Eugene, OR, USA
N54CB
MCCLURE B J GLASAIR III
The pilot departed on a daytime cross-country flight in visual meteorological conditions. Automatic dependent surveillance-broadcast (ADS-B) data indicated a normal flight and a cruising altitude of about 2,500 ft mean sea level. The airplane generally flew a south-southwest heading toward the destination airport. About 1.5 nautical miles north of the destination airport, the airplane entered a descending left-hand spiraling turn, after which the track data ended. During the approach to land, the pilot radioed two times that he was ‘going down.’ The airplane impacted terrain about 1.5 nautical miles north of the airport. Postaccident examination of the engine revealed no preimpact mechanical anomalies that would have precluded normal operation of the airplane. Examination of the airframe revealed that the flap system is connected via a tubular bar in the center of the wing that extends out into each wing root. At each end of the bar is a welded plate which a flap actuator push-pull assembly is connected to and terminates at the wing flap. The pilot manipulates the flaps from inside the cockpit via a flap switch which electrically actuates the flaps into various positions depending on the phase of flight. The right-wing flap hardware remained connected from the wing root out to the flap. The left-wing flap was disconnected at the flap bar welded plate. The left-wing flap non-threaded steel clevis pin and cotter key, which connected the welded plate to the flap actuator turnbuckle fork at the wing root, were missing and not located within the wreckage. Review of the aircraft records revealed no evidence of any recent maintenance within the area of the missing clevis pin and cotter key. A condition inspection was completed 45 days prior to the accident. The aircraft records also identified maintenance performed on the landing gear six days prior to the accident. This situation likely created an asymmetrical “split” flap condition, with only one flap deploying when the pilot extended the flaps during the approach to landing, causing the airplane to depart controlled flight. The pilot would likely not have been aware of a faulty flap until the landing approach.
History of Flight On May 20, 2021, about 1030 Pacific daylight time, an experimental amateur-built McClure Glasair III, N54CB, was substantially damaged when it was involved in an accident near Eugene, Oregon. The pilot was seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. Recorded automatic dependent surveillance-broadcast (ADS-B) data provided by the Federal Aviation Administration (FAA) showed that the airplane departed from runway 35 at Aurora State Airport (UAO), Aurora, Oregon, about 1007. The airplane made a right turn onto a south-southwest heading and climbed to a cruise altitude of about 2,500 ft mean sea level (msl) en route toward Mahlon Sweet Field Airport (EUG), Eugene, Oregon. According to the FAA, the pilot contacted Cascade approach control, and a controller cleared the airplane to land on runway 16R at EUG. The controller also cautioned the pilot about wake turbulence from landing traffic. About 8 nautical miles (nm) north of EUG, the airplane made a left turn that was consistent with a straight-in approach to runway 16 at EUG and began a descent, leveling off briefly at an altitude of 1,200 ft msl. ADS-B data showed that, when the airplane was about 1.5 nm from the runway 16 threshold, the airplane entered a left-hand spiral descent and continued to lose altitude. The airplane’s groundspeed was between 115 and 125 knots until about 1031, when the ADS B data track ended, and the airplane was about 1.5 nm north of the accident site. During the approach to land, the pilot reported, “going down, going down.” No further radio communications were received from the pilot. The airplane impacted tall grass about 1.5 nm north of EUG. The figure below shows the accident site and the surrounding area. Witnesses in the surrounding area reported observing a low-flying airplane that made a banking turn before it disappeared. Figure 1. Airplane track and accident area overview. Aircraft Information A review of the airplane’s records revealed that the landing gear had been inspected and returned to service on May 14, 2021; at that time, the tachometer showed 188.1 hours. There was no evidence found of any recent maintenance on the flaps to include the clevis pin and cotter key. Wreckage and Impact Information Examination of the accident site revealed that the first identified point of contact was the left-wing tip; the wreckage continued for about 150 ft, where the engine was located. Flight control continuity could not be established due to impact damage and multiple separations. All major structural components were observed at the accident location. Postaccident examination of the recovered airframe revealed that the entire wing assembly with landing gear separated from the fuselage in one piece. The left-wing flap actuator push-pull tube assembly was detached from the welded plate at the adjustable turnbuckle fork, but it remained attached to the flap actuator rod end at the wing-to-flap attachment. The left steel clevis pin and cotter key were not found. The right wing flap hardware remained connected and intact from the flap tubular bar welded plate to the wing-to-flap attachment. The engine crankshaft was manually rotated via the propeller, and mechanical and valve train continuity was established. The engine examination revealed no mechanical anomalies that would have precluded normal operation.
The pilot’s loss of airplane control during the approach to landing due to an asymmetrical flap deployment for reasons that could not be determined based on the available evidence.
Source: NTSB Aviation Accident Database
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