Incident Overview
While towing a banner at an altitude of 1,300 feet, the aircraft's engine began to experience severe vibrations and a loss of power. The pilot identified a suitable field for dropping the banner and descended to 500 feet to perform the release. Following the drop, the airplane was unable to climb, and the vibrations intensified. The pilot decided to execute a forced landing in the field while retaining control of the aircraft.
Landing and Accident
During the approach, the pilot needed to clear trees and reported coming in "a little high and fast." After touching down on a grassy field, he applied the toe brakes, and the airplane nosed over. The extent of damage to the aircraft was not specified.
Post-Flight Examination
A post-flight inspection of the engine revealed that the number 3 cylinder was cracked and its exhaust valve had seized. Further examination showed a continuous fracture around the cylinder head, located near the fourth and fifth cooling fins. The fracture surface exhibited characteristics consistent with fatigue cracking. The cylinder barrel had been remanufactured and joined to a new cylinder head. Threads 1, 2, and 3 of the cylinder barrel displayed protruding material that corresponded with matching indentations in the cylinder head. No evidence of material defects or dimensional anomalies from the manufacturing process was found. Additionally, there was no evidence indicating the specific nature or extent of possible forces that initiated the crack.
Service History
According to logbook records, the cylinder was installed in 1999 and had accumulated approximately 635 hours of service at the time of the incident.
Related Investigations
Two other accident investigations involving similar issues are referenced: CHI01FA329 and NYC02FA178.