# NTSB MKC89FA191: Piper PA-20, N2841P, Moose Lake, MN, August 30, 1989

- Type: NTSB accident investigation
- Classification: Accident · Fatal · Field investigation · Final report
- Date: August 29, 1989, 19:45 local (Aug 30, 1989, 00:45 UTC)
- Place: Moose Lake, MN
- Coordinates: 46.439006, -92.759742 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=46.4390&lon=-92.7597&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Fatal
- Injuries: 2 fatal
- Status: Completed, report December 10, 1990
- Report: Approved by Office Director
- ADs cited in the narratives: AD 77-03-08 (OpenAirDocs)
- NTSB case key (mKey): 34694
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MKC89FA191
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/34694/pdf
- Page: https://openairdocs.org/ntsb/MKC89FA191

## Probable cause

SEVERE CORROSION OF THE LOWER FORWARD LIFT STRUT FOR THE RIGHT WING, INADEQUATE INSPECTION OF THE LIFT STRUT BY MAINTENANCE PERSONNEL, AND SUBSEQUENT FAILURE OF THE LIFT STRUT, WHICH RESULTED IN AN OVERLOAD FAILURE (FOLDING BACK) OF THE WING.  RELATED FACTORS WERE: INADEQUATE INSPECTION PROCEDURES PROVIDED BY THE MANUFACTURER & INADEQUATE SURVEILLANCE BY THE FAA.

## Sequence of events

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

- Airframe/component/system failure/malfunction, cruise
  - wing,bracing strut - corroded (cause)
  - maintenance,inspection - inadequate, other maintenance personnel (cause)
  - procedure inadequate, manufacturer (contributing factor)
  - inadequate surveillance of operation, faa(organization) (contributing factor)
  - wing,bracing strut - failure,total (cause)
  - wing - overload
- In flight collision with terrain/water, descent - uncontrolled

## Analysis

THE ACFT (PIPER PA-22, CONVERTED TO A PA-20, IAW STC SA45AM) WAS BEING USED TO PROVIDE A BIENNIAL FLT REVIEW FOR THE OWNER/PLT (CONSIDERED AS PIC ON THIS FLT). DRG FLT, THE RGT WING FOLDED BACK OVER THE FUSELAGE & THE ACFT CRASHED. AN EXAM OF THE WRECKAGE REVEALED THE FWD LIFT STRUT FOR THE RGT WING HAD FAILED IN AN AREA OF SEVERE CORROSION. THE FAILUREOCCURRED AT THE LOWER PART OF THE LIFT STRUT NEAR THE FUSELAGE ATTACHMENT POINT. AN EXAM OF THE ANNUAL INSPN CHECKLIST INDCD ALL APPLICABLE AIRWORTHINESS DIRECTIVES (AD'S) WERE COMPLIED WITH AS OF 7/21/89 & THAT THE LIFT STRUTS WERE VISUALLY INSPD AT THE ANNUAL INSPN. THE ACFT LOGBOOK SHOWED THAT AD 77-03-08 (REQUIRING MECHANICAL TESTING OF THE LIFT STRUT FOR EVIDENCE OF CORROSION AT 5 YR INTERVALS) HAD BEEN COMPLIED WITH IN JULY 1988. THE AROMA OF LINSEED OIL WAS NOTED IN ALL LIFT STRUTS, BUT POLYMERIZED LINSEED OIL WAS FOUND IN THE RGT & LEFT REAR STRUTS. INTERNAL CORROSION HAD PERFORATED THE RGT FWD LIFT STRUT PRIOR TO ITS FAILURE.

## Aircraft

- Registration: [N2841P](https://openairdocs.org/deregistered/N2841P-2012-09-24), registration cancelled 2012-09-24, S/N 22-3138, built 1955 (OpenAirDocs)
- Reported make and model: PIPER PA-20
- Registry model: [Piper PA-22-150](https://openairdocs.org/model/piper-pa-22-150) (registry code 7102210) (OpenAirDocs)
- Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: 22-3138
- Engines: LYCOMING O-360-A4A 180 horsepower reciprocating
- Damage: Destroyed
- Flight: Instructional, Part 91
- Operator: Prachar, Kenneth M
- Registered owner: Prachar, Kenneth M
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, July 21, 1989
- Departed: 21Y, MOOSE LAKE, MN

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 44; private; airplane ratings: single-engine land; medical: class 3, valid medical--no waivers/lim.; seat: left; toxicology performed; flight hours: 246 total, 218 in this make and model

## Weather

- Conditions: Visual (VMC), Day
- Wind: 360° at 19 knots
- Visibility: 15 statute miles
- Lowest ceiling: none
- Temperature: 61 °F, dew point 57 °F
- Altimeter: 29.00 inHg
- Observed at: DLH, 38 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 19890829032469A](https://openairdocs.org/incident/19890829032469A), Aug 29, 1989: Piper STCPA22, Moose Lake, MN, Destroyed, 2 fatal. Corroded wing strut broke near fuselage attachment and wing folded. Vertical impact. Service directive not complied

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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