Accident Overview
On October 27, 2018, at about 0915 central daylight time, a Cessna 172 G airplane, registration N3973L, impacted a creek near Houston, Texas, during a forced landing following a loss of engine power. The commercial pilot and two passengers were uninjured. The airplane sustained substantial wing damage during the forced landing. The aircraft was registered to IFR Flyers LLC and operated by the pilot as a personal flight under Title 14 Code of Federal Regulations Part 91. Day visual meteorological conditions prevailed, and the flight was not operated on a flight plan. The local flight originated from West Houston Airport (IWS).
Flight and Pilot Actions
According to the pilot's accident report, the purpose was an orientation flight for two Young Eagles passengers. After departing runway 15, the pilot followed Interstate 10 to highway 99, then flew north about 5 miles. He then flew east and entered a final for runway 15. On short final, the pilot added power, but the engine did not respond. He checked the fuel valve and mixture, engaged the starter, but the engine did not respond. He stated, "I saw the aircraft was headed directly to the concrete revetment on the south bank of Bear Creek. I banked the aircraft left, striking the water nose down and with a left bank."
Wreckage Examination
A recovery company representative forwarded pictures of the airplane; the fuel selector was positioned on both, and the throttle, mixture, and carburetor heat controls were in their forward positions. A National Transportation Safety Board investigator and a technical representative from the engine manufacturer examined the wreckage at a salvage yard, where it had been for several weeks. The engine oil dipstick was removed, and water flowed from the tube. A visual inspection found no obvious abnormalities other than water submersion. The engine was not free to rotate initially, but after removing water from the cylinders, it rotated freely, and magneto impulse coupling sounds were noted. The engine oil drained from the sump appeared to be a mixture of oil and water. The spark plugs were wet with water. A thumb compression test showed suction and compression on each cylinder, and borescope inspection revealed no preimpact abnormalities. Both magnetos and the carburetor were removed; the magnetos produced spark when rotated by an impact driver. The carburetor finger screen was not contaminated, but the carburetor bowl contained a dirty-brown liquid that tested positive for water with water-detecting paste. A small amount of liquid consistent with aviation fuel was present in the accelerator pump section. No preimpact mechanical anomalies were found during the engine examination.
Weather Conditions
At 0915, weather at Houston Executive Airport was: wind calm, visibility 10 statute miles, sky clear, temperature 18°C, dew point 16°C, altimeter 30.10 inches of mercury. At 0853, weather at David Wayne Hooks Memorial Airport was: wind calm, visibility 9 statute miles, sky clear, temperature 15°C, dew point 15°C, altimeter 30.08 inches of mercury. At 0853, weather at Sugar Land Regional Airport was: wind calm, visibility 10 statute miles, sky clear, temperature 16°C, dew point 14°C, altimeter 30.08 inches of mercury.
Carburetor Icing Potential
The recorded temperature and dew point data near the time of the power loss were plotted on a carburetor icing chart. The charted data showed that weather in the area was conducive to serious icing at any power to moderate icing at cruise power/serious icing at descent power. The Pilot's Handbook of Aeronautical Knowledge notes that when conditions are conducive to carburetor icing, periodic checks should be made and full carburetor heat applied if detected.