Incident Overview
On April 21, 2024, at approximately 1530 mountain daylight time, an experimental Schleicher Alexander Gmbh & Co Ash 26E motor glider, registration N644CC, sustained substantial damage when it impacted terrain near Heber, Utah. The pilot, the sole occupant, was not injured. The flight was conducted as a personal operation under Title 14 Code of Federal Regulations Part 91.
Flight Details
The pilot reported planning to practice takeoffs and landings. He added fuel and oil, performed a preflight inspection using the manufacturer's checklist, and started the engine without difficulty. After warming the engine and completing pre-takeoff checks, he departed runway 22 and climbed to about 1,200 ft above ground level (agl). He then shut down the engine and stowed the propeller mast. ADS-B data indicated the motorglider lifted off, maneuvered north, reached a maximum altitude of 7,150 ft mean sea level (msl), then returned to land on runway 22.
After landing, the pilot deployed the propeller mast and completed the pre-takeoff checklist, which included closing the airbrake paddles. During startup, the engine ran rough—a condition the pilot described as common for warm starts. Once the engine smoothed out, he advanced the engine speed to about 7,000 rpm and began a second takeoff from runway 22. Shortly after takeoff, the pilot realized the motorglider was not climbing or maintaining altitude. He could not hear the engine through his headset and did not recall the engine rpm or altitude at that time. Believing insufficient runway remained to land, he decided to return to the airport. ADS-B data showed the motorglider climbed to a maximum of about 150 ft agl, then began a descending left turn of approximately 180°. The pilot stated that low altitude and a weather observation system tower on airport property prevented him from continuing the left turn to the taxiway. The motorglider descended and impacted rough terrain to the right of the taxiway. The pilot deployed the airbrakes and wheel brakes to shorten the landing roll, exited without assistance, and reported that the engine had shut down on its own.
Engine and Performance Data
A security video recorded on airport property captured the second takeoff. The motorglider appeared to stop climbing and entered a descending left turn about 30 seconds after takeoff. The engine sound decreased before dust appeared near the motorglider's last position. A sound spectrum study of the video examined variations in the recorded engine sound. At the beginning of the video, the engine was near the maximum takeoff speed of 7,500 rpm for the first four seconds, then decreased to near the maximum continuous speed of 6,900 rpm between 12 and 27 seconds elapsed video time, with a brief increase at 19 seconds. This loss of engine speed equated to about a 10% loss in rate of climb. After that, engine speed decreased steadily to 6,568 rpm at 33 seconds, and the engine was no longer heard after 34 seconds.
ADS-B data for the entire flight was examined. During the first takeoff, the motorglider accelerated to about 57 knots calibrated airspeed (KCAS), or about 65 knots true airspeed (KTAS), and climbed at a maximum rate of about 540 ft per minute. During the second takeoff, it accelerated to about 52 KCAS (59 KTAS) and climbed at a maximum rate of about 280 ft per minute, consistent with about a 50% reduction in climb rate compared to the first takeoff.
Postaccident Examination
The motorglider was equipped with a 49-horsepower Wankel type, single-rotor, dual-spark, liquid-cooled rotor housing, forced-air-cooled rotor, normally aspirated rotary engine. Postaccident examination revealed that the engine remained secured in the engine bay, with only the forward right mount damaged. One of the two spark plugs was removed and exhibited a normal appearance (dry, tan color). When the engine was rotated, the spark plug showed a spark, confirming continuity of the magneto, lead, and spark plug. The fuel pump delivered fuel through an intact fuel line. A test run was attempted; the engine rotated freely but would not start despite multiple attempts. The engine was removed and visually inspected, showing no visible damage.
Airframe examination revealed impact damage to the fuselage consistent with ground impact. The empennage was partially separated from the fuselage. The main landing wheel was extended and displaced left of centerline. The left wing flap remained attached and was lowered downward. The right wing flap remained attached near the root but exhibited a fracture separation from the remaining flap section at about 6 ft outboard; the remaining section was attached and appeared extended. The right wing airbrake paddle was extended, and the left wing airbrake paddle was retracted. Recovery actions included cutting the wings, which precluded determination of the preaccident flap setting. Examination found no mechanical malfunctions or failures that would have precluded normal operation.
Maintenance and Flight Manual Information
Maintenance records showed the engine was removed for inspection on May 8, 2015, and reinstalled at a total time of 654.11 hours. The last annual inspection occurred on April 13, 2024, at 879.6 hours airframe time and 76.2 hours engine time.
According to the ASH 26E Flight Manual, the motorglider is a shoulder-wing sailplane with damped T-tail and sprung, retractable landing gear with a hydraulic disc brake. The wing is equipped with trailing edge flaps extending the full span. The manual states that during climbing flight, the engine should be run at maximum 7,500 rpm at Vy (95 km/h, 51 knots). The flaps have five settings: Flap 1 (-1.0°), Flap 2 (0.0°), Flap 3 (+10°), Flap 4 (+23°), and Flap L (+38° for landing). For self-launch, experienced pilots should start the takeoff run at Flap 1, then increase to Flap 4 at about 50 km/h (27 knots) for the climb. On concrete runways, the procedure is to accelerate with wide-open throttle in Flap 2, lift off at about 50 km/h, then set Flap 4.