History of Flight
On March 26, 2014, at 1743 local time, a Cessna 172P, registration N9551L, landed in a field following a loss of engine power near Inarajan, Guam. The airplane was registered to Trend Vector Aviation International and operated under 14 CFR Part 91 as an introductory flight lesson. The flight instructor (CFI) and two passengers were not injured. The airplane sustained substantial damage to the forward fuselage and left wing. The flight departed Guam International Airport, Barrigada, Guam, about 1725. Visual meteorological conditions prevailed, and no flight plan had been filed.
The CFI reported that after takeoff, he initiated a left turn and, upon reaching 1,500 feet mean sea level (msl), began a turn southwest toward Apra Harbor. He continued the flight while maintaining about 1,500 feet msl, an airspeed of 95–100 knots indicated, and engine speed of 2,300 rpm. About 20 minutes after takeoff, engine speed began to decrease. He confirmed the mixture control was full rich, then applied full forward throttle. Engine speed increased momentarily but then decreased, producing only partial power. He applied full carburetor heat, but the engine did not respond.
The airplane could not maintain altitude, so the pilot initiated an approach to a landfill for a forced landing. Approaching the landing area, he saw heavy equipment on the intended landing zone and turned toward a tall-grass field for a tailwind landing. He stated that during final approach, the engine was no longer producing power and the propeller appeared windmilling. The airplane came to rest nose-down after the nose gear dug into the ground.
Aircraft Information
Maintenance records revealed that the airplane underwent an annual inspection completed on January 30, 2014. At that time, the airframe had accrued 18,766.1 flight hours since manufacture in 1986, and the engine had accrued 2,360 hours since overhaul. The airplane flew 90 hours between the annual inspection and the accident.
Meteorological Information
The closest aviation weather observation station was Guam International Airport, 14 miles north-northwest of the accident site. An aviation routine weather report recorded at 1754 reported: wind from 070 degrees at 13 knots gusting to 20 knots; visibility 10 miles with clear skies; temperature 28°C; dew point 23°C; altimeter 29.91 inches of mercury.
Additional Information
According to the Cessna 172 service manual, fuel tank venting is accomplished by an overboard vent line in the left fuel tank, protruding through the bottom of the left wing. A vent crossover line connects the left tank airspace to the right tank airspace, where a vented fuel tank cap is installed.
The Cessna 172P Pilot's Operating Handbook, "EMERGENCY PROCEDURES, Rough Engine Operation or Loss of Power, Carburetor Icing" section states: "A gradual loss of engine RPM and eventual engine roughness may result from the formation of carburetor ice. To clear the ice, apply full throttle and pull the carburetor heat knob full out until the engine runs smoothly; then remove carburetor heat and readjust the throttle. If conditions require the continued use of carburetor heat in cruise flight, use the minimum amount of heat necessary to prevent ice from forming and lean the mixture for smoothest engine operation."
The carburetor icing probability chart from FAA Special Airworthiness Information Bulletin CE-09-35, June 30, 2009, shows a probability of serious icing at glide power given the reported temperature and dew point.
Tests and Research
The airplane was examined by a local mechanic, who reported each fuel tank contained about 12 gallons of fuel, with no fuel or oil leaks. Oil was present in the sump, free of contamination or metal particles. The carburetor bowl was full of fuel; spark plugs exhibited normal operation signatures; both magnetos were intact with correct engine timing; cylinder compressions were about 64/80; engine controls were intact with the carburetor heat control in the full forward (off) position. The examination revealed no anomalies that would have precluded normal operation.
A mechanic from Trend Vector Aviation subsequently examined the airplane and reported that the left wing fuel tank vent line allowed air passage but appeared to offer greater resistance compared to other Cessna 172 airplanes in their fleet.
According to representatives from Trend Vector Aviation, the airplane was refueled on the morning of the accident and subsequently performed an uneventful flight. Another Cessna 172 refueled from the same pump flew all day without problems. After the accident, the fuel storage facility was checked for possible contamination, none was found.