ERA25LA064

The pilot of the motor glider stated that about 1 hour after departure, the motor glider’s engine lost partial power and began to run rough. Shortly thereafter, the engine lost power completely and the pilot’s attempt to restore power was unsuccessful. He located a nearby private airport on his GPS and attempted to perform a forced landing to its turf runway. As he approached the runway, he observed cattle and a fence on the runway and realized it was not an actual airport but was unable to make any corrections due to altitude and airspeed. During the landing, the motor glider landed hard and came to rest inverted resulting in substantial damage to the fuselage. Postaccident examination of the motor glider’s engine revealed that the No. 4 cylinder intake valve had separated from its two keepers/safety wedges and had fractured into three sections. The valve face was located inside the cylinder, and the valve stem was deformed and found in the intake manifold. One valve keeper was found inside the valve cover and exhibited abrasion at its rotocap contact surface; the second keeper was not located. The intake rocker arm adjustment screw was backed off, and its corresponding jamb nut was found in the valve cover. The exhaust rocker arm adjustment screw for the No. 4 cylinder was also backed off, though its jamb nut remained in place. These conditions differed from those found on the remaining three cylinders. Abrasion marks on the intake and exhaust rocker arm adjustment areas were consistent with contact between the rocker arms and rotocaps during engine operation. The engine manufacturer’s maintenance publications required a minimum 1 mm clearance between the rocker arm and rotocap when the valve was fully depressed and specified that the clearance be visually inspected at intervals not exceeding 100 hours. The engine had accumulated 107.1 tachometer hours since the valves were last replaced and 54.9 hours since the most motor glider’s most recent condition inspection. Based on this information, the wear and damage observed during the postaccident examination of the engine likely the result of improper clearance between the rocker arm and rotocap, which resulted in unseating of the keepers and valve separation. Although the private use airport was charted, the local municipality had not approved the airport, and the airport had been erroneously activated; thus the airport should not have been charted. The airport owner later requested its deactivation, which became effective about 3 months after the accident.

On November 20, 2024, about 1330 eastern standard time, an AMS Flight D O O Carat A motor glider, N17GF, was substantially damaged when it was involved in an accident at Sunset Strip Airport (7GE5), Centralhatchee, Georgia. The pilot sustained serious injuries. The motor glider was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that the motor glider departed with 13 gallons of fuel from Thomas Ridge Airport (3GA7), Rupert, Georgia, and was destined for Northeast Alabama Regional Airport (KGAD), Gadsden, Alabama. About 1 hour after departure, the pilot described that the engine experienced a partial loss of engine power and began to run rough. Shortly thereafter, the engine lost power completely. The pilot’s attempt to restore power was unsuccessful. He selected the nearest airport in his GPS database and performed a forced landing to Sunset Strip (7GE5), Centralhatchee, Georgia. As he approached the runway, he observed cattle and a fence on the turf runway. During the landing, the motor glider landed hard and came to rest inverted. A Federal Aviation Administration inspector examined the motor glider at the accident site, and observed that the motor glider’s engine was impact-separated and the airframe exhibited fractures in several areas. A postaccident examination of the engine revealed that the No. 4 cylinder intake valve had separated from its two keepers/safety wedges and had fractured into three sections. The valve face was found inside the cylinder, and the valve stem was deformed and observed in the intake manifold. Impact damage was noted to the interior of the cylinder bore, piston and head. One valve keeper was located in the valve cover and exhibited abrasion at its rotocap contact surface; the other keeper was not located. The intake rocker arm adjustment screw was backed off, and the corresponding jamb nut was separated and found in the valve cover. The exhaust rocker arm jamb nut for the No. 4 cylinder remained in place, but its adjustment screw was backed off. These settings differed from those observed on the remaining three cylinders. Abrasion was noted on both the intake and exhaust rocker arm adjustment areas, consistent with contact between the rocker arms and the rotocaps during engine operation. Maintenance records showed the motor glider’s most recent condition inspection was completed on May 20, 2024, at a tachometer time of 114.0 hours and a total airframe time of 259.6 Hobbs hours. The intake and exhaust valves were last replaced on May 18, 2017, at a tachometer time of 45.2 hours. At the time of the accident, the airframe Hobbs time was 314.5 hours, and the tachometer time was 152.3 hours. Thus, the motor glider had accrued 54.9 hours since its last condition inspection, and the engine had accrued 107.1 tachometer hours since replacement of the valves. Sauer Aircraft Engine’s maintenance publications, Technical Note Nos. 25 & 26, dated December 14, 2016, specified thatthe clearance between the rocker arm and rotocap must be at least 1 millimeter (mm) when the valve was fully depressed, and that this clearance must be visually inspected at intervals not exceeding 100 hours. The publications stated that rocker arm contact with the rotocap may allow unseating of the valve keepers/safety wedges and result in a loss of engine power. At the time of the accident, 7GE5 was charted as a private use airport requiring permission prior to landing. The single turf runway was oriented in a 04/22 configuration and was 2,300 ft-long and 75 ft-wide. The airport’s activation was dated February 2005. The FAA Office of Airports reported that although the property owner submitted an FAA Form 7480-1 and received a determination letter, the local municipality did not approve the airport. Because the owner did not return a signed FAA Form 5010-1, the airport should not have been activated or charted in an aviation database for an available airport. At the owner’s request, the FAA submitted a subsequent Form 7480-1 to deactivate the airport; the deactivation became effective March 10, 2025, 110 days after the accident.