# NTSB CHI91DEP09: Bowers Flybaby 1A, N8084D, Stoughton, WI, June 17, 1991

- Type: NTSB accident investigation
- Classification: Accident · Fatal · Final report
- Date: June 16, 1991, 19:15 local (Jun 17, 1991, 00:15 UTC)
- Place: Stoughton, WI
- Coordinates: 42.91949, -89.219779 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=42.9195&lon=-89.2198&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: Fatal
- Injuries: 1 fatal
- Status: Completed, report March 24, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 14842
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI91DEP09
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/14842/pdf
- Page: https://openairdocs.org/ntsb/CHI91DEP09

## Probable cause

THE INADEQUATE DESIGN BY THE MANUFACTURER TO PROVIDE FOR ADEQUATE PROTECTION FROM MOISTURE ACCUMULATION IN THE FORM OF DRAIN HOLES. CONTRIBUTING FACTORS WERE THE DETERIORATION (WOOD ROT) OF THE WING SPAR ATTACH AND THE LACK OF INSPECTION ACCESS.

## 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
  - wing - separation
  - wing,wing attachment fitting - rotted/weathered (contributing factor)
  - maintenance,inspection - restricted, other maintenance personnel (contributing factor)
  - acft/equip,inadequate design, manufacturer (cause)
- Loss of control - in flight, maneuvering
- In flight collision with terrain/water, descent - uncontrolled

## Analysis

WHILE PERFORMING AN AEROBATIC MANEUVER THE RIGHT WING FAILED AND DEPARTED THE AIRPLANE.  THE AIRPLANE THEN DESCENDED INTO THE TERRAIN.  SUBSEQUENT EXAMINATION REVEALED WOOD ROT AT THE FUSELAGE CARRY THRU SPAR ATTACHMENT WHERE THE FAILURE OCCURRED.  EXAMINATION REVEALED SIMILAR ROT ON THE LEFT SIDE. THERE WERE NO DRAIN HOLES IN THE AREA OF THE SPAR ATTCHMENT WHERE MOISTURE COULD ACCUMULATE. IT WAS FURTHER DETERMINED THAT THE AREA WHERE THE DETERIORATION OCCURRED WAS NOT VISIBLE DURING NORMAL INSPECTION.

## Aircraft

- Registration: [N8084D](https://openairdocs.org/deregistered/N8084D-1991-10-31), registration cancelled 1991-10-31, S/N 7030 (OpenAirDocs)
- Reported make and model: BOWERS FLYBABY 1A
- Registry model: [Otterback BOWERS FLYBABY 1A](https://openairdocs.org/model/otterback-bowers-flybaby-1a) (registry code 1410127) (OpenAirDocs)
- Category: Airplane, amateur-built
- Serial number: 70-30
- Airframe hours: 250
- Engines: CONTINENTAL C-85-12F 85 horsepower reciprocating
- Damage: Destroyed
- Flight: Personal, Part 91
- Operator: James H. Otterback, doing business as Harold A. Otterback
- Registered owner: James H. Otterback
- Airworthiness certificate: Special, Experimental (Special)
- Last inspection: Annual, April 4, 1991, 8 hours before
- Departed: 2W16, STOUGHTON, WI
- Destination: WI06, WAUNAKEE, WI

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 41; private; airplane ratings: single-engine land; medical: class 2, valid medical--no waivers/lim.; seat: center; toxicology performed; flight hours: 642 total, 100 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: 330° at 6 knots
- Visibility: 20 statute miles
- Lowest ceiling: none
- Observed at: MSN, 10 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 19910616021869A](https://openairdocs.org/incident/19910616021869A), Jun 16, 1991: Amtrbw FLYBABY1, Stoughton, WI, Destroyed, 1 fatal. Right wing separated during a low level loop. Other parts separated prior to impact into trees.

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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