Accident Details
On March 18, 2008, at approximately 1055 mountain standard time, a Cessna 150L (registration N19521) collided with trees during a forced landing in Mesa, Arizona. The airplane was operated by Arizona Aviation under 14 Code of Federal Regulations Part 91. The certified flight instructor (CFI) and the student pilot sustained minor injuries. The airplane sustained substantial damage to both wings and the fuselage. The local instructional flight had departed Mesa about 1040. Visual meteorological conditions prevailed, and no flight plan was filed.
Flight Sequence
The CFI reported that the taxi, run-up, and first two takeoffs and landings in the local traffic pattern were uneventful. On the third takeoff, as the airplane climbed to approximately 75 feet above ground level, the engine sputtered. The CFI took control from the student, pulled the carburetor heat handle to the hot position, and set the mixture selector to full rich. The airplane was slightly above 100 feet but did not produce enough power to maintain flight. During the descent for an off-airport landing onto a street, a wing struck trees. The airplane spun around upon hitting the ground.
Post-Accident Examination
On April 1, 2008, a representative from Teledyne Continental Motors (TCM) examined the engine components under Federal Aviation Administration (FAA) supervision. The components had been transported to Air Transport in Phoenix, Arizona, for storage and testing. Recovery personnel had removed the wings to transport the wreckage, noting that the nose gear had collapsed and the front of the engine rested on the ground.
Investigators observed that the bottom of the fuselage and horizontal stabilizer were stained with a substance similar in color, odor, and consistency to oil. The propeller exhibited leading-edge damage and aft bending near the tips; the spinner had impact damage with longitudinal striations on a flattened area.
The engine and accessories were intact, but the induction system had impact damage. The crankcase split line contained a rubber-like material. Spark plugs appeared normal with dark sooty deposits when compared to the Champion Aviation Check-A-Plug Comparison Chart. A borescope inspection revealed deposits on piston tops, cylinder heads, and valves; the engine manufacturer representative considered the deposit amount above normal for the low time since last overhaul.
The TCM investigator replaced the damaged propeller for an engine run. A fuel container was attached to the left wing fuel line. The mixture control bottomed out before reaching the full idle stop. The air filter was removed, and the throttle cable had to be straightened for normal actuation.
During the engine run, no anomalies were noted at different power ranges. A magneto check revealed rough operation on the left magneto. After shutdown, all four cylinders showed temperatures consistent with normal operation. A second run with only the left magneto active was performed; after shutdown, the number one cylinder was cold compared to others. Ignition leads produced sparks when the propeller was rotated by hand, but the number one bottom spark plug (connected to the left magneto) did not spark. That spark plug was dark and coated with oil.
A compression test by an FAA inspector revealed air heard within the crankcase while pressure was applied to the number four cylinder. After removal, the number four cylinder compression ring gaps were aligned on the piston. Several cylinder base studs were found to be the improper size. According to engine manufacturer representatives, the engine had a total time of 10,547.9 hours, with 284.7 hours since the last major overhaul.