ERA24LA333

The pilot reported that while climbing shortly after takeoff, he felt a “kick” to the right side of the plane and the engine began to run rough, followed by a partial loss of power. The pilot was unable to maintain altitude, so he turned back toward the departure airport. He determined he was not going to be able to reach the airport and as he lined up for an off airport forced landing, the engine regained full power. He turned back toward the departure airport and initiated a climb, but after about 30 seconds the engine power reduced a second time and remained at partial power. With no suitable landing area, the pilot activated the airframe parachute system. The airplane descended under canopy, coming to rest in a wooded area and resulting in substantial damage to the airframe. Recorded engine and performance data from the flight were consistent with a partial loss of engine power and corresponding fluctuations in fuel flow and rpm in the minutes preceding the accident. A postaccident test run of the engine was successfully completed, though some engine roughness, backfires and brief puffs of white smoke were observed. After running for several minutes, the engine began to operate smoothly and normally. Detailed postaccident examination of the engine and its constituent components revealed that half of the alternate air valve was unattached and was loose inside the engine induction housing assembly. The opposing half remained partially installed on its respective mount/actuator inside the induction tube. Based on the available information, it is likely that when the valve failed, it separated and was pulled into the induction housing, partially obstructing induction airflow and disrupting the engine’s fuel/air mixture. The inconsistent loss and subsequent gain of power that occurred during the accident flight was likely attributable to the valve shifting inside the induction housing. Metallurgical examination of the fractured rivets that held the valve assembly together revealed fatigue fracture signatures alongside small areas of ductile dimples consistent with final overstress failure. No evidence of a preexisting induction system issue was documented in the airplane’s maintenance records and the airframe manufacturer reported that no similar failures in other airplanes had been previously documented.

On July 31, 2024, at 1540 eastern daylight time, a Cirrus SR20, N124RR, was substantially damaged when it was involved in an accident near Egg Harbor City, New Jersey. The private pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot departed, Atlantic City International Airport (ACY), Atlantic City, New Jersey with an intended destination of East Hampton Town Airport (JPX), East Hampton, New York; a distance of about 150 miles to the northeast. The preflight inspection and taxi were normal with no issues observed. During the takeoff and initial climb, the engine operated normally. As the airplane was climbing through 2,500 ft above mean sea level (msl), the pilot described that he felt a “kick” to the right side of the airplane and the engine began to run rough. The engine roughness was followed by a partial loss of power, and the pilot was no longer able to maintain altitude. He notified air traffic control and received clearance from the controller to return to ACY, which was about 6 miles away. As he approached ACY, the engine began to lose additional power, and it became clear that he would be unable to reach the runway. The controller provided him with radar vectors toward a nearby highway, but he elected to attempt a forced landing in a nearby field. The pilot performed the emergency checklist, lined up for final approach to the field, and put the flaps down; however, the pilot realized that he was not properly lined up and there was an obstruction and a ditch in the middle of the field. Around this time the engine suddenly came back to full power. As he was now only 3 miles from the ACY runway, he thought he could reach the airport, so he turned toward the runway and initiated a shallow climb, but within 30 seconds of getting full power restored the engine lost power a second time and only retained partial power. Now, out of position for a safe forced landing, he activated the Cirrus Airframe Parachute System (CAPS). The airplane descended under the parachute canopy into tree-covered terrain and became suspended within the trees, after which the pilot egressed. The airplane sustained substantial damage to the fuselage and empennage. The airplane’s recoverable data module (RDM) was downloaded and showed data parameters consistent with a partial loss of engine power, with corresponding significant fluctuations in engine fuel flow and engine rpm in the minutes preceding the CAPS deployment. The airplane was recovered and transported to a secured hangar facility for further examination. While recovering the airplane from the accident site, the recovery personnel documented angular cuts in tree limbs that were consistent with propeller blade contact with the trees while operating under power. During the postaccident examination the engine crankshaft was rotated via the propeller and continuity of the crankshaft to the rear accessory gears and to the valvetrain wasconfirmed. Compression and suction were observed from all four cylinders. The throttle and mixture control were cycled through their full ranges of travel. The fuel had the odor and color of aviation gasoline (100LL) and showed no indication of water or contamination. The fuel supply was plumbed into the fuel line from the left fuel tank and the fuel selector was placed in the left tank position and the electric fuel pump was successfully operated. The engine was started through normal engine starting procedures and run for a total of about 10 minutes at varying speeds from idle to 2,700 rpm, with some engine roughness, backfires and brief puffs of white smoke observed. After several minutes, the engine began to operate smoothly and normally. Examination of the engine and corresponding components was conducted. The fuel injector servo was removed revealing a circular aluminum disc inside the engine induction housing assembly, as shown in figure 1. Further examination revealed that the rivets attaching the two portions of the induction alternate air valve were separated. One of those portions was identified as the disc observed in the induction housing assembly. Figure 1. Alternate air valve as discovered during the engine exam. Left photograph shows location of ½ of the valve in the induction housing assembly. The photograph on the right shows the opposing 1/2 of the valve in the induction tube alternate air mount. The induction tube and valve were sent to the National Transportation Safety Board Materials laboratory for detailed examination. One half of the valve contained four fractured rivets embedded into the surface. These fracture surfaces were visible on the interior of the valve. All the broken rivets protruded about 0.11 inch above the interior face, as measured with digital calipers. One rivet head remained attached to the other half of the valve. Examination of the rivet fracture surfaces under an optical stereoscope showed striations on all four surfaces, interspersed with shiny planes consistent with rubbing or contact postfracture. The rivets were labeled Nos. 1 to 4. The rivets were examined using a field-emission scanning electron microscope (SEM). All four fracture surfaces showed striations consistent with fatigue crack propagation alongside small areas of ductile dimples consistent with final overstress failure. Rivets Nos. 1, 2, and 3 also showed ratchet marks, indicating multiple cracks originating from the outer edge of the rivet. The fracture surface features, including the location and shape of the ductile dimpling surfaces, were consistent with bending or torsion-bending stresses on the rivets. A review of the historical maintenance records going back 24 months did not reveal any maintenance or other repair work on the induction system, nor the alternate air valve. The maintenance records indicated that maintenance routine 50-hour, 100-hour, and annual inspections had been performed and no irregularities were documentedwith the induction system or any related components. The airframe manufacturer reported that no similar failures have been documented.