# NTSB CEN23LA254: Let L-23 Super Blanik, N10BR, Gregory, MI, June 21, 2023

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Class 3 · Limited · Final report
- Date: June 21, 2023, 15:30 local (19:30 UTC)
- Place: Gregory, MI
- Coordinates: 42.44208, -84.06436
- Nearby events: https://openairdocs.org/map.md?lat=42.4421&lon=-84.0644&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Defining event: [Approach-VFR pattern final: Aerodynamic stall/spin](https://openairdocs.org/ntsb-events/241)
- Highest injury: Serious injuries
- Injuries: 1 serious, 1 minor
- Status: Completed
- Report: Approved by Office Director
- Investigation class: Class 3
- NTSB office: Central Region
- Parties: FAA - East Michigan
- NTSB case key (mKey): 192425
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN23LA254
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/192425/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=192425
- Page: https://openairdocs.org/ntsb/CEN23LA254

## Probable cause

The flight instructor’s failure to maintain adequate airspeed and his exceedance of the glider’s critical angle of attack, leading to an aerodynamic stall during the off-field landing.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Performance/control parameters: angle of attack](https://openairdocs.org/ntsb-findings/01062042): Aircraft › Aircraft oper/perf/capability · Capability exceeded (probable cause); cases with it: [Let L-23 SUPER BLANIK, 5 cases](https://openairdocs.org/ntsb-findings/01062042/cases.md?model=1360308), [All aircraft, 990 cases](https://openairdocs.org/ntsb-findings/01062042/cases.md)
- [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Instructor/check pilot (probable cause); cases with it: [Let L-23 SUPER BLANIK, 10 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=1360308), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Approach-VFR pattern final: Aerodynamic stall/spin](https://openairdocs.org/ntsb-events/241) (defining event); cases with it: [Let L-23 SUPER BLANIK, 5 cases](https://openairdocs.org/ntsb-events/241/sequence.md?model=1360308), [All aircraft, 1,529 cases](https://openairdocs.org/ntsb-events/241/sequence.md)

## Analysis

The student pilot reported that he was flying the glider until about 10 minutes before the accident, when the flight instructor took over control and started looking for thermals to gain altitude. He said the flight instructor was mostly quiet until he said they were going to perform an off-field landing. The glider flew across a tree line about 150 ft above ground level and turned to land in a bean field. Neither the student nor the flight instructor had any recollection of the accident. Postaccident examination showed that the forward fuselage was crushed upward, and rearward and the outboard 6 ft of the left wing was separated. The separation point had signatures indicating upward bending of the tip. The damage to the glider was consistent with a nose-low, left-wing-low impact. Flight control continuity was verified from the cockpit to all control surfaces. No anomalies were detected. Based on the available information, the glider likely had insufficient altitude to return to the departure airstrip and the flight instructor attempted an off-field landing. The nose-low, left-wing-low impact suggested that the instructor likely exceeded the glider’s critical angle of attack and encountered an aerodynamic stall at low altitude during the landing attempt.

## Factual narrative

On June 21, 2023, about 1530 eastern daylight time, a Let L-23 Super Blanik, N10BR, was substantially damaged when it was involved in an accident near Richmond Field Airport (69G), Gregory, Michigan. The flight instructor was seriously injured, and the student pilot received minor injuries. The glider was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The glider came to rest about 3,500 ft northwest of the north end of the runway at 69G. The student pilot reported that he was flying the glider until about 10 minutes before the accident when the flight instructor took over control and started looking for thermals to gain altitude. He said the flight instructor was mostly quiet until he said they were going to perform an off-field landing. The glider flew across a tree line about 150 ft above ground level and turned to land in a bean field. The student had no further recollection of the accident. The flight instructor also reported that he had no recollection of the flight. The glider sustained substantial damage to the fuselage and both wings. Postaccident examination showed that the forward fuselage was crushed upward, and rearward and the outboard 6 ft of the left wing was separated. The separation point had signatures indicating upward bending of the tip. The damage to the glider was consistent with a nose-low, left-wing -ow impact. Flight control continuity was verified from the cockpit to all control surfaces. No preimpact anomalies were detected.

## Aircraft

- Registration: [N10BR](https://openairdocs.org/aircraft/N10BR), registered now, S/N 917826, built 1991 (OpenAirDocs)
- Reported make and model: LET L-23 SUPER BLANIK
- Registry model: [Let L-23 SUPER BLANIK](https://openairdocs.org/model/let-l-23-super-blanik) (registry code 1360308) (OpenAirDocs)
- Registry engine: [NONE](https://openairdocs.org/engine/none) (registry code 00000, none) (OpenAirDocs)
- Category: Glider
- Serial number: 917826
- Year built: 1991
- Damage: Substantial damage
- Flight: Instructional, Part 91
- Operator: Sandhill Soaring Club Inc
- Registered owner: Sandhill Soaring Club Inc
- Airworthiness certificate: Standard, Utility
- Last inspection: Annual, May 5, 2023
- Airport: 69G
- Equipment: Unknown

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 68; injuries: serious; airline transport, commercial, flight instructor; airplane ratings: single-engine sea, single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; seat: rear; restraint: 4-point; flight hours: 24,700 total, 130 in this make and model
- Student pilot; age 15; injuries: minor; seat: front; restraint: 4-point; flight hours: 4 total, 3 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: 100° at 9 knots
- Visibility: 10 statute miles
- Temperature: 84 °F, dew point 55 °F
- Altimeter: 30.13 inHg
- Observed at: KOZW, 12 nm away
- METAR: METAR KOZW 211935Z AUTO 10009KT 10SM SCT060 SCT080 29/13 A3013 RMK AO2 T02910127=

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 20230621008479A](https://openairdocs.org/incident/20230621008479A), Jun 21, 2023: Let L-23 SUPER BLANIK, Gregory, MI, Substantial damage. CFI took controls from student pilot to find thermals. CFI made decision to do off field landing. Glider came to rest in bean field approximately half way up…

## Docket (5 files)

The files NTSB released with the investigation on November 21, 2024, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=192425. 5.0 MB in all.

- Maintenance records (item 1, PDF, 4 pages, 628 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17580609&FileExtension=pdf&FileName=Maint%20records_Redacted-Rel.pdf
- Email correspondence with FAA inspector (item 2, PDF, 4 pages, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17592029&FileExtension=pdf&FileName=FAA%20Email%20of%20pilot%20statements._Redacted-Rel.pdf
- Email correspondence with flight instructor (item 3, PDF, 2 pages, 1.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17580859&FileExtension=pdf&FileName=Emails%20with%20CFI_Redacted-Rel.pdf
- Email correspondence with father of minor student pilot (item 4, PDF, 2 pages, 599 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17591275&FileExtension=pdf&FileName=Email%20with%20father%20of%20student%20pilot_Redacted-Rel.pdf
- Aircraft examination notes and photographs (item 5, PDF, 9 pages, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=17590994&FileExtension=pdf&FileName=Aircraft%20examination-Rel.pdf

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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