# NTSB WPR15CA110: Raytheon B300, N49WC, Mammoth Lakes, CA, February 10, 2015

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Data collection · Final report
- Date: February 9, 2015, 17:00 local (Feb 10, 2015, 01:00 UTC)
- Place: Mammoth Lakes, CA
- Coordinates: 37, -118 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=37.0000&lon=-118.0000&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Defining event: [Enroute-descent: Turbulence encounter](https://openairdocs.org/ntsb-events/360)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed, report June 1, 2015
- Report: Approved by Office Director
- NTSB office: Western Pacific Region
- Parties: Textron Aviation, FAA
- NTSB case key (mKey): 90758
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR15CA110
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/90758/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=90758
- Page: https://openairdocs.org/ntsb/WPR15CA110

## Probable cause

The airplane encountered extreme turbulence during descent.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Turbulence](https://openairdocs.org/ntsb-findings/03032000): Environmental issues › Conditions/weather/phenomena · Effect on equipment (probable cause); cases with it: [Raytheon B300, 1 case](https://openairdocs.org/ntsb-findings/03032000/cases.md?model=7150007), [All aircraft, 92 cases](https://openairdocs.org/ntsb-findings/03032000/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Enroute-descent: Turbulence encounter](https://openairdocs.org/ntsb-events/360) (defining event); cases with it: [Raytheon B300, 1 case](https://openairdocs.org/ntsb-events/360/sequence.md?model=7150007), [All aircraft, 423 cases](https://openairdocs.org/ntsb-events/360/sequence.md)

## Analysis

The pilot reported that while in a descent from 16,000 feet, at 1,500 feet per minute, slowing from 190 knots indicated airspeed to 160 knots, the airplane encountered extreme turbulence. The pilot reported one hard jolt up/down followed by about 15 seconds of light turbulence then one final hard jolt similar to the first. The weather was visual conditions and no turbulence was encountered prior to or after the event. A postflight examination of the airplane revealed that the extreme turbulence encountered resulted in substantial structural damage to both wings spars. The pilot reported there were no pre-impact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.

## Factual narrative

The pilot reported that while in a descent from 16,000 feet, at 1,500 feet per minute, slowing from 190 knots indicated airspeed to 160 knots, the airplane encountered extreme turbulence. The pilot reported one hard jolt up/down followed by about 15 seconds of light turbulence then one final hard jolt similar to the first. The weather was visual conditions and no turbulence was encountered prior to or after the event. A postflight examination of the airplane revealed that the extreme turbulence encountered resulted in substantial structural damage to both wings spars. The pilot reported there were no pre-impact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.

## Aircraft

- Registration: [N49WC](https://openairdocs.org/aircraft/N49WC), registered now, S/N FL-144, built 1996 (OpenAirDocs)
- Reported make and model: RAYTHEON AIRCRAFT COMPANY B300 (UNDESIGNAT)
- Registry model: [Raytheon B300](https://openairdocs.org/model/raytheon-b300) (registry code 7150007) (OpenAirDocs)
- Registry engine: [Pratt & Whitney PT6A series](https://openairdocs.org/engine/pratt-whitney-pt6a-series) (registry code 52032, turbo-prop) (OpenAirDocs)
- Category: Airplane
- Serial number: FL-144
- Year built: 1996
- Airframe hours: 9205.5
- Engines: Pratt & Whitney PT6A-60A 1050 horsepower turbo prop; Pratt & Whitney PT6A-60A 1050 horsepower turbo prop
- Damage: Substantial damage
- Flight: Positioning, Part 91
- Operator: West Coast Charters Inc
- Registered owner: American Career College Inc
- Airworthiness certificate: Standard, Commuter
- Last inspection: Continuous airworthiness, January 6, 2015, 55 hours before
- Departed: SNA, Santa Ana, CA
- Destination: MMH, Mammoth Lakes, CA
- Flight plan: IFR
- Airport: MMH, Mammoth Yosemite, runway 27, 7,000 × 100 ft, asphalt
- Equipment: Electronic multifunction display, Electronic flight bag or handheld device, Auto-pilot, Stall warning system, Onboard weather, Electronic primary flight display

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 36; injuries: none; flight instructor, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review January 14, 2015; seat: left; restraint: 4-point; flight hours: 3,800 total, 1,300 in this make and model, 3,009 as pilot in command, 110 in the last 90 days, 22 in the last 30 days, 7 in the last 24 hours
- Co-pilot; age 28; injuries: none; commercial, flight instructor; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review June 20, 2014; seat: right; restraint: 4-point; flight hours: 2,180 total, 100 in this make and model, 2,035 as pilot in command, 18 in the last 90 days, 9 in the last 30 days, 1.2 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 210° at 5 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 64 °F, dew point 12 °F
- Altimeter: 30.02 inHg
- Observed at: KBIH, 28 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 20150209001259A](https://openairdocs.org/incident/20150209001259A), Feb 9, 2015: Raytheon Aircraft Company B300, Mammoth Lakes, CA, Substantial damage. The pilot in command stated that while descending through 16,000 ft MSL, and slowing from 190 knots to 160 knots, the aircraft encountered "severe turbulance."…

## Docket (7 files)

The files NTSB released with the investigation on May 18, 2015, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=90758. 2.6 MB in all.

- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 683 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40426551&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF
- Record of Conversation - Mechanic (item 2, .PDF, 176 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40426552&FileExtension=.PDF&FileName=Record%20of%20Conversation%20-%20Mechanic-Master.PDF
- Statement of Party Representatives to NTSB Investigation (item 3, .PDF, 81 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40426553&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF
- Photo 1 - Back Left of Airplane (Photo Courtesy of Operator) (item 4, .PDF, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40426554&FileExtension=.PDF&FileName=Photo%201%20-%20Back%20Left%20of%20Airplane%20(Photo%20Courtesy%20of%20Operator)-Master.PDF
- Photo 2 - Left Wing (Photo Courtesy of Operator) (item 5, .PDF, 27 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40426555&FileExtension=.PDF&FileName=Photo%202%20-%20Left%20Wing%20(Photo%20Courtesy%20of%20Operator)-Master.PDF
- Photo 3 - Left Wing Damage (Photo Courtesy of Operator) (item 6, .PDF, 32 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40426556&FileExtension=.PDF&FileName=Photo%203%20-%20Left%20Wing%20Damage%20(Photo%20Courtesy%20of%20Operator)-Master.PDF
- Photo 4 - Right Wing (Photo Courtesy of Operator) (item 7, .PDF, 27 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40426557&FileExtension=.PDF&FileName=Photo%204%20-%20Right%20Wing%20(Photo%20Courtesy%20of%20Operator)-Master.PDF

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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