Haverhill, MA, USA
N269PW
Pipistrel SINUS
The pilot departed in his motorized glider, climbed to 3,500 ft, then turned off the engine and feathered the two-bladed propeller once he reached the area where he wanted to soar. Since weather conditions were not conducive to soaring, he attempted to return to the airport. In preparation to land he said he restarted the engine without using the glider's documented procedures. The engine started but was not producing the expected power. The pilot thought he had a fuel problem and was not aware that the propeller was still in a feathered condition. Although the engine was operating normally, the feathered propeller was unable to produce the thrust needed to maintain altitude. The pilot subsequently made a forced landing and the airplane impacted a fence about 1.5 miles short of the runway. The glider sustained substantial damage. Postaccident examination of the glider revealed that both propeller blades and the propeller control knob were in the feathered position. Examination of the engine and airplane revealed no mechanical deficiencies that would have precluded normal operation at the time of impact.
On July 3, 2019, about 2000 eastern daylight time, a Pipistrel Sinus motorized glider, N269PW, was substantially damaged when it was involved in an accident near Lawrence Municipal Airport (LWM) Lawrence, Massachusetts. The pilot was not injured. The personal flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. The pilot reported that he flew about 16 miles to the coast after departure from LWM at an altitude of 3,500 ft mean sea level (msl). As he got over the spot where he normally conducts his soaring, he turned off the engine power, feathered the propeller, and soared for a few minutes as he looked for thermals. Finding none, and with little westerly wind, he elected to restart the engine and return to LWM as his altitude descended through 2,500 ft msl. During his attempted engine restart, the engine started but it seemed "sluggish" and he was not getting the normal performance out of the engine. In addition, he stated that his fuel flow was higher than normal. The pilot attempted to troubleshoot the problem but was unable to achieve normal power. He thought he may have had contaminated fuel or excessive air in the tanks or fuel line. He switched fuel tanks, but the problem continued. Because he was approaching from the east, he lined up for runway 23; however, he was unable to maintain altitude. About 1-1/2 miles from the approach end of the runway, the glider struck a fence on a hilltop at an elevation of about 300 ft and skidded to a stop next to the LMW VOR. A postaccident examination of the glider revealed substantial damage to the landing gear structure, the lower portion of the fuselage, and the left wing. The aircraft came to rest on a magnetic heading of about 200°. About 8 gallons of fuel was drained from the fuel tanks. Both composite propeller blades sheared off about 8 inches from the hub from impact and were in a feathered position. In addition, the propeller control knob in the center console of the cockpit indicated the propeller was feathered. Examination of the engine and fuel system revealed no discrepancies that would have precluded normal operation at the time of impact. Following the accident, an FAA inspector interviewed the pilot, and the pilot stated that he did not use the documented engine restart procedure. A review of the glider's Flight Manual and Maintenance Manual under the Normal Procedures Section, page 39 stated; Restarting the engine in flight This procedure applies only for restarting the engine following an intentional unpowered flight. Reduce speed to 90 km/h (50 kts) and set propeller to minimum pitch setting Master switch ON (key in full right position) Magnetos ON WARNING! Before you activate the starter make sure the propeller is not feathered any more but at minimum pitch setting (propeller pitch knob full forward and screwed left fully) In addition, a description of the procedures to increase/decrease pitch and feathering were found on pages 62 and 63 of the Flight Manual and Maintenance Manual described the procedures. The propeller is controlled by a knob in the middle of the instrument panel. If the knob is turned counterclockwise (left), the pitch decreases. Turning the knob clockwise (right) the propeller pitch increases. WARNING! Feather propeller only after the engine has stopped and at minimum pitch. To feather the propeller, first reduce airspeed to 90 km/h, then pull the propeller pitch knob's metal base backwards fully and then rotate it 20° clockwise. A propeller pitch of approximately 70° is reached by doing so. To feather the propeller fully (90°), rotate the knob clockwise a couple of times until it stops. Propeller unfeathering To unfeather the propeller, first reduce airspeed to 90 km/h. Now pull the propeller pitch knob's metal base slightly, then rotate it counterclockwise and gently push it all the way to the instrument panel.
The pilot's failure to utilize the proper procedure and unfeather the motorized glider’s propeller prior to an in-flight engine restart, resulting in a lack of thrust and subsequent forced landing.
Source: NTSB Aviation Accident Database
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