Front Royal, VA, USA
N912ES
Aviastroitel AC 4C
Prior to the flight, the pilot told a fellow soaring club member that he was going to practice speed control in the traffic pattern. The panel-mounted radio in the glider was not working, so the pilot had to use a handheld radio to communicate. However, no witnesses recalled hearing any communications from the pilot after he disconnected from the tow plane. About 1 hour after the pilot departed, a club member saw his glider on downwind for runway 28. The glider appeared to have a nose-up attitude, was moving "slower than normal," and appeared to be at "minimum sink" speed. At this time, another club glider had just executed a practice premature termination of tow (PTT) maneuver from runway 28 and was landing in the opposite direction on runway 10. The club member thought that the accident pilot had slowed down to wait for that glider to clear the runway, and due to spacing, the accident pilot might have to fly over the top of them and land. The club member turned his attention away from the accident glider and did not see the accident. The flight instructor who had just completed the PTT maneuver said that they had just finished their landing rollout on runway 10 when he looked up and saw the glider in a fully involved spin toward the ground. The glider impacted wooded terrain about a 1/2 mile northwest of the airport. Postaccident examination of the glider revealed no mechanical anomalies that would have precluded normal operation prior to the accident. An index card with airspeeds written on it was found in the wreckage. According to the airspeeds listed, the glider's minimum sink speed was 39 knots, and the stall speed was 37 knots. The pilot's handheld radio was found stowed in a storage pouch that was attached to the right side of the cockpit wall. The radio exhibited some impact damage to the battery section and was inoperable. It was not determined why the pilot was not using his handheld radio to communicate. The club's duty officer who was monitoring the airport's traffic frequency the accident pilot was always meticulous with making radio calls, and it was unlike him not to do so on the day of the accident. Since the pilot stated that he was going to practice speed control in the pattern and was observed flying slower than normal and near minimum sink speed on the downwind leg of the traffic pattern, he may have been distracted by traffic on the runway. It is likely the pilot exceeded the glider's critical angle of attack and entered an aerodynamic stall at an altitude that was too low to recover.
HISTORY OF FLIGHTOn February 9, 2020, about 1320 eastern standard time, an experimental amateur-built Aviastroitel AC-4C glider, N912ES, was substantially damaged when it was involved in an accident near the Front-Royal Warren County Airport (FRR), Front Royal, Virginia. The pilot was fatally injured. The glider was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot was a member of the Skyline Soaring Club, which was based at FRR. A club member helped the pilot assemble his glider and complete a comprehensive positive flight control check. The club member said the flight control check (which included the divebrakes) was normal. The pilot told him that he planned to practice "speed control" in the traffic pattern. The glider's panel mounted radio was not working, so the pilot had to use a handheld radio. However, another club member who was monitoring the airport's common traffic advisory frequency (CTAF) that afternoon as duty officer did not hear the pilot make any radio calls prior to the accident. According to club records, the pilot departed FRR about 1225. A third club member said that he and a passenger were flying in another glider when they caught up with the accident pilot while airborne. About 10-15 minutes prior to the accident, they flew a thermal together before the third club member and his passenger returned to FRR. The third club member said he encountered "a huge updraft" when he made a right turn from the downwind leg to base leg of the traffic pattern for runway 28. He said the updraft, which he estimated was about 10 knots, caught him off guard, but he was able to correct for it and land uneventfully. Once the third club member exited his glider, he saw the accident glider in the traffic pattern. It was midfield on the right downwind leg for runway 28. He said the glider appeared to have a nose-up attitude and was moving "slower than normal." The third club member thought that the pilot was flying at "minimum sink" speed, which he said was not unusual in the traffic pattern. At this time, another club glider had just executed a practice premature termination of tow (PTT) maneuver from runway 28 and was landing in the opposite direction on runway 10. The third club member thought that the accident pilot had slowed down to wait for that glider to clear the runway, and he made a comment to his passenger that the accident pilot might have to fly over the top of them and land. The third club member turned his attention away from the accident glider and when he looked back up, the glider was no longer in the traffic pattern. He said he never heard the accident pilot make any radio calls that day. The flight instructor who had just completed the PTT maneuver said that they had just finished their landing rollout on runway 10 when he looked up to his left and saw a "white glider" in a fully involved spin toward the ground. He did not see the impact and was unsure what direction it was spinning. The flight instructor said that he did not hear any radio communications from the pilot prior to the accident. The soaring club's tow pilot flew over the area where the spinning glider was last observed and located it in the woods about a 1/2 mile northwest of the airport. The tow pilot also said that he had towed the accident glider to altitude about an hour earlier. During the tow flight, he was communicating over the radio with the accident pilot. The club's duty officer at the time of the accident said he never would have launched the glider performing the PTT maneuver if he had known that another glider was in the traffic pattern. The duty officer said the accident pilot was always meticulous with making radio calls and it was unlike him not to do so on the day of the accident. WRECKAGE AND IMPACT INFORMATIONOn-scene examination revealed the glider came to rest upright on rolling terrain at the base of a cluster of trees. The cockpit area was displaced to the right. Several broken tree branches were on top of and around the main wreckage. All major components of the glider were accounted for at the accident site. Both wings remained attached to the fuselage, and the tail section had separated but remained attached via control cables. A portion of the left wing's wing tip was located about 20 ft southwest of the main wreckage. Several broken pieces of the Plexiglas canopy were found around the main wreckage. The right wing exhibited some impact damage, but the aileron was secure and undamaged. The divebrake was extended and was being held up by tree branches. When the branches were removed, the divebrake fully retracted into its wing box. The left wing exhibited more impact damage than the right wing. There was a large gash in the leading edge of the left wing and the top of the wing was fractured back to the aileron's inboard attach point. The aileron was separated from the inboard attach point but remained attached to the outboard attach point. The aileron was also fractured mid-span. The trailing edge of the left wing at the wing root was crushed and appeared to be slightly pulled away from the fuselage. The divebrake was fully retracted in its respective wing box. Flight control continuity was established for the ailerons, the rudder and the divebrakes from the cockpit to the flight control surfaces. The divebrake handle in the cockpit was found in the forward and unlocked position. The divebrake's aluminum control rod aft of the handle was bent about 30° consistent with impact damage. When the divebrake handle was pushed aft, both divebrakes simultaneously extended. The trim was set in the second notch position. The elevator did not move when the flight control stick was moved. Further examination revealed that that the elevator control tube rod end that attached to the elevator bell crank located directly below the control stick was impact damaged and fractured. When the fractured elevator control tube was manually moved, the glider's elevator moved freely. An index card was found in the wreckage that contained several flight speeds written on it. According to the card, the glider's minimum sink speed was calculated to be 39 knots and the stall speed was 37 knots. The pilot's handheld radio was found stowed in a storage pouch that was attached to the right side of the cockpit wall. The radio exhibited some impact damage to the battery section and was inoperable.
The pilot's exceedance of the glider’s critical angle of attack while maneuvering for landing, which resulted in an aerodynamic stall and subsequent loss of control.
Source: NTSB Aviation Accident Database
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