# NTSB LAX91FA052: de Havilland DHC-6-100, N121PM, Perris Valley, CA, December 9, 1990

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Field investigation · Final report
- Date: December 9, 1990, 14:00 local (22:00 UTC)
- Place: Perris Valley, CA
- Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 1 minor, 20 uninjured
- Status: Completed, report August 6, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 26968
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX91FA052
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/26968/pdf
- Page: https://openairdocs.org/ntsb/LAX91FA052

## Probable cause

A LOSS OF POWER ON THE LEFT ENGINE DUE TO A FATIGUE FAILURE OF A COMPRESSOR TURBINE BLADE LEADING TO FURTHER COMPRESSOR BLADE DAMAGE; A WORN POWER TURBINE GOVERNOR THROTTLE CAM ASSEMBLY WHICH LED TO LOSS OF POWER ON THE RIGHT ENGINE; AND INADEQUATE MAINTENANCE AND INSPECTION BY THE OPERATOR.

## Sequence of events

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

- Loss of engine power(partial) - mech failure/malf, takeoff - initial climb
  - 1 engine
  - compressor assembly,blade - fatigue (cause)
  - compressor assembly - failure,partial (cause)
- Loss of engine power(partial) - mech failure/malf, descent - emergency
  - 1 engine
  - bleed air system,governor - worn (cause)
  - maintenance - inadequate, company maintenance personnel (cause)
- Forced landing, landing - flare/touchdown
- On ground/water collision with object, landing - roll
  - object - fence
  - object - tree(s)

## Analysis

AFTER LIFT-OFF, AT ABOUT 100 FT AGL AND 85 KTS, THE LEFT ENG DECELERATED AND THE AIRPLANE BEGAN TO YAW AND ROLL LEFT. THE PIC ABORTED THE TAKEOFF, TURNED LEFT AND LANDED ON A FLAT LEVEL FIELD. THE AIRPLANE STRUCK A FENCE, THEN TREES. EXAMINATION OF THE LEFT ENG REVEALED THE LOSS OF POWER WAS ATTRIBUTED TO A FATIGUE FRACTURE OF A COMPRESSOR TURBINE BLADE, WHICH LED TO SUBSEQUENT BLADE FRACTURES. THE RIGHT ENG WAS EXAMINED AND FOUND TO HAVE ADVANCE WEAR ON THE THROTTLE CAM ASSEMBLY OF THE POWER TURBINE GOVERNOR. IN A TEST CELL, ONLY APRX 28% OF TAKEOFF POWER COULD BE ACHIEVED. THE CAM LOBE WEAR HAD PROGRESSED OVER AN EXTENDED PERIOD OF TIME. THE RIGHT ENGINE PROP GOVERNOR WAS REPLACED 11/18/90, FOLLOWED BY A TEST RUN.

## Aircraft

- Registration: [N121PM](https://openairdocs.org/aircraft/N121PM), registered now, S/N 14, built 1966 (OpenAirDocs)
- Reported make and model: de Havilland DHC-6-100
- Registry model: [Dehavilland DHC-6 TWIN OTTER](https://openairdocs.org/model/dehavilland-dhc-6-twin-otter) (registry code 2802606) (OpenAirDocs)
- Registry engine: [U/A Canada PT6 SER 578HP](https://openairdocs.org/engine/u-a-canada-pt6-ser-578hp) (registry code 61501, turbo-prop) (OpenAirDocs)
- Category: Airplane
- Serial number: 14
- Airframe hours: 45332
- Engines: P&W PT6-20 550 horsepower turbo prop
- Damage: Substantial damage
- Flight: Part 91
- Operator: One Papa Mike Corp.
- Airworthiness certificate: Standard, Utility; Standard, Normal
- Last inspection: Continuous airworthiness, August 1, 1990, 81 hours before
- Airport: L65, Perris Valley, runway 15, 5,100 × 65 ft, asphalt

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 36; flight instructor, airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, valid medical--no waivers/lim.; seat: left; flight hours: 5,527 total, 333 in this make and model, 2,576 as pilot in command, 55 in the last 90 days, 30 in the last 30 days, 9 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Visibility: 20 statute miles
- Lowest ceiling: none
- Temperature: 70 °F

## 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 19901209053309A](https://openairdocs.org/incident/19901209053309A), Dec 9, 1990: Dhav DHC6100, Perris, CA, Substantial damage. Lost left engine after liftoff. Aborted. Overran open field into trees. Left turbine failed. Right engine problem.

## Other investigations on N121PM (3)

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.

- [NTSB NYC71AN117](https://openairdocs.org/ntsb/NYC71AN117), Jun 4, 1971: Dehavilland DHC-6 (N121PM), Flushing, NY, minor damage
- [NTSB NYC70AN096](https://openairdocs.org/ntsb/NYC70AN096), Mar 6, 1970: Dehavilland DHC-6 (N121PM), Windsor Lock, CT, substantial damage
- [NTSB NYC67I0103](https://openairdocs.org/ntsb/NYC67I0103), Jan 19, 1967: Dehaviland DHC-6 (N121PM), Farmingdale, NY, incident, no damage

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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