# NTSB NYC92LA166: Mitsubishi MU-2-60, N66LA, Philadelphia, PA, August 18, 1992

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: August 18, 1992, 05:58 local (09:58 UTC)
- Place: Philadelphia, PA
- Coordinates: 40.070541, -75.000778 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=40.0705&lon=-75.0008&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed, report May 26, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 37209
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=NYC92LA166
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/37209/pdf
- Page: https://openairdocs.org/ntsb/NYC92LA166

## Probable cause

THE IN-FLIGHT SEPARATION OF A PROPELLER BLADE AS A RESULT OF FATIGUE CRACKING INITIATED FROM MULTIPLE SITES LOCATED AT CORROSION PITS IN THE BALANCING HOLE.  CONTRIBUTING FACTORS IN THE ACCIDENT WERE: THE FAILURE TO DETECT THE CORROSION DURING THE LAST OVERHAUL PROCEDURE; AND A COMPLETE LOSS OF ELECTRICAL POWER AS RESULT OF THE SEPARATED BLADE BREAKING THE ELECTRICAL LINES.

## 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 - corroded (contributing factor)
  - maintenance,inspection - inaccurate, company maintenance personnel (contributing factor)
  - propeller system/accessories,blade - fatigue (cause)
  - propeller system/accessories,blade - separation (cause)
  - electrical system - failure,total (contributing factor)
  - emergency procedure - initiated, pilot in command
- Forced landing, descent - emergency
- Gear not extended, landing - flare/touchdown

## Analysis

AT 6000 FEET MSL, WHILE IN CRUISE FLIGHT, A PROPELLER BLADE FROM THE LEFT PROPELLER ASSEMBLY SEPARATED IN-FLIGHT, PENETRATED THE FUSELAGE, BREAKING ELECTRICAL LINES AND CAUSING A LOSS OF ELECTRICAL POWER.  AT THE TIME THE AIRPLANE WAS IN IMC, SO THE PILOT ELECTED TO TURN 180 DEGREES IN AN ATTEMPT TO FLY TO AN AREA OF BETTER WEATHER. HE FLEW WITHOUT ELECTRICAL POWER OR MOST OF THE INSTRUMENTS FOR ABOUT 40 MINUTES, UNTIL REACHING AN AREA OF CLEAR WEATHER. ONCE THE PILOT WAS ABLE TO IDENTIFY HIS LOCATION HE ELECTED TO MAKE A GEAR UP LANDING AT THE NEAREST AIRPORT. METALLURGICAL EXAMINATION OF THE SEPARATED BLADE REVEALED THAT THE SEPARATION OF THE BLADE WAS THE RESULT OF FATIGUE CRACKING THAT INITIATED FROM MULTIPLE SITES LOCATED AT CORROSION PITS IN THE BALANCING HOLE.  IT WAS DETERMINED THAT THE CORROSION PITTING HAD NOT BEEN DETECTED DURING THE LAST OVERHAUL AND PROCEDURES TO SHOT PEEN AND PAINT THE BALANCING HOLE WERE NOT PERFORMED.

## Aircraft

- Registration: N66LA (not matched to a registry record)
- Reported make and model: MITSUBISHI MU-2-60
- Category: Airplane
- Serial number: 792SA
- Airframe hours: 4018
- Engines: GARRETT TPE331-10-511 1000 horsepower turbo prop
- Damage: Substantial damage
- Flight: Part 135
- Operator: Epps Air Service
- Registered owner: Epps Air Service
- Airworthiness certificate: Standard, Normal
- Last inspection: AAIP, August 10, 1992, 90 hours before
- Departed: TEB, TETERBORO, NJ
- Destination: BKL, CLEVELAND, OH
- Flight plan: IFR
- Airport: PNE, Northeast Philadelphia, runway 6, 7,000 × 150 ft, asphalt

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 47; airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane, helicopter; medical: class 2, valid medical--no waivers/lim.; seat: left; flight hours: 17,883 total, 2,900 in this make and model, 15,000 as pilot in command, 209 in the last 90 days, 68 in the last 30 days, 4 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Night/dark
- Wind: 360° at 4 knots
- Visibility: 5 statute miles
- Lowest ceiling: 1,400 ft overcast
- Temperature: 64 °F, dew point 64 °F
- Altimeter: 30.00 inHg
- Observed at: PNE, 1 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 19920818035699A](https://openairdocs.org/incident/19920818035699A), Aug 18, 1992: Mtsbsi MU2B60, Philadelphia, PA, Substantial damage. Propeller blade left engine separated. Struck cabin. Cut all electric lines, landed gear up. Fatigue cracks existed

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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