Pilot Debrief

Schleicher ASW27 near Ely, NV — 2020-07-11

Final reportWPR20LA216
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Date
2020-07-11
Location
Ely, NV, USA
Aircraft
Schleicher ASW27
Registration
N167TM
Category
Glider
Highest injury
Fatal
Fatalities
1
Phase of flight
Descent

Probable cause

The pilot’s loss of glider control while maneuvering near a mountain ridge in downdrafts and dry microbursts at an altitude that precluded recovery.

NTSB narrative

The experienced glider pilot reportedly planned to establish new records for either speed, distance, or both on the day of the accident. He departed about 1119 attached to a towplane. According to data obtained from an onboard air data computer, the glider was released about 5 minutes later at an altitude of about 7,800 ft mean sea level (msl). For the next 17 minutes, the glider made a series of climbing turns and then began a descent toward a nearby mountain range with a field elevation of 8,500 msl. The glider impacted terrain immediately after completing a climbing right turn over the mountain. The glider’s left wing impacted the ground first, and the fuselage and empennage came to rest about 100 ft forward of the initial impact point. The right wing and most of the left wing came to rest about 60 ft forward of the fuselage/empennage, resulting in a long debris field. Postaccident examination did not reveal any preimpact mechanical anomalies or malfunctions that could have precluded normal operation. The examination found that the right wing was mostly intact with some fractures while the left wing was extensively damaged from the impact with the ground. The wing’s water quantity at the time of impact could not be determined by the available evidence. The control cables that open and close the wing ballast tank dump valves were separated from their brass fittings. A laboratory analysis of the control cables and brass tubes revealed that most of the cable separations were the result of the accident sequence, except for one, which was cut by recovery personnel. While there is insufficient evidence to determine what the water levels were at the time of impact, there is also no evidence that suggests the wing ballast control system was not functional at the time of impact. Although weather observations suggested the presence of strong thermals in the vicinity at the time of the accident, which would normally be conducive to soaring conditions, the air was also turbulent, with high wind, conditions favorable to dry microburst development, and strong downdrafts all present at the time of the accident. It is likely that these winds disturbed the thermal activity at the time as evidenced by the pilot’s flight track, which indicated that the glider was being pushed toward the northeast while climbing. The southwest wind would have brought rising air on the windward side of the ridge and downdrafts, and descending air (or sink) over the accident site where the glider was maneuvering just prior to impact. The pilot was attempting to maneuver the glider at an altitude of about 400 ft above ground level over mountainous terrain with full water ballast tanks. The high volume of water carried by the glider at the time would have reduced the overall effectiveness of the pilot’s aileron flight control movements while attempting to navigate through the strong downdrafts and dry microbursts. As there were no preimpact mechanical anomalies with the glider, the evidence suggests the accident was the result of the pilot’s loss of glider control while maneuvering near a mountain ridge in downdrafts and microbursts at an altitude that precluded a successful recovery. Toxicology testing of the pilot’s specimens detected evidence of ethanol in only his muscle tissue. When consumed, ethanol distributes quickly and uniformly to body tissues based on water content. As there was no ethanol in two of the three tissue samples, and the ethanol muscle tissue concentration itself was very low, it is likely that the identified ethanol was from sources other than ingestion. Thus, the identified ethanol did not contribute to this accident.

Analysis

Primary failure mode
Loss of control
First missed decision gate
Pilot could have chosen to avoid flying in strong wind conditions.

NTSB coding

Evidence available

  • Photos
  • 16 docket documents
View NTSB final reportView NTSB docket

Docket documents16

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