# NTSB MIA90IA148: Mitsubishi MU-2B, N722DM, Tyndall Afb, FL, July 2, 1990

- Type: NTSB incident investigation
- Classification: Incident · No injuries · Incident investigation · Final report
- Date: July 2, 1990, 14:00 local (19:00 UTC)
- Place: Tyndall Afb, FL
- Coordinates: 30.05067, -85.549163 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=30.0507&lon=-85.5492&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed, report November 9, 1992
- Report: Approved by Office Director
- NTSB case key (mKey): 32584
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MIA90IA148
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/32584/pdf
- Page: https://openairdocs.org/ntsb/MIA90IA148

## Probable cause

A PROPELLER BLADE FATIGUE FAILURE DUE TO IMPROPER OVERHAUL BY OTHER MAINTENANCE PERSONNEL NOT PERFORMING OVERHAUL IN ACCORDANCE WITH FACTORY SERVICE BULLETINS.

## Sequence of events

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

- Airframe/component/system failure/malfunction, cruise - normal
  - propeller system/accessories,blade - fatigue
  - maintenance,rebuild/remanufacture - improper, other maintenance personnel (cause)
  - maintenance,service bulletin/letter - not followed, other maintenance personnel (cause)

## Analysis

THE PILOT NOTED A SEVERE VIBRATION IN FLIGHT FROM THE LEFT ENGINE. HE SHUT THE ENGINE DOWN AND LANDED. ONE PROPELLER BLADE WAS MISSING PART OF THE BLADE. THE FAILED ASSEMBLY WAS EXAMINED AND THE FAILED BLADE SHOWED EVIDENCE OF HIGH CYCLE, LOW STREES FATIGUE WITH A SURFACE ORIGIN. THE OTHER TWO BLADES WERE FOUND TO BE LESS THAN MINIMUM DIMENSIONS AND HAD IMPROPERLY POLISHED AND PROTECTED SURFACES.

## Aircraft

- Registration: [N722DM](https://openairdocs.org/deregistered/N722DM-1994-11-17), registration cancelled 1994-11-17, S/N 245 (OpenAirDocs)
- Reported make and model: MITSUBISHI MU-2B
- Registry model: [Mitsubishi MU-2B-25](https://openairdocs.org/model/mitsubishi-mu-2b-25) (registry code 5780409) (OpenAirDocs)
- Category: Airplane
- Serial number: 245
- Airframe hours: 7059
- Engines: GARRETT TPE-331-251 715 horsepower turbo prop
- Damage: Minor damage
- Flight: Other work use, Part 91
- Operator: Flight International
- Registered owner: Flight International Of Fl.
- Airworthiness certificate: Standard, Normal
- Last inspection: AAIP, March 21, 1990, 97 hours before
- Flight plan: IFR
- Airport: KPAM, Tyndall Afb

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--w/ waivers/lim; seat: left; flight hours: 6,641 total, 1,533 in this make and model, 6,441 as pilot in command, 143 in the last 90 days, 39 in the last 30 days, 3 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 110° at 10 knots
- Visibility: 7 statute miles
- Lowest ceiling: none
- Temperature: 82 °F, dew point 64 °F
- Altimeter: 29.00 inHg
- Observed at: PAM, 5 nm away

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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