Accident Details
On December 5, 2014, at about 1110 eastern standard time, a Cessna 150J airplane (registration N50709) was substantially damaged after colliding with terrain near Brookline Airport (NH16), Brookline, New Hampshire. The student pilot, who was on a solo cross-country instructional flight, received minor injuries. Visual meteorological conditions prevailed, and no flight plan was filed.
The flight originated from Lawrence Municipal Airport (LWM), Lawrence, Massachusetts, at approximately 1000, with a destination of Dillant-Hopkins Airport (EEN), Keene, New Hampshire. The pilot reported departing with about 20 gallons of 100LL fuel. The engine was preheated for about 20 minutes before departure, and a run-up performed according to the checklist showed no anomalies; each magneto dropped about 100–200 rpm from a run-up reading of 2200 rpm.
While cruising at 2,500 feet mean sea level with VFR flight following to remain under a cloud ceiling, the pilot noticed lower ceilings than anticipated about 30 minutes into the flight and decided to return to LWM. Two minutes after turning around, engine rpm declined below 2000 rpm. The pilot applied carburetor heat and noted abnormal resistance but did not observe a change in engine power. He reported a "system malfunction" to air traffic control and navigated toward NH16. The pilot attempted to restart the engine three times while it was still producing power. As the airplane lost engine rpm during approach to runway 01, the pilot decided to land in a small field to avoid stalling. During landing, the airplane "clipped the wire" and impacted the ground, damaging the right wing and firewall.
Post-Accident Examination
The wreckage came to rest about half a mile southeast of the approach end of runway 01 in a field adjacent to a road, in a slight nose-down attitude on a heading of about 075 degrees magnetic. The FAA inspector estimated about 10 gallons of fuel remained in the wing tanks. The outboard section of the right wing leading edge showed impact damage with traces of dirt. The nose landing gear was found about 25 feet from the main wreckage between two parallel landing gear marks. One propeller blade was bent forward slightly, the other slightly aft.
The airplane was moved to a hangar for examination. Crankshaft and valvetrain continuity were established, and all cylinders operated normally. Thumb compression was confirmed on all cylinders. Spark plugs were oil-soaked at the bottom and had lead deposits on top. The carburetor was disassembled; fuel was present in the bowl, and the accelerator pump operated without anomalies. The carburetor float showed no anomalies. The carburetor heat cable had excessive length creating an "S" turn at the engine truss, but it could be manipulated to operate the carburetor heat door. The right magneto produced a spark on all towers when rotated; the left magneto produced a small spark. Disassembly of the left magneto revealed severe cam wear and burnt points. The carbon brush and rotor assembly also exhibited wear.
Maintenance History
The airplane was a 1968 single-engine all-metal design equipped with a Continental Motors O-200-A, 100 horsepower engine. Its most recent 100-hour inspection was completed on August 10, 2014, when the engine had 1,395 hours since major overhaul. The Slick 4301 magnetos had not been overhauled or inspected since the engine's most recent overhaul on April 16, 1998. According to the magneto manufacturer, a single magneto failure would not have prevented the engine from producing power.
Weather Conditions
The 1051 weather observation at Boire Field (ASH), Nashua, New Hampshire, about 9 miles east of the accident site, reported scattered clouds at 2,800 feet, calm wind, temperature -1°C, dew point -8°C, and an altimeter setting of 30.65 inches of mercury. The carburetor icing probability chart from the FAA Special Airworthiness Information Bulletin (SAIB): CE-09-35 showed a probability of light icing at cruise or descent power given these conditions.