# NTSB LAX90LA157: Robinson R22, N8560M, Mammoth Lakes, CA, April 29, 1990

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: April 29, 1990, 07:10 local (14:10 UTC)
- Place: Mammoth Lakes, CA
- Coordinates: 37.579673, -118.840011 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=37.5797&lon=-118.8400&mi=10
- Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 2 minor
- Status: Completed, report October 2, 1992
- Report: Approved by Office Director
- NTSB case key (mKey): 26787
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX90LA157
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/26787/pdf
- Page: https://openairdocs.org/ntsb/LAX90LA157

## Probable cause

PILOT'S ENCOUNTER WITH A STRONG DOWNDRAFT WHILE CRUISING AT AN INADEQUATE ALTITUDE. A CONTRIBUTING FACTOR WAS THE HIGH ALTITUDE WHICH LIMITED AVAILABLE ENGINE POWER FOR RECOVERY.

## Sequence of events

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

- In flight encounter with weather, cruise - normal
  - weather condition - downdraft (contributing factor)
  - altitude - inadequate, pilot in command (cause)
  - weather condition - high density altitude (contributing factor)
- Loss of control - in flight, cruise - normal
- In flight collision with terrain/water, descent - uncontrolled

## Analysis

THE PILOT ENCOUNTERED A STRONG DOWNDRAFT WHILE CRUISING AT 250 TO 300 FEET AGL. HE LOST CONTROL OF THE HELICOPTER, WAS UNABLE TO ARREST THE DESCENT, AND COLLIDED WITH 7000 MSL TERRAIN.

## Aircraft

- Registration: [N8560M](https://openairdocs.org/aircraft/N8560M), registered now, S/N 0476 (OpenAirDocs)
- Reported make and model: ROBINSON R22
- Registry model: [Robinson Helicopter R22](https://openairdocs.org/model/robinson-helicopter-r22) (registry code 7640102) (OpenAirDocs)
- Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs)
- Category: Helicopter
- Serial number: 0476
- Engines: LYCOMING O-320-B2C 160 horsepower reciprocating
- Damage: Substantial damage
- Flight: Personal, Part 91
- Registered owner: Louis W. Thacker
- Departed: B1H, BISHOP, CA
- Destination: MEV, MINDEN, NV

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 57; private; medical: class 3, valid medical--w/ waivers/lim; flight hours: 131 total, 131 in this make and model, 65 as pilot in command, 32 in the last 90 days, 20 in the last 30 days, 2 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 0° at 6 knots
- Visibility: 50 statute miles
- Lowest ceiling: none

## 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 19900429013099A](https://openairdocs.org/incident/19900429013099A), Apr 29, 1990: Robsin R22, Mammoth, CA, Substantial damage. Flying low in mountain terrain got uncontrollable downdraft. Collidew with 7000FT terrain.

## Other investigations on N8560M (1)

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 ERA16LA055](https://openairdocs.org/ntsb/ERA16LA055), Dec 1, 2015: Robinson R22 (N8560M), Venice, FL, substantial damage. Probable cause: The flight instructor's failure to maintain control of the helicopter during an autorotation, which resulted in a hard landing.

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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