane was attempting a descending left 180° turn to land on runway 36. He stated that the airplane completed about 90° of turn when it entered an aerodynamic spin and descended to the ground in a nose-down pitch attitude.
Aircraft Information
The airplane was equipped with a 26-gallon (22.5 gallons usable) fuel system, consisting of two 13-gallon main fuel tanks (11.25 gallons usable each). The two fuel tanks are combined before the fuel shutoff valve.
On December 9, 2022, the flight instructor, who was also the airplane owner, made an entry in the airplane’s discrepancy record that the airplane was using fuel from the left tank “slower” than the right tank. The airframe total time was 8,024.9 hours at the time of the discrepancy. The discrepancy was deferred until the next annual inspection. The entry further noted that the issue could not be duplicated during the annual inspection dated August 15, 2023. The signature on the discrepancy entry was comparable to signatures found in the flight instructor’s pilot logbook.
A postaccident review of the airplane’s maintenance logbooks revealed that the last maintenance of the fuel shutoff valve was completed about 8 years before the accident, on July 20, 2015, at 7,950.7 total airframe hours. The associated airframe logbook entry stated, in part, “Lubed fuel valve and installed new o-ring.”
According to maintenance documentation, about 20 days before the accident, on August 15, 2023, the last annual inspection of the airplane was completed at 8,029 total airframe hours and 2,723.2 hours since the last engine overhaul. A 100-hour inspection was completed on August 23, 2023, after the airplane was painted.
The airplane’s electronic tachometer was destroyed during impact. As such, the airplane’s total airframe and engine times at the time of the accident could not be precisely determined. However, according to an airplane utilization log, the last recorded flight was completed on September 4, 2023, at 8,041.4 hours total airframe time. Based on ADS-B flight track data, the accident flight was about 1.4 hours in duration.
Wreckage and Impact Information
The airplane crashed into an open grass area about 407 ft south of the end of runway 18 at UTS and about 40 ft east of the extended runway centerline. The airplane came to rest upright and nose down on a west heading. All structural components and flight control surfaces were located at the accident site. The left and right wings and their wing struts remained attached. The leading edge of both wings were crushed aft to their respective main spars. The tail was canted forward and to the right beginning about 3 ft aft of the rear cabin window. The empennage was relatively undamaged.
The elevators, ailerons, rudder, trim tabs, and flaps were accounted for. Continuity of flight control cables was confirmed from the cockpit to the surfaces. The left and right flaps were found fully retracted, consistent with a flap handle in the UP position. The wreckage examination did not reveal any preimpact flight control anomalies.
Fuel system examination revealed debris obstructing the fuel shutoff valve inlet and outlet ports, as well as debris in the fuel lines and tanks. The NTSB Materials Laboratory identified the debris as mostly silicon, iron, and lead, consistent with soil and leaded fuel contact. The engine examination found no preexisting mechanical malfunction or failure. The carburetor contained about 1 fluid ounce of uncontaminated fuel with no sediment.
Medical and Pathological Information
The Fort Bend County Medical Examiner's Office performed autopsies on both occupants. The cause of death for both was blunt force injuries, manner of death accident. FAA toxicological testing on the flight instructor detected no carboxyhemoglobin, ethanol, glucose, or tested-for drugs. For the student pilot, testing detected cetirizine (24 ng/mL in cavity blood, 631 ng/mL in urine) and metoprolol (detected in cavity blood and urine). Cetirizine is an antihistamine with potential sedative effects; the FAA advises a 48-hour wait before flying. Metoprolol is a beta-blocker not generally considered impairing. The student pilot's mother reported he had been diagnosed with hypertension and began medication weeks before the accident.