History of Flight
On April 18, 2010, at approximately 1010 eastern daylight time, a Cessna 152, registration N5499B, was substantially damaged during a forced landing near Avon Park, Florida, after a loss of engine power. The 18-year-old certificated private pilot and a passenger were not injured. The flight was conducted under 14 CFR Part 91 in visual meteorological conditions; no flight plan was filed.
The pilot regularly rented the airplane from Bobby’s Landing at North Perry Airport (HWO), Hollywood, Florida. About one week before the accident, he flew the airplane from HWO to Flagler County Airport (XFL). While refueling at XFL, he observed fuel leaking from the carburetor. He contacted a mechanic from the rental FBO, who stated the leak was a “float problem” and that the pilot could stop it by knocking on the carburetor with a screwdriver. The pilot did so, and the leak stopped. On the return flight to HWO, the pilot experienced a temporary rpm decrease of about 500 rpm lasting about 2 seconds. After landing, he reported the problem to the chief mechanic.
The airplane was not flown again until the day before the accident. The pilot and his younger brother (who was not a pilot) planned to travel to Lakeland Linder Regional Airport (LAL) for an overnight aviation convention. Before departure, the pilot asked the FBO mechanic if the carburetor had been fixed. The mechanic said no maintenance was conducted but assured the pilot the airplane was “fine.” After a preflight inspection, the pilot and passenger departed HWO about 0730, made a fuel stop at Bartow Municipal Airport (BOW), and continued uneventfully to LAL, where they spent the night camping with the airplane.
The next morning, the pilot obtained a telephone weather briefing and decided to depart earlier than planned. He performed a preflight inspection, verifying no water or contamination in the fuel. The airplane departed LAL about 1000. The pilot turned on course for HWO but, due to unfavorable winds at higher altitudes, cruised at 2,000 feet above mean sea level (msl). He set power to 2,500 rpm and leaned the mixture. Initially, engine performance was “perfect.”
While in cruise, the pilot established communications with air traffic control (ATC) for flight following. About 20 to 40 minutes after takeoff, engine rpm suddenly decreased below 2,000 rpm. The pilot moved the mixture to full rich, applied carburetor heat slowly, and checked ignition and other controls. The rpm continued to drop; about 30 seconds later, the propeller appeared to be windmilling. He established best glide speed of 65 knots and turned toward Avon Park Executive Airport (AVO), about 7 miles southeast, using a handheld GPS.
The pilot informed ATC of engine problems and his diversion to AVO. At about 1,000 feet altitude, the propeller stopped completely. He executed the engine failure checklist and attempted several restarts without success. Realizing he would not reach AVO, he decided to land on a dirt road and informed ATC. At about 500 feet above ground level (agl), he noticed powerlines near the landing site and maneuvered to avoid them. At about 100 feet agl, he saw another set of powerlines directly ahead and increased pitch to clear them, causing a speed decay and activating the stall warning horn. After clearing the powerlines, he pushed the nose down to regain airspeed, but the airplane landed “hard” on the road shoulder. Both occupants were uninjured. The pilot used the radio to inform ATC of a safe landing. Upon exiting, the pilot saw left wing damage; he walked back and realized the left wing had struck a fence post. Law enforcement arrived about 1049.
Personnel Information
Federal Aviation Administration (FAA) records and pilot testimony showed the pilot held a private pilot certificate with an airplane single-engine land rating. He had about 190 total hours of flight experience, all in single-engine airplanes, with 50 hours in the accident make and model. His 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 first registered to the FBO in April 2008. Just before purchase, the engine was replaced with the accident engine on March 25, 2008. The airplane had a four-cylinder, normally aspirated engine and a fixed-pitch propeller. Total fuel capacity was 26 gallons in two equal-size tanks. At the time of the accident, the tachometer read 252.4 hours and the hour meter read 2,279.0 hours. The most recent carburetor maintenance was on May 22, 2009, when the carburetor was drained, and the screen was removed, inspected, cleaned, and reinstalled. The engine was also cleaned and run for operational checks.
Meteorological Information
The 0951 weather observation at BOW, 25 miles northwest of the accident site, reported wind from 060 degrees at 4 knots, visibility 10 miles, scattered clouds at 5,500 feet, broken clouds at 8,500 feet, temperature 21°C, dew point 18°C, and altimeter 29.94 inches of mercury. Ground-based temperature and dew point about 15 minutes before the accident, at an airport 25 nautical miles away, indicated relative humidity around 60 percent. On a carburetor icing chart, the intersection of those values fell in the region labeled “Serious Icing (Glide Power).”
Wreckage and Impact Information
The FAA inspector reported the accident site was about 5 miles west-northwest of AVO. Both wings were dented and torn; the left aileron was partially detached. The rear window was fractured, and some airframe pieces had separated. The nose landing gear was folded underneath; the propeller was undamaged. The airplane appeared to have slid about 100 feet after the nose gear collapsed, coming to rest in a ditch. The inspector verified sufficient fuel remained in both tanks, with no apparent contamination, and the fuel selector valve was positioned correctly. The fuel selector placard was not installed. The airplane was recovered to HWO for further examination.
Tests and Research
A post-accident engine examination and test run were conducted four days later by an FAA inspector. Engine oil was uncontaminated and adequate. An external fuel tank was jury-rigged to the carburetor inlet flange; the engine started and ran at various rpm settings with no anomalies. Fuel was placed in the fuel lines from the wing roots, and the fuel selector was rotated; fuel flowed normally.
The carburetor was removed and examined at an AvStar Fuel Systems facility by AvStar and NTSB personnel. When fuel was introduced to the carburetor inlet on a test bench, immediate flooding and leaking from the venturi occurred, consistent with the float valve not fully closing. The throttle lever was worn with excessive side-to-side free play. The mixture control arm shaft was installed with two washers; the manufacturer’s information did not specify washers. Disassembly revealed the metal float assembly was slightly twisted, causing misalignment: one float above its design position, one below. The retainer cup in the idle mixture screen was installed backwards. Debris, rust, and corrosion were found within the carburetor bowl. Some debris floated in fuel, some sank. No fuel was found in the floats, and they were determined to be leak-free.