# NTSB CHI88DER14: Homebuilt Woodstock, N369DK, Mankato, MN, September 5, 1988

- Type: NTSB accident investigation
- Classification: Accident · Fatal · Final report
- Date: September 5, 1988, 18:30 local (23:30 UTC)
- Place: Mankato, MN
- Coordinates: 44.159568, -93.989364 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=44.1596&lon=-93.9894&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: Fatal
- Injuries: 1 fatal
- Status: Completed, report June 25, 1990
- Report: Approved by Office Director
- NTSB case key (mKey): 13898
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI88DER14
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/13898/pdf
- Page: https://openairdocs.org/ntsb/CHI88DER14

## Probable cause

AIRCRAFT STRUCTURAL FAILURE DUE TO OVERLOAD INDUCED BY PILOT IN THE PERFORMANCE OF UNAUTHORIZED MANEUVERS.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, maneuvering
  - aerobatics - performed, pilot in command (cause)
  - design stress limits of aircraft - exceeded, pilot in command (cause)
  - wing - failure,total (cause)
- Loss of control - in flight, maneuvering
- In flight collision with terrain/water, descent - uncontrolled
  - terrain condition - crop

## Analysis

THE HOMEBUILT EXPERIMENTAL GLIDER EXPERIENCED AN INFLIGHT STRUCTURAL FAILURE OF BOTH WINGS WHICH SUBSEQUENTLY RESULTED IN A LOSS OF CONTROL AND IMPACT WITH THE TERRAIN. EXAMINATION REVEALED THE WINGS FAILED DUE TO OVERLOAD AT WING MIDSPAN NEAR THE SPOILERS. RECOVERY FROM LOOPS UTILIZING THE SPOILERS AS AIR BRAKES WILL CAUSE AN INCREASED BENDING MOMENT OUTBOARD OF THE SPOILERS AND REDUCE WING STRENGTH IN THE SPOILER BOX AREA. THE PLT HAD 35 HRS OF FLT TIME IN THE ACFT, AND HAD LOGGED PERFORMANCE OF LOOPS IN HIS PLT LOGBOOK. AEROBATICS ARE PROHIBITED IN THIS ACFT.

## Aircraft

- Registration: [N369DK](https://openairdocs.org/deregistered/N369DK-1992-04-06), registration cancelled 1992-04-06, S/N 369 (OpenAirDocs)
- Reported make and model: HOMEBUILT WOODSTOCK
- Registry model: [Kause Dennis R WOODSTOCK](https://openairdocs.org/model/kause-dennis-r-woodstock) (registry code 1130812) (OpenAirDocs)
- Category: Glider, amateur-built
- Serial number: 369
- Airframe hours: 35
- Engines: unknown
- Damage: Destroyed
- Flight: Personal, Part 91
- Registered owner: Dennis R. Kruse
- Airworthiness certificate: Special, Experimental (Special)
- Last inspection: Annual, March 24, 1988, 35 hours before

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 59; private; airplane ratings: single-engine land; medical: class 3, valid medical--w/ waivers/lim; seat: center; toxicology performed; flight hours: 182 total, 35 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: 320° at 5 knots
- Visibility: 15 statute miles
- Lowest ceiling: 6,000 ft broken
- Temperature: 66 °F, dew point -0 °F
- Altimeter: 29.00 inHg
- Observed at: MKT, 15 nm away

## 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 19880905036639A](https://openairdocs.org/incident/19880905036639A), Sep 5, 1988: Amtr WOODSTOCK1, Mankato, MN, Destroyed, 1 fatal. Wings failed during acrobatic maneuver. Glider was placarded against acrobatics. Had previously looped the glider.

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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