WPR25LA037

According to the pilot, the purpose of the flight was to conduct a sunrise flight for his passenger. He reported that it was the airplane’s first flight of the morning and after a thorough preflight inspection, engine runup, and departure, he climbed the airplane to about 1,400 above ground level (agl) and completed the level-off checklist. Moments later, the engine began to lose power, and he turned on the carburetor heat and continued the climb. He made a right turn back toward the airport but realized that the airplane’s altitude was insufficient to make it to the runway, and he performed a forced landing to the nearest open area. During the landing roll, the airplane nosed over and came to rest inverted, resulting in substantial damage. A witness, who was a Federal Aviation Administration (FAA) inspector, observed the accident airplane take off on the accident flight. He stated that the engine was running rough, but it was not emitting smoke or vapor. Examination of the airframe and engine revealed no evidence of preimpact malfunctions or anomalies. Residual fuel was found in fuel lines and fuel components in the airframe and engine, and there was evidence of fuel spillage at the accident site. Review of weather information indicated that the conditions at the departure airport were conducive to the development of serious carburetor icing at glide power settings. Based on the lack of mechanical anomalies found during postaccident examination, carburetor ice likely developed while the airplane was operating on the ground at reduced power settings before takeoff, which resulted in the engine roughness during takeoff observed by the witness and the subsequent partial loss of engine power.

On November 14, 2024, about 0704 Pacific standard time, a Cessna 172 airplane, N46028, was substantially damaged when it was involved in an accident near Van Nuys, California. The pilot and passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to the pilot, his intent was to perform a sunrise flight for his passenger. He reported that this was the airplane’s first flight of the day, and that his preflight inspection and engine runup were normal, with minimal drop in rpm during the magneto check, carburetor heat application, and idle power check. The pilot reported that the carburetor heat was off for takeoff, and recalled that the takeoff and initial climb were normal, and about 1,400 ft agl, he completed the cruise checklist. Shortly thereafter, the engine began to sputter and lost partial power. He contacted the tower controller, declared an emergency, pitched for the airplane’s best glide airspeed, and attempted to return to the airport. The pilot reported that he turned on carburetor heat, verified that the fuel selector was in the “both” position, and performed a magneto check. He was unable to restore engine power and realized that he would not be able to make it to the airport. The pilot initiated a forced landing to an open area about 2 nautical miles from the departure runway. During the landing roll, the airplane impacted vegetation and nosed over, resulting in substantial damage to the right wing’s lift strut, the vertical stabilizer, and the rudder. During a subsequent conversation, the pilot reported that the engine was “sputtering” during the initial climb, between 500 ft and 1,000 ft agl. He stated that he turned on the carburetor heat and continued the climb. He subsequently noted a loss of engine rpm between 1,000 and 1,400 ft agl and turned back toward the airport. An FAA inspector was present at the departure airport the morning of the accident and witnessed the takeoff, but not the accident. The inspector reported that the engine was running rough, but it was not emitting smoke or vapor. Around the time of the accident, the temperature was 48°F, the dew point was 32°F, and relative humidity was about 55 percent. According to the Griffith Park Observatory in conjunction with the United States Naval Observatory, the morning of the accident, civil twilight began at 0559 and sunrise occurred at 0626. The carburetor icing probability chart contained in FAA Special Airworthiness Information Bulletin (SAIB) CE-09-35, indicated that the potential for serious icing conditions were present at glide power settings. FAA Advisory Circular (AC) 20-113, “Pilot Precautions and Procedures to be Taken in Preventing Aircraft Reciprocating Engine Induction System and Fuel System Icing Problems,” advises pilots to apply carburetor heat briefly immediately before takeoff, when the relative humidity is above 50 percent and the temperature is below 70°F, particularly withfloat type carburetors, to remove any ice that may have accumulated during taxi and runup. Postaccident examination of the airplane’s engine revealed no evidence of any preimpact mechanical malfunctions or failures that would have precluded normal operation. Valvetrain continuity was observed at each of the cylinders, with equal intake and exhaust valve rocker arm movement in the correct firing order when the propeller was rotated by hand. Thumb compression and suction were observed when the propeller was rotated by hand. Borescope examination of each cylinder revealed normal wear signatures. No signs of obstruction were observed within the induction or the exhaust systems. The left magneto (not equipped with an impulse coupling) produced spark on all leads. Although the right magneto (not equipped with impulse couplings) did not produce spark during the initial examination, it was removed and bench tested, during which it produced spark normally when rotated at sufficient speed. The recovery crew noted little fuel in either fuel tank at the site due to it leaking out while being inverted. Fuel consistent with color and smell of 100LL was present at the fuel selector from both tanks. Fuel was drained from the fuel strainer and tested negative for water. The fuel strainer screen was clean; the bowl showed mild pitting in the bottom and was clear of debris. The carburetor was disassembled, the fuel bowl was clean, and the floats were intact and did not exhibit evidence of leaking. The accelerator pump inlet screen was clean. Air was introduced through the passage from the mixture metering sleeve and the discharge nozzle to verify there were no obstructions or debris. The airplane’s maintenance records indicated that, three days before the accident, the carburetor cable was found broken and was replaced by a mechanic. Examination of the carburetor confirmed that the throttle control linkage remained connected at the control arm and operated throughout its full range of travel. The mixture control was fracture-separated at the carburetor, and the carburetor heat linkage remained attached to the control arm. The primer control was found stowed and locked.