WPR24LA198

The pilot was departing in the experimental, amateur-built airplane to accumulate hours under its Phase I flight testing. He reported that, during the initial climb, about 100 ft above the ground, the engine started running rough. He attempted to troubleshoot the problem and elected to turn toward an adjacent taxiway. During the turn, the left wing dipped. He corrected the bank, but the left wing dipped a second time, and the nose dropped. The airplane impacted the ground, substantially damaging the right wing, right horizontal stabilizer, and the fuselage. The pilot stated that he shut the engine down before he egressed the airplane. Postaccident examination of the airframe and engine revealed dirt located in the air intake and the carburetor air inlet, likely as a result of impact. Each of the spark plugs were carbon fouled. Further examination found that the No. 1 cylinder compression was low. The No. 1 cylinder valve cover was removed, and the exhaust valve adjustment screw jam nut was found loose inside the valve cover and the rocker arm had excessive movement. The cylinder was removed; the oil control ring on the piston was stuck in the piston groove and there were rub marks on the piston and cylinder walls. No additional anomalies were noted with the airframe or engine. The loose exhaust valve adjustment screw jam nut likely caused the exhaust valve to stop operating properly, which resulted in a loss of compression to the No. 1 cylinder. The stuck oil control ring and rub marks in the cylinder likely resulted from the inoperable exhaust valve. The engine was overhauled about three years before the accident and at the time of the accident, had accumulated 31 hours of operation since overhaul. The exhaust valve lash adjustment screw jam nut was likely not secured properly by maintenance personnel during the overhaul. The accident is consistent with the pilot’s exceedance of the airplane’s critical angle of attack while maneuvering for landing following a partial loss of engine power, which resulted in an aerodynamic stall and loss of control. The loss of engine power likely resulted from an improperly secured lash adjustment screw jam nut during engine overhaul.

On June 13, 2024, about 1210 mountain daylight time, an experimental, amateur-built Breezy, N409WC, was substantially damaged when it was involved in an accident near Albuquerque, New Mexico. The pilot received minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The purpose of the flight was to accumulate flight hours on the airframe as part of its Phase I flight testing. The pilot reported that, shortly after takeoff from runway 4 at Double Eagle II Airport (AEG), Albuquerque, New Mexico, about 100 ft above ground level, the engine started running rough. He attempted to troubleshoot; however, he was unable to restore engine power and attempted to land on an adjacent taxiway. During the left turn toward the runway, the left wing dipped into a steep bank. He corrected the bank, but the left wing dipped a second time. While trying to correct the steep bank, the airplane impacted a dirt field, substantially damaging the right wing, right horizontal stabilizer, and the fuselage. The pilot stated that he shut down the engine before he egressed the airplane. The wreckage was recovered to a secure location and examined. Dirt was found in the air intake and carburetor air inlet. The spark plugs were removed and all eight spark plugs exhibited carbon fouling. An engine compression check revealed that the No. 1 cylinder compression measured 80/10. The No. 1 cylinder valve cover was removed, and the exhaust lash adjustment screw jam nut was found loose under the intake valve spring retainer. The No. 1 cylinder was removed, and the oil control ring was found stuck in the ring land. There were rub marks on both the piston and cylinder walls. There were no additional anomalies noted during the examination of the airframe and engine. According to the airplane’s maintenance logs, the engine was overhauled about three years before the accident and at the time of the accident had accumulated about 31 hours since overhaul. The most recent condition inspection was completed on August 4, 2023.