SCHLEICHER ALEXANDER GMBH & CO ASH 26 E

Full Narrative

On April 21, 2024, about 1530 mountain daylight time, an experimental Schleicher Alexander Gmbh & Co Ash 26E motor glider, N644CC, was substantially damaged when it was involved in an accident near Heber, Utah. The pilot was not injured. The motorglider was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
The pilot reported that he planned to practice takeoffs and landings. Before the flight, he added fuel and oil, and conducted a preflight inspection using the manufacturer’s checklist. The engine started without difficulty. He warmed the engine and performed the pre-takeoff and engine checks using their respective checklists. He reported that the engine “ran fine” during his departure from runway 22 and climb to about 1,200 ft above ground level (agl). He then shut down the engine and stowed the propeller mast into the engine bay. ADS-B data showed that the motor glider lifted off the runway, maneuvered north of the airport, climbed to a maximum altitude of 7,150 ft mean sea level (msl), then turned back to the airport and landed on runway 22.
After landing, the pilot deployed the propeller mast and completed the pre-takeoff checklist, which included closing the airbrake paddles. On startup the engine ran rough, which the pilot stated was common for this engine during a warm start. Once the engine “smoothed out,” the pilot advanced the engine speed to about 7,000 rpm and began takeoff from runway 22. The pilot stated that, “shortly after takeoff,” he realized that the motorglider was not climbing or maintaining altitude. The pilot could not hear if the engine was running rough through his headset and did not recall the engine rpm or the motorglider’s altitude at that time.
The pilot stated that he felt there was inadequate runway remaining on which to land and elected to return to the airport. ADS-B data showed that the motorglider climbed to a maximum altitude of about 150 ft agl, then began descending while turning about 180° to the left. According to the pilot, the low altitude and the weather observation system tower on airport property precluded his continuation of the left turn to the taxiway. The motorglider descended and impacted rough terrain to the right of the taxiway. The pilot reported that he deployed the airbrakes and wheel brakes to shorten the landing roll. The pilot exited without assistance and reported that the engine had shut down on its own. Figure 1 is a photo taken shortly after the accident showing the airbrakes, main wheel, and flaps extended.

Figure 1. Image showing the motor glider with the airbrakes, flaps, and main gear extended.
A security video recorded from a location on airport property captured the second takeoff. The motorglider appeared to stop climbing, then entered a descending left turn about 30 seconds after the takeoff. The sound of the engine could be heard decreasing before dust appeared near the motorglider’s last position. .
A sound spectrum study conducted on the security video footage, examined the variations in the recorded engine sound during the accident flight. At the beginning of the video/second takeoff, the study indicated that the engine was near the maximum takeoff speed of 7,500 rpm during the first four seconds of the video and subsequently decreased to near the maximum continuous speed of 6,900 rpm between 12 seconds and 27 seconds elapsed video time (with a brief increase in speed at 19 seconds) The loss of engine speed equated to about a 10% loss in rate of climb. After that, the engine speed decreased steadily to 6,568 rpm at 33 seconds. The engine was no longer heard after 34 seconds.
ADS-B data was examined for the entire flight, including the first takeoff and landing. 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, the motorglider accelerated to about 52 KCAS, or about 59 KTAS, and climbed at a maximum rate of about 280 ft per minute, which was consistent with about a 50% reduction in the rate of climb when compared to the first takeoff.
The motorglider was equipped with a 49-horsepower Wankel type, single-rotor, dual spark, liquid-cooled rotor housing, forced-air-cooled rotor and 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 of a dry, tan color. When the engine was rotated, the spark plug exhibited a spark, confirming continuity of the magneto, lead, and spark plug. The fuel pump delivered fuel through the intact fuel line. A test run was then attempted. The engine rotated freely; however, the engine would not start despite multiple attempts. The engine was removed from the engine bay and visually inspected. The engine showed no visible damage.
Postaccident examination of the airframe revealed impact damage to the fuselage that was consistent with ground impact. The empennage was partially separated from the fuselage. The main landing wheel was extended and displaced to the left of centerline. The left wing flap remained attached to the wing and was lowered downward. The right wing flap remained attached to the wing and appeared retracted from the wing root outboard to about 6 ft, where it exhibited a fracture separation from the remaining flap section. The remaining flap section was attached to the wing 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 of the airframe revealed no mechanical malfunctions or failures that would have precluded normal operation.
Maintenance records showed that 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 ASH 26 E is a shoulder wing sailplane with damped T-tail and sprung, retractable landing gear with hydraulic disc brake. The wing is equipped with trailing edge flaps extending over the full span, to allow a choice of optimum wing camber in relation to drag throughout the speed range. With landing flap selected the deflection of these flaps will generate high drag combined with good control which, together with the airbrake paddles on the upper side, permits very short landing approaches.”
The Flight Manual also stated, in part, “During climbing flight, the engine should be run at maximum 7,500 rpm at Vy = 95 km/h = 51 kts (blue line on ASI scale).”
The motorglider was equipped with trailing edge flaps that had five settings, Flap 1 (-1.0°), Flap 2 (0.0°), Flap 3 (+10°), Flap 4 (+23°), and Flap L (+38°) for landing. The Flight Manual stated, in part, , (3) Self-Launch. “Experienced Pilots should start their take-off run at the most negative flap setting 1. This flap setting affords excellent lateral control. At an indicated airspeed of about 50 km/h = 27 kts the flap should be increased to Flap 4(+23°). For the remainder of the climb Flap 4 should be maintained. For pilots without experience of flapped aircraft, we recommend setting Flap 4 both during take-off and throughout the climb.” The Flight Manual also stated, in part, “Concrete runways: Accelerate with “Wide Open” throttle in Flap setting 2 and slightly push the stick until the tail wheel is unloaded. Up to a speed of about 50 km/h (27 knots) acceleration continues on the main wheel, then set Flap 4 and at the same time gently pull the stick until the aircraft lifts off.”