Accident Summary
On September 12, 2009, about 1230 Pacific daylight time, a Grumman AA-1B, registration N9682L, nosed over during an attempted emergency landing soon after takeoff from Hobby Field in Creswell, Oregon. The private pilot and his passenger received minor injuries, and the airplane sustained substantial damage. The flight was operating under Title 14 Code of Federal Regulations Part 91 for personal transportation in visual meteorological conditions. No flight plan had been filed.
Pilot's Account
According to the pilot, soon after taking off from runway 33, the engine experienced a partial loss of power. The pilot was able to climb to about 300 feet above ground level but could not climb higher. He switched fuel tanks, tried carburetor heat, and turned on the electric fuel pump, but none of those actions helped, and the airplane began to lose altitude. He then tried switching to the right magneto alone, and then to the left magneto alone. While on the right magneto only, the engine appeared to "stumble badly" and seemed to be trying to kick back. When he switched to the left magneto only, the engine smoothed out, but there was insufficient power to maintain altitude, and the airplane continued to descend. Approaching some trees that he did not feel he would clear, the pilot made a forced landing in a rough open field. Although the touchdown was uneventful, during the landing roll the pilot realized he was heading toward a manufactured home and did not think he could stop before impacting it. He pushed full forward on the control wheel and applied hard braking, causing the nose wheel to dig into the rough terrain, and the airplane nosed over onto its back.
Post-Accident Inspection
After the accident, a Federal Aviation Administration Airworthiness Inspector supervised an inspection of the engine and fuel delivery system. Both magnetos and their wiring harnesses were removed for testing and teardown inspection. The carburetor was removed, disassembled, and inspected, revealing no anomalies or issues with the float, float valve, or accelerator pump, and no signs of contamination in the carburetor bowl or intake finger screen.
Inspection of the magneto/spark plug system showed spark plugs with normal wear patterns and no sign of shorting or contamination, except the spark plugs in the number one cylinder were oil soaked due to the engine's inverted position. The magnetos were correctly set at 25 degrees before top dead center and securely fastened. The ignition switch operated correctly, and the "P" leads were in good condition and securely fastened.
The magnetos and wiring harnesses were taken to FlightCraft Portland, where, after replacement of wire leads damaged during the accident, each magneto was run on a test bench and fired on all four cylinder positions. Each magneto was then disassembled and inspected. The left magneto internal condition was rated "good" with no defects, and all components tested within serviceable limits. The right magneto was rated in "fair" condition. During testing, the secondary coil windings failed serviceable limits tests. According to the Slick Magneto Manual, the serviceable resistance limit is 13,000 to 20,500 ohms; the right magneto secondary coil windings tested at 81,000 ohms in an air-conditioned facility. The technician noted that under high temperature conditions, resistance could be expected to become further out of serviceable limits. The pilot reported the ambient temperature at takeoff was 82 degrees Fahrenheit.
No other anomalies or evidence of malfunctions that would have contributed to a loss of power were found.