Avon Park, FL, USA
N5499B
CESSNA 152
About one week prior to the accident, the pilot noticed fuel leaking from the accident airplane’s carburetor. He informed a mechanic responsible for the airplane, who assured him that the airplane was fine and that the leak could be stopped by knocking a screwdriver against the carburetor. The pilot did as instructed, and the leak stopped. The day before the accident, the pilot asked the mechanic whether any maintenance was conducted on the carburetor, and the mechanic informed him that no maintenance was conducted, because it was not necessary. The pilot then rented the airplane from the operator and conducted an uneventful flight to his destination. The next day, during the cruise portion of the return flight, the engine rpm suddenly decreased below 2,000 rpm. The pilot manipulated the mixture and carburetor heat controls, and verified that the ignition switch and master switches were appropriately set. The rpm continued to decrease, and about 30 seconds after the onset of the rpm drop, the engine stopped producing power. The pilot initiated a forced landing on a road, and the airplane was substantially damaged when the left wing struck a fence post. Meteorological conditions recorded about 25 miles from the accident location indicated the conditions were conducive to carburetor icing with the engine at glide power, but not at cruise power. On-scene examination of the airplane revealed that sufficient, uncontaminated fuel was available, and that the fuel selector valve was properly set. The engine was test run on the airplane, at various rpm settings, with no anomalies noted. The carburetor was removed and further examined. When fuel was introduced via the fuel inlet, the carburetor immediately started flooding and leaking from the venturi, which was consistent with an open float valve. Further examination and teardown revealed multiple anomalies, including internal contamination and corrosion, excessive wear, incorrect parts, incorrectly installed parts, and a damaged float assembly. Some of the internal contaminants floated, and some sank in the fuel, which allowed for the possibility that the contaminants could prevent full closure of the float valve. The excessive wear and twisted float assembly could also prevent proper float operation. Improper float valve or float operation could result in either intermittent abnormal engine operation or a complete loss of power.
HISTORY OF FLIGHT On April 18, 2010, about 1010 eastern daylight time, a Cessna 152, N5499B, was substantially damaged during a forced landing near Avon Park, Florida, following a loss of engine power. The 18 year-old certificated private pilot and passenger were not injured. The flight was operated under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight. According to the pilot, he regularly rented the airplane from Bobby’s Landing, a fixed base operator (FBO) at North Perry Airport (HWO), Hollywood, Florida. About one week prior to the accident, he flew the accident airplane from HWO to Flagler County airport (XFL). While refueling the airplane at XFL, he observed fuel leaking from the carburetor. He contacted an airframe and powerplant mechanic from the rental FBO; the mechanic informed him that the leak was a “float problem,” and that the pilot could stop the leak by knocking on the carburetor with a screwdriver. The pilot did as instructed, and the leak stopped. He flew the airplane back to HWO uneventfully, except for a temporary rpm decrease of about 500 rpm, which lasted about 2 seconds. After he returned to HWO, the pilot reported the problem to the chief mechanic at the FBO. The airplane was not flown again until the day before the accident, when the pilot and his younger brother, who was not a pilot, planned to use the airplane to travel to Lakeland Linder Regional Airport (LAL), Lakeland, FL for an overnight stay at an aviation convention. Before the flight, the pilot again spoke with the FBO mechanic, and asked if the carburetor had been fixed. The mechanic stated that no maintenance was conducted, and assured the pilot that the airplane was “fine.” The pilot conducted a preflight inspection of the airplane, and he and the passenger departed HWO about 0730. The pilot made a fuel stop at Bartow Municipal Airport (BOW), Bartow, Florida, and then continued uneventfully to LAL. As planned, the pilot and passenger spent the night at LAL, and camped with the airplane. The next day, the pilot's original plan was to conduct the return flight to HWO in the afternoon. However, after he obtained a telephone weather briefing for the return flight, he decided to depart LAL in the morning. He performed a preflight inspection of the airplane, and verified that there was no water or other contamination in the fuel. The pilot and the passenger departed LAL in the airplane about 1000. The pilot turned on course for HWO, but due to unfavorable winds at higher altitudes, he decided to cruise at an altitude of 2,000 feet above mean sea level (msl). Once at cruise altitude, the pilot set the power to 2,500 rpm, and leaned the mixture accordingly. The pilot stated that initially, the airplane and engine performance was "perfect." While in cruise flight, the pilot established communications with air traffic control (ATC) for flight following services. About "20 to 40" minutes after takeoff from LAL, the engine rpm suddenly decreased to a value below 2,000 rpm. The pilot positioned the mixture control to full rich, applied carburetor heat "slowly," and verified that the ignition, master switch and other controls were appropriately set. The rpm continued to decrease, and about 30 seconds after the onset of the rpm drop, the pilot observed that the propeller appeared to be windmilling. He established the airplane at a "best glide speed of 65 knots," and, based on information from his handheld global positioning system unit, he turned towards Avon Park Executive Airport (AVO), Avon Park, Florida, which was approximately 7 miles to the southeast. The pilot informed ATC that he was having engine problems, and that he was diverting to AVO for a precautionary landing. When the airplane was at an altitude of about 1,000 feet, the propeller stopped completely. The pilot executed the "Engine Failure in Flight" checklist, and conducted several unsuccessful engine re-start attempts. He realized that he would not reach AVO, decided to land on a dirt road, and informed ATC of his intentions. When the airplane was about 500 feet above ground level (agl), the pilot noticed some powerlines near the selected landing site, and maneuvered to avoid them, still with the intention of landing on the road. When the airplane was about 100 feet agl, the pilot noticed a second set of powerlines directly ahead of him, and he increased the airplane pitch attitude enough to climb and avoid the powerlines. The climb resulted in a speed decay, and the stall warning horn sounded. After the airplane cleared the powerlines, the pilot pushed the nose down to gain airspeed, but the airplane landed "hard" on the shoulder of the road. The airplane came to a stop, and the two occupants were uninjured. The pilot used the airplane radio to contact ATC, and inform them that he was safely on the ground. The pilot and passenger exited the airplane, and the pilot noticed that the left wing was damaged, but it was not immediately clear to him why the wing was damaged. He walked back along the rollout path, and realized that the left wing had struck a fence post. Law enforcement personnel arrived at the site at approximately 1049. PERSONNEL INFORMATION Federal Aviation Administration (FAA) records and pilot testimony indicated that the pilot held a private pilot certificate, with an airplane single engine land rating. He had accumulated approximately 190 total hours of flight experience, all of which were in single-engine airplanes, and 50 of which were in the accident airplane make and model. The pilot's most recent FAA third-class medical certificate was issued in November 2008. AIRCRAFT INFORMATION According to FAA records, the airplane was manufactured in 1979, and was first registered to the FBO in April 2008. Just prior to the purchase, the airplane’s engine was replaced with the accident engine on March 25, 2008. The airplane was equipped with a four-cylinder, normally aspirated engine, and a fixed-pitch propeller. It had a total fuel capacity of 26 gallons, which was stored in two equal-size tanks. At the time of the accident, the tachometer registered 252.4 hours, and the hour meter registered 2,279.0 hours. The airplane’s most recent carburetor maintenance was conducted on May 22, 2009, the carburetor was drained and the screen was removed, inspected, cleaned and reinstalled. In addition to the carburetor inspection, the engine was cleaned and it was run on the ground for operational, temperature, and pressure checks. METEOROLOGICAL INFORMATION The 0951 recorded weather observation at BOW, located 25 miles northwest of the accident site, included wind from 060 degrees at 4 knots, visibility 10 miles, scattered clouds at 5,500 feet, a broken cloud layer at 8,500 feet, temperature 21 degrees C, dew point 18 degrees C, and an altimeter setting of 29.94 inches of mercury. Ground-based temperature and dew point values obtained about 15 minutes prior to the accident, at an airport about 25 nautical miles from the accident location, indicated that the relative humidity was approximately 60 percent. When the intersection of the two temperature values was located on a chart that depicted carburetor icing envelopes, the point was in the region labeled "Serious Icing (Glide Power)." WRECKAGE AND IMPACT INFORMATION According to the FAA inspector who responded to the event, the accident site was located approximately 5 miles west-northwest of AVO. The left and right wings were dented and torn, and the left aileron was partially detached from the wing. The rear window was fractured, and some airframe pieces had separated from the fuselage. The nose landing gear was folded underneath the airplane, but the propeller was undamaged. The inspector stated that the airplane appeared to have slid about 100 feet after the nose gear collapsed, and came to rest in a ditch. The inspector verified that sufficient fuel, which did not appear to be contaminated, remained in the two fuel tanks, and that the fuel selector valve was properly positioned to provide fuel to the engine. The inspector further stated that the fuel selector placard was not installed on the airplane. The airplane was recovered to HWO, and retained for further examination. TESTS AND RESEARCH A post accident engine examination and test run were conducted by an FAA Inspector four days after the accident. The engine oil was examined and found to be uncontaminated and in adequate supply. In order to facilitate an engine run, an external fuel tank was jury-rigged with a hose to the carburetor inlet flange. The engine was started and run at various rpm settings with no anomalies noted. Fuel was then placed in the fuel lines starting at the wing roots and the fuel selector was rotated; fuel flowed through the system without any anomalies noted. The carburetor was removed from the engine, and examined at an AvStar Fuel Systems facility (which designs, manufactures and overhauls carburetors) by AvStar and NTSB personnel. The carburetor was visually placed on a test bench and fuel was introduced into the carburetor fuel inlet; the carburetor immediately started flooding and leaking from the venturi, which was consistent with the float valve not being fully closed. The carburetor was removed from the bench for further examination. The throttle lever was found to be worn and exhibited excessive side-to-side free play. The mixture control arm shaft was installed with two washers; the carburetor manufacturer’s information did not specify that any washers were to be used. When the carburetor was disassembled, the metal float assembly was found to be slightly twisted, which caused the two floats to not be aligned properly relative to their design locations or each other; one float was above its design position, and one was below. The retainer cup in the idle mixture screen was installed backwards. Debris, rust and corrosion were found within the carburetor bowl. The debris was removed from the carburetor bowl and placed in fuel; some debris floated, while some debris sank. No fuel was observed in the floats, and the floats were determined to be free of leaks.
The operator's failure to correct known deficiencies with the carburetor, which resulted in a complete loss of engine power and subsequent forced landing by the pilot. Also causal was the operator's decision to rent the airplane in an unairworthy condition.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
