ERA20CA116

NTSB accident investigation · Let L 23 Super Blanik · Huntsville, AL · March 1, 2020

Accident · Serious injuriesData collectionFinal report
Date
March 1, 2020, 14:00 local (20:00 UTC)
Place
Huntsville, AL
Injuries
2 serious
Damage
Substantial damage
Phase of flight
Approach
Aircraft
N296BALet L 23 Super Blanik
Defining event
Approach: Loss of control in flight
Weather
Visual (VMC) · Day
Status
Completed · report June 29, 2020
Report
Approved by Office Director
NTSB office
Eastern Region Aviation
Parties
FAA/FSDO
FAA report
20200301006099A
Case key
101021

From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.

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Probable cause

The pilot's failure to maintain glider control and his exceedance of the glider's critical angle of attack while maneuvering in gusting wind conditions, which resulted in an aerodynamic stall.

Findings · 3

NTSB’s coded findings. Those marked are part of the probable cause; the rest are factors or other findings. Under each, the cases with the same finding.

Performance/control parameters: angle of attackAircraft › Aircraft oper/perf/capability · Capability exceededLet L-23 SUPER BLANIK: 5 casesAll aircraft: 990 casesProbable cause
Wind: gustsEnvironmental issues › Conditions/weather/phenomena · Effect on operationLet L-23 SUPER BLANIK: 1 caseAll aircraft: 1,199 casesProbable cause

Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event is the one that best describes the accident. Under each, the cases with the same event anywhere in their sequence.

Analysis

According to the glider pilot, the purpose of the flight was to release from the tow about 300 ft above ground level, return to the airport, and land on the departure runway in the opposite direction, which would simulate the response to a "rope-break" emergency during the initial climb. After departure from the runway and release from the tow, the pilot completed a 270° turn on the north side of the runway and had to make another 90°, left base-to-final turn to return toward the runway. While still on the base leg, the glider encountered an 11-knot wind from the south, gusting to 18 knots. The pilot believed that the glider must have encountered "wind shear" as he "lost all elevator control," and the glider then impacted terrain. The Federal Aviation Administration inspector who conducted a postaccident examination of the glider reported that he established flight control continuity. The pilot reported that there were no preaccident mechanical malfunctions or failures with the glider that would have precluded normal operation.

Factual narrative

According to the glider pilot, the purpose of the flight was to release from the tow about 300 ft above ground level, return to the airport, and land on the departure runway in the opposite direction, which would simulate the response to a "rope-break" emergency during the initial climb. After departure from runway 27 and release from the tow, the pilot completed a 270° turn (to his right) on the north side of the runway and had a 90°, left base-to-final turn remaining to return to the runway. While still on the base leg, the glider encountered an 11-knot wind from the south that gusted to 18 knots, and the pilot surmised that he must have encountered "wind shear" as he "lost all elevator control" and impacted terrain.Postaccident examination of the flight control system did not reveal any anomalies and the pilot reported that there were no preimpact mechanical malfunctions or failures with the glider that would have precluded normal operation.

Aircraft

Registration
N296BA
Reported as
Let L 23 Super Blanik (No Series)
Category
Glider
Serial number
948117
Built
1994
Airframe hours
1,680
Damage
Substantial damage
Flight
Instructional · Part 91
Operator
Huntsville Soaring Club
Registered owner
Huntsville Soaring Club
Airworthiness certificate
Standard, Normal
Last inspection
Annual · March 30, 2019 · 90 hours before
Departed
3M5 · Huntsville, AL
Destination
3M5 · Huntsville, AL
Airport
3M5 · Moontown, runway 09, 2,180 × 160 ft, grass/turf
Equipment
Unknown

Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.

Flight crew

As NTSB recorded them. NTSB leaves out names.

Role
Pilot
Age
69
Injuries
Serious
Certificates
Private, Commercial, Flight instructor
Airplane ratings
Single-engine land, Multi-engine land
Instrument ratings
Airplane
Medical
Class 3, With waivers/limitations
Seat
Rear
Restraint
4-point
Flight hours
1,834 total · 295 in this make and model

Weather

Conditions
Visual (VMC) · Day
Wind
190° at 11 knots, gusting 18
Visibility
10 statute miles
Lowest ceiling
None
Temperature
66 °F, dew point 37 °F
Altimeter
30.12 inHg
Observed at
KMDQ, 8 nm away

Docket · 5

The files NTSB released with the investigation on April 23, 2020, on NTSB’s docket system: statements, records, photos and specialists’ reports. 5.2 MB in all.

FAA reports on this event · 1

The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.